Changing Views - cdn. Web viewZeus himself, I take my fill of ambrosia, the food ... Hubble discovered an odd ... “How can I get the facts out of the textbook and onto the test?

UNIT 2—THE BIG BANG

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CHANGING VIEWS...............................................................................2PTOLEMY............................................................................................................................2

GALILEO..............................................................................................................................8

COPERNICUS...................................................................................................................21

NEWTON...........................................................................................................................31

HUBBLE.............................................................................................................................38

APPROACHES TO KNOWLEDGE..........................................................46STRUCTURE OF SCIENTIFIC REVOLUTIONS..........................................55HENRIETTA LEAVITT..........................................................................66TYCHO BRAHE..................................................................................73SCIENCE, THEOLOGY, & COPERNICAN REVOLUTION.............................77THE VATICAN OBSERVATORY.............................................................87

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UNIT 2—THE BIG BANG TEXT READER 1

Changing ViewsThis is a collection of articles that details the changing view of the Universe from geocentric to heliocentric. There is an article on each of these scientists: Ptolemy, Galileo, Copernicus, Newton, and Hubble.

PtolemyHe studied the stars with his naked eye, and put us at the center of the Universe.

Claudius Ptolemy: An Earth-Centered View of the Universe (1260L)By Cynthia Stokes Brown

The Earth was the center of the Universe, according to Claudius Ptolemy, whose view of the cosmos persisted for 1,400 years until it was overturned — with controversy — by findings from Nicolaus Copernicus, Galileo Galilei, and Isaac Newton.

An astronomer in ancient timesClaudius Ptolemy lived in Alexandria, Egypt, from about 85 to 165 CE. The city was established by Alexander the Great about 400 years before Ptolemy’s birth. Under its Greek rulers, Alexandria cultivated a famous library that attracted many scholars from Greece, and its school for astronomers received generous patronage. After the Romans conquered Egypt in 30 BCE, Alexandria became the second-largest city in the Roman Empire and a major source of Rome’s grain, but less funding was provided for scientific study of the stars. Ptolemy was the only great astronomer of Roman Alexandria.

Ptolemy was also a mathematician, geographer, and astrologer. Befitting his diverse intellectual pursuits, he had a motley cultural makeup: he lived in Egypt, wrote in Greek, and bore a Roman first name, Claudius, indicating he was a Roman citizen — probably a gift from the Roman emperor to one of Ptolemy’s ancestors.

A geocentric viewPtolemy synthesized Greek knowledge of the known Universe. His work enabled astronomers to make accurate predictions of planetary positions and solar and lunar eclipses, promoting acceptance of his view of the cosmos in the Byzantine and Islamic worlds and throughout Europe for more than 1,400 years.

Ptolemy accepted Aristotle’s idea that the Sun and the planets revolve around a spherical Earth, a geocentric view. Ptolemy developed this idea through observation and in mathematical detail. In doing so, he rejected the hypothesis of Aristarchus of Samos, who came to Alexandria about 350 years before Ptolemy was born. Aristarchus had made the


claim that the Earth revolves around the Sun, but he couldn’t produce any evidence to back it up.

Based on observations he made with his naked eye, Ptolemy saw the Universe as a set of nested, transparent spheres, with Earth in the center. He posited that the Moon, Mercury, Venus, and the Sun all revolved around Earth. Beyond the Sun, he thought, sat Mars, Jupiter, and Saturn, the only other planets known at the time because they were visible to the naked eye. Beyond Saturn lay a final sphere — with all the stars fixed to it — that revolved around the other spheres.

This idea of the Universe did not fit exactly with all of Ptolemy’s observations. He was aware that the size, motion, and brightness of the planets varied. So he incorporated Hipparchus’s notion of epicycles, put forth a few centuries earlier, to work out his calculations. Epicycles were small circular orbits around imaginary centers on which the planets were said to move while making a revolution around the Earth. By using Ptolemy’s tables, astronomers could accurately predict eclipses and the positions of planets. Because real visible events in the sky seemed to confirm the truth of Ptolemy’s views, his ideas were accepted for centuries until the Polish astronomer, Copernicus, proposed in 1543 that the Sun, rather than the Earth, belonged in the center.

After the Roman Empire dissolved, Muslim Arabs conquered Egypt in 641 CE. Muslim scholars mostly accepted Ptolemy’s astronomy. They referred to him as Batlaymus and called his book on astronomy al-Magisti, or “The Greatest.” Islamic astronomers corrected some of Ptolemy’s errors and made other advances, but they did not make the leap to a heliocentric (Sun-centered) universe.

Ptolemy’s book was translated into Latin in the 12th century and was known as The Almagest, from the Arabic name. This enabled his teachings to be spread throughout Western Europe.

We know few details of Ptolemy’s life. But he left one personal poem, inserted right after the table of contents in The Almagest:

Well do I know that I am mortal, a creature of one day.

But if my mind follows the wandering path of stars

Then my feet no longer rest on earth, but standing by

Zeus himself, I take my fill of ambrosia, the food of the gods.

Claudius Ptolemy: An Earth-Centered View of the Universe (1090L)By Cynthia Stokes Brown, adapted by Newsela

Ptolemy's view of the earth-centered view of the cosmos persisted for 1,400 years. Only until findings from Nicolaus Copernicus, Galileo Galilei, and Isaac Newton was it overturned.


An astronomer in ancient timesClaudius Ptolemy lived in Alexandria, Egypt, from about 85 to 165 CE. The city was founded by Alexander the Great. Under its Greek rulers, Alexandria developed a famous library that attracted many scholars from Greece, and its school for astronomers received generous funding. After the Romans conquered Egypt in 30 BCE, Alexandria became the second-largest city in the Roman Empire, but less money was provided for astronomy. Ptolemy was the only great astronomer of Roman Alexandria.

Ptolemy was also a mathematician, geographer, and astrologer. Along with many intellectual interests, he had many different cultural influences in his life. He lived in Egypt, wrote in Greek, and had a Roman first name, Claudius, which showed he was a Roman citizen.

A geocentric viewPtolemy collected and summarized Greek knowledge of the known Universe. His work enabled astronomers to pinpoint the planets and predict solar and lunar eclipses. Because of this, his ideas were accepted by Byzantine, Islamic and Europe scholars for more than 1,400 years.

Ptolemy accepted Aristotle’s idea that the Sun and the planets revolve around a spherical Earth, a geocentric view. Ptolemy developed this idea through observation and in mathematical detail. In doing so, he rejected the hypothesis of Aristarchus of Samos, who came to Alexandria about 350 years before Ptolemy was born. Aristarchus had made the claim that the Earth revolves around the Sun, but he couldn’t produce any evidence to back it up.

Based on observations he made with his naked eye, Ptolemy saw the Universe as a set of nested, transparent spheres, with Earth in the center. He posited that the Moon, Mercury, Venus, and the Sun all revolved around Earth. Beyond the Sun, he thought, sat Mars, Jupiter, and Saturn, the only other planets known at the time because they were visible to the naked eye. Beyond Saturn lay a final sphere — with all the stars fixed to it — that revolved around the other spheres.

This idea of the Universe did not fit exactly with all of Ptolemy’s observations. He was aware that the size, motion, and brightness of the planets varied. So he incorporated Hipparchus’s notion of epicycles to work out his calculations. Epicycles were small circular orbits around imaginary centers on which the planets were said to move while making a revolution around the Earth. By using Ptolemy’s tables, astronomers could accurately predict eclipses and the positions of planets. Because real visible events in the sky seemed to confirm the truth of Ptolemy’s views, his ideas were accepted for centuries. They only came into doubt when the Polish astronomer, Copernicus, proposed in 1543 that the Sun belonged in the center – not the earth.

After the Roman Empire dissolved, Muslim Arabs conquered Egypt in 641 CE. Muslim scholars mostly accepted Ptolemy’s astronomy. They referred to him as Batlaymus and called his book on astronomy al-Magisti, or “The Greatest.” Islamic astronomers corrected


some of Ptolemy’s errors and made other advances, but they did not make the leap to a heliocentric (Sun-centered) universe.

Ptolemy’s book was translated into Latin in the 12th century and was known as The Almagest, from the Arabic name. This enabled his teachings to be spread throughout Western Europe.







The Earth was the center of the Universe, according to Claudius Ptolemy. His view of the cosmos was accepted for 1,400 years. Later, Nicolaus Copernicus, Galileo Galilei, and Isaac Newton contradicted Ptolemy’s ideas.

An astronomer in ancient timesClaudius Ptolemy lived in Alexandria, Egypt from about 85 to 165 CE. Alexandria was established by Alexander the Great about 400 years before Ptolemy’s birth.

Under its Greek rulers, Alexandria had a famous library that attracted many scholars from Greece. Its school for astronomers received generous support.

After the Romans conquered Egypt in 30 BCE, there was less funding provided for scientific study of the stars. Ptolemy was the only great astronomer of Roman Alexandria.

Ptolemy was also a mathematician, geographer, and astrologer. Along with many intellectual interests, he had many cultural influences. He lived in Egypt, wrote in Greek, and had a Roman first name, Claudius, which showed he was a Roman citizen.

A geocentric viewPtolemy collected and summarized Greek knowledge of the known Universe. His work allowed astronomers to predict eclipses of the sun and moon, and the positions of planets. His view of the cosmos was accepted for more than 1,400 years in the Byzantine and Islamic worlds and throughout Europe.

Ptolemy accepted Aristotle’s idea that the Sun and the planets revolve around a spherical Earth. This is called a geocentric view. Ptolemy developed this idea by observing the sky and using mathematics.


Aristarchus of Samos lived in Alexandria about 350 years before Ptolemy. Aristarchus claimed that the Earth revolves around the Sun. He couldn’t produce any evidence to support his view, and Ptolemy rejected it.

Ptolemy made observations of the stars and planets with his naked eye. He imagined a Universe with Earth in the center. Around Earth was a set of transparent spheres. He thought that the Moon, Mercury, Venus, and the Sun all revolved around Earth. Past the Sun were Mars, Jupiter, and Saturn. Past Saturn was a final sphere that had all the stars attached to it. This final sphere revolved around the other ones.

This idea of the Universe did not fit exactly with all of Ptolemy’s observations. He knew that the size, motion, and brightness of the planets changed. Ptolemy solved this problem by borrowing a centuries-old idea from Hipparchus. The idea was epicycles: mini-orbits that the planets made while revolving around the Earth.

Astronomers could accurately predict eclipses and the positions of planets by using Ptolemy’s tables. His ideas were accepted for centuries because real visible events in the sky seemed to confirm his views. But in 1543, the Polish astronomer Copernicus proposed that the Sun, not the Earth, belonged in the center.

After the Roman Empire dissolved, Muslim Arabs conquered Egypt in 641 CE. Muslim scholars mostly accepted Ptolemy’s astronomy. They referred to him as Batlaymus and called his book on astronomy al-Magisti, or “The Greatest.” Islamic astronomers corrected some of Ptolemy’s errors and made other advances, but they did not consider a heliocentric (Sun-centered) universe.

Ptolemy’s book was translated into Latin in the 12th century. It was known as The Almagest, from the Arabic name. This allowed his teachings to be spread throughout Western Europe.







Claudius Ptolemy was an ancient astronomer who studied the skies with his naked eye. He believed the Earth was at the center of the Universe. This view was accepted for 1,400 years until Nicolaus Copernicus, Galileo Galilei, and Isaac Newton came along.


Ancient astronomer in AlexandriaPtolemy lived in Alexandria, Egypt. The famous ancient city was founded by Alexander the Great.

At the time, Alexandria was a great center of learning. There was a famous library where many Greek scholars studied. There was a school for astronomers. Wealthy families gave money to the library and schools.

But then the Romans conquered Egypt in 30 BCE. There was less money for studying the stars. Ptolemy was the only great astronomer from Alexandria during this time.

Claudius Ptolemy wasn’t only interested in stars and planets. He also studied maps, math, and astrology. He lived in Egypt, wrote in Greek, and had a Roman first name.

Earth at the center of the universe?Ptolemy studied the Greek knowledge of the known Universe. Aristotle said that the Sun and the planets all revolve around Earth. This geocentric view sees Earth as the center of the Universe. (geo - Earth, centric - centered).

Ptolemy agreed with Aristotle.

Of course, the Earth is not the center of the Universe, as we now know. But amazingly, Ptolemy’s system worked. He could accurately predict the positions of planets. He could also accurately predict when the Sun and Moon would be eclipsed.

Ptolemy studied the sky with his naked eye — no telescope. He used math to track the planets and stars.

He saw a Universe with Earth in the center. Around Earth were huge transparent spheres.

He thought that the Moon, Mercury, Venus, and the Sun all revolved around Earth. Past the Sun were Mars, Jupiter, and Saturn. Past Saturn was a final sphere that had all the stars attached to it. This final sphere revolved around the other spheres.

Because his system worked, it was believed all over the world. For more than 1,400 years people accepted Ptolemy’s spheres.

In 1543, though, Polish astronomer Copernicus correctly claimed that the Sun is at the center of our Universe, not the Earth.

His work lives onThe Roman Empire dissolved, and Muslim Arabs conquered Egypt in 641 CE. Muslim scholars mostly accepted Ptolemy’s astronomy. They corrected some of his errors, and made some advances, but they did not consider a heliocentric (Sun-centered) Universe.

Ptolemy’s book was translated into Latin in the 12th century. This allowed his teachings to be spread throughout Western Europe.

We know few details of Ptolemy’s life. But he left one personal poem, inserted right after the table of contents in his book:






GalileoAn Italian Renaissance man, Galileo used a telescope of his own invention to collect evidence that supported a Sun-centered model of the Solar System.

Galileo Galilei: The Father of Modern Observational Astronomy (1220L)By Cynthia Stokes Brown

Galileo Galilei, an Italian Renaissance man, used a telescope of his own invention to collect evidence that supported a Sun-centered model of the Solar System.

Youth and educationGalileo Galilei was born in Pisa, Italy, on February 15, 1564, the first of seven children of Vincenzo Galilei and Giulia Ammanati. Galileo’s father was a musician — a lute player — from a noble background.

When Galileo was 10, his family moved to Florence, northeast of Rome, where he was educated in a monastery. He was attracted to the priesthood, but his father steered him to study medicine from 1581 to 1585 at the University of Pisa, 40 miles west of Florence on the coast, and very near Galileo’s childhood home.

University studies at that time were based primarily on Aristotle’s philosophy, but Galileo’s acute observations caused him to question some of these accepted views. He noticed that hailstones of different sizes reached the ground simultaneously, contradicting Aristotle’s rule that bodies fall with speeds proportional to their size. At this time, Galileo also sat in on lectures by a practical mathematician, apart from his university studies.

Professor at Pisa and PaduaAfter four years at university, Galileo gave private lessons in mathematics and wrote his first scientific paper, about how things float on water. In 1587, he got a position teaching mathematics at the University of Pisa, which paid him a very modest salary. Two years later, Galileo’s father died, leaving Galileo responsible for the promised dowries of his two sisters. The next year he secured the chair of mathematics at the renowned University of Padua, and the new position paid three times as much. In addition to mathematics, Galileo gave private instruction in military architecture, fortification, surveying, and mechanics.


At the age of 31, Galileo showed his first interest in astronomy, while working to explain the cause of the tides. Padua was 20 miles inland from Venice, an important trading port on the Adriatic Sea. Astronomy was considered part of mathematics at the time, while cosmology was part of philosophy. Most scholars still held the views of Ptolemy, who followed Aristotle in thinking that all heavenly bodies revolve around Earth (a geocentric model). But other views were being considered, including that of Nicolaus Copernicus, who claimed that all bodies revolve around the Sun (a heliocentric model), and of Danish astronomer Tycho Brahe, who held that Earth was fixed but other planets are in orbit around the Sun.

In 1597, Galileo read a book by German astronomer Johannes Kepler, who was enthusiastically pro-Copernicus. Galileo wrote a letter to Kepler stating that he had long agreed with Copernicus, but that he had not dared to make his thoughts public because he was frightened that he would become, like Copernicus, “mocked and hooted by an infinite multitude.” In the same year, Galileo invented a mechanical device for mathematical calculations. He had a craftsman make them, so that Galileo could sell them and give classes on how to use them.

Professors at Padua tended not to marry, and prominent families there did not view Galileo as a catch. Instead, Galileo established a lasting relationship with a non-noble woman 14 years younger, Marina Gamba, and had three children with her. He never married her, and she and the children lived separately, around the corner from him. When he later left Padua in 1610 to move to Florence, he put their two daughters in a convent as soon as possible, and he left his son, Vincenzo, in Padua in Marina’s care.

Galileo’s first known astronomical observation occurred in 1604, when a supernova (the explosive death of a high-mass star) was visible in the sky. Such an event clearly challenged Aristotle’s claim that no change could ever take place in the heavens. From then on, observation and experimentation became the basis for Galileo’s work. Galileo’s prominence as a mathematician and scholar grew, and in the summer of 1605 he arranged to tutor Cosimo de Medici, the son of the Grand Duke of Tuscany.

In July 1609, Galileo heard about a Dutch device for making distant objects look nearer. A friend who saw it described it to Galileo as having two lenses, one on each end of a 4-foot tube. Within about a month, Galileo had made an instrument three times as powerful as the Dutch device.

Galileo continued to work on his telescope, grinding his own lenses. By December 1609, he had seen for the first time the four largest moons orbiting around Jupiter, which contradicted Ptolemaic theory that Earth is the center of all orbiting bodies. Galileo published his findings in March 1610 as The Starry Messenger. The general public was excited, but most philosophers and astronomers declared it an optical illusion.

Mathematics at the court of TuscanyGalileo was offered life tenure at the University of Padua, but Florence was his home, and he wanted freedom from teaching. So he took the job of court mathematician in Florence, where his former math student had become Cosimo II, the Grand Duke of Tuscany.


Soon after his arrival in Florence in September 1610, Galileo began his observations of Venus. Over time he discovered that the Moon-like phases of Venus demonstrated that the neighboring planet had an orbit independent of Earth. This showed conclusively that Venus circled the Sun, as Copernicus thought, not Earth, as Ptolemy thought. But it did not yet prove conclusively that Earth circled the Sun.

In 1613, Galileo published his Letters on Sunspots, based on his observations of the dark spots on the Sun that are caused by intense magnetic activity.

In an appendix, he noted that he agreed with Copernicus, mentioning the fact that he had seen eclipses of the satellites of Jupiter, further evidence that they orbited the planet. This is the only time that Galileo expressed in print his support of the Copernican model. Galileo had no definitive evidence that Copernicus was right, and he didn’t claim that he did. Galileo’s main pieces of evidence were the phases of Venus; the eclipses of Jupiter’s moons; the existence of tides, which Galileo believed could only occur if the Earth moved; observable planetary speeds, and the distances of planets from the Sun.

Drama with the InquisitionDuring the first part of the 16th century, the Catholic Church was facing the challenge of Protestants, who were breaking away from the Church over certain doctrines. By this time, there were printers in many European cities and ideas were spreading quickly, some of them in opposition to the Catholic Church and its beliefs. To combat all heresies, the Pope set up a system of tribunals, or courts, called the Inquisition.

In 1616, the year of Shakespeare’s death, the authorities of the Inquisition in Rome decided to prohibit Copernicus’s book, On the Revolutions of the Celestial Spheres, and any other books that argued in favor of a Copernican Sun-centered model for the Solar System. Galileo traveled to Rome to try to prevent this; he thought it was a mistake that would eventually tarnish the Church’s reputation. He believed that the Catholic Church should keep science and religion completely separate and not interfere with scientific research. The Church upheld its position, and Galileo agreed to obey the ban.

In 1623, a Florentine who admired Galileo became Pope Urban VIII. Galileo had six audiences (meetings) with the Pope in 1624 and received permission to publish his theory on the causes of tides, provided he did not take sides on the cosmological debate. For the next six years, Galileo worked on this book, which turned into a dialogue concerning the relative merits of the Ptolemaic and the Copernican conceptions of the Universe, without reaching a conclusion of one over the other. To carry out the discussion, Galileo invented three characters: Salviati, who gave Copernicus’s views; Simplicio, who presented Aristotelian/Ptolemaic views; and Sagredo, an interested layman. Simplicio was named for an ancient Greek commentator on Aristotle. The title in English was Dialogue Concerning the Two Chief World Systems – Ptolemaic and Copernican.

The publisher of the book received a license to print, and the book appeared in Florence in March 1632. An outbreak of the plague delayed copies being sent to Rome. In August of the same year, an order came from the Roman Inquisition to stop all sales.


Galileo’s student and friend, the Grand Duke Cosimo II, had died in 1621. The new Grand Duke of Tuscany, Ferdinand, protested the book, which seemed to him, and to many of the Church leaders, to portray Simplicio as a simpleton and fool, and thus to take sides in the debate. The Pope considered the character of Simplicio an insult, as did the other Church leaders. In September 1632, Galileo was charged with “vehement suspicion of heresy” and ordered to come to Rome for a trial. Ill, he did not appear until February 1633.

Galileo denied that he was defending heliocentrism, but he finally admitted that one could get that impression from the book. He was threatened with torture, forced to recant the heliocentric model, and, in June of that year, sentenced to indefinite imprisonment in Rome. His book was put on the Index of Prohibited Books. Three of the 10 judges disagreed with the verdict. Legend has it that as Galileo left the courtroom he whispered, “Eppur si muove [Still it (Earth) moves],” but this was most likely invented later.

Galileo was crushed by the harsh verdict. The archbishop of Siena, who had disagreed with the verdict, got permission to take Galileo into his home and helped him through his depression. Two years before his trial, Galileo had taken a villa on the outskirts of Florence, to be next to the convent where his daughters were nuns. After a few months in Rome, Galileo received permission to return to his own villa, to be guarded by representatives of the Inquisition, a house arrest. He was ill with a hernia, heart palpitations, and insomnia. A few months after his return home, his older daughter, Maria Celeste, with whom he was very close, died in April 1634.

The following year Galileo’s book, Dialogue Concerning the Two Chief World Systems –Ptolemaic and Copernican, was published in Latin in Strasburg, Alsace (France), outside the grasp of the Catholic Inquisition, thereby reaching a much more cosmopolitan audience than the suppressed Italian text.

Blindness and a legacy of truthGalileo rallied and in his last years wrote a book summarizing all his ideas, published in 1637 in Holland in Italian. This book was translated into English in 1661 as Discourses and Mathematical Demonstrations Relating to Two New Sciences, and Isaac Newton read it in 1666.

By 1638, Galileo had become totally blind. He was allowed to live with his son in Florence and have visitors as long as they were not mathematicians. He carried on a great deal of correspondences by dictating his letters to others. He died on January 9, 1642, in Florence, at the age of 77. He was not allowed to be buried in the main body of the Basilica of Santa Croce, but in a small room at the end of a corridor; he was reburied in the main part in 1737.

The Catholic Church took 200 years to remove Galileo’s book from the Index of Prohibited Books, finally doing so in 1835. In 1992, Pope John Paul II expressed regret at how the Church had handled Galileo and issued a declaration acknowledging the errors committed by the court of the Catholic Church. In 2008, plans were announced for a statue of Galileo inside the Vatican walls, but in 2009 these plans were suspended.

Galileo’s own words to a friend about his blindness serve as a suitable epitaph:


Alas, your friend and servant Galileo has for the last month been irremediably blind, so that this heaven, this Earth, this Universe which I, by my remarkable discoveries and clear demonstrations had enlarged a hundred times beyond what had been believed by wise men of past ages, for me is from this time forth shrunk into so small a space as to be filled by my own sensations. (Drake, p. 107)

Galileo Galilei: The Father of Modern Observational Astronomy (1030L)By Cynthia Stokes Brown, adapted by Newsela

Galileo Galilei, an Italian scholar, invented a telescope to collect evidence that supported a Sun-centered model of the Solar System.

Youth and educationGalileo Galilei was born in Pisa, Italy, on February 15, 1564. He was the first of seven children. Galileo’s father was a musician — a lute player — from a noble background.

When Galileo was 10, his family moved to Florence, northeast of Rome, where he was educated in a monastery. He wanted to become a priest, but his father pushed him to study medicine at the University of Pisa.

University studies at that time were based primarily on Aristotle’s philosophy, but Galileo’s sharp observations caused him to question some of these accepted views.

For example, he noticed that hailstones of different sizes reached the ground simultaneously, contradicting Aristotle’s rule that objects of different sizes fall at different speeds.

At this time, Galileo also sat in on lectures by a practical mathematician.

Professor at Pisa and PaduaAfter four years at the university, Galileo gave private lessons in mathematics and wrote his first scientific paper, about how things float on water. In 1587, he got a position teaching mathematics at the University of Pisa, which paid him a small salary.

Two years later, Galileo’s father died, leaving Galileo with financial responsibilities. The next year he became the chair of mathematics at the famous University of Padua. The new position paid three times as much. In addition to mathematics, Galileo gave private instruction in military architecture, fortification, surveying, and mechanics.

At the age of 31, Galileo showed his first interest in astronomy, while studying tides. Padua is near Venice, an important trading port on the Adriatic Sea.

Astronomy was considered part of mathematics at the time, while cosmology, which is the study of the origins of the Universe, was part of philosophy.


Most scholars still agreed with Ptolemy and Aristotle that all heavenly bodies revolve around Earth (a geocentric model).

But other views were being considered. Nicolaus Copernicus claimed that all bodies revolve around the Sun (a heliocentric model). Danish astronomer Tycho Brahe believed that Earth was fixed but other planets orbited around the Sun.

In 1597, a German visitor gave Galileo a book by German astronomer Johannes Kepler, who was enthusiastically pro-Copernicus. Galileo wrote a letter to Kepler stating that he had long agreed with Copernicus but that he hadn’t made his thoughts public because he was frightened that he would become, like Copernicus, “mocked and hooted by an infinite multitude.”

In the same year, Galileo invented a mechanical device for mathematical calculations. Galileo had a craftsman make them, so that he could sell the devices and give classes on how to use them.

Professors at Padua usually didn’t marry. Anyway, prominent families in Padua did not view Galileo as a suitable husband.

Instead, Galileo established a long relationship with a non-noble woman 14 years younger than him. He never married Marina Gama, but he had three children with her. She and the children lived separately, around the corner from him.

When Galileo left Padua in 1610 to move to Florence, he put their two daughters in a convent and left his son with Marina.

Galileo’s first known astronomical observation occurred in 1604, when a supernova was visible in the sky. A supernova is the explosive death of a large star.

This event clearly challenged Aristotle’s claim that no change could ever take place in the heavens. From then on, observation and experimentation became the basis for Galileo’s work.

In July 1609, Galileo heard about a Dutch device for making distant objects look nearer — an early telescope. A friend who saw it described it to Galileo as having two lenses, one on each end of a 4-foot tube. Within about a month, Galileo had made a telescope three times as powerful as the Dutch device. Galileo continued to work on his telescope, making his own lenses.

Using the telescope, Galileo saw four moons orbiting Jupiter. This contradicted Ptolemy’s idea that the Earth is the center of all orbiting bodies.

Galileo published his findings in March 1610 as The Starry Messenger. The general public was excited, but most philosophers and astronomers declared it an optical illusion.

Mathematics at the court of TuscanyGalileo was offered a lifetime job at the University of Padua, but Florence was his home, and he wanted freedom from teaching. So he took the job of court mathematician in Florence.


Soon after his arrival in Florence in September 1610, Galileo began his observations of Venus. Over time, he discovered that the Moon-like phases of Venus demonstrated that the neighboring planet had an orbit independent of Earth. This showed conclusively that Venus circled the Sun, as Copernicus thought, not Earth, as Ptolemy thought. But it did not yet prove conclusively that Earth circled the Sun.

In 1613, Galileo published his Letters on Sunspots, based on his observations of the dark spots on the Sun that are caused by intense magnetic activity.

In an appendix, he noted that he agreed with Copernicus. Galileo had no definitive evidence that Copernicus was right, and he didn’t claim that he did. Galileo’s main pieces of evidence were the phases of Venus; the eclipses of Jupiter’s moons; the existence of tides, which Galileo believed could only occur if the Earth moved; observable planetary speeds, and the distances of planets from the Sun.

Drama with the InquisitionIn the early 1500s, the Catholic Church had a problem. Many people disagreed with the Church on different issues. Protestants were breaking away to form their own Church. Printers in many European cities helped ideas spread quickly. Some of these ideas went against the Catholic Church.

To fight the spread of these ideas, the Pope set up a system of tribunals, or courts. It was called the Inquisition.

In 1616 — the year of Shakespeare’s death — the Inquisition authorities in Rome decided to ban Copernicus’s book, On the Revolutions of the Celestial Spheres. They banned the book because it argued for a Sun-centered solar system.

They also banned any other books that agreed with Copernicus. This included Galileo’s works.

Galileo traveled to Rome. He thought the Church was making a mistake that would hurt its reputation. He believed the Catholic Church should keep science and religion completely separate. The Church did not agree with Galileo. In the end, he agreed to obey the ban.

In 1623, Pope Urban VIII gave Galileo permission to publish his theory on the causes of tides, as long as he did not take sides on the cosmological debate.

For the next six years, Galileo worked on this book. His book didn’t take one position on the heliocentric versus geocentric debate. Instead, his book presented a discussion of the two views. One character gave Copernicus’s view, another gave Aristototle/Ptolemy’s view, and a third character was an interested regular person. The book was called Dialogue Concerning the Two Chief World Systems – Ptolemaic and Copernican.

The book appeared in Florence in March 1632. An outbreak of the plague delayed copies being sent to Rome. In August, an order came from the Roman Inquisition to stop all sales.

The Grand Duke of Tuscany, Ferdinand, protested the book. He felt the book actually argued for a heliocentric model, even though it wasn’t supposed to take sides.


In September 1632, Galileo was charged with “heresy” — disagreeing with the Church. He was ordered to come to Rome for a trial. He did not appear until February 1633 because he was ill.

Galileo denied that he was defending heliocentrism, but he finally admitted that one could get that impression from the book. He was threatened with torture and forced to publicly give up the Sun-centered model. His book was banned.

Legend has it that as Galileo left the courtroom he whispered, “Eppur si muove [Still it (Earth) moves],” but this was most likely invented later.

Galileo was crushed by the harsh verdict. The Inquisition put him under house arrest at his villa outside Florence. He was ill with a hernia, heart palpitations, and insomnia. A few months after his return home, his older daughter, Maria Celeste, who he was very close to, died.

The following year, Galileo’s book was published in Latin in France, outside the grasp of the Catholic Inquisition, thereby reaching a much more sophisticated audience than the banned Italian text.

Blindness and a legacy of truthGalileo recovered from his serious setbacks. In 1637, he wrote a book summarizing all his ideas. The book was translated into English, and Isaac Newton read it in 1666.

By 1638, Galileo had become totally blind. He wrote many letters by dictating them to others. He died on January 9, 1642, in Florence, at the age of 77.

The Catholic Church didn’t lift the ban on Galileo’s book for 200 years — not until 1835. In 1992, Pope John Paul II expressed regret at how the Church treated Galileo.

Galileo’s own words to a friend about his blindness serve as a suitable epitaph:

Alas, your friend and servant Galileo has for the last month been irremediably blind, so that this heaven, this Earth, this Universe which I, by my remarkable discoveries and clear demonstrations had enlarged a hundred times beyond what had been believed by wise men of past ages, for me is from this time forth shrunk into so small a space as to be filled by my own sensations. (Drake, p. 107)


Galileo Galilei was an Italian scholar who invented a telescope. With it, he collected evidence of a Sun-centered Solar System.


Youth and educationGalileo Galilei was born in Pisa, Italy, on February 15, 1564. He was the first of seven children. Galileo’s father was a musician — a lute player — from a noble background.

Galileo wanted to become a priest, but his father pushed him to study medicine at the University of Pisa.

University courses at this time were based on Aristotle’s teachings. But Galileo made sharp observations and began to question some of Aristotle’s ideas.

For example, Aristotle had said that objects of different sizes fall at different speeds. Galileo observed hailstones all hitting the ground at the same time. He decided that Aristotle was wrong.

Is the Earth or the Sun at the center of it all?Galileo became a professor of mathematics, first in Pisa, then in Padua. He also gave private lessons in military architecture, fortification, surveying, and mechanics.

Galileo began studying tides, and became interested in astronomy.

At this time, most scholars still agreed with Ptolemy and Aristotle that all heavenly bodies revolve around Earth (a geocentric model).

But other views were being considered. Nicolaus Copernicus claimed that all bodies revolve around the Sun (a heliocentric model). Danish astronomer Tycho Brahe believed that Earth was fixed but other planets orbited around the Sun.

In 1597, Galileo read a book by German astronomer Johannes Kepler that argued for a heliocentric universe. Galileo wrote a letter to Kepler, saying he agreed, but was keeping quiet, because he didn’t want to be mocked.

Galileo looks at the skyGalileo’s first known astronomical observation occurred in 1604, when a supernova was visible in the sky. A supernova is the explosive death of a large star.

Aristotle had said that no change could ever take place in the heavens. This event proved him wrong. From then on, Galileo began to observe the sky, perform experiments, and make his own conclusions.

In 1609, the Dutch had made an early telescope. A friend who saw it described it to Galileo as having two lenses, one on each end of a 4-foot tube. Within about a month, Galileo had made a telescope three times as powerful as the Dutch device. Galileo continued to work on his telescope, making his own lenses.



Galileo published his findings in March 1610 as The Starry Messenger. The general public was excited by his work. However, most philosophers and astronomers disagreed with Galileo and said the moons weren’t really there.

Galileo stopped teaching and became mathematician for the royal family in Florence. It was there that he began to observe Venus.

His observations demonstrated that Venus orbits the Sun. This proved Copernicus right and Ptolemy wrong. Galileo believed that the Earth also orbits the Sun, but he had not proved it yet.

The Inquisition targets GalileoIn the 16th century, the Catholic Church was facing many problems. Some people broke from the Church because of a disagreement and became Protestants. Printers in many European cities helped ideas spread quickly. Some of these ideas went against the teachings of the Church.

To fight the spread of these ideas, the Pope set up a system of tribunals, or courts. It was called the Inquisition.

In 1616, Inquisition authorities banned Copernicus’s book On the Revolutions of the Celestial Spheres because it argued for a Solar System with the Sun at the center. They also banned any other books that agreed with Copernicus, which included Galileo’s work.


Galileo got permission from Pope Urban II to write a book, but he was not allowed to take sides in the Earth versus Sun debate. Galileo worked on his book for six years. In the book, one character argued for a heliocentric model, and another character argued for a geocentric model. A third character was a regular person, listening to both sides.

The book appeared in Florence in March 1632. In August, an order came from the Roman Inquisition to stop all sales.

Leaders in the Catholic Church felt that Galileo’s book was arguing for a heliocentric model, even though the book wasn’t supposed to take sides.

In September 1632, Galileo was charged with “heresy” — disagreeing with the Church. He was ordered to come to Rome for a trial.

Galileo tried to argue that his book showed both sides, but finally admitted that maybe the book leaned toward the Sun-centered argument.

He was threatened with torture. He had to publicly admit he was wrong. His book was banned.

Legend has it that as Galileo left the courtroom he whispered, “Eppur si muove [Still it (Earth) moves],” but this was most likely invented later.


Galileo was crushed by the harsh verdict. The Inquisition put him under house arrest at his villa outside Florence. He was ill with a hernia, heart palpitations, and insomnia. A few months after his return home, his older daughter, Maria Celeste, who he was very close to, died.

The following year, Galileo’s book was published in Latin in France, outside the grasp of the Catholic Inquisition. This allowed his ideas to reach a wide audience.

Blindness and a legacy of truthGalileo bounced back from these serious setbacks. In 1637, he wrote a book summarizing all his ideas. The book was translated into English, and Isaac Newton read it in 1666.


The Catholic Church didn’t end the ban on Galileo’s book for 200 years — not until 1835. In 1992, Pope John Paul II expressed regret at how the Church treated Galileo.

Galileo’s own insights about his blindness may be the best way to remember him. The following lines have been adapted from a letter he wrote to a friend:

Well, your friend Galileo has been blind these last few months. Through my remarkable discoveries and observations, I have greatly expanded our past ideas of our Universe. But now, the whole Universe for me is shrunk down to my own sensations — what I can hear, touch, smell, taste...


Galileo Galilei was an Italian scholar who invented a telescope. With it, he collected evidence of a Sun-centered Solar System.

Youth and educationGalileo Galilei was born in Pisa, Italy, in 1564. He was the first of seven children. Galileo’s father was a musician — a lute player — from a noble background.

Galileo's wish was to become a priest, but his father pushed him to study medicine. He attended the University of Pisa.

University courses at this time were based on Aristotle’s teachings. But Galileo made clever observations and began to question some of Aristotle’s ideas.

For example, Aristotle taught that objects of different sizes fall at different speeds. Galileo observed hailstones all hitting the ground at the same time. He decided Aristotle was wrong.


Is the Earth or the Sun at the center of it all?Galileo became a professor of mathematics. He also gave private lessons in architecture, surveying, and mechanics. He also began studying tides, and became interested in astronomy.

Most scholars at this time still agreed with Ptolemy and Aristotle that all heavenly bodies revolve around Earth. Their view was called a geocentric model.

But other views were being considered. Nicolaus Copernicus claimed that all bodies revolve around the Sun. His was called a heliocentric model. Astronomer Tycho Brahe believed that Earth stayed still but other planets orbited around the Sun.

In 1597, Galileo read a book by German astronomer Johannes Kepler that argued for a heliocentric universe. Galileo wrote a letter to Kepler saying he agreed, but was keeping quiet. He didn’t want to be mocked for his ideas.

Galileo looks at the skyGalileo observed a remarkable event in 1604, when a large star died in an explosion. It's called a supernova.

Aristotle had said that no change could ever take place in the heavens. The supernova proved him wrong.

From then on, Galileo began to observe the sky. He performed experiments and made his own conclusions.

In 1609, the Dutch made an early telescope. A friend who saw it described it to Galileo. He reported that it had two lenses, one on each end of a 4-foot tube. Within about a month, Galileo had made a telescope three times as powerful as the Dutch device. Galileo continued to work on his telescope, making his own lenses.


Galileo published his findings in March 1610 as The Starry Messenger. The general public was excited by what he wrote. However, most philosophers and astronomers disagreed with Galileo. They said the moons weren’t really there.

Galileo stopped teaching and became a mathematician for the royal family in Florence. It was there that he began to observe Venus.

His observations demonstrated that Venus orbits the Sun. This proved Copernicus right and Ptolemy wrong. Galileo believed that the Earth also orbits the Sun, but he had not proved it yet.

The Inquisition targets GalileoIn the 16th century, the Catholic Church was facing many problems. Some people separated from the Church because of a disagreement and became Protestants. Printers in many


European cities helped ideas spread quickly. Some of these ideas went against the teachings of the Catholic Church.

To fight the spread of these ideas, the Pope set up a system of courts. It was called the Inquisition.

In 1616, the Inquisition banned Copernicus’s book because it argued for a Solar System with the Sun at the center. The Church also banned Galileo’s book because he agreed with Copernicus.


Galileo got permission from Pope Urban II to write a book, as long as he didn’t take sides in the Earth versus Sun debate. Galileo worked on his book for six years. In the book, one character argues for a heliocentric model, and another character argues for a geocentric model. The third character was a regular person, listening to both sides.

The book appeared in Florence in March 1632. In August, an order came from the Roman Inquisition to stop all sales. The Catholic Church felt that Galileo’s book was arguing for a Sun-centered model.

In September 1632, Galileo was charged with “heresy” — disagreeing with the Church. He was ordered to come to Rome for a trial.

Galileo tried to argue that his book showed both sides. Finally, he admitted that maybe the book leaned toward the Sun-centered argument. He was threatened with torture. He had to publicly admit he was wrong. His book was banned.

Galileo was crushed by the harsh verdict. The Inquisition put him under house arrest at his villa outside Florence. He suffered from many illnesses. A few months after his return home, his beloved, older daughter died.

The following year, Galileo’s book was published in France, outside the grasp of the Catholic Inquisition. This allowed his ideas to reach a wide audience.

Blindness and a legacy of truthGalileo bounced back from these serious difficulties. In 1637, he wrote a book summarizing all his ideas. The book was translated into English, and Isaac Newton read it in 1666.


It took the Catholic Church 200 years to lift the ban on Galileo’s book. In 1992, Pope John Paul II apologized for how the Church treated Galileo.

Galileo may be best remembered by his own self-reflection. Here is an adapted section of a letter he wrote about his blindness:


Well, your friend Galileo has been blind these last few months. Through my remarkable discoveries and observations, I have greatly expanded our past ideas of our Universe. But now, the whole Universe for me is shrunk down to my own sensations — what I can hear, touch, smell, taste...

CopernicusCopernicus was a Catholic, Polish astronomer who declared that the Sun — not the Earth — was at the center of the Universe. His ideas launched modern astronomy, and started a scientific revolution.

Nicolaus Copernicus: A Renaissance man who started a scientific revolution (1180L)By Cynthia Stokes Brown

In the middle of the 16th century, a Catholic, Polish astronomer, Nicolaus Copernicus, synthesized observational data to formulate a comprehensive, Sun-centered cosmology, launching modern astronomy and setting off a scientific revolution.

Renaissance manHave you ever heard the expression “Renaissance man?” The phrase describes a well-educated person who excels in a wide variety of subjects or fields. The Renaissance is the name for a period in European history, the 14th through the 17th centuries, when the continent emerged from the “Dark Ages” with a renewed interest in the arts and sciences. European scholars were rediscovering Greek and Roman knowledge, and educated Europeans felt that humans were limitless in their thinking capacities and should embrace all types of knowledge.

Nicolaus Copernicus fulfilled the Renaissance ideal. He became a mathematician, an astronomer, a church jurist with a doctorate in law, a physician, a translator, an artist, a Catholic cleric, a governor, a diplomat, and an economist. He spoke German, Polish, and Latin, and understood Greek and Italian.

Family and studiesNicolaus was born February 19, 1473 to wealthy parents who lived in the center of what is now Poland. His father, named Nicolaus Koppernigk, was a copper merchant from Krakow, and his mother, Barbara Watzenrode, was the daughter of a wealthy local merchant. Nicolaus was the youngest of four children; he had a brother and two sisters. His father died when he was 10 and his mother at about the same time. His mother’s brother adopted Nicolaus and his siblings and secured the future of each of them.

This maternal uncle, Lucas Watzenrode, was a wealthy, powerful man in Warmia, a small province in northeast Poland under the rule of a prince-bishop. Since 1466 Warmia had been part of the kingdom of Poland, but the king allowed it to govern itself. Watzenrode


became the prince-bishop in Warmia when Copernicus was 16. Three years later he sent Copernicus and his brother to the University of Krakow, where Copernicus studied from 1492 to 1496. He was in his first year at the university when Columbus sailed to a continent that was then unknown in Europe. Copernicus changed his last name, Koppernigk, to its Latin version while at the university, since scholars used Latin as their common language.

At Krakow Copernicus studied mathematics and Greek and Islamic astronomy. After studying at Krakow, Copernicus’s uncle sent him to Italy, where he studied law at the University of Bologna for four years, and then medicine at the University of Padua for two years. These were two of the earliest and best European universities and Copernicus had to travel two months by foot and horseback to reach Italy.

At these universities, Copernicus began to question what he was taught. For example, his professors at Krakow taught about both Aristotle’s and Ptolemy’s views of the Universe. However, Copernicus became aware of the contradictions between Aristotle’s theory of the Earth, the Sun and the planets as a system of concentric spheres and Ptolemy’s use of eccentric orbits and epicycles. Even though his professors believed that the Earth was in the center of the Universe and it did not move, Copernicus began to question those ideas. While at the University of Padua, there is some evidence that he had already developed the idea of a new system of cosmology based on the movement of the Earth.

Copernicus returned to Warmia in 1503, at age 30, to live in his uncle’s castle and serve as his secretary and physician. He stayed at this job, which gave him free time to continue his observations of the heavens, until 1510, two years before his uncle’s death.

Life as a canonThanks to help from his uncle, Copernicus was elected in 1497 a canon of the cathedral in Frombork, a town in Warmia on the Baltic Sea coast. Canons were responsible for administering all aspects of a cathedral. Copernicus did not assume his position there until 1510, when he took a house outside the cathedral walls and an apartment inside a tower of the fortifications. He had many duties as canon, including mapmaking, collecting taxes and managing the money, serving as a secretary, and practicing medicine. He led a half-religious, half-secular life and still managed to continue his astronomical observations from his tower apartment. He conducted these with devices that looked like wooden yardsticks joined together, set up to measure the angular altitude of stars and planets and the angles between two distant bodies in the sky. He had a simple metal tube to look through, but no telescope had yet been invented.

By 1514 Copernicus had written a short report that he circulated among his astronomy-minded friends. This report, called the Little Commentary, expounded his heliocentric theory. He omitted mathematical calculations for the sake of brevity, but he confidently asserted that the Earth both revolved on its axis and orbited around the Sun. This solved many of the problems he found with Ptolemy’s model, especially the lack of uniform circular motion.

By 1531 the bishop-prince of Warmia believed that Copernicus had a mistress, Anna Schilling, whom he called his housekeeper. The next bishop-prince worked persistently to force Copernicus to give up his companion. Lutheran Protestantism was springing up


nearby, as cities, dukes, and kings renounced their loyalty to the Catholic Church. The Catholic Church responded by trying to enforce more obedience to its rules. However, Copernicus and Schilling managed to keep seeing each other, although not living together, until much later when she moved to the city of Gdansk.

A heliocentric theoryBy 1532 Copernicus had mostly completed a detailed astronomical manuscript he had been working on for 16 years. He had resisted publishing it for fear of the ensuing controversy and out of hope for more data. Finally, in 1541, the 68-year-old Copernicus agreed to publication, supported by a mathematician friend, Georg Rheticus, a professor at the University of Wittenberg, in Germany. Rheticus had traveled to Warmia to work with Copernicus, and then took his manuscript to a printer in Nuremberg, Johannes Petreius, who was known for publishing books on science and mathematics. Copernicus gave his master work the Latin title De Revolutionibus Orbium Coelestium(translated to English as On the Revolutions of the Celestial Spheres).

In this work Copernicus began by describing the shape of the Universe. He provided a diagram to help the reader. In the diagram he showed the outer circle that contained all the fixed stars, much further away than previously believed. Inside the fixed stars were Saturn, then Jupiter and Mars, then Earth, Venus, and Mercury, all in circular orbits around the Sun in the center.

He calculated the time required for each planet to complete its orbit and was off by only a bit. Copernicus’s theory can be summarized like this:

The center of the Earth is not the center of the Universe, only of Earth’s gravity and of the lunar sphere.

The Sun is fixed and all other spheres revolve around the Sun. Copernicus retained the idea of spheres and of perfectly circular orbits. In fact, the orbits are elliptical, which the German astronomer Johannes Kepler demonstrated in 1609.

Earth has more than one motion, turning on its axis and moving in a spherical orbit around the sun.

The stars are fixed but appear to move because of the Earth’s motion.

Death and legacyLegend has it that Copernicus, in a sickbed when his great work was published, awoke from a stroke-induced coma to look at the first copy of his book when it was brought to him. He was able to see and appreciate his accomplishment, and then closed his eyes and died peacefully, on May 24, 1543. Thus he avoided both scorn and praise.

Copernicus was thought to be buried in the cathedral at Frombork, but no marker existed. Some of his bones were finally identified there, with a DNA match from a strand of his hair found in a book owned by him, and in 2010 he was given a new burial in the same spot, now marked with a black granite tombstone.


The Roman Catholic Church waited seven decades to take any action against On the Revolutions of the Celestial Spheres. Why it waited so long has been the subject of much debate. In 1616 the Church issued a decree suspending On the Revolutions of the Celestial Spheres until it could be corrected and prohibiting any work that defended the movement of Earth. A correction appeared in 1620, and in 1633 Galileo Galilei was convicted of grave suspicion of heresy for following Copernicus’s position.

Scholars did not generally accept the heliocentric view until Isaac Newton, in 1687, formulated the Law of Universal Gravitation. This law explained how gravity would cause the planets to orbit the much more massive Sun and why the small moons around Jupiter and Earth orbited their home planets.

How long did it take for Copernicus’s ideas to reach the general public? Does anyone nowadays still believe the apparent evidence before their eyes that the Sun moves around the Earth to set and rise? Almost everyone learns in childhood that, despite appearances, the Earth moves around the Sun.

Copernicus’s model asked people to give up thinking that they lived in the center of the Universe. For him the thought of the Sun illuminating all of the planets as they rotated around it had a sense of great beauty and simplicity.

Nicolaus Copernicus: A Renaissance man who started a scientific revolution (1070L)By Cynthia Stokes Brown, adapted by Newsela

In the middle of the 16th century, a Catholic, Polish astronomer, Nicolaus Copernicus, used observational data to diagram a Sun-centered view of the Universe. His work launched modern astronomy and set off a scientific revolution.

Renaissance manHave you ever heard the expression “Renaissance man?” The phrase describes a well-educated person who excels in a wide variety of subjects or fields. The Renaissance is the name for a period in European history, the 14th through the 17th centuries, when the continent emerged from the Dark Ages with a renewed interest in the arts and sciences. European scholars were rediscovering Greek and Roman knowledge, and educated Europeans felt that humans were limitless in their thinking capacities and should embrace all types of knowledge.

Nicolaus Copernicus was a true Renaissance man. He became a mathematician, an astronomer, a church judge with a doctorate in law, a physician, a translator, an artist, a Catholic cleric, a governor, a diplomat, and an economist. He spoke German, Polish, and Latin, and understood Greek and Italian.


Family and studiesCopernicus was born to wealthy parents in what is now Poland on February 19, 1473. Both his parents died when he was young. His wealthy, powerful uncle adopted him and his siblings.

Copernicus studied mathematics and astronomy at the University of Krakow from 1492 to 1496. He changed his last name, Koppernigk, to its Latin version while at the university, since scholars used Latin as their common language.

He also studied law at the University of Bologna and medicine at the University of Padua. It took two months to travel from Poland to Italy by foot and horseback, but the two schools in Italy were among the best in the world at that time.

As a student, Copernicus began to question what he was taught. He learned Aristotle’s and Ptolemy’s views of the Universe. Even though his professors believed that the Earth was at the center of the Universe and it did not move, Copernicus began to question those ideas.

Even as a young university student, there is evidence that Copernicus was beginning to envision a Universe where the Earth moved.

Copernicus returned to Poland in 1503, at age 30, to live in his uncle’s castle and serve as his secretary and physician. He stayed at this job, which gave him free time to continue his observations of the heavens, until 1510, two years before his uncle’s death.

Life as a canonIn 1497, Copernicus was elected canon of the cathedral in Frombork. Canons were responsible for administering all aspects of a cathedral. He had many duties as canon, including mapmaking, collecting taxes and managing the money, serving as a secretary, and practicing medicine.

He led a half-religious, half-secular life and still managed to continue his astronomical observations from his tower apartment. He conducted these with devices that looked like wooden yardsticks joined together, set up to measure the angular altitude of stars and planets and the angles between two distant bodies in the sky. He had a simple metal tube to look through, but no telescope had yet been invented.

By 1514, Copernicus had written a short report that he gave to his astronomy-minded friends. This report, called the Little Commentary, explained his heliocentric theory. In it, Copernicus confidently said that the Earth both revolved on its axis and orbited around the Sun.

A heliocentric theoryCopernicus worked on a detailed astronomical book for 16 years. He didn’t want to publish it because he was afraid of the huge controversy it would produce. He also hoped to gather more data.


Finally, in 1541, when he was 68, he agreed to publish it after a mathematician friend helped convince him. Copernicus gave his master work the title On the Revolutions of the Celestial Spheres.

In this work, Copernicus began by describing the shape of the Universe. He provided a diagram to help the reader. In the diagram, he showed the outer circle that contained all the fixed stars, much further away than previously believed. Inside the fixed stars were Saturn, then Jupiter, and Mars, then Earth, Venus, and Mercury, all in circular orbits around the Sun in the center.

He calculated the time required for each planet to complete its orbit, and was off by only a bit. Copernicus’s theory can be summarized like this:

The center of the Earth is not the center of the Universe, only of Earth’s gravity and of the Moon. The Sun is fixed and all other spheres revolve around the Sun. Copernicus kept the idea of spheres and of perfectly circular orbits. In fact, the orbits are elliptical, which the German astronomer Johannes Kepler demonstrated in 1609. Earth has more than one motion, turning on its axis and moving in a spherical orbit around the sun.

The stars are fixed, but appear to move because of the Earth’s motion.

Death and legacyLegend has it that Copernicus, in a sickbed when his great work was published, awoke from a coma to look at the first copy of his book when it was brought to him. He was able to see and appreciate his accomplishment, and then closed his eyes and died peacefully, on May 24, 1543. He didn’t live to hear the praise or criticism of his ideas.

The Catholic Church waited seven decades to take any action against On the Revolutions of the Celestial Spheres. Why it waited so long has been the subject of much debate. In 1616, the church banned the book and any other work that defended the movement of the Earth. In 1633, Galileo Galilei was convicted of defying Church teachings for following Copernicus’s position.

Scholars did not generally accept the heliocentric view until Isaac Newton, in 1687, formulated the Law of Universal Gravitation. This law explained how gravity would cause the planets to orbit the much more massive Sun, and why the small moons around Jupiter and Earth orbited their home planets.

How long did it take for Copernicus’s ideas to reach the general public? Does anyone nowadays still believe the apparent evidence before their eyes that the Sun moves around the Earth to set and rise? Almost everyone learns in childhood that, despite appearances, the Earth moves around the Sun.

Copernicus’s model asked people to give up thinking that they lived in the center of the Universe. For him, the thought of the Sun illuminating all of the planets as they rotated around it had a sense of great beauty and simplicity.



Copernicus was a Polish astronomer who declared that the Sun — not the Earth — was at the center of the Universe. His ideas launched modern astronomy, and started a scientific revolution.

Renaissance manHave you ever heard the expression “Renaissance man?” The phrase describes a well-educated person who does well in many different fields. The Renaissance is the name for a period in European history, the 14th through the 17th centuries, when the continent emerged from the Dark Ages.

The Renaissance brought a renewed interest in the arts and sciences to Europe.

Nicolaus Copernicus was a true Renaissance man. He became a mathematician, an astronomer, a church judge with a doctorate in law, a physician, a translator, an artist, an official in the Catholic Church, a governor, a diplomat, and an economist. He spoke German, Polish, and Latin, and understood Greek and Italian.

Family and studiesCopernicus was born February 19, 1473 to wealthy parents who both died when he was young. He and his siblings were adopted by his rich and powerful uncle.

He studied mathematics and astronomy at the University of Krakow from 1492 to 1496. He changed his last name, Koppernigk, to its Latin version while at the university, since scholars used Latin as their common language.

Copernicus also studied law at the University of Bologna and medicine at the University of Padua. These two schools were among the best in the world at that time. It was not an easy journey, though. It took two months to travel from Poland to Italy by foot and horseback

As a student, Copernicus began to question what he was taught. He learned Aristotle’s and Ptolemy’s views of the Universe. His professors believed that the Earth was at the center of the Universe and it did not move. Copernicus began to question those ideas.

Even as a young university student, Copernicus was beginning to see a Universe where the Earth moved.

Life at the cathedralIn 1497, Copernicus was elected canon of the cathedral in Frombork. Canons were responsible for all aspects of a cathedral. He had many duties as canon, including mapmaking, collecting taxes and managing the money, serving as a secretary, and practicing medicine.


His life was half-religious and half-scientific. He continued making astronomical observations from his tower apartment.

He didn’t have a telescope, because the telescope hadn’t been invented yet. Instead, he looked through a simple metal tube. He also had a device that looked like two wooden yardsticks joined together. He used it to measure the angles of stars and planets in the sky.

By 1514, Copernicus had written a short report that explained his heliocentric theory. In it, Copernicus confidently said that the Earth both revolved on its axis and orbited around the Sun.

A heliocentric theoryCopernicus worked on a major astronomical book for 16 years. He didn’t want to publish it because he was afraid of the fierce debate it would spark. He also hoped to gather more data.

In 1541, when he was 68, he agreed to publish it after a mathematician friend helped convince him. Copernicus titled his master work On the Revolutions of the Celestial Spheres.

In this work, Copernicus began by describing the shape of the Universe. He provided a diagram to help the reader. In the diagram, he showed the outer circle that contained all the fixed stars, much further away than previously thought. Inside the fixed stars were Saturn, then Jupiter, and Mars, then Earth, Venus, and Mercury. All of these planets made circular orbits around the Sun in the center.

He calculated the time required for each planet to complete its orbit, and was off by only a bit. Copernicus’s theory can be summarized like this:

The center of the Earth is not the center of the Universe, only of Earth’s gravity and of the lunar sphere. The Sun is fixed, and all other spheres revolve around the Sun. Earth has more than one motion, turning on its axis and moving in a spherical orbit around the Sun. The stars are fixed, but appear to move because of the Earth’s motion.

Death and legacyLegend has it that Copernicus was on his deathbed, in a coma, when his great work was published. He awoke from the coma to see the first copy of his book. After he had seen and appreciated his accomplishment, he died peacefully on May 24, 1543. He didn’t live to hear the praise or criticism of his ideas.

The Catholic Church banned Copernicus’s book more than 70 years later. It also banned any other book that agreed with Copernicus’s heliocentric argument. In 1633, Galileo Galilei was convicted of defying Church teachings for following Copernicus’s position.

Copernicus’s heliocentric model was not widely accepted until Isaac Newton developed the Law of Universal Gravitation in 1687. This law explained how gravity would cause the planets to orbit the Sun, which is much larger than the Earth. It also explained why small moons around Jupiter and Earth orbited their home planets.


It appears that the Sun rises each morning and sets every night. But really, it is the Earth, not the Sun, that is moving. Copernicus asked people to give up thinking that they lived in the center of the Universe.

For him, the idea of the Sun shining on all the planets as they rotated around it had great beauty and simplicity.


Copernicus was a Polish astronomer who said that the Sun – not the Earth – was at the center of the Universe. His ideas launched a scientific revolution.

Renaissance manHave you ever heard the expression “Renaissance man?” This term describes a person who is very good at many different things.

Nicolaus Copernicus was not only an astronomy genius. He was also a mathematician, a church judge, a doctor, a translator, an artist, an official in the Catholic Church, a governor, a diplomat, and an economist. He spoke German, Polish, and Latin, and understood Greek and Italian.

Family and studiesCopernicus was born February 19, 1473 to wealthy parents who both died when he was young. He and his siblings were adopted by his rich and powerful uncle.

He studied mathematics and astronomy at the University of Krakow from 1492 to 1496. While there he changed his original last name, Koppernigk, to its Latin version. Latin was the common language of scholars at the time.

Copernicus also studied law and medicine in Italy. The journey from Poland to Italy took two months by foot and horseback. But the universities in Italy were some of the best in the world at the time.

As a student, Copernicus began to question what he was taught. His professors taught him Aristotle’s and Ptolemy’s views: the Earth was at the center of the Universe. It did not move.

Copernicus began to develop his theory that the Sun was at the center of the universe while he was a student.

Life at the cathedralCopernicus became canon of Frombork cathedral in 1497. He had many duties as canon. These included mapmaking, collecting taxes, serving as a secretary, and practicing medicine.


He continued his study of the skies. He made astronomical observations from his tower apartment.

Copernicus didn’t have a telescope, because the telescope hadn’t been invented yet. Instead, he looked through a simple metal tube. He also had a device that looked like two wooden yardsticks joined together. He used it to measure the angles of stars and planets in the sky.

Based on his observations, he wrote a short report in which he explained his heliocentric theory. Copernicus confidently said that the Earth both turned on its axis and orbited around the Sun.

A heliocentric theoryIt took Copernicus 16 years to write his masterwork on astronomy. Even then, he didn’t want to publish it. He was afraid of the huge controversy it would create. He also wanted time for more research.

Finally, a mathematician friend convinced Copernicus to publish the book. He was 68.

The book was called On the Revolutions of the Celestial Spheres. In it, Copernicus described the shape of the Universe. He provided a diagram to help readers. In the diagram, we see the Sun at the center. Orbiting around the Sun are the planets, including Earth. On the outside are the fixed stars.

Copernicus’s theory can be summarized like this:

The center of the Earth is not the center of the Universe, only of Earth’s gravity and the moon. The Sun doesn’t move, and all other spheres revolve around the Sun. Earth has more than one motion. It turns on its axis and moves in a spherical orbit around the Sun. The stars appear to move, but really it is the Earth that is moving.

Death and legacyLegend says that Copernicus was on his deathbed when his great work was published. He woke from a coma to see and appreciate his accomplishment. He died peacefully on May 24, 1543. He didn’t live to hear any praise or criticism of his ideas.

The Catholic Church banned Copernicus’s book more than 70 years later. It also banned any other book that agreed with Copernicus’s heliocentric argument — Galileo Galilei’s for example.

Copernicus’s heliocentric model wasn’t widely accepted for hundreds of years.

Isaac Newton’s laws of gravity helped to confirm Copernicus’s theories. The laws explained why planets would orbit the Sun and not the Earth. Because the Sun is much larger, the pull of its gravity is stronger.

It appears that the Sun rises each morning and sets every night. But really, it is the Earth, not the Sun, that is moving. Copernicus asked people to give up thinking that they lived in the center of the Universe.


For him, the idea of the Sun shining on all the planets as they rotated around it had great beauty and simplicity.

NewtonA falling apple plants the seed for the discovery of the Law of Universal Gravitation.

Sir Isaac Newton: Physics, Gravity, and Laws of Motion (1240L)By Cynthia Stokes Brown

Newton developed the three basic laws of motion and the theory of universal gravity, which together laid the foundation for our current understanding of physics and the Universe.

Early life and educationIsaac Newton was born prematurely on January 4, 1643, in Lincolnshire, England. His father had died before his birth. When he was 3, his mother remarried and left him with his grandparents on a farm, while she moved to a village a mile and a half away from him. He grew up with few playmates, and amused himself by contemplating the world around him.

His mother returned when Newton was 11 years old and sent him to King’s School. Rather than playing after school with the other boys, Newton spent his free time making wooden models, kites of various designs, sundials, even a water clock. When his mother, who was hardly literate, took him out of school at 15 to turn him into a farmer, the headmaster, who recognized where Newton’s talents lay, prevailed on her to let Newton return to school.

Early discoveriesNewton attended Cambridge University from 1661 to 1665. The university temporarily closed soon after he got his degree because people in urban areas were dying from the plague. Newton retreated to his grandparents’ farm for two years, during which time he proved that “white” light was composed of all colors, and started to figure out calculus and universal gravitation — all before he was 24 years old.

It was on his grandparents’ farm that Newton sat under the famous apple tree and watched one of its fruits fall to the ground. He wondered if the force that pulled the apple to the ground could extend out to the Moon and keep it in its orbit around Earth. Perhaps that force could extend into the Universe indefinitely.

After the plague subsided, Newton returned to Cambridge to earn his master’s degree and become a professor of mathematics there. His lectures bored many of his students, but he continued his own thinking and experiments, undaunted. When his mother died, he inherited enough wealth to leave his teaching job and move to London, where he became the president of the Royal Society of London for Improving Natural Knowledge, the top organization of scientists in England.


Laws of motion and gravityNewton’s most important book was written in Latin; its title was translated as Mathematical Principles of Natural Philosophy. It was published in 1687. The book proved to be one of the most influential works in the history of science. In its pages, Newton asserted the three Laws of Motion, elaborated Johannes Kepler’s Laws of Motion, and stated the Law of Universal Gravitation. The book is primarily a mathematical work, in which Newton developed and applied calculus, the mathematics of change, which allowed him to understand the motion of celestial bodies.

To reach his conclusions, he also used accurate observations of planetary motion, which he made by designing and building a new kind of telescope, one that used mirrors to reflect, rather than lenses to refract, light.

Newton’s three Laws of Motion1. Every body continues at rest or in motion in a straight line unless compelled to

change by forces impressed upon it. Galileo Galilei first formulated this, and Newton recast it.

2. Every change of motion is proportional to the force impressed and is made in the direction of the straight line in which that force is impressed. A planet would continue outward into space but is perfectly balanced by the Sun’s inward pull, which Newton termed “centripetal” force.

3. To every action there is always opposed an equal reaction, or the mutual action of two bodies on each other is always equal and directed to contrary parts.

Law Of Universal GravitationPutting these laws together, Newton was able to state the Law of Universal Gravitation: “Every particle of matter attracts every other particle with a force proportional to the product of the masses of the two particles and inversely proportional to the square of the distance between them.” Stated more simply, the gravitational attraction between two bodies decreases rapidly as the distance between them increases.

This calculation proved powerful because it presented the Universe as an endless void filled with small material bodies moving according to harmonious, rational principles. Newton understood gravity as a universal property of all bodies, its force dependent only on the amount of matter contained in each body. Everything, from apples to planets, obeys the same unchanging laws.

By combining physics, mathematics, and astronomy, Newton made a giant leap in human understanding of Earth and the cosmos. Newton’s mathematical method for dealing with changing quantities is now called calculus. He did not publish his method, but solved problems using it. Later, the German scientist Gottfried Wilhelm von Leibniz also worked out calculus, and his notation proved easier to use. Newton accused Leibniz, in a nasty dispute, of stealing his ideas, but historians now believe that each invented calculus independently.


Newton was made a knight by Queen Anne in 1705. At his death in 1727, he was buried in London’s Westminster Abbey. Shortly before he died, Newton remarked:

I do not know what I may appear to the world, but to myself I seem to have been only like a boy playing on the seashore and diverting myself in now and then finding a smoother pebble or prettier shell than ordinary, while the great ocean of truth lay all undiscovered before me.

Sir Isaac Newton: Physics, Gravity, and Laws of Motion (1030L)By Cynthia Stokes Brown, adapted by Newsela

Newton developed the three basic laws of motion and the theory of universal gravity. Today, these discoveries form the basis of our understanding of physics and the Universe.

Early life and educationIsaac Newton was born prematurely on January 4, 1643. After his father died and his mother moved away, he grew up with his grandparents on a farm. As a child he had few playmates, and amused himself by contemplating the world around him.

At school, Newton didn’t spend his free time after school playing with the other boys. Instead, he made wooden models, kites, sundials, and even a water clock.

When he was 15, his mother took him out of school to become a farmer. But the director of his school recognized Newton’s talents and convinced his mother to let him return to school.

Newton attended Cambridge University from 1661 to 1665. The university temporarily closed soon after he got his degree because people in urban areas were dying from the plague.

Early discoveriesNewton retreated to his grandparents’ farm for two years. During this time, he proved that “white” light was composed of all colors, and started to figure out calculus and universal gravitation — all before he was 24 years old.

Newton was on his grandparents’ farm when he sat under the famous apple tree and watched an apple fall to the ground.

He wondered if the force that pulled the apple to the ground could extend out to the Moon and keep it in its orbit around Earth. Perhaps that force could extend into the Universe indefinitely.

After the plague subsided, Newton returned to Cambridge. He earned his master’s degree and became a professor of mathematics there. His lectures bored many of his students, but he continued his own thinking and experiments, undaunted. Later, he became the president of the Royal Society of London for Improving Natural Knowledge — the top organization of scientists in England.


Laws of motion and gravityNewton’s most important book was written in Latin; its title was translated as Mathematical Principles of Natural Philosophy and was published in 1687.

It proved to be one of the most influential works in the history of science. The book explained Newton’s three Laws of Motion and the Law of Universal Gravitation.

Newton used advanced math and observation of the heavens to develop his laws. To track the stars and planets, he used a new type of telescope that he designed and built himself.

Newton’s three Laws of Motion1. An object at rest will stay at rest and an object in motion will stay in motion along a

straight line unless an external force is applied to it.

2. An object will accelerate if force is applied to it. The acceleration will happen in the direction of the force. The acceleration will be less as the object gets bigger.

3. For every action there is always an equal and opposite reaction.

Putting these laws together, Newton was able to state the Law of Universal Gravitation: “Every particle of matter attracts every other particle with a force proportional to the product of the masses of the two particles and inversely proportional to the square of the distance between them.”

Stated more simply, the gravitational attraction between two objects decreases rapidly as the objects get farther apart.

This calculation proved powerful because it presented the Universe as an endless void filled with small objects moving according to rational principles.

Everything, from apples to planets, obeys the same unchanging laws. By combining physics, mathematics, and astronomy, Newton made a giant leap in human understanding of Earth and the cosmos.

CalculusNewton’s mathematical method for dealing with changing quantities is now called calculus. Newton did not publish his method, but solved problems using it.

Later, the German scientist Gottfried Wilhelm von Leibniz also worked out calculus, and his notation proved easier to use. Newton accused Leibniz, in a nasty dispute, of stealing his ideas, but historians now believe that each invented calculus independently.





Newton developed the three basic laws of motion and the theory of universal gravity. Today, these discoveries form the basis for our understanding of physics and the Universe.

Early life and educationIsaac Newton was born prematurely on January 4, 1643. He grew up with his grandparents on a farm after his father died and his mother moved away.

As a child he had few playmates. He amused himself by thinking about the world around him. At school, Newton didn’t play much with the other boys. Instead, he made wooden models, kites, sundials, and even a water clock.

When he was 15, his mother took him out of school to become a farmer. But the director of his school recognized the boy’s talents and convinced his mother to let him return to school.

Newton went Cambridge University from 1661 to 1665. The university temporarily closed soon after he got his degree because people in European cities were dying from the plague.

Early discoveriesNewton moved back to his grandparents’ farm for two years. During this time, he proved that “white” light was composed of all colors and started to figure out calculus and universal gravitation. He did all this before he was 24 years old.

Newton was on his grandparents’ farm when he sat under the famous apple tree and watched an apple fall to the ground.

He wondered if the force that pulled the apple to the ground could extend out to the Moon and keep it in its orbit around Earth. Perhaps that force extended throughout the whole Universe.

After the plague abated, Newton returned to Cambridge. He earned his master’s degree and became a professor of mathematics there.

His lectures bored many of his students, but he continued his own thinking and experiments. Later, he became the president of the Royal Society of London for Improving Natural Knowledge — the top organization of scientists in England.

Laws of motion and gravityNewton’s most important book was written in Latin; its English title was Mathematical Principles of Natural Philosophy and was published in 1687.

It proved to be one of the most influential works in the history of science. The book explained Newton’s three Laws of Motion and the Law of Universal Gravitation.

Newton used advanced math and observation of the heavens to develop his laws. To track the stars and planets, he used a new type of telescope that he designed and built himself.


Newton’s three Laws of Motion1. An object at rest will stay at rest unless a force is applied to it. An object in motion will

stay in motion along a straight line unless an external force is applied to it.



Putting these laws together, Newton was able to state the Law of Universal Gravitation: the gravitational pull between two objects decreases as the objects get farther apart.

Newton’s Universe was a powerful idea because it said that all objects move according to rational principles.


CalculusNewton came up with a new mathematical method for dealing with changing quantities. It is now called calculus. Newton didn’t publish his method, he used it to solve problems.

Later, the German scientist Gottfried Wilhelm von Leibniz also worked out calculus. His system was easier to use.

Newton accused Leibniz of stealing his ideas, but historians now believe that each invented calculus independently.




Newton developed the three basic laws of motion and the theory of universal gravity. His work formed our understanding of physics and the Universe.

Early life and educationIsaac Newton was born on January 4, 1643, too soon before his due date. After his father died and his mother moved away, he grew up with his grandparents on a farm.

As a child, he didn’t have many friends. He amused himself by thinking about the world around him.


At school, Newton didn’t play much with other students. Instead, he made wooden models, kites, sundials, and even a water clock.

When he was 15, his mother took him out of school to become a farmer. But the director of his school recognized his genius and convinced his mother to let him return to school.

Newton went Cambridge University from 1661 to 1665. He then moved back to his grandparents’ farm for two years.

During this time, he proved that “white” light was made up of all colors. He also started to figure out calculus and universal gravitation. He did all this before he was 24 years old.

Early discoveriesAt his grandparents’ farm, Newton sat under the famous apple tree and watched an apple fall to the ground.

He wondered if the force that pulled the apple to the ground could extend out to the Moon and keep it in its orbit around Earth. Perhaps that force extended throughout the whole Universe.

Newton became a professor of mathematics at Cambridge. His lectures bored many of his students, but he didn’t care. He continued his own thinking and experiments.

Later, he became the president of the top organization of scientists in England.

Laws of motion and gravityNewton’s most important book was written in Latin and published in 1687. Its English title wasMathematical Principles of Natural Philosophy.

It was one of the most influential works in the history of science. The book explained Newton’s three Laws of Motion and the Law of Universal Gravitation.

To develop his laws, Newton used advanced math. He also designed and built his own telescope to study the heavens.

Newton’s three Laws of Motion1. An object at rest will stay at rest unless a force is applied to it. An object in motion will

stay in motion along a straight line unless an external force is applied to it.



Putting these laws together, Newton was able to state the Law of Universal Gravitation: the gravitational pull between two objects decreases as the objects get farther apart.

Newton’s Universe was a powerful idea because it said that all objects move according to rational principles.



CalculusNewton came up with a new mathematical system for dealing with changing quantities. It is now called calculus. Newton didn’t publish his method. He used it to solve problems.

Later, German scientist Gottfried Wilhelm von Leibniz also worked out “the calculus.” His system was easier to use.

Newton accused Leibniz of stealing his ideas. Historians now believe that each invented the calculus on their own.

Newton was made a knight by Queen Anne in 1705. At his death in 1727, he was buried in London’s Westminster Abbey.

Hubble Looking through a telescope, Hubble proved that the Universe is expanding.

Edwin Hubble: Evidence for an Expanding Universe (1150L)By Cynthia Stokes Brown

In the course of five years, Edwin Hubble twice changed our understanding of the Universe, helping to lay the foundations for the Big Bang theory. First he demonstrated that the Universe was much larger than previously thought, then he proved that the Universe is expanding.

Early life and educationEdwin Powell Hubble was the son of an insurance executive who grew up outside Chicago. He was more outstanding as an athlete than as a student, although he did earn good grades in every subject (except spelling).

At the University of Chicago, Hubble studied mathematics, astronomy, and philosophy — and played for the school’s basketball team. He graduated with a bachelor of science in 1910, and then spent 1911 to 1914 earning his master’s as one of Oxford University’s first Rhodes scholars. Though he studied law and Spanish there, his love of astronomy never diminished.

At Yerkes ObservatoryMoving back to the United States, Hubble enrolled as a graduate student at the University of Chicago and studied the stars at their Yerkes Observatory in Wisconsin. It was here that he began to study the faint nebulae that would be the key to his greatest discoveries. After


receiving his doctorate in astronomy from the University of Chicago in 1917, he won an offer to join the staff at the prestigious Mount Wilson Observatory, near Pasadena, California.

At Mount Wilson ObservatoryArriving at Mount Wilson in 1919, he joined an astronomy establishment that was just beginning to grasp cosmic distances. The key to that effort was work that had been done studying Cepheid variable stars, roughly a decade earlier, by Henrietta Swan Leavitt at Harvard. These stars brighten and dim in a predictable pattern, and their distance from us can be worked out by measuring how bright they appear to us.

Another astronomer at the observatory, Harlow Shapley, built on Leavitt’s findings and shocked the world with his conclusions about the size of the Milky Way. Using the Cepheid variables, Shapley judged that the Milky Way was 300,000 light years across — 10 times bigger than previously thought.

Hubble began his work at Mount Wilson just as the new 2.56-meter Hooker Telescope, the most powerful on Earth, was completed. With it, he was able to peer into the sky with greater detail than anyone had previously. After years of observation, Hubble made an extraordinary discovery. In 1923 he spotted a Cepheid variable star in what was known as the Andromeda Nebula. Using Leavitt’s techniques, he was able to show that Andromeda was nearly 1 million light years away and clearly a galaxy in its own right, not a gas cloud.

Hubble then went on to discover Cepheids in multiple nebulae, and proved, in a 1924 paper called “Cepheids in Spiral Nebula,” that galaxies existed outside our own. Overnight, he became the most famous astronomer in the world, and people everywhere had to get used to the fact that the Universe was far vaster than anyone had imagined. Shapley, for one, was shaken by the news. He wrote Hubble, “I do not know whether I am sorry or glad to see this break in the nebular problem. Perhaps both.”

In 1926, while developing a classification system for galaxies, Hubble discovered an odd fact: Almost every galaxy he observed appeared to be moving away from the Earth. He knew this because the light coming from the galaxies exhibited redshift. Light waves from distant galaxies get stretched by the expansion of the Universe on their way to Earth. This shifts visible light toward the red end of the spectrum.

Building on the work of Vesto Slipher, who measured the redshifts associated with galaxies more than a decade earlier, Hubble and his assistant, Milton Humason, discovered a rough proportionality between the distances and redshifts of 46 galaxies they studied. By 1929 they had formulated what became known as Hubble’s Law. Hubble’s Law basically states that the greater the distance of a galaxy from ours, the faster it recedes. It was proof that the Universe is expanding.

It was also the first observational support for a new theory on the origin of the Universe proposed by Georges Lemaitre: the Big Bang. After all, an expanding Universe must once have been smaller.


Later lifeHubble achieved scientific superstardom for his discoveries and is still considered a brilliant observational astronomer. He ran the Mount Wilson Observatory for the rest of his life, popularized astronomy through books and lectures, and worked to have astronomy recognized by the Nobel Prize committee.

He also played a pivotal role in the design and construction of the Hale Telescope, on Palomar Mountain, California. At 5.08 meters, the Hale was four times as powerful as the Hooker Telescope and existed as the most advanced telescope on Earth for some time. After its completion in 1948, Edwin Hubble was given the honor of first use. When asked by a reporter what he expected to find, Hubble answered: “We hope to find something we hadn’t expected.”

Edwin Hubble: Evidence for an Expanding Universe (1000L)By Cynthia Stokes Brown, adapted by Newsela

In the course of five years, Edwin Hubble made two major discoveries that changed our understanding of the Universe. He demonstrated that the Universe was much larger than previously thought. He also proved that the Universe is expanding.

His discoveries helped to support the Big Bang theory.

Early life and educationEdwin Hubble was born on November 20, 1889, and grew up outside Chicago. He was a better athlete than a student, although he did earn good grades in every subject, except spelling.

At the University of Chicago, Hubble studied mathematics, astronomy, and philosophy — and played for the school’s basketball team.

He graduated with a bachelor of science in 1910, and then spent 1911 to 1914 earning his master’s degree at Oxford University. Though he studied law and Spanish there, his love of astronomy never diminished.

At Yerkes ObservatoryHubble moved back to the U.S. and enrolled as a graduate student at the University of Chicago. He studied the stars at its Yerkes Observatory in Wisconsin.

It was here that he began to study the distant nebulae that would be the key to his greatest discoveries. A nebula is a cloud of dust and gasses in outer space. The plural of nebula is nebulae.

After receiving his doctorate in astronomy from the University of Chicago in 1917, he joined the staff at the prestigious Mount Wilson Observatory, near Pasadena, California.


Major discoveries at Mount Wilson ObservatoryWhen Hubble arrived at Mount Wilson in 1919, astronomers around the world were trying to grasp cosmic distances.

Scientists measured the immense distances using Cepheid variable stars. These stars brighten and dim in a predictable pattern, and their distance from us can be worked out by measuring how bright they appear to us. An astronomer at the observatory used Cepheid stars to determine that the Milky Way was 300,000 light years across — 10 times bigger than previously thought.

Hubble began his work at Mount Wilson just as the new 2.56-meter Hooker Telescope, the most powerful on Earth, was completed. With it, he was able to peer into the sky with greater detail than anyone had previously.

After years of observation, Hubble made an extraordinary discovery. In 1923, he spotted a Cepheid star in what was known as the Andromeda Nebula. He was able to show that Andromeda was nearly 1 million light years away and clearly a galaxy in its own right, not a gas cloud.

Hubble then went on to discover Cepheids in multiple nebulae, and proved that galaxies existed outside our own. Overnight, he became the most famous astronomer in the world, and people everywhere had to get used to the fact that the Universe was far vaster than anyone had imagined.

In 1926, Hubble discovered an odd fact: Almost every galaxy he observed appeared to be moving away from the Earth. He knew this because the light coming from the galaxies exhibited redshift. Light waves from distant galaxies get stretched by the expansion of the Universe on their way to Earth. This shifts visible light toward the red end of the spectrum.

Hubble and his assistant, Milton Humason, discovered a relationship between the distances and redshifts of 46 galaxies they studied. By 1929, they had formulated what became known as Hubble’s Law. Hubble’s Law basically states that the greater the distance of a galaxy from ours, the faster it recedes. It was proof that the Universe is expanding.


His later lifeHubble achieved scientific superstardom for his discoveries. He is still considered a brilliant observational astronomer. He ran the Mount Wilson Observatory for the rest of his life, and popularized astronomy through books and lectures.

He also worked to have astronomy recognized by the Nobel Prize committee.

Hubble made important contributions to the design and construction of the Hale Telescope, on Palomar Mountain in California. At 5.08 meters, the Hale was four times as powerful as the Hooker Telescope and was the most advanced telescope on Earth for some time. After its completion in 1948, Edwin Hubble was given the honor of first use. When asked by a


reporter what he expected to find, Hubble answered: “We hope to find something we hadn’t expected.” He died in 1953 in San Marino, California.

Edwin Hubble: Evidence for an Expanding Universe (850L)By Cynthia Stokes Brown, adapted by Newsela

American astronomer Edwin Hubble made two major discoveries that changed our understanding of the Universe. He showed that the Universe is much larger than previously thought. He also proved that the Universe is expanding.


Early life and educationEdwin Hubble was born on November 20, 1889, and grew up outside Chicago. He was a better athlete than a student; although he did earn good grades in every subject, except spelling.

At the University of Chicago, Hubble studied mathematics, astronomy, and philosophy. He also played for the school’s basketball team.

He graduated in 1910, and then went to England to earn his master’s degree at Oxford University. Though he studied law and Spanish there, his never lost his love of astronomy.

At Yerkes ObservatoryHubble moved back to the U.S. and enrolled as a graduate student at the University of Chicago. He studied the stars at its Yerkes Observatory in Wisconsin.

It was here that he began to study the distant nebulae that would be the key to his greatest discoveries. A nebula is a cloud of dust and gasses in outer space. The plural of nebula is nebulae.

Hubble received his doctorate in astronomy from the University of Chicago in 1917. He then joined the staff at the respected Mount Wilson Observatory, near Pasadena, California.

Major discoveries at Mount Wilson ObservatoryWhen Hubble arrived at Mount Wilson in 1919, astronomers were trying to measure the huge distances in space.

Scientists measured the massive distances using Cepheid variable stars. These stars brighten and dim in a predictable pattern. Their distance from us can be worked out by measuring how bright they appear to us.

An astronomer at the observatory used Cepheid stars to determine that the Milky Way was 300,000 light years across. That was 10 times bigger than people previously thought.


Hubble began his work at Mount Wilson just as the new 2.56-meter Hooker Telescope was completed. This telescope was the most powerful on Earth. With it, he was able to look into the sky with greater detail than anyone had before.

After years of observation, Hubble made an extraordinary discovery. In 1923, he spotted a Cepheid star in what was known as the Andromeda Nebula. He showed that Andromeda was nearly 1 million light years away and clearly a galaxy in its own right, not a gas cloud.

Hubble then went on to prove that galaxies existed outside our own. Overnight, he became the most famous astronomer in the world. People everywhere had to get used to the fact that the Universe was much larger than anyone had imagined.

In 1926, Hubble discovered an odd fact: Almost every galaxy he observed appeared to be moving away from the Earth.

He knew this because the light coming from the galaxies exhibited redshift. Light waves from distant galaxies get stretched by the expansion of the Universe on their way to Earth. This shifts visible light toward the red end of the spectrum.

Hubble and his assistant discovered a relationship between the distances and redshifts of 46 galaxies they studied. By 1929, they had written what became known as Hubble’s Law. Hubble’s Law basically states that the greater the distance of a galaxy from ours, the faster it moves away from us. It was proof that the Universe is expanding.


His later lifeHubble achieved scientific superstardom for his discoveries. He is still considered a brilliant observational astronomer. For the remainder of his life, he ran the Mount Wilson Observatory and popularized astronomy through books and lectures.

He also worked to have astronomy recognized by the Nobel Prize committee.

Hubble contributed greatly to the design and construction of the Hale Telescope, on Palomar Mountain in California. At 5.08 meters, the Hale was four times as powerful as the Hooker Telescope and was the most advanced telescope on Earth for some time.

After its completion in 1948, Edwin Hubble was given the honor of first use. When asked by a reporter what he expected to find, Hubble answered: “We hope to find something we hadn’t expected.” He died in 1953 in San Marino, California.

Edwin Hubble: Evidence for an Expanding Universe (720L) By Cynthia Stokes Brown, adapted by Newsela


Edwin Hubble was an American astronomer who made two major discoveries. Hubble showed that the Universe is much larger than anyone thought. He also proved that the Universe is expanding. Both changed the way we understand the Universe.


Early life and educationEdwin Hubble was born on November 20, 1889, and grew up outside Chicago. When he was young, he was a better athlete than a student. He did earn good grades in every subject, except spelling.

At the University of Chicago, Hubble studied mathematics, astronomy, and philosophy. He also played for the school’s basketball team.

After he graduated, he went to England to get his master’s degree. He studied law and Spanish there, but he never lost his love of astronomy.

At Yerkes ObservatoryHubble moved back to the United States and enrolled at the University of Chicago. He studied the stars at the Yerkes Observatory in Wisconsin.

It was here that Hubble began to study nebulae. A nebula is a cloud of dust and gasses in outer space. The plural of nebula is nebulae. Far-away nebulae were the key to his greatest discoveries.

Hubble got his Ph.D. in astronomy from the University of Chicago in 1917. He then joined the staff at the famous Mount Wilson Observatory in California.

Major discoveries at Mount Wilson ObservatoryHubble arrived at Mount Wilson in 1919. At that time, astronomers were trying to measure the huge distances in space.

Scientists measured these massive distances using Cepheid variable stars. Cepheid stars brighten and dim in a pattern. If we measure how bright they are, we can figure out how far away they are.

The Mount Wilson Observatory was using a new telescope when Hubble started work. The 2.56-meter Hooker Telescope was the most powerful on Earth. Hubble used it to see the sky in greater detail than anyone had before.

Hubble made an extraordinary discovery in 1923. He used Cepheid stars to show that one nebula was one million light years away.

He also proved that other galaxies exist outside our own. He became the most famous astronomer in the world.

People now had to accept that the Universe was much larger than anyone had imagined.


In 1926, Hubble discovered an odd fact. Almost every galaxy he observed appeared to be moving away from the Earth. The light coming from these galaxies showed “redshift.” As light travels to Earth from distant galaxies, it gets stretched by the expansion of the Universe. This makes it appear red.

After studying 46 galaxies, Hubble and his assistant wrote Hubble’s Law. It states that the farther a galaxy is from us, the faster it moves away from us. It was proof that the Universe is expanding.

It also supported the new Big Bang theory. After all, an expanding Universe must once have been smaller.

His later lifeHubble became a scientific superstar for his discoveries. He is still remembered as a brilliant astronomer.

He ran the Mount Wilson Observatory for the rest of his life. His books and lectures helped make astronomy more popular among the public. He also worked to make astronomers able to win the Nobel Prize.

Hubble helped design the Hale Telescope in California. It was the most advanced telescope on Earth for some time.

After its completion in 1948, Hubble was allowed to use it first. When asked by a reporter what he expected to find, Hubble answered: “We hope to find something we hadn’t expected.” He died in 1953 in San Marino, California.


Approaches to KnowledgeHow do people create knowledge? It starts by being puzzled, curious, or even confused about the world. There's a sense of wonder in it all.

Approaches to Knowledge (960L)By Bob Bain

Here in a library, surrounded by books, I’ve set out to write about knowledge. Libraries make such appropriate places to discuss knowledge because their purpose is to store knowledge — that’s why communities build them. In many ways, libraries are repositories of collective learning, an idea that is very important in the Big History course.

In this library and others, knowledge exists in many forms: books, maps, films, videos, CDs, and, of course, textbooks.

The Big History class does not have a textbook, but it’s still useful to think about them and the knowledge within.

I’ll tell you how I approached textbooks when I was in school and how most of my high school and college students approach their textbooks.

They typically ask one big question: “How do we get the stuff out of that textbook and into our heads or, more important, onto the tests?” And frankly, that was the question I asked as a student: “How can I get the facts out of the textbook and onto the test?”

Big History asks questions about knowledgeIn Big History, we ask a very different question: “How did that knowledge get into the textbook?” How did people discover the facts or create the ideas that are in our textbooks or in our courses?

Did you ever wonder how people create knowledge? Well, in this course you are going to meet many people who discovered or created the information that is in your textbooks. You will meet cosmologists, physicists, geologists, biologists, historians, and more. They are excited to tell you what they have learned. But they are also excited to tell you how they learned it. They are going to tell you how people in their field approach knowledge, the questions that interest them, and how they used intuition, authority, logic, and evidence to support their claims.

In Big History, we want you to pay attention to the questions these scientists and scholars ask and the tools and evidence they use to answer their questions.


Questions, tools, and evidenceLet’s look more carefully at how scholars use questions, tools, and evidence to create or discover ideas, facts, and knowledge.

Most of the scholars you’ll meet in this course begin their investigations with questions. They are puzzled, curious, or even baffled about the world around them. Sometimes their inquiry begins in wonder.

Unlike textbooks that place questions at the end of learning, scholars pose the questions first and use them to drive forward their learning.

Have you noticed that your teacher, the Big History units, and David Christian’s videos all use questions — big questions — to launch your study?

Before conducting an inquiry, scholars speculate or make a thoughtful guess about what they’ll learn. We often call these thoughtful guesses “conjectures” or “hypotheses.” But a question or a hypothesis isn’t knowledge yet. Scholars need to gather information to answer their questions. As you’ll learn in later units, sometimes people create or use new tools to help them gather new information. For example, Galileo used a telescope he made to collect new data about the heavens and the planets.

Scholars turn information into evidence to support claimsGathering information does not automatically answer scholars’ questions. The information must also be organized, analyzed, and then evaluated to see if it answers the initial or driving questions.

Scholars may then make claims that answer their questions, and use the information as evidence to support their claims. The stronger the evidence, the better the support for the claim — and the greater chance it has to enter a textbook, for others to learn about it.

Scholars must show how they answered their questionsLet’s review. In this essay, I wondered how knowledge gets in textbooks and, in answer to my question, I have described a few steps:

First, scholars have questions or they are curious or puzzled about something. Second, they make a conjecture — a thoughtful guess or hypothesis. Next, they gather information to answer the question, often using new tools in the

process. They then analyze the information, think about it, and, perhaps, use some of it to

answer their question. Scholars use information as evidence to support or make their claims. When claims become well supported, they enter textbooks for students to learn.

But the scholars’ work is still not finished. They also must share what they learned and show how they learned it. Why do they have to show how they learned it? Isn’t simply telling what they learned enough? Why must they also explain how they conducted their investigation, how they analyzed their information, and how they supported their claims?


Scholars want to contribute to collective learning. They want people to see how they arrived at their claims and what evidence supports the claims.

They do not want people to simply trust their claims based only on intuition, logic, or authority.

Scholars also want others to improve their claims. This might involve using new tools or new methods to gather new evidence to support or challenge the claims. Or it might mean asking a different question entirely.

Different approaches to knowledgeAll scholars ask important questions whether they are archaeologists, anthropologists, biologists, or experts in another field. They all make conjectures, gather data, and analyze it to make claims, but there are differences among and between these individuals. While they all ask important questions, make conjectures, gather data, and analyze it to make claims, there are differences among and between these scholars. They all begin asking questions, but they ask different questions. They all have ways to gather data, but they often have different ways to gather data.

As you meet the instructors in this course, do more than just learn what they are teaching; try as well to understand how they do their work, what questions they ask, and how they answer their questions. You might ask each of them:

What are the big questions that have interested you and driven you to personally pursue the answers?

What were your guesses, speculations, and hypotheses? How did you collect your evidence? Where did you see the patterns in your evidence? What did those patterns seem to

indicate? What were your biggest ideas? How did you make your ideas public? Why should others believe your ideas? When and why have you changed your mind?

Make sure to pay attention to big questions that haven’t been answered. These are questions that you and your friends might take up. Who knows? Maybe you can contribute to the textbooks of the future.

Big History’s approach to knowledgeAs you might have already guessed, in Big History we ask lots of big questions. We’re going to ask questions about the physical world, the living world, and the human world. This will require us to use many different approaches to knowledge. One of the most exciting things about Big History is that we will use ideas that come from many different places. That is why you’re going to meet such a great variety of people who have contributed to our collective learning.


And why we want to give you the chance to ask, “How did that knowledge get into the textbook?”

Approaches to Knowledge (800L)By Bob Bain, adapted by Newsela

I’m writing about knowledge here in a library, surrounded by books. A library is a good place to discuss knowledge because its purpose is to store knowledge. That’s why communities build them. Libraries are basically collections of collective learning. Collective learning is an idea that is very important in the Big History course.

In this library and others, knowledge exists in many forms: books, maps, films, videos, CDs, and, of course, textbooks.

The Big History class does not have a textbook. But it’s still useful to think about textbooks and the knowledge they contain.

Most of my high school and college students ask just one big question about their textbooks. “How can I get the facts out of the textbook and onto the test?” That was the same question I asked when I was a student.

Big History asks questions about knowledgeIn Big History, we ask a very different question: “How did that knowledge get into the textbook?” How did people discover the facts or create the ideas that are in our textbooks?

Did you ever wonder how people create knowledge? Well, in this course you are going to meet many people who discovered or created the information that is in your textbooks. You will meet cosmologists, physicists, geologists, biologists, historians and more.

They are excited to tell you what they have learned. But they are also excited to tell you how they learned it. They are going to tell you how people in their field approach knowledge and the questions that interest them. They’ll also share with you how they used intuition, authority, logic, and evidence to support their claims.

In Big History we want you to pay attention to the questions these scientists and scholars ask. Also, pay attention to the tools and evidence they use to answer their questions.

Questions, tools, and evidenceHow do scholars create or discover ideas, facts and knowledge? They use questions, tools, and evidence.

Most of the scholars you’ll meet in this course begin their investigations with questions. They are puzzled, curious, or even confused about the world around them.

Unlike textbooks that place questions at the end of learning, scholars ask the questions first. They use the questions to drive their learning forward.

Have you noticed that the Big History course uses big questions to launch your study?


Before investigating a question, scholars make a thoughtful guess about what they’ll learn. We often call these thoughtful guesses “conjectures” or “hypotheses.” But a question or a hypothesis isn’t knowledge yet. Scholars need to gather information to answer their questions. As you’ll learn in later units, sometimes people create or use new tools to help them gather new information. For example, Galileo made his own telescope to collect new data about the heavens and the planets.

Scholars turn information into evidence to support claimsGathering information does not automatically answer scholars’ questions. The information must also be organized and analyzed. It must be evaluated to see if it answers the driving questions that were asked at the beginning.

Scholars may then make claims that answer their questions, and use the information as evidence to support their claims. The stronger the evidence, the better the support for the claim. A better-supported claim is more likely to enter a textbook, for others to learn about it.

Scholars must show how they answered their questionsLet’s review. In this essay, I wondered how knowledge gets in textbooks and, in answer to my question, I described a few steps:

First, scholars have a question or they are curious or puzzled about something. Second, they make a conjecture — a thoughtful guess or hypothesis. Next, they gather information to answer the question, often using new tools. They then analyze the information, think about it, and perhaps use some of it to

answer their question. Scholars use information as evidence to support their claims. When claims become well supported, they enter textbooks for students to learn.

But the scholars’ work is still not finished. They must also show how they learned this new information. Why do they have to show how they learned it? Isn’t simply telling what they learned enough? Why must they also explain how they conducted their investigation, how they analyzed their information, and how they supported their claims?

Scholars want to contribute to collective learning. They want people to see how they arrived at their claims and what evidence supports the claims.

They do not want people to simply trust their claims based only on intuition, logic, or authority.

Scholars also want others to improve their claims. This might mean using new tools or new methods to gather new evidence to support or challenge the claims. Or it might mean asking a different question entirely.

Different approaches to knowledgeAll scholars ask important questions whether they are archaeologists, anthropologists, biologists, or other scientists. They all begin asking questions, but they ask different


questions. They all have ways to gather data, but they often have different ways to gather data.

As you meet the instructors in this course, do more than just learn what they are teaching. Try to understand how they do their work, what questions they ask, and how they answer their questions. You might ask each of them:

What are the big questions that have interested you and driven you to personally search for the answers?

What were your guesses, speculations, and hypotheses? How did you collect your evidence? Where did you see the patterns in your evidence? What did those patterns seem to

show? What were your biggest ideas? How did you make your ideas public? Why should others believe your ideas? When and why have you changed your mind?

Make sure to pay attention to big questions that haven’t been answered. These are questions that you and your friends might take up. Who knows? Maybe you can add to the textbooks of the future.

Big History’s approach to knowledgeIn Big History we ask lots of big questions. We’re going to ask questions about the physical world, the living world, and the human world. We will need to use many different approaches to knowledge. One of the most exciting things about Big History is that we will use ideas that come from many different places. That is why you’re going to meet many different people who have contributed to our collective learning.

We want you to ask, “How did that knowledge get into the textbook?”

Approaches to Knowledge (700L)By Bob Bain, adapted by Newsela

I’m writing about knowledge here in a library. I’m surrounded by books. A library is a good place to write about knowledge. Libraries hold our collective learning. That is why communities build them. The idea of collective learning is very important in the Big History course.

Libraries hold knowledge of many kinds: books, maps, movies, CDs, and of course, textbooks.

The Big History class does not have a textbook. But it’s still useful to think about textbooks and the knowledge they contain.


Most of my students ask just one big question about their textbooks. “How can I get the facts out of the textbook and onto the test?” That was the same question I asked when I was a student.

Big History asks questions about knowledgeIn Big History, we ask a very different question: “How did that knowledge get into the textbook?” We want to find out how people came up with the facts or ideas that are in our textbooks.

Did you ever wonder how people create knowledge? In this course you will meet many scientists who created the information that is in your textbooks.

They are excited to tell you what they have learned. But they are also excited to tell you how they learned it.

In Big History we want you to pay attention to the questions these scientists ask. Also, pay attention to the tools and evidence they use to answer their questions.

Questions, tools, and evidenceHow do scholars create or discover ideas, facts and knowledge? They use questions, tools and evidence. Most begin their investigations with questions. They are curious about the world around them.

Textbooks place questions at the end of learning. Scholars ask the questions first. They use questions to drive their learning forward.

Have you noticed that the Big History course uses big questions to begin your study?

Before investigating a question, scholars make a thoughtful guess about what they’ll learn. We call these thoughtful guesses “conjectures” or “hypotheses.” Scholars need to gather information to answer their questions. Sometimes people create or use new tools to help them gather new information. For example, Galileo made a telescope to collect new data about the planets.

Scholars turn information into evidence to support claimsOnce scholars gather information, their job is just beginning. They must organize the information and analyze it. They must see if it answers their questions. Scholars may then make claims that answer their questions. They use the information as evidence to support their claims. With strong evidence, a claim may enter a textbook, where others can learn about it.

Scholars must show how they answered their questionsLet’s review. In this essay, I wondered how knowledge gets in textbooks. In answer to my question, I described a few steps:

First, scholars have a question or they are curious or puzzled about something. Second, they make a thoughtful guess.


Next, they gather information to answer the question, often using new tools. They then study the information, think about it, and perhaps use some of it to answer

their question. Scholars use information as evidence to support their claims. When claims become well supported, they enter textbooks for students to learn.

But scholars must also show how they learned this new information. They must explain what questions they asked, how they answered them, what information they gathered.

Scholars want to add to our collective learning. They want people to see how they arrived at their claims and what evidence supports the claims. They do not want people to trust them just because they are scholars or scientists.

Scholars also want others to improve their claims. This might mean using new tools to gather new evidence. It might mean asking a different question entirely.

Different approaches to knowledgeAll scholars ask important questions, from archaeologists to zoologists. They all begin asking questions, but they ask different questions. They all gather data, but they gather data differently.

As you meet the instructors in this course, don’t just learn what they are teaching. Try to understand how they do their work. What questions do they ask? How do they answer them?

You might ask them:

What are the big questions that have interested you? What were your guesses, speculations, and hypotheses? How did you collect your evidence? Where did you see the patterns in your evidence? What did those patterns seem to

show? What were your biggest ideas? How did you make your ideas public? Why should others believe your ideas? When and why have you changed your mind?

Make sure to pay attention to big questions that haven’t been answered. These are questions that you and your friends might take up. Who knows? Maybe you can add to the textbooks of the future.

Big History’s approach to knowledgeIn Big History we ask lots of big questions. We’re going to ask questions about the physical world, the living world, and the human world. We will need to use many different approaches to knowledge.


The ideas we use will come from many different places. You will meet many different people who contributed to our collective learning. In the end, we want you to ask, “How did that knowledge get into the textbook?”


Structure of Scientific RevolutionsIn his famous book, Kuhn argued that science does not advance in a steady march, but rather discoveries come in sudden bursts of progress.

In Their Own Words: Thomas Kuhn's The Structure of Scientific Revolutions (1350L)By Big History Project

Thomas Kuhn (1922–1996) was an American historian and philosopher of science who began his career in theoretical physics before switching career paths. His book The Structure of Scientific Revolutions, which was first published in 1962, is one of the most cited academic books of all time and made Kuhn perhaps the most influential philosopher of science in the twentieth century. His work challenged the prevailing view of progress in “normal science,” which was that science has been a continuous increase in a set of accepted facts and theories. He argued that, instead, the history of science has been episodic, with periods of continuity interrupted by revolutionary science during which a new “paradigm” changes the rules and direction of scientific research. His analysis of science, which called into question its objectivity, caused a firestorm of controversy and continues to inspire reaction and debate in and beyond scientific communities. Read these excerpts from Kuhn's book, and consider the questions that follow each section.

I. A role for scienceNormal science, the activity in which most scientists inevitably spend almost all their time, is predicated on the assumption that the scientific community knows what the world is like. Much of the success of the enterprise derives from the community’s willingness to defend that assumption, if necessary at considerable cost. Normal science, for example, often suppresses fundamental novelties because they are necessarily subversive of its basic commitments. Nevertheless, so long as those commitments retain an element of the arbitrary, the very nature of normal research ensures that novelty shall not be suppressed for very long. Sometimes a normal problem, one that ought to be solvable by known rules and procedures, resists the reiterated onslaught of the ablest members of the group within whose competence it falls. On other occasions a piece of equipment designed and constructed for the purpose of normal research fails to perform in the anticipated manner, revealing an anomaly that cannot, despite repeated effort, be aligned with professional expectation. In these and other ways besides, normal science repeatedly goes astray. And when it does — when, that is, the profession can no longer evade anomalies that subvert the existing tradition of scientific practice — then begin the extraordinary investigations that lead the profession at last to a new set of commitments, a new basis for the practice of science. The extraordinary episodes in which that shift of professional commitments occurs are the


ones known in this essay as scientific revolutions. They are the tradition-shattering complements to the tradition-bound activity of normal science.

The most obvious examples of scientific revolutions are those famous episodes in scientific development that have often been labeled revolutions before ... the major turning points in scientific development associated with the names of Copernicus, Newton, Lavoisier, and Einstein. More clearly than most other episodes in the history of at least the physical sciences, these display what all scientific revolutions are about. Each of them necessitated the community’s rejection of one time-honored scientific theory in favor of another incompatible with it. Each produced a consequent shift in the problems available for scientific scrutiny and in the standards by which the profession determined what should count as an admissible problem or as a legitimate problem-solution. And each transformed the scientific imagination in ways that we shall ultimately need to describe as a transformation of the world within which scientific work was done. Such changes, together with the controversies that almost always accompany them, are the defining characteristics of scientific revolutions.

II. The route to normal scienceIn this essay, "normal science" means research firmly based upon one or more past scientific achievements, achievements that some particular scientific community acknowledges for a time as supplying the foundation for its further practice. Today such achievements are recounted, though seldom in their original form, by science textbooks, elementary and advanced. These textbooks expound the body of accepted theory, illustrate many or all of its successful applications, and compare these applications with exemplary observations and experiments. Before such books became popular early in the nineteenth century (and until even more recently in the newly matured sciences), many of the famous classics of science fulfilled a similar function. Aristotle’s Physica, Ptolemy’s Almagest, Newton’s Principia and Opticks, Franklin’s Electricity, Lavoisier’s Chemistry, and Lyell’s Geology — these and many other works served for a time implicitly to define the legitimate problems and methods of a research field for succeeding generations of practitioners. They were able to do so because they shared two essential characteristics. Their achievement was sufficiently unprecedented to attract an enduring group of adherents away from competing modes of scientific activity. Simultaneously, it was sufficiently open-ended to leave all sorts of problems for the redefined group of practitioners to resolve.

Achievements that share these two characteristics I shall henceforth refer to as "paradigms," a term that relates closely to "normal science." By choosing it, I mean to suggest that some accepted examples of actual scientific practice — examples which include law, theory, application, and instrumentation together — provide models from which spring particular coherent traditions of scientific research. These are the traditions which the historian describes under such rubrics as "Ptolemaic astronomy" (or "Copernican"), "Aristotelian dynamics" (or "Newtonian"), … and so on. The study of paradigms, including many that are far more specialized than those named illustratively above, is what mainly prepares the student for membership in the particular scientific community with which he will later practice. Because he there joins men who learned the bases of their field from the same


concrete models, his subsequent practice will seldom evoke overt disagreement over fundamentals. Men whose research is based on shared paradigms are committed to the same rules and standards for scientific practice. That commitment and the apparent consensus it produces are prerequisites for normal science, that is, for the genesis and continuation of a particular research tradition.

History suggests that the road to a firm research consensus is extraordinarily arduous ...

History also suggests, however, some reasons for the difficulties encountered on that road. In the absence of a paradigm or some candidate for paradigm, all of the facts that could possibly pertain to the development of a given science are likely to seem equally relevant. As a result, early fact-gathering is a far more nearly random activity than the one that subsequent scientific development makes familiar. Furthermore, in the absence of a reason for seeking some particular form of more recondite information, early fact-gathering is usually restricted to the wealth of data that lie ready to hand … Because the … facts … could not have been casually discovered, technology has often played a vital role in the emergence of new sciences.

… No natural history can be interpreted in the absence of at least some implicit body of intertwined theoretical and methodological belief that permits selection, evaluation, and criticism. If that body of belief is not already implicit in the collection of facts — in which case more than “mere facts” are at hand — it must be externally supplied … No wonder, then, that in the early stages of the development of any science different men confronting the same range of phenomena, but not usually all the same particular phenomena, describe and interpret them in different ways. What is surprising, and perhaps also unique in its degree to the fields we call science, is that such initial divergences should ever largely disappear.

… To be accepted as a paradigm, a theory must seem better than its competitors, but it need not, and in fact never does, explain all the facts with which it can be confronted ...

… When, in the development of a natural science, an individual or group first produces a synthesis able to attract most of the next generation’s practitioners, the older schools gradually disappear. In part their disappearance is caused by their members’ conversion to the new paradigm. But there are always some men who cling to one or another of the older views, and they are simply read out of the profession, which thereafter ignores their work. The new paradigm implies a new and more rigid definition of the field. Those unwilling or unable to accommodate their work to it must proceed in isolation or attach themselves to some other group. [I]t is sometimes just its reception of a paradigm that transforms a group previously interested merely in the study of nature into a profession or, at least, a discipline …

When the individual scientist can take a paradigm for granted, he need no longer, in his major works, attempt to build his field anew, starting from first principles and justifying the use of each concept introduced. That can be left to the writer of textbooks…


In Their Own Words: Thomas Kuhn's The Structure of Scientific Revolutions (1040L)By Big History Project, adapted by Newsela

Thomas Kuhn (1922–1996) was an American historian and philosopher of science. He began his career in theoretical physics before switching career paths. His book, The Structure of Scientific Revolutions, which was first published in 1962, is one of the most cited academic books of all time and made Kuhn perhaps the most influential philosopher of science in the twentieth century.

People had previously thought of progress in “normal science” as a continuous increase in a set of accepted facts and theories. Kuhn disagreed. He argued that the history of science has come in sudden bursts. Sometimes discoveries build on each other, but sometimes there is revolutionary science that interrupts the steady march of progress. In revolutionary science, a new “paradigm,” or worldview, changes the rules and direction of scientific research.

His analysis of science, which called into question its objectivity, caused a firestorm of controversy. It continues to inspire reaction and debate in scientific communities and beyond.

The following excerpts have been adapted from his book to provide a simplified view of Kuhn's arguments. Consider the questions that follow each section.

I. A role for scienceNormal science, what most scientists spend most of their time doing, assumes that the scientific community knows what the world is like. The scientific community must defend this assumption if it wants to be successful.

Normal science often holds back fundamental novelties because they go against the accepted way of thinking. Still, as long as scientists are willing to be proved wrong, these novelties will eventually come out.

Sometimes a normal problem, one that should be solvable by known rules and procedures, cannot be solved by the experts. Other times, a piece of equipment made for doing normal research gives results that don’t make sense to the experts.

In these and other ways, normal science repeatedly goes off track. Scientists have to face anomalies, or unexpected results they can’t explain. This is when they may begin extraordinary investigations that lead science to a new way of thinking, a new basis for the practice of science.

These times, when science must accept new realities, are known in this essay as scientific revolutions. They shatter tradition, whereas normal science is bound to tradition.


The most obvious examples of scientific revolutions are those famous episodes in scientific development that are already called revolutions. These include the major turning points in science associated with Copernicus, Newton, Lavoisier, and Einstein.

These episodes display what all scientific revolutions are all about. Each of them caused the community to reject one accepted scientific theory for another one that was incompatible with it. Each brought a new set of questions for scientists to answer. Each brought new problems and new ways to solve these problems. Finally, each transformed the scientific imagination — transformed the world where scientific work was done.

These changes, and the controversies that go with them, are what define scientific revolutions.

Questions In this excerpt, Kuhn introduces the term “normal science,” which he later defines as

“research firmly based upon past scientific achievements … “ What are anomalies in science? What role do anomalies play in the development of

science? How does Kuhn define “scientific revolutions”? According to Kuhn, what features do scientific revolutions have in common? What is a theory? How is it different from a hypothesis or conjecture? How are

theories related to “normal science”?

II. The route to normal scienceIn this essay, "normal science" means research firmly based on past scientific achievements. These past achievements form the foundation for further study.

Today these achievements are described by science textbooks. These textbooks provide the core of accepted theory. They give examples of successful uses of these achievements, and compare these uses with observations and experiments.

Before such books became popular early in the nineteenth century, many of the famous classics of science served a similar function. Aristotle’s Physica, Ptolemy's Almagest, Newton’s Principia and Opticks, Franklin’s Electricity, Lavoisier's Chemistry, and Lyell’s Geology — these and many other works defined the problems and methods of research for future scientists. They were able to do so because they shared essential characteristics:

First, the discoveries they presented had never before been seen. This attracted people from all fields to study them more. Also, these discoveries were open-ended enough to leave more questions for future researchers to answer.

I’ll call achievements that share these two characteristics “paradigms.” These paradigms provide models that produce unified traditions of scientific research.

These are traditions that historians call “Copernican astronomy” or “Newtonian dynamics” and so on. A beginning scientist must study all the paradigms in his or her field before starting research. Scientists in a field rarely disagree over fundamentals, since they all have


accepted the same paradigm. They share the same rules and standards. That agreement it produces is necessary for normal science — for the creation and continuation of a research tradition.

History suggests that the road to a firm research agreement is extraordinarily difficult. History also suggests, however, some reasons for the difficulties encountered on that road.

Without a paradigm, or a possible paradigm, all the facts that may relate to a given science all seem worth considering equally. In a new field of science, fact-gathering is more random that in a well-developed one.

Furthermore, without a reason for seeking out more hard-to-find information, early fact-gathering tends to find the data that is convenient to find. Because the facts could not have been casually discovered, technology has often played a vital role in the emergence of new sciences.

We can’t study and interpret the natural world without a system of theories and methods that permits selection, evaluation and criticism. If that system is not in place, we have just “facts.”

No wonder then, that in the early stages of any science different scientists seeing roughly the same things describe and interpret them in different ways. What is surprising, and maybe even unique in science, is that such differences should ever disappear.

To be accepted as a paradigm, a theory must seem better than its competitors. But a theory never does explain all the facts it may face, nor does it have to.

When, in science, an individual or group produces a new system that attracts most of the next-generation scientists, the older systems gradually disappear. In part, they disappear because members accept the new paradigm.

But there are always some scientists who cling to older views, but they are often ignored by the scientific community. The new paradigm gives a stricter definition of what is acceptable. Those who don’t agree with it must work alone or attach themselves to some other group.

A paradigm can transform people merely studying nature into a profession.

When an individual scientist can take a paradigm for granted, she doesn’t have to explain the basic system in her works. She can assume that other scientists know the basic paradigm.

It is textbooks, then, that still have to explain things step by step, from the beginning.

Questions Kuhn believes textbooks hide the historical processes that create scientific theory

because they only discuss the finished products. Think about the science textbooks you use. Do you agree with Kuhn?

What function did the “famous classics of science” play in their field? Why were they able to serve this function?


“Paradigm” is a word that Kuhn helped to popularize. How does he define it? What role do paradigms play in normal science? How are paradigms and normal science different?

How is Kuhn using the term “facts”? How are facts different from theories? What role do paradigms play in “fact-gathering”?

How do paradigms come to be “paradigms”? How are paradigms and disciplines related? How do paradigms help shape a

discipline? Textbooks might be considered products of collective learning at some particular

point in time. How does collective learning relate fit into Kuhn’s argument about scientific revolutions?


Thomas Kuhn (1922–1996) was an American historian and philosopher of science. He began his career in theoretical physics before switching career paths. His book, The Structure of Scientific Revolutions, was first published in 1962. It is one of the most cited scholarly books of all time and made Kuhn perhaps the most influential philosopher of science in the twentieth century.

People often think of science as a steady increase in accepted facts and theories. This is what Kuhn calls “normal science.” But Kuhn argued that this was not always how things worked.

He said that sometimes discoveries build on each other, but sometimes there is a sudden burst of revolutionary science. In revolutionary science, a new “paradigm” changes the rules and direction of scientific research. A paradigm is a way of thinking about the world.

His analysis said that science was not always strictly fact-based, but could affected by people's views. This caused a lot of controversy. His work continues to spark reaction and debate among scientists and others.

The following selections have been adapted from his book to provide a simplified view of Kuhn's arguments. Consider the questions that follow each section.

I. A role for scienceNormal science is what most scientists do most of the time. Normal science assumes that we know what the world is like. This is a necessary assumption.

Normal science often holds back new information that goes against the basic view of what the world is like. Still, as long as scientists are willing to be proved wrong, this new information will eventually come out.


Sometimes a normal problem that should be solvable by normal procedures stumps the experts. Other times, a piece of equipment made for normal research gives results that don’t seem to make sense.

In these and other ways, normal science can go off track. Scientists must face anomalies — results that are different from what is expected — that they can’t explain. This is when they begin new investigations that lead scientists to a new way of thinking.

These are scientific revolutions. Science must accept new realities. These include the major turning points in science associated with Copernicus, Newton, Lavoisier, and Einstein.

These episodes are great examples of scientific revolutions. Each of them caused the community to reject one scientific theory for another. Each brought a new set of questions for scientists to answer. Each brought new problems and new ways to solve these problems. Finally, each transformed the scientific imagination. Each transformed the world where scientific work was done.

These changes and the controversy they cause are what define scientific revolutions.

II. The route to normal scienceIn this essay, “normal science” means research firmly based on past scientific achievements. These past achievements form the base for further study.

Today, these achievements are described in science textbooks. The textbooks provide the core of accepted theory. They give examples of successful uses of the achievements, and compare these uses with observations and experiments.

Before textbooks became popular, the famous classics of science served a similar purpose. Aristotle’s Physica, Ptolemy’s Almagest, Newton’s Principia and Opticks, Franklin’s Electricity, Lavoisier’s Chemistry, and Lyell’s Geology — these and many other works defined the problems and methods of research for future scientists. They were able to do so because they shared essential characteristics:

First, the discoveries they presented were completely new. This attracted people from all fields to study them more. Also, these discoveries were open-ended enough to leave more questions for future researchers to answer.

I’ll call achievements that share these two characteristics “paradigms.” These paradigms provide models that produce traditions of scientific research.

These are traditions that historians call “Copernican astronomy” or “Newtonian dynamics,” for example. A beginning scientist must study all the paradigms in her field before starting research. Scientists in a field rarely disagree over fundamentals, since they all have accepted the same paradigm. They share the same rules and standards. That agreement it produces is necessary for normal science — for the creation and continuation of a research tradition.

History shows that coming to such an agreement is quite difficult. History also shows some reasons that it is so difficult.


Without a paradigm, all facts that a scientists comes across seem worth considering equally. Fact-gathering can seem random.

Furthermore, without a reason for seeking out more hard-to-find information, early fact-gathering tends to find the data that is convenient to find. Technology has often played a very important role in the emergence of new sciences because it can uncover information that is not convenient to find.

We can’t study and interpret the world without a system of theories and methods that permits selection, evaluation and criticism. If that system is not in place, we have just “facts.”

It’s not surprising that in the early stages of any science, different scientists seeing roughly the same things describe and interpret them in different ways. What is surprising, and maybe even unique in science, is that such differences can disappear.

To be accepted as a paradigm, a theory must seem better than its competitors. But it doesn’t have to, and never does, explain all the facts it may face.

When a new scientific paradigm arrives on the scene, the older systems gradually disappear because members accept the new paradigm.

Scientists who cling to older views are often ignored by the rest of the community. The new paradigm gives a stricter definition of what is acceptable. Those who don’t agree with it must work alone or attach themselves to some other group.

When an individual scientist can take a paradigm for granted, she doesn’t have to explain the basic system in her works. She can assume that other scientists know the basic paradigm.



Thomas Kuhn (1922–1996) was an American historian and philosopher of science. He was a physicist before changing careers. He published The Structure of Scientific Revolutions in 1962. It made Kuhn one of the most influential science philosophers of the twentieth century.

People often think of science as a steady process, building on itself. Kuhn calls this “normal science.” But he stresses that, sometimes, there is a revolution in science.

In revolutionary science a new paradigm, or worldview, changes the rules of scientific research.

His book argued that science is not always objective. This caused a lot of controversy. His work continues to cause debate among scientists and others.

The following selections have been adapted from his book. They give a simplified view of Kuhn's arguments. Think about the questions that follow each section.


I. A role for scienceNormal science is what most scientists do most of the time. Normal science assumes that we know what the world is like.

In normal science, if there is some new information that doesn’t fit into the system, it may be held back. Still, as long as scientists are willing to be proved wrong, this new information will come out at some point.

Sometimes a normal problem stumps the experts. Other times, a piece of equipment gives results that don’t seem to make sense. In these and other ways, science can go off track. These are anomalies, something that is different than what is expected. When scientists can’t explain an anomaly, they begin new investigations. Those investigations can lead to a new way of thinking in science.

These are scientific revolutions. Science must accept new realities. These include the major turning points in science associated with Copernicus, Newton, Lavoisier, and Einstein.

These episodes are good examples of scientific revolutions. Each of them caused scientists to reject one theory for another. Each brought a new set of questions for scientists to answer. Each brought new problems and new ways to solve these problems. Finally, each transformed the scientific imagination. Each transformed the world where scientific work was done.

These changes and the controversy they cause are what define scientific revolutions.

II. The route to normal scienceIn this essay, “normal science” means research that is firmly based on past scientific achievements.

Today, these achievements are described in science textbooks. Textbooks explain the accepted theory and show how it is successful through observations and experiments.

Before textbooks became popular, the classic works served this purpose. Ptolemy’s Almagest, Newton’s Principia and Opticks, Franklin’s Electricity, and Lyell’s Geology — these works defined ways of thinking for future scientists. They were able to do so because they shared some important things in common:

First, they presented new discoveries. This attracted new people to study them more. Second, the new discoveries were open-ended. It meant there was still much more to discover.

Achievements that share these two things in common I’ll call “paradigms.” These paradigms produce traditions of scientific research.

These are traditions that historians call “Copernican astronomy” or “Newtonian dynamics,” for example. A beginning scientist must study the paradigms in her field before starting research.


Scientists in a field rarely disagree over fundamentals, since they all have accepted the same paradigm. They share the same rules and standards. The agreement it produces is necessary for normal science — for the creation and continuation of a research tradition.

History shows that coming to such an agreement is quite difficult. History also shows some reasons why it is so difficult.

In the early stages of a field of science, researchers seeing the same thing may describe and interpret it in different ways. That's no surprise. What is surprising is that these differences can disappear.

To be accepted as a paradigm, a theory must seem better than its competitors. But it doesn’t have to, (and never does) explain all the facts it may face.

When a new scientific paradigm arrives, members of the community begin to accept it. The older systems slowly disappear.

Scientists who stick with older views are often ignored by the rest of the community. The new paradigm gives a stricter definition of what is acceptable. Scientists who don’t agree with it must work alone or join another group.

When a scientist can take a paradigm for granted, she doesn’t have to explain the basic system in her works. She can assume that other scientists know the basic paradigm.



Henrietta LeavittLeavitt was an important contributor to our understanding of the size of the Universe.

Henrietta Leavitt: Measuring Distance in the Universe (1300L)By Cynthia Stokes Brown

Henrietta Leavitt discovered the relationship between the intrinsic brightness of a variable star and the time it took to vary in brightness, making it possible for others to estimate the distance of these faraway stars, conclude that additional galaxies exist, and begin mapping the Universe.

Early life and educationHenrietta Swan Leavitt was a minister's daughter whose family moved frequently. When she was about 14, the family moved to Cleveland, Ohio, and in 1885 Leavitt enrolled in Oberlin College to prepare for the strict entrance requirements of the college she really wanted to attend — the Society for Collegiate Instruction of Women, later known as Radcliffe College (now part of Harvard University), in Cambridge, Massachusetts – a dream she achieved at age 20. She discovered her calling in her senior year when she took a course in astronomy.

At the Harvard College ObservatoryLeavitt liked astronomy so much that after graduation she became a volunteer at the Harvard College Observatory as a “computer.” This was the name used for women who examined tiny dots on time-exposed photographs of the night sky and then measured, calculated, and recorded their observations in ledger books. Eventually, in 1902, Leavitt was hired at 30 cents an hour; she continued to work at the observatory for the remaining 19 years of her life.

Leavitt took a special interest in the Magellanic Clouds, a pair of luminous hazes now known to be irregular galaxies, the nearest ones to our Milky Way. At the time, no one knew what the clouds were. Since the Magellanic Clouds are only visible in the southern hemisphere, Leavitt could not see them directly. She could merely look at photographic plates taken at Harvard’s auxiliary observatory, in Arequipa, Peru, and sent to Cambridge by ship around the tip of South America.

Using Cepheid variablesOne of Leavitt’s jobs was to examine the variable stars, which, unlike most stars, vary in brightness because of fluctuations within themselves. In the course of her work, Leavitt discovered 2,400 new variable stars, half the known ones in her day. A certain group of variable stars, later called Cepheid variables, fluctuate in brightness (luminosity) in a regular pattern called their “period.” This period ranges from about one day to nearly four months.


By comparing thousands of photographic plates, Leavitt discovered a direct correlation between the time it takes for a Cepheid variable to go from bright to dim and back to bright, and how bright the star actually is (its “intrinsic brightness”). The longer the period of fluctuation, the brighter the star. This meant that even though a star might appear extremely dim, if it had a long period it must actually be extremely large; it appeared dim only because it was extremely far away. By calculating how bright it appeared from Earth and comparing this to its intrinsic brightness, one could estimate how much of the star’s light had been lost while reaching Earth, and how far away the star actually was.

Leavitt published her first paper on the period-luminosity correlation in 1908. Four years after that, she published a table of the periods of 25 Cepheid variables. Nine years later, in 1921, she died of cancer at age 53 in Cambridge.

Leavitt's LegacyBefore Leavitt established the period-luminosity relationship, astronomers could determine cosmic distances out only about 100 light years. Using her insights, astronomers were able to estimate the Magellanic Clouds to be in the range of 100,000 light years from Earth — much further than anyone had imagined — meaning they could not be within the Milky Way galaxy.

The largest telescope then in existence opened in 1904 at Mount Wilson, near Los Angeles, California. In 1919, the astronomer Edwin Hubble took a job there, after finishing his PhD in astronomy at the University of Chicago. Using the Mount Wilson telescope and building on Leavitt’s work, Hubble located Cepheid variables so far away that they conclusively established the presence of other galaxies. By 1925, most astronomers agreed that our galaxy is one among a multitude — a small outpost in a Universe full of galaxies.

Leavitt initially worked under a director of the Harvard College Observatory who did not encourage theorizing but preferred only to accumulate data. A later director even tried to take some of the credit for her work after her death. Now, however, Leavitt is recognized as a key contributor to our understanding of the size of the Universe.

A modest lifeLeavitt never married. She gradually became deaf, starting with an illness when she was a young adult. She was buried in Cambridge in the family plot, near the graves of Henry and William James. Her total estate was appraised at $314.91. In her obituary, a senior colleague wrote: “[She] was possessed of a nature so full of sunshine that, to her, all of life became beautified and full of meaning.”

Henrietta Leavitt: Measuring Distance in the Universe (980L)By Cynthia Stokes Brown, adapted by Newsela

Henrietta Swan Leavitt studied distant stars that dim and brighten. These are called Cepheid variable stars. She made it possible for others to measure huge cosmic distances, discover additional galaxies, and begin mapping the universe.


Leavitt was a minister's daughter. Her family moved frequently.

She attended the Society for Collegiate Instruction of Women, which is now part of Harvard University. It was a school she had dreamed of attending. In her senior year she discovered her calling — astronomy.

At the Harvard College ObservatoryLeavitt liked astronomy so much that after graduation she became a volunteer at the Harvard College Observatory as a “computer.” This was the name used for women who examined tiny dots on photographs of the night sky. They then measured, calculated, and recorded their observations in ledger books.

Eventually, Leavitt was hired at 30 cents an hour. She continued to work at the observatory for the remaining 19 years of her life.

Leavitt was very interested in the Magellanic Clouds, two glowing hazes in space. At the time, no one knew what the clouds were. Since the Magellanic Clouds are only visible in the southern hemisphere, Leavitt could not see them directly. She could merely look at photographic plates taken at Harvard’s observatory in Peru, and sent to Cambridge by ship around the tip of South America.

Using Cepheid variablesOne of Leavitt’s jobs was to examine the variable stars, which, unlike most stars, vary in brightness because of changes within themselves. In the course of her work, Leavitt discovered 2,400 new variable stars, half the known ones in her day.

A certain group of variable stars, later called Cepheid variables, fluctuate in brightness (luminosity) in a regular pattern called their “period.” This period ranges from about one day to nearly four months.

Leavitt studied thousands of photographs of these stars. She discovered a way to determine how bright they are and how far away they are.

She found that the longer a star’s period, the brighter it was. By comparing how bright a star appeared, and how bright it actually was, Leavitt could estimate how much of the star’s light had been lost while reaching Earth, and how far away the star actually was.

Leavitt published her first paper on the period-luminosity relationship in 1908. Four years after that she published a table of the periods of 25 Cepheid variables. Nine years later, in 1921, she died of cancer at age 53 in Cambridge, Massachusetts.

Leavitt's LegacyBefore Leavitt established the period-luminosity relationship, astronomers could only measure cosmic distances up to about 100 light years. Using her insights, astronomers were able to estimate the Magellanic Clouds to be about 100,000 light years from Earth — much further than anyone had imagined — meaning they could not be within the Milky Way galaxy.


Edwin Hubble at the Mount Wilson Observatory near Los Angeles used a state-of-the-art telescope to find Cepheid variable stars that were extremely far away. They were so far away, they proved the existence of other galaxies.

By 1925, most astronomers agreed that our galaxy is just one of many.

Leavitt initially worked under a director of the Harvard College Observatory who did not encourage theorizing but preferred only to accumulate data. A later director even tried to take some of the credit for her work after her death. Now, however, Leavitt is recognized as a key contributor to our understanding of the size of the Universe.

A modest lifeLeavitt never married. She gradually became deaf, starting with an illness when she was a young adult. She was buried in Cambridge in the family plot. Her total estate was appraised at $314.91. In her obituary, a senior colleague wrote: “[She] was possessed of a nature so full of sunshine that, to her, all of life became beautified and full of meaning.”


Henrietta Swan Leavitt studied distant stars that dim and brighten. By studying how long it takes for them to change brightness, she determined how bright they were and how far away they were.

She made it possible for others to measure huge cosmic distances, discover additional galaxies, and begin mapping the universe.


She went to the Society for Collegiate Instruction of Women (now part of Harvard University). It was a school she had dreamed of attending. In her senior year, she discovered her calling — astronomy.

At the Harvard College ObservatoryLeavitt liked astronomy so much that after graduation she became a volunteer at the Harvard College Observatory as a “computer.” This was the name used for women who examined tiny dots on photographs of the night sky. They then measured, calculated and recorded their observations in ledger books.

Eventually, Leavitt was hired at 30 cents an hour. She continued to work at the observatory for the remaining 19 years of her life.

Leavitt was very interested in the Magellanic Clouds, two glowing hazes in space. At the time, no one knew what the clouds were.

The Magellanic Clouds are only visible in the southern hemisphere, so Leavitt could not see them directly. She could only look at photographic plates taken at Harvard’s observatory in Peru. The photographs were sent to Cambridge by ship around the tip of South America.


Using Cepheid variablesOne of Leavitt’s jobs was to examine variable stars. These stars get more and less bright because of changes inside them. Most stars don’t do this.

In the course of her work, Leavitt discovered 2,400 new variable stars.

Some variable stars, later called Cepheid variables, dim and brighten on a regular schedule. This is called their “period.” This period can range from one day to four months.

Leavitt studied thousands of photographs of these stars. She discovered a way to determine how bright they were (their luminosity) and how far away they were.

She found that the longer a star’s period, the brighter it was. Leavitt compared how bright a star appeared, and how bright it actually was. By doing this, she could estimate how far away the star actually was.

Leavitt published her first paper on the period-luminosity relationship in 1908. Four years after that she published a table of the periods of 25 Cepheid variables.

Nine years later, in 1921, she died of cancer at age 53 in Cambridge, Massachusetts.

Leavitt's LegacyBefore Leavitt established the period-luminosity relationship, astronomers could only measure cosmic distances up to about 100 light years. Using her discovery, astronomers were able to estimate the Magellanic Clouds to be about 100,000 light years from Earth. This was much farther than anyone had imagined. It meant the clouds could not be within the Milky Way galaxy.

Edwin Hubble at the Mount Wilson Observatory near Los Angeles was studying Cepheid variable stars. He used Leavitt’s findings and a state-of-the-art telescope to find Cepheid variables that were extremely far away. They were so far away that they proved the existence of other galaxies.


Leavitt’s first director at the Harvard College Observatory did not encourage his staff to develop theories. He preferred only to collect data.

Another director even tried to take some of the credit for her work after her death. Leavitt is now recognized as a key contributor to our understanding of the size of the Universe.

A modest lifeLeavitt never married. She gradually became deaf, starting with an illness when she was a young adult. She was buried in Cambridge in the family plot. Her total estate was worth $314.91.

When she died, one of the people who worked with her wrote in her obituary: “[She] was possessed of a nature so full of sunshine that, to her, all of life became beautified and full of meaning.”



Henrietta Swan Leavitt studied distant stars that dim and brighten. She was able to determine how bright these stars were and how far away they were.

Her work greatly helped other astronomers. They were able to measure huge distances in space, find new galaxies, and begin mapping the Universe.


She went to the Society for Collegiate Instruction of Women. It was her dream to attend. In her senior year, she found that she loved astronomy.

At the Harvard College ObservatoryAfter graduation, Leavitt became a volunteer at the Harvard College Observatory. She worked as a computer. At that time “computers” were women who looked at tiny dots on photographs of the night sky. They kept detailed records of the stars and planets in notebooks.

Leavitt was then hired at 30 cents an hour. She worked at the observatory for the rest of her life.

Using Cepheid variablesOne of Leavitt’s jobs was to examine variable stars. These stars change their brightness. Most stars don’t.

Leavitt discovered 2,400 new variable stars.

Some variable stars dim and brighten on a regular schedule. This is called their “period.” This period can range from one day to four months.

Leavitt studied thousands of photographs of these stars. They were called Cepheid variables. She discovered a way to figure out how bright they were and how far away they were.

She found that the longer a star’s period, the brighter it was. Leavitt compared how bright a star appeared, and how bright it actually was. She could estimate how far away the star actually was this way.

Leavitt published her first paper on the period-brightness relationship in 1908. Four years later, she published a table of the periods of 25 Cepheid variables.

In 1921, she died of cancer at age 53 in Cambridge, Massachusetts.

Leavitt's LegacyBefore Leavitt, astronomers could only measure distances up to 100 light years away. Her discovery improved their ability. They were now able to pinpoint some objects at 100,000


light years away. These objects were farther away than anyone had imagined. It meant they could not be within our Milky Way galaxy.

Edwin Hubble was studying Cepheid variables near Los Angeles. He used Leavitt’s findings and a new telescope to find Cepheid variables that were extremely far away. They were so far away that they could not be in our galaxy.


Leavitt's work faced challenges. Her first director at Harvard only wanted his staff to collect information. He didn't want them try and put the information together as a theory. Another director tried to take some credit for her work after her death. Yet today, Leavitt is seen as someone who helped us understand the size of the Universe.

A modest lifeLeavitt never married. She gradually became deaf, starting with an illness she had as a young adult. She was buried in Cambridge in the family plot. All she left was worth $314.91.

Upon her death, someone who worked with her wrote: “[She] was possessed of a nature so full of sunshine that, to her, all of life became beautified and full of meaning.”


Tycho BraheAfter impressing the Danish king with his discoveries, Brahe built the most advanced observatory in the world.

Tycho Brahe: The last great naked-eye astronomer (1410L)By Cynthia Stokes Brown

Tycho Brahe was the last great naked-eye astronomer. His legacy is a star chart of considerable accuracy and proof that the heavens were not fixed.

At the time of Brahe’s birth, the dominant model of the Universe had the Sun, Moon, and five planets rotating around the Earth on crystalline spheres against an unchanging backdrop of the stars. All of the star charts of that time were based on this geocentric (Earth-centered) system.

At age 16, newly arrived at the University of Leipzig from his uncle’s palace in Copenhagen, Brahe discovered an error in the existing star charts: a conjunction of Saturn and Jupiter that had not been predicted. In an age of Royal Astrologers and navigation by sextant, which relied on the positioning of celestial bodies, this was a significant error. Having shown the existing charts to be inadequate, Brahe then devoted his life to recording the location and movement of everything in the night sky with greater accuracy than anyone before him did.

After nearly 10 years of diligently studying and recording the night sky, using instruments and techniques he had developed himself (the telescope was yet to be invented), Brahe was stunned to look up one night and see a bright star where none had been before.

The heavens had changedUsing his own techniques, Brahe was able to prove that the new star (actually a supernova now known as SN 1572) was beyond the Moon, in the celestial realm — the supposedly unchanging backdrop of stars. The heavens had changed, and he had observed and recorded it for science.

This discovery focused attention on Brahe from astronomers in Europe and beyond, and greatly impressed the Danish king. With help from the king, he built one of the first real astronomical research institutes and the most advanced observatory in the world, called Uraniborg (Fortress of the Sky), on an island in Copenhagen Sound.

Soon after taking up his work there, he observed a comet moving beyond the “sphere” of the Moon. By proving that the comet was not in our atmosphere, he shattered the theory that the planets were nested around the Earth on crystalline spheres and laid the foundation for our modern understanding of an evolving cosmos. Brahe’s influence extended to one of his most famous students, Johannes Kepler, who used Brahe’s detailed observational record to develop his own Laws of Planetary Motion.


Tycho Brahe: The last great naked-eye astronomer (1170L)By Cynthia Stokes Brown, adapted by Newsela

Tycho Brahe was the last great naked-eye astronomer. He devoted his life to recording the location and movement of everything in the night sky with greater accuracy than anyone before him

He produced an accurate star chart and proved that the heavens are not fixed.

At the time of Brahe’s birth in 1546, it was thought that the Sun, Moon, and five planets rotated around the Earth attached to crystal spheres. In this model, the stars did not change. All of the star charts of that time were based on this geocentric (Earth-centered) system.

Only 16, Brahe arrived at the University of Leipzig and discovered an error in existing star charts. At this time, people navigated using sextants and the stars, so any error in star charts was significant.

Brahe then dedicated his life to tracking the position and movement of all stars and planets with great accuracy.

The heavens had changedAfter nearly 10 years of studying and recording the night sky, using instruments and techniques he had developed himself, Brahe looked up one night and saw a bright star where none had been before. He was stunned.

Using his own techniques, Brahe was able to prove that the new star was beyond the Moon, in the celestial realm — the supposedly unchanging backdrop of stars. The heavens had changed, and he had observed and recorded it for science.

This discovery brought Brahe fame among astronomers around the world, and greatly impressed the Danish king. With help from the king, he built one of the first real astronomical research institutes and the most advanced observatory in the world, called Uraniborg (Fortress of the Sky), on an island in Copenhagen Sound.

Soon after starting work there, he observed a comet moving beyond the “sphere” of the Moon. By proving that the comet was not in our atmosphere, he shattered the theory that the planets were nested around the Earth on crystalline spheres.

This laid the foundation for our modern understanding of an evolving cosmos. Brahe’s influence extended to one of his most famous students, Johannes Kepler, who used Brahe’s detailed observations to develop his own Laws of Planetary Motion.


Tycho Brahe was the last great naked-eye astronomer. He dedicated his life to recording the location and movement of everything in the night sky with great accuracy.


He produced an accurate star chart and proved that the heavens can change.

When Brahe was born in 1546, it was thought that the Sun, Moon, and five planets rotated around the Earth attached to crystal spheres.

In this model, the stars did not change. All of the star charts of that time were based on this geocentric (Earth-centered) system.

Brahe arrived at the University of Leipzig at age 16. There, he discovered an error in existing star charts. At this time, people navigated the sea using the stars, so any error in star charts caused serious problems.

Brahe then devoted his life to tracking the position and movement of all stars and planets with great accuracy.

The heavens had changedBrahe studied and recorded the night sky using instruments and techniques he had developed himself. After 10 years, he was stunned to look up one night and see a bright star where none had been before.

Using his own techniques, Brahe was able to prove that the new star was beyond the Moon. It was in the celestial realm — what everyone thought was the unchanging backdrop of stars.

The heavens had changed, and Brahe had observed and recorded it for science.

This discovery brought Brahe fame among astronomers around the world. It greatly impressed the Danish king, who helped Brahe build one of the most advanced observatories in the world, called Uraniborg (Fortress of the Sky), on an island in Copenhagen Sound.

Soon after starting work there, he observed a comet moving beyond the “sphere” of the Moon. By proving that the comet was not in our atmosphere, he disproved the theory that the planets were placed around the Earth on crystal spheres.

This laid the foundation for our modern understanding of a changing cosmos. Brahe’s influence extended to Johannes Kepler, one of his most famous students. Kepler used Brahe’s detailed observations to develop his own Laws of Planetary Motion.


Tycho Brahe was the last great astronomer who worked before telescopes. He dedicated his life to accurately recording the location and movement of everything in the night sky.

He improved the star charts of his time and proved that the heavens can change.

Brahe was born in 1546. At this time, it was thought that the Sun, Moon, and five planets rotated around the Earth attached to spheres made of crystal.


In this model, the stars did not change. All of the star charts of that time were based on this geocentric system with Earth at the center of the Universe.

Brahe was only 16 when he arrived at the University of Leipzig. He immediately discovered an error in existing star charts. People at this time used the stars to guide them. Any error in star charts was serious.

He then devoted his life to tracking the position and movement of all stars and planets with great accuracy.

Brahe developed his own techniques and instruments. He used these to examine the night sky.

The heavens had changedAfter 10 years of studying the heavens, he was shocked one night to see a new bright star in the sky.

He was able to prove that this new star was beyond the Moon. Everyone had thought this area of stars never changed.

But the heavens had changed, and Brahe had observed and recorded it for science.

This discovery made Brahe famous and impressed the Danish king. With help from the king, he built the most advanced observatory in the world. It was called “Uraniborg,” Fortress of the Sky.

At this new observatory, Brahe spotted a comet. He proved that the comet was not in our atmosphere. This meant that the planets could not be attached to crystal spheres after all.

Johannes Kepler was one of Brahe's most famous students. Kepler used Brahe’s detailed observations to develop his own Laws of Planetary Motion. In this way, we can think of Brahe’s discoveries like a set of building blocks. They led us to discover that the cosmos is changing.


Science, Theology, & Copernican RevolutionWhy is there such resistance to science by so many religious believers? It is partly because faith has always been closely tied to a particular age’s picture of the natural world.

Science, Theology and the Copernican Revolution (1340L)By John F. Haught

At the beginning of the scientific age, people were not only intellectually shocked but also spiritually threatened by the news that the Sun was being asked to exchange places with the Earth. In 1612, the devout Anglican poet John Donne wrote these anguished lines in his poem “Anatomy of the World”:

And new philosophy calls all in doubt,

The element of fire is quite put out;

The sun is lost, and th’ earth, and no man’s wit

Can well direct him where to look for it

’Tis all in pieces, all coherence gone; (lines 205–208, 213)

The “new philosophy” that Donne refers to — since there was no word for “science” at the time — is the Copernican revolution. In 1610, two years before Donne’s poem appeared, Galileo Galilei (1564–1642) had published the world’s first scientific bestseller, The Starry Messenger. This revolutionary work argued that the heavens are not organized the way astronomers, philosophers, and theologians had taught for ages. As far as Donne was concerned, however, Galileo’s ideas threatened not only the entrenched cosmology of Plato, Aristotle, and Ptolemy but also the religious sensibilities associated for centuries with an Earth-centered (geocentric) vision of nature.

In 1543, the Polish astronomer and cleric Nicolaus Copernicus had already proposed that movements in the skies could be predicted more accurately than before if one supposes that the Earth and other planets revolve around the Sun. However, prior to Galileo’s release of The Starry Messenger, Copernicus’s new model of the heavens seemed little more than an abstract mathematical scheme for making astronomical predictions. Those who read Copernicus’s work often took it simply as an experiment in thought rather than a realistic representation of the heavens and Earth. For Galileo, on the other hand, the Copernican system was not a mental exercise but an approximation of the way the heavens really do hang together.

In his later and more controversial work, Dialogue of the Two Chief World Systems, Galileo could scarcely conceal his growing conviction that the Copernican universe must now replace the Ptolemaic one. His increasingly bold teachings and writings eventually led, in


1633, to the Catholic Church’s notorious condemnation of Galileo’s new science and to his being put under house arrest until his death in 1642.

The Church now regrets its mistake and insists that there can be no genuine conflict between science and faith. However, in the seventeenth century, Donne and many of his contemporaries interpreted the new science as a great threat to spiritual as well as intellectual life: “’Tis all in pieces, all coherence gone,” the poet worried, expressing a kind of religious anxiety that still occurs among many people of faith when they hear about new scientific discoveries.

A crossroads for science and theologyWhy is there such fierce resistance to science by so many religious believers? It is partly because faith, theology, and spirituality have always been closely tied to a particular age’s picture of the natural world. In biblical times, for example, the religious drama of salvation assumed a three-level picture of the cosmos: the heavens fixed firmly above; the Earth beneath; and then, lower still, the underworld (Sheol), the dwelling place of the dead. In the seventeenth century, most religious believers took the biblical portrait of nature literally. Certain passages in the Bible insinuated that the Sun moves and the Earth stands still. Thus, the Bible seemed to support the Ptolemaic picture of the Universe, while Copernican astronomy seemed to contradict God’s word.

Galileo’s opinion, however, was that the Bible should not be read as a source of scientific information, a position that the Catholic Church now officially accepts. The Bible has nothing to contribute to any knowledge that human beings can gather on their own, that is, with their own natural powers of observation and mathematical reasoning. Galileo continued to believe that the Bible was inspired literature, but he cautioned that people miss the religious meaning of Scripture whenever they treat it as a source of scientific truths.

In his Letter to the Grand Duchess Christina, Galileo claimed the support of the renowned early Christian writer Augustine of Hippo (354–430 CE). Augustine had pointed out that Christian instruction should not insist that converts to Christianity take the cosmology of the Bible literally. To do so would only prevent those who can’t accept the literal cosmology from taking the religious meaning seriously in the Scriptures.

Some historians and scientists have assumed wrongly that Galileo’s clash with his Church means that he saw a conflict between science and faith. However, he never thought of his observations and ideas as contrary to the basic teachings of his faith. For him science has little or nothing to do with theology. Nonetheless, the case of Galileo and the entire Copernican revolution, as Donne’s poem indicates, did have implications for human spirituality.

“Spirituality” is the quest for a vision of reality that will give people courage, hope, and some degree of happiness in the midst of life’s inevitable tribulations. For centuries, Ptolemaic astronomy had provided a framework for spiritual inspiration. For most people, the skies held visible hints of a better world. The perfectly circular movement of heavenly bodies and the faultless spherical geometry of the Sun and Moon, for example, offered at least a hint of the infinite beauty that seemed to lie beyond our shadowy and perishable world.


The new science, however, seemed to call all of this “in doubt,” as Donne puts it. With the more precise astronomical measurements by Copernicus, Brahe, Kepler, and Galileo, the heavens were undergoing a series of demotions that dimmed their luster. Consequently, the Copernican revolution produced a massive upheaval not only in science but also in spiritual life.

The final blowAncient astronomy, philosophy, and theology had all assumed that the superlunary world — the world beyond the orbit of the moon — is special. Above the Moon’s orbit the heavens seemed immune to change, novelty, and collapse. Their immutability pointed both minds and hearts toward a better and more permanent world than that which existed on Earth. Aristotle (384–322 BCE) had even portrayed the heavens as a “quintessential” (fifth) kind of reality far surpassing in value the four mundane elements (earth, air, fire, and water) that make up the sublunary world “down here.” In contrast to imperfect earthly things that change and eventually perish, the heavens seemed to mirror the changeless eternity of God.

Modern astronomy, however, gradually robbed the heavens of their transparency to God — at least for many thoughtful people like Donne. Tycho Brahe (1546–1601), for example, demonstrated to his shocked contemporaries that comets and supernovae — both implying change and novelty — existed beyond, rather than beneath, the Moon’s orbit. Thus the superlunary heavenly vault showed itself to be imperfect after all and could no longer adequately represent the unchanging perfection of God. Johannes Kepler (1571–1630), moreover, calculated that planets move in “ugly” elliptical patterns rather than perfectly circular orbits. Careful new observations increasingly demonstrated that the heavens, like things on Earth, are ordinary after all.

It was left to Galileo, however, to deliver the decisive insult to the heavens, although even he still believed that celestial orbits were perfectly circular. His lively writings delivered the news that the Moon is pocked with craters, Venus goes through phases, Jupiter has satellites, and the Sun is blemished with dark spots.

Finding perfection in changeGalileo’s view of the Copernican model was both simple and profound. What is so great, he asked, about changelessness? And what is so bad about the dirty, changing Earth that we inhabit? Look carefully at what lies beneath our feet and not just over our heads! If the total amount of dirt on Earth were as small as the tiny amount of precious jewels, what ruler or king would not gladly exchange all his diamonds for just enough dirt to bring forth a tangerine or jasmine tree?

Isn’t life, in other words, a much richer symbol of perfection than the mistaken idea of changeless heavens could ever be? Little did Galileo know, however, of the remarkably tight narrative connection that astronomy and astrophysics would eventually draw between the existence of life and the seemingly unchanging and impersonal heavens.


Science, Theology and the Copernican Revolution (1100L)By John Haught, adapted by Newsela

At the beginning of the scientific age, people were shocked by the news that the Sun and the Earth were switching places. Not only that, they felt spiritually threatened by the news.

In 1612, poet John Donne, who was a devout Christian, wrote these lines:





’Tis all in pieces, all coherence gone;

The “new philosophy” that Donne refers to is the Copernican Revolution. There was no word for “science” at the time.

Two years before Donne wrote those words, Galileo Galilei had published the world’s first scientific bestseller, The Starry Messenger. This revolutionary book argued that the heavens were different than everyone had thought.

Polish astronomer Nicolaus Copernicus had pointed out that movements in the sky could be predicted more easily if you assumed that the Earth revolved around the Sun. But people at the time accepted this as a thought experiment — not the way things actually were.

For Galileo, on the other hand, the Copernican system was not a mental exercise, but a description of the way things really worked.

After Galileo published his later and more controversial work, Dialogue of the Two Chief World Systems, the Catholic Church famously condemned him. He lived under house arrest until his death in 1642.

The Church now regrets its mistake and insists that there is no genuine conflict between science and faith. However, people like Donne in the seventeenth century certainly felt that science was a threat to their spiritual life. This anxiety still occurs among many people of faith when they hear about new scientific discoveries.

A crossroads for science and theologyWhy is there such fierce resistance to science by so many religious believers?

It is partly because religion often gives us a picture of the natural world. For example, in biblical times, people assumed a three-level picture of the cosmos: the heavens fixed firmly above; the Earth beneath; and then, lower still, the underworld, the dwelling place of the dead.

In the seventeenth century, most religious believers took the biblical portrait of nature literally. Certain Bible passages implied that the Sun moves and the Earth stands still. The


Bible seemed to support the Ptolemaic picture of the Universe, while Copernican astronomy seemed to contradict God’s word.

Galileo believed, however, that the Bible should not be read as a source of scientific information. The Catholic Church now officially accepts this position. Galileo still believed the Bible was inspired literature, but he warned people that they miss the religious meanings when they treat the text as a source of scientific truths.

Some historians and scientists have assumed wrongly that Galileo’s clash with his Church means that he saw a conflict between science and faith. However, he never thought of his observations and ideas as contrary to the basic teachings of his faith. For him, science has little or nothing to do with theology.

But the case of Galileo and the Copernican revolution did have implications for human spirituality.

“Spirituality” is the quest for a vision of reality that will give people courage, hope, and some degree of happiness in the midst of life’s inevitable tribulations.

For centuries, Ptolemy’s worldview had provided a framework for spiritual inspiration. The skies held visible hints of a better world.

The perfectly circular orbits of the planets and the perfect spheres of the Sun and Moon seemed to offer a hint of the infinite beauty that lies beyond our shadowy and temporary world.

All this was in doubt, though, thanks to the new science. Copernicus, Brahe, Kepler, and Galileo were making more accurate astronomical measurements. They were finding that the heavens were not so “perfect” after all.

Their findings caused a massive change not only in science, but also in spiritual life.

The final blowAncient astronomy, philosophy, and religion had assumed that the skies beyond the Moon were special. The heavens above the Moon seemed unchangeable, indestructible.

Because the skies above seemed to be unchanging, they pointed both hearts and minds toward a better and more permanent world than the one on Earth.

Aristotle had called the heavens a fifth kind of reality, better than the four common elements (earth, air, fire and water) that made up the world “down here.” In contrast to imperfect earthly things that change and eventually perish, the heavens seemed to mirror the changeless eternity of God.

Modern astronomy gradually robbed the heavens of their perfection, and their transparency to God.

Tycho Brahe (1546–1601), for example, shocked people by showing that comets and supernovae existed beyond the Moon. Both of these show change and newness in an area that was thought to be perfectly stable.


Now the sky above showed itself to be imperfect after all. It could no longer adequately represent the unchanging perfection of God.

Johannes Kepler (1571–1630), moreover, calculated that planets move in “ugly” elliptical (oval) patterns rather than perfectly circular orbits. Careful new observations increasingly demonstrated that the heavens, like things on Earth, are ordinary after all.

Galileo, though, delivered the final insults to the idea of perfection in space. He spread the news that the Moon is covered with craters, Jupiter has satellites, and the Sun has dark spots on it.

Finding perfection in changeGalileo’s view of the Copernican model was both simple and profound. What is so great, he asked, about changelessness? And what is so bad about the dirty, changing Earth that we inhabit? Look carefully at what lies beneath our feet and not just over our heads!

Isn’t life, in other words, a much richer symbol of perfection than the mistaken idea of changeless heavens could ever be?


At the beginning of the scientific age, people were shocked that the Sun and the Earth were switching places. Not only that, they felt spiritually threatened by the news.

In 1612, poet John Donne, a committed Christian, wrote these lines:





’Tis all in pieces, all coherence gone;

The “new philosophy” that Donne refers to is the Copernican Revolution and science in general. Though there was no word for “science” at the time.

Donne wrote those words two years after Galileo Galilei had published The Starry Messenger. This bestselling book changed long-held views about the skies above.

Polish astronomer Nicolaus Copernicus had imagined a world where the Earth revolves around the Sun. But people at the time just thought he was doing a thought experiment.

For Galileo, on the other hand, the Copernican system was not a mental exercise, but a description of the way things really worked.

The Catholic Church famously called Galileo wrong and sentenced him to the rest of his life under house arrest.


The Church now regrets its mistake and insists that there is no real conflict between science and faith. However, people like Donne in the seventeenth century certainly felt that science was a threat to their spiritual life. This anxiety still occurs among many religious people when they hear about new scientific discoveries.

A crossroads for science and theologyWhy is there such fierce resistance to science by so many religious believers?

It is partly because religion often gives us a picture of the natural world. Science can disrupt this.

For example, in biblical times, people thought of the cosmos in three levels: the heavens above, never moving; the Earth beneath; and lower still, the underworld, the land of the dead.

In the seventeenth century, most religious believers took the biblical picture of nature literally. Certain Bible passages implied that the Sun moves and the Earth stands still.

The Bible seemed to support the Ptolemaic picture of the Universe, while Copernican astronomy seemed to contradict God’s word.

Galileo believed, however, that the Bible should not be read as a source of scientific information. The Catholic Church now officially accepts this position. Galileo still believed the Bible was special, but he said that people missed the religious meanings when they treated it as a source of scientific truths.

Some historians and scientists have assumed that Galileo’s fight with his Church means that he saw a conflict between science and faith. This is not true. For him science has little or nothing to do with religion.

But the discoveries of Copernicus and Galileo did have consequences for human spirituality.

“Spirituality” is the quest for a vision of reality that will give people courage, hope, and some degree of happiness in the midst of life’s inevitable tribulations.

For centuries, people had taken comfort in Ptolemy’s view of an ordered and regular universe.

In this view, planets orbited on perfectly circular paths. The Sun and Moon were perfect spheres. This perfection seemed to offer a hint of the infinite beauty that lies beyond our shadowy and temporary world.

The new science put this all in doubt. Copernicus, Brahe, Kepler, and Galileo were making more accurate astronomical measurements. They found that the heavens were not so “perfect” after all.

Their findings caused a massive change not only in science, but also in spiritual life.


The final blowAncient astronomy, philosophy, and religion had all assumed that the skies past the Moon were special. The heavens above the Moon seemed unchangeable, indestructible.

Because the skies above seemed to be unchanging, they pointed hearts and minds toward a better and more permanent world than the one on Earth.

Aristotle had called the heavens a fifth kind of reality, better than the four common elements (earth, air, fire and water) that made up the world “down here.” While things on Earth change and eventually die, the heavens seemed to mirror the changeless eternity of God.

Modern astronomy gradually robbed the heavens of their perfection, and their connection to God.

Tycho Brahe, for example, shocked people by showing that comets and supernovae existed beyond the Moon. Both of these show change and newness in an area that was thought to be perfectly stable.

Now the sky above was imperfect after all. It could no longer represent the unchanging perfection of God.

Other scientists also helped to destroy the image of the heavens as perfect and unchanging. Johannes Kepler showed that planets’ orbits are not perfect circles. Rather, they travel in oval-like elliptical patterns. Galileo discovered that the Moon is covered with craters. He found Jupiter has satellites and the Sun has dark spots on it.

Careful new observations increasingly demonstrated that the heavens, like things on Earth, are ordinary after all.

Finding perfection in changeGalileo was not bothered by these imperfections. What is so great about changelessness? he asked. And what is so bad about the dirty, changing Earth that we inhabit? Look carefully at what lies beneath our feet and not just over our heads!

Isn’t life, in other words, a much richer symbol of perfection than the mistaken idea of changeless heavens could ever be?


When Galileo announced that the Sun was at the center of our Solar System, people were shocked. Many people felt the news contradicted their religious beliefs.

Poet John Donne was a committed Christian. He wrote these lines in 1612:


The element of fire is quite put out...


The “new philosophy” Donne mentions is science. Donne wrote those words two years after Galileo Galilei published The Starry Messenger. In this book, Galileo presented a world that was very different than what people had believed.

Copernicus had thought about the Earth revolving around the Sun. At the time, though, people thought he was just doing a thought experiment. Galileo knew that this was how the world really worked.

The Catholic Church famously called Galileo wrong. It forced him to spend the rest of his life confined to his house.

The Church now regrets its mistake. It insists there is no real conflict between science and faith. However, for many religious people, new scientific discoveries can bring worry.

A crossroads for science and theologyWhy do so many religious believers seem to be against science? It is partly because religion paints a picture of the natural world. Science can disturb this picture.

For example, in biblical times, people thought of the Universe in three levels. First were the heavens above. They were perfect and unchanging. Below the heavens was the Earth. Below the Earth was the underworld, the land of the dead.

In the 1600s, most religious believers took the Bible word for word. It seemed to support the idea that Earth was at the center of the Universe. So had Ptolemy and Aristotle. Galileo and Copernicus seemed to be going against the Bible.

Galileo believed the Bible was special. But he didn't think it should be read for scientific information. The Catholic Church now agrees with him.

Some assume that because Galileo argued with the Church, he saw a conflict between science and faith. This is not true. For him, science and religion were almost completely separate.

But the discoveries of Copernicus and Galileo did affect spirituality.

Life has unavoidable difficulties. "Spirituality” is what gives people courage, hope, and happiness to face those difficulties. For centuries, people were comforted by Ptolemy’s view of an orderly Universe.

In this view, planets traveled on perfectly circular paths. The Sun and Moon were perfect spheres. In this perfection, people saw a hint of the unending beauty that lies beyond our world.

The new science put this all in doubt. Copernicus, Brahe, Kepler, and Galileo were making new astronomical measurements. Their findings showed the heavens were not so “perfect” after all.

Their discoveries greatly changed spiritual life.


The final blowIn ancient astronomy, philosophy and religion, the skies beyond the Moon were special. They seemed unchanging, indestructible. The skies above seemed permanent and perfect. They pointed to a better and more permanent world than the one here on Earth.

Aristotle called the heavens a fifth kind of reality. The heavens were better than the four common elements down here — earth, air, fire and water. While all things on Earth change and eventually die, the heavens showed the unchanging, never-ending nature of God.

Modern astronomy gradually showed that the heavens weren’t perfect. They weren’t a reflection of a perfect God anymore.

Other scientists helped to end the idea that the heavens are perfect and unchanging. Johannes Kepler showed that planets move in oval patterns. Previously, people thought they moved in perfect circles. Tycho Brahe showed that comets and exploding stars were out beyond the Moon. He shocked people by showing changing heavens. Galileo showed that the Moon is covered with craters. He pointed out that the Sun has dark spots on it.

Careful observation showed that the heavens are ordinary after all.

Finding perfection in changeGalileo was religious, but he was not bothered by these imperfections. What’s so great about not changing, he asked. And what is so bad about the dirty, changing Earth where we live? Look carefully at what lies beneath our feet and not just over our heads!

Isn’t life a better symbol of perfection than changeless heavens could ever be?


The Vatican ObservatoryEquipped with one of the world’s oldest telescopes, the Catholic Church has sought to answer a question of interest to people of all faiths: How did this Universe come to be?

The Vatican Observatory: At the Intersection of Faith and Science (1330L)By Michelle Feder

Every summer, the pope leaves the heat of Rome and heads to his vacation home at Castel Gandolfo, in the Alban hills. The sixteenth century monastery sits on a high ridge, a perfect spot to view and reflect upon the heavens.

Castel Gandolfo serves as the main headquarters for the Vatican Observatory, one of the oldest astronomical institutes in the world. It operates under the jurisdiction of the pope and the Roman Catholic Church.

Since 1891, when the observatory was founded, the pope’s astronomers have used it to study the night sky. Equipped with one of the world’s oldest telescopes, they have applied their scientific expertise to fundamental questions that engage people of all faiths: How did this Universe come to be, and what is our place in it?

For more than a century, this research center has been a bridge between theology and science. In addition to the telescopes, private rooms, working quarters, and kitchen, the facility at Castel Gandolfo has a museum of meteorites and two large libraries containing more than 22,000 volumes, including historic works by Copernicus, Galileo, Newton, and Kepler. Every summer, the astronomers at the observatory update the pope about their work.

Father George Coyne, who was appointed director of the Vatican Observatory by Pope John Paul I in 1978, remembers well his early experiences at the Vatican Observatory. He recalls the excitement of observing the stars from the telescopes inside Gandolfo’s notable domes, and the satisfaction that came from doing “good science” while serving the Church. “Science is an attempt to explain natural events by natural causes,” says Coyne. “The Church has a serious interest in understanding the Universe and everything in it.” But in his view, “True science, good science, does not conflict with religious belief.”

Roots in controversyThe relationship between the papacy and astronomy has not always been so smooth. Earlier Christian astronomers may have tried to detect which wandering star or supernova led three wise men to a stable in Bethlehem — the birthplace of Jesus Christ. More precisely, papal interest in stargazing can be traced to more than four centuries ago, when Pope Gregory XIII


(papal reign 1572–1585) set up a committee to examine the implications for science related to the pope’s 1582 reform of the calendar.

Enter Italian astronomer Galileo Galilei (1564–1642), whom Albert Einstein called “the father of modern science.” Using observational evidence, Galileo challenged the teachings of the past. In 1609 and 1610, Galileo used a telescope of his own design to see the surface of the Moon, the phases of Venus, and the moons of Jupiter, compiling strong evidence for Copernicus’s Sun-centered theory (Farndon, 2007). Galileo, who was born and educated in Pisa, first visited Rome in March 1611 to demonstrate the power of the telescope to Church officials.

Galileo suggested that his studies supported the theories of Polish mathematician and scholar Nicolaus Copernicus (1473–1543). It was Copernicus who theorized — a century before Galileo — that the Earth moved around the Sun, and not vice versa.

But the Catholic Church, which backed the Earth-centered, geocentric teachings of Aristotle and Ptolemy, was not accepting of these new ideas. The Church was already dealing with the Reformation, a movement that challenged the authority of the pope and the Catholic Church in Rome. In 1542, the Church began the Inquisition, an organization that made decisions on questions of morality and faith. It analyzed books and individuals to determine if what they said agreed with the Bible. Some people were sentenced to death for airing their beliefs.

The Inquisition found Galileo’s writings of an Earth in motion around the Sun heretical and incorrect, and banned the teaching of Copernicus’s theories. Galileo was forced to renounce his approval of the Copernican heliocentric model. In 1633, he was convicted of heresy for defending that model and placed under a life sentence of house arrest. He died on January 8, 1642, still in confinement.

Dedication to discoveryNevertheless, the Church has, since Galileo’s time, expressed an interest in astronomical research. Three early observatories were founded by the papacy: the Observatory of the Roman College (1774– 1878); the Observatory of the Capitol (1827–1870); and the first incarnation of the Vatican Observatory (1789–1821), housed in a building called the Tower of the Winds that still exists within the Vatican.

A breakthrough came in the mid-nineteenth century with research conducted at the Roman College by Father Angelo Secchi. He was the first to classify stars according to their spectra, the color of light that stars emit. Modern spectroscopy is very important in astronomy today because scientists know that different elements have their own emission spectra, and can contribute to the “chemical signature” that a star’s light reveals.

On March 14, 1891, Pope Leo XIII (papal reign 1878–1903), in an attempt to counter the persistent perception of hostility by the Church toward science, set up another small astronomical observatory on a hill behind the dome of Saint Peter’s Basilica.

In 1910, Pope Pius X (papal reign 1903–1914) gave the observatory a new, larger space at a villa built in the Vatican Gardens by Leo XIII. From 1914 to 1928, the observatory


contributed to the Astrographic Catalogue, an ambitious map of the sky that was undertaken in conjunction with 17 observatories around the world. The Vatican printed 10 volumes, which listed the brightness and positions of 481,215 stars.

By the 1930s, however, light pollution from the city of Rome prevented the study of the fainter stars and galaxies. Pope Pius XI (papal reign 1922–1939) relocated the observatory to Castel Gandolfo and put it in the hands of Jesuits; three new telescopes were constructed, an astrophysical laboratory for spectral analysis of the light from distant celestial bodies was installed, and research programs began on Cepheid variables. A Schmidt wide-angle telescope, installed in 1957, allowed for further work on the classification of stars.

Advances in researchThe telescopes at Castel Gandolfo are rarely used anymore for astronomical research, reserved instead for visiting groups and summer-school students. All serious study is performed using other telescopes around the world, mainly in Arizona.

Father Coyne helped establish the Vatican Observatory Research Group (VORG) in Tucson, Arizona. Problems with nighttime viewing conditions around Rome spurred the need for this mountaintop institute, founded in 1981. In 1993, the observatory completed the construction of the Vatican Advanced Technology Telescope (VATT) on Mount Graham, Arizona; its optical mirrors are among the most exact surfaces ever made for a ground-based telescope. And the telescope’s observational abilities are augmented by the skies above — some of the clearest and darkest in North America.

The observatory’s 15 staff members collaborate with astronomical research institutes in countries around the globe, and as members of the International Astronomical Union and the International Center for Relativistic Astrophysics.

“The first priority of the Vatican Observatory is scientific research, and the VATT is our tool,” said VORG director Jose G. Funes at a February 2009 research seminar at the University of Arizona. “We are priests and religious men, but we also are scientists …Astronomy is our main service to the church” (Stiles, 2009).

New points of viewOn the evening of September 16, 2009, Pope Benedict XVI inaugurated the new facility of the Vatican Observatory with a prayer and blessing. The facility includes two floors in a renovated building on the grounds of the Pontifical Villas of Gandolfo, and has a library, conference room, offices, guest quarters, laboratory, and chapel (Vatican Observatory Newsletter, Fall 2009, p. 1). The unveiling took place in what was dubbed the “International Year of Astronomy,” which honored Galileo’s first scientific use of the telescope 400 years prior.

The subject of Galileo has remained a tricky one for the Church throughout the years. In 1992, Pope John Paul II (papal reign 1978–2005) expressed regret at the way Galileo had been treated, stating, “The error of the theologians of the time, when they maintained the


centrality of the Earth, was to think that our understanding of the physical world’s structure was, in some way, imposed by the literal sense of sacred Scripture.” (BBC News, 2008).

Father Coyne, who ran the Vatican Observatory throughout Pope John Paul II’s reign, says, “The Church is a human institution, and a human institution can make, and has made, mistakes.” In the 1600s, Coyne says, the Church believed that Galileo contradicted Scripture. “We can’t judge by the modern day what happened 300 to 400 years ago,” Coyne continues. “We do have to say the Church was wrong in thinking Scripture teaches science … The Church now knows that.”

Such thinking didn’t change overnight. The sense and sensibility of the appropriate relationship between faith and reason, science and Scripture, has evolved over time. Each pope’s approach may yield subtle shifts. In 1998, Pope John Paul II wrote in an official letter:

Faith and reason are like two wings on which the human spirit rises to the contemplation of truth; and God has placed in the human heart a desire to know the truth — in a word, to know himself — so that, by knowing and loving God, men and women may also come to the fullness of truth about themselves.

Near the end of the same letter, he said:

I cannot fail to address a word to scientists, whose research offers an ever greater knowledge of the Universe as a whole and of the incredibly rich array of its component parts, animate and inanimate, with their complex atomic and molecular structures. So far has science come, especially in this century, that its achievements never cease to amaze us. In expressing my admiration and in offering encouragement to these brave pioneers of scientific research, to whom humanity owes so much of its current development, I would urge them to continue their efforts without ever abandoning the sapiential horizon within which scientific and technological achievements are wedded to the philosophical and ethical values which are the distinctive and indelible mark of the human person.

But the papal understanding of the right rapport between reason and faith is still emerging. In January 2008, Pope Benedict XVI (papal reign 2005–2013) canceled a visit to a university in Rome where lecturers and students had protested against his views on Galileo. The university’s rector cited Benedict’s 1990 statement, when, as Cardinal Ratzinger, he said the Church’s verdict against Galileo had been “rational and just.”

However, in 2009 Pope Benedict XVI dedicated a plaque that attests to the “Church’s steadfast support for the work of the observatory at the nexus of faith and science.” Father Coyne emphasizes that Galileo paved the way for a harmonious relationship between religious belief and scientific inquiry. “Galileo anticipated by four centuries what the Church would finally say about the interpretation of Scripture,” he says. “Galileo said that Scripture was written to teach us how to go to heaven, not how the heavens go.”

And Galileo never turned away from the faith that had sentenced him. “[He] was a devout Catholic and was not trying to start a conflict between science and religion,” writes Rachel Hilliam in Galileo Galilei: Father of Modern Science. “He believed that the Bible was there to instruct people in how to get to heaven and was not meant to be a scientific book explaining how the Universe worked” (p. 78) His recantation, or confession, on June 22, 1633, “did not


include two points because Galileo was opposed to them: that he was not a good Catholic and that he had deceived others by publishing his book” (p. 79).

Coyne believes faith and science complement each other. He says, “Faith is: ‘God loves me.’ I accept God’s love. I try to return that love to God each day.” At the same time, he notes, “We are human beings. Science is instrumental to improving our knowledge of the Universe. But we will never have the final answer.”

The Vatican Observatory: At the Intersection of Faith and Science (1100L)By Michelle Feder, adapted by Newsela

Every summer, the pope leaves the heat of Rome and heads to his vacation home at Castel Gandolfo, in the Alban hills, overlooking Lake Albano. The sixteenth century monastery sits on a high ridge, a perfect spot to view and reflect upon the heavens.

Castel Gandolfo is the main headquarters for the Vatican Observatory, one of the oldest astronomical institutes in the world. It is run by the pope and the Roman Catholic Church.

Since 1891, when the observatory was founded, the pope’s astronomers have used it to study the night sky. Equipped with one of the world’s oldest telescopes, they have applied their scientific expertise to fundamental questions that engage people of all faiths: How did this Universe come to be, and what is our place in it?

For more than a century, this research center has been a bridge between theology and science. Castel Gandolfo has a museum of meteorites and two large libraries containing more than 22,000 volumes, including historic works by Copernicus, Galileo, Newton, and Kepler. Every summer, the astronomers at the observatory update the pope about their work.

Father George Coyne was appointed director of the Vatican Observatory by Pope John Paul I in 1978. He recalls the satisfaction that comes from doing “good science” while serving the church.

“Science is an attempt to explain natural events by natural causes,” says Coyne. “The Church has a serious interest in understanding the Universe and everything in it.”

In his view, “True science, good science, does not conflict with religious belief.”

Roots in controversyThe relationship between the popes and astronomy has not always been so smooth.

In the sixteenth century, Pope Gregory XIII reformed the calendar and set up a committee to examine the implications for science.

Enter Italian astronomer Galileo Galilei, whom Albert Einstein called “the father of modern science.” Using observational evidence, Galileo challenged the teachings of the past.


In 1609 and 1610, Galileo used a telescope of his own design to see the surface of the Moon, the phases of Venus, and the moons of Jupiter. These were all strong evidence for Copernicus’s Sun-centered theory.

Galileo suggested that his studies supported the theories of Polish mathematician and scholar Nicolaus Copernicus. Copernicus had theorized — a century before Galileo — that the Earth moved around the Sun, and not vice versa.

But the Catholic Church, which backed the Earth-centered, geocentric teachings of Aristotle and Ptolemy, was not accepting of these new ideas.

The Church was already dealing with the Reformation, a movement that challenged the authority of the pope and the Catholic Church in Rome. In 1542, the Church began the Inquisition, an organization that made decisions on questions of morality and faith. It analyzed books and individuals to determine if what they said agreed with the Bible. Some people were sentenced to death for their beliefs.

The Inquisition found Galileo’s writings of an Earth in motion around the Sun heretical and incorrect, and banned the teaching of Copernicus’s theories. Galileo was forced to take back his approval of the Copernican heliocentric model. In 1633, he was convicted of heresy for defending that model and placed under a life sentence of house arrest. He died on January 8, 1642, still in confinement.

Dedication to discoveryNevertheless, the Church has, since Galileo’s time, expressed an interest in astronomical research. Three different observatories were founded by popes in the eighteenth and nineteenth centuries.

Vatican astronomers made a major breakthrough in the mid-nineteenth century. Father Angelo Secchi was the first to classify stars according to their spectra, the color of light they emit. Modern spectroscopy is very important in astronomy today because scientists know that different elements have their own emission spectra, and can contribute to the “chemical signature” that a star’s light reveals.

Today’s Vatican Observatory traces its roots back to 1891 when Pope Leo XIII set up a small observatory on the Vatican grounds. In 1910, Pope Pius X gave the observatory a new, larger space.

From 1914 to 1928, the observatory contributed to the Astrographic Catalogue, an ambitious map of the sky that was undertaken in conjunction with 17 observatories around the world.

By the 1930s, light pollution from Rome prevented the study of the fainter stars and galaxies. Pope Pius XI moved the observatory to Castel Gandolfo. Three new telescopes were constructed, an astrophysical laboratory was installed, and research programs began on Cepheid variable stars.


Advances in researchThe telescopes at Castel Gandolfo are rarely used anymore for astronomical research. They are reserved instead for visiting groups and summer-school students. All serious study is performed using other telescopes around the world, mainly in Arizona.

Father Coyne helped establish the Vatican Observatory Research Group (VORG) in Tucson, Arizona. Problems with nighttime viewing conditions around Rome created the need for this mountaintop institute, founded in 1981.

In 1993, the observatory completed construction of a state-of-the-art telescope. The Vatican Advanced Technology Telescope (VATT) has optical mirrors that are among the most exact surfaces ever made for a ground-based telescope.

The skies above Arizona are dark and clear, making the telescope even more useful.

The observatory’s 15 staff members work with astronomers around the world.

“The first priority of the Vatican Observatory is scientific research, and the VATT is our tool,” said VORG director Jose G. Funes. “We are priests and religious men, but we also are scientists. Astronomy is our main service to the Church.”

New points of viewThe subject of Galileo has remained a tricky one for the Church throughout the years. In 1992, Pope John Paul II expressed regret at the way Galileo had been treated. He said, “The error of the theologians of the time, when they maintained the centrality of the Earth, was to think that our understanding of the physical world’s structure was, in some way, imposed by the literal sense of sacred Scripture.”

Father Coyne, who ran the Vatican Observatory says, “The Church is a human institution, and a human institution can make, and has made, mistakes.”

In the 1600s, Coyne says, the Church believed that Galileo contradicted Scripture. “We can’t judge by the modern day what happened 300 to 400 years ago,” Coyne continues. “We do have to say the Church was wrong in thinking Scripture teaches science. The Church now knows that.”

Such thinking didn’t change overnight. Each pope takes his own approach. In 1998, Pope John Paul II wrote in an official letter: "Faith and reason are like two wings on which the human spirit rises to the contemplation of truth."

But the balance between faith and reason is sometimes difficult for popes to manage.

Pope Benedict XVI was criticized in 2008 for saying the Church’s verdict against Galileo had been “rational and just.”

However, in 2009, Pope Benedict XVI dedicated a plaque that attests to the “Church’s steadfast support for the work of the observatory at the nexus of faith and science.”

Father Coyne emphasizes that Galileo paved the way for a harmonious relationship between religious belief and scientific inquiry.


“Galileo anticipated by four centuries what the Church would finally say about the interpretation of Scripture,” he says. “Galileo said that Scripture was written to teach us how to go to heaven, not how the heavens go.”

And Galileo never turned away from the faith that had sentenced him.

“Galileo was a devout Catholic and was not trying to start a conflict between science and religion,” writes Rachel Hilliam in a book on Galileo. “He believed that the Bible was there to instruct people in how to get to heaven and was not meant to be a scientific book explaining how the Universe worked.”

Coyne believes faith and science complement each other. He says, “Faith is: ‘God loves me.’ I accept God’s love. I try to return that love to God each day.” At the same time, he notes, “We are human beings. Science is instrumental to improving our knowledge of the Universe. But we will never have the final answer.”

The Vatican Observatory: At the Intersection of Faith and Science (950L)By Michelle Feder, adapted by Newsela

When Rome gets too hot in the summer, the pope heads for the hills. The Alban Hills outside of Rome, overlooking scenic Lake Albano, are home to Castel Gandolfo, the pope’s vacation home.

Castel Gandolfo is a sixteenth century monastery that sits on a high ridge, a perfect spot to view and reflect on the heavens. It is the main headquarters of the Vatican Observatory, one of the oldest astronomical institutes in the world. The observatory is run by the Catholic Church.

The pope’s astronomers have been using the observatory to study the night sky since 1891. They have used one of the world’s oldest telescopes and the scientific method to try to answer the fundamental questions of life, the Universe, and everything: How did the Universe begin? What is our place in it?

For more than a century, this research center has been bridging religion and science. Castel Gandolfo has a museum of meteorites. Its two large libraries contain more than 22,000 volumes, including historic works by Copernicus, Galileo, Newton, and Kepler. Every summer, the astronomers at the observatory update the pope on their work.

“Science is an attempt to explain natural events by natural causes,” says Father George Coyne, who directed the observatory. “The Church has a serious interest in understanding the Universe and everything in it.”


A history of controversyToday, popes support astronomy. But in the past, the relationship was not always so smooth.


In the 1600s, Italian astronomer Galileo Galilei challenged the teachings of the past.

Galileo observed the sky and concluded that the Sun was the center of our Solar System.

But the Catholic Church backed the Earth-centered, geocentric teachings of Aristotle and Ptolemy. It did not accept these new ideas.

The Church was already dealing with the Reformation. The Reformation was a movement that challenged the authority of the pope and the Catholic Church in Rome.

In 1542, the Church began the Inquisition, an organization that made decisions on questions of morality and faith.

The Inquisition found Galileo’s writings about the Earth revolving around the Sun heretical and incorrect. They banned his ideas and placed him under a life sentence of house arrest. He died in 1642, still in confinement.

Since Galileo’s time though, the Church has expressed an interest in astronomical research. Popes founded three different observatories in the eighteenth and nineteenth centuries.

Vatican astronomers made a major breakthrough in the mid-nineteenth century. Father Angelo Secchi was the first to classify stars according to their spectra, the color of light they give off. Modern spectroscopy is very important in astronomy today.

Advances in researchThese days the telescopes at Castel Gandolfo are rarely used for astronomical research. They are reserved for visiting groups and summer-school students. All serious study is performed using other telescopes around the world, mainly in Arizona.

The Vatican set up an observatory in Tucson, Arizona, in 1981 after viewing conditions around Rome got worse. The skies above Arizona are particularly dark and clear, making it a perfect place for an observatory.

In 1993, the observatory finished building a state-of-the-art telescope. The Vatican Advanced Technology Telescope has optical mirrors that are cutting edge.

“We are priests and religious men, but we also are scientists. Astronomy is our main service to the Church,” said observatory director Jose G. Funes.

The Church reconsiders GalileoThe subject of Galileo has remained a tricky one for the Church throughout the years. In 1992, Pope John Paul II expressed regret at the way Galileo had been treated.

Later, in an official letter, he called for a balance between faith and reason: “Faith and reason are like two wings on which the human spirit rises to the contemplation of truth.”

But the balance between faith and reason is sometimes difficult for popes to manage.

Pope Benedict XVI was criticized in 2008 for saying the Church’s verdict against Galileo had been “rational and just.”


“Galileo was a devout Catholic and was not trying to start a conflict between science and religion,” writes Rachel Hilliam in a book on Galileo.

The Vatican Observatory: At the Intersection of Faith and Science (720L)

By Michelle Feder, adapted by Newsela

The pope’s vacation home is Castel Gandolfo, outside Rome. This quiet monastery sits on a hill. It is a perfect place to look at and think about the sky.

Castel Gandolfo is also home to the Vatican Observatory. This observatory is one of the oldest in the world. It is run by the Catholic Church. Since 1891, the pope’s astronomers have been using the observatory to study the night sky. They have one of the oldest telescopes in the world.

They hope to use science to answer a question that occurs to all people: How did the Universe begin? What is our place in it?

The Vatican Observatory has been bridging religion and science for more than 100 years. Its library holds more than 22,000 books. It includes historic works by Copernicus, Galileo, Newton, and Kepler. Every summer, the astronomers at the observatory update the pope on their work.

“The Church has a serious interest in understanding the Universe and everything in it,” said Father George Coyne. Father Coyne used to run the Observatory.


A history of controversyToday, the Catholic Church supports astronomy. But in the past, this was not always true. In the 1600s, Italian astronomer Galileo Galilei challenged the teachings of the past. Galileo observed the sky. He concluded that the Sun was the center of our Solar System.

But the Church supported the Earth-centric views of Ptolemy and Aristotle. It did not accept Galileo’s new ideas.

In 1542, the Church began the Inquisition. Authorities in the Church investigated religious questions. The Inquisition found Galileo’s writings about the Earth revolving around the Sun incorrect. They banned his ideas. Galileo himself was punished with house arrest. He died in 1642, still not allowed to leave his house.

Since then though, the Church has supported astronomy. Popes set up three different observatories in the 1700s and 1800s.

Vatican astronomers made a major breakthrough in the mid-1800s. Father Angelo Secchi was the first to sort stars based on their spectra. The spectra were determined by the color of light they give off. Modern spectroscopy is very important in astronomy today.


Moving to ArizonaToday, the telescopes at Castel Gandolfo are rarely used for astronomical research. They are usually used by visiting groups or students. The Vatican’s serious research now takes place in Arizona.

Eventually, the skies around Rome became too bright. The Vatican set up an observatory in Arizona. The skies there are very dark and clear. It's a perfect place for stargazing. The Vatican’s telescope there is cutting-edge.

“We are priests and religious men, but we also are scientists. Astronomy is our main service to the Church,” said observatory director Jose G. Funes.

The Church reconsiders GalileoEven today, the subject of Galileo is tricky for the Church. In 1992, Pope John Paul II showed regret for the way Galileo had been treated. Later, he called for a balance between faith and reason. “Faith and reason are like two wings on which the human spirit rises to the contemplation of truth,” he wrote in a letter.

But the balance between faith and reason is sometimes difficult for popes.

Pope Benedict XVI said in 2008 that the Church’s decision against Galileo made sense. Many did not welcome his remarks.

Rachel Hilliam authored a book on Galileo. She wrote that Galileo never turned away from the Catholic faith. He was "not trying to start a conflict between science and religion,” she wrote. “He believed that the Bible was there to instruct people in how to get to heaven and was not meant to be a scientific book explaining how the Universe worked.”


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