ASTRONOMY TIMELINE

TIME EVENTAncient Astronomy: 2800 B.C. to 1600 A.D.2,800 B.C. First phase of Stonehenge begins, it is used as a solar/lunar

observatory2,000 B.C. Egypt and Mesopotamia build first solar/lunar calendars280 B.C. Greek astronomer, Aristarchus of Samos shows the Earth revolves

around the Sun

240 B.C. Greek mathematician Eratosthenes measures the circumference of theearth

130 B.C. Greek astronomer Hipparchus develops the first accurate star map and star catalogue, and a reliable method to predict solar eclipses

46 B.C. Julius Caesar, after consulting the astronomer Sosigenes of Alexandria,introduces the Julian Calendar, a regular year of 365 days divided into 12 months, and a leap day is added to February every four years

0 A.D. – Start of the Common Era140 Greek astronomer Ptolemy develops geocentric theory of the universe

with Earth at the center

400 – 1200 Pacific Islanders use constellations to travel across the Pacific Ocean1050 Mayan Pyramid of Kukulkan at Chichén Itzá is also used as calendar1054 Chinese astronomers observe supernova in Taurus1120 First astronomical observatory built in Cairo, Egypt1259 Persian astronomer Nasir al-Din al-Tusi builds Iran’s first astronomical

observatory

1420 Astronomer Ulugh Beg builds astronomical observatory built in Samarkand, Central Asia

1543 Polish astronomer Nicolaus Copernicus publishes his heliocentric theory of the Universe

1572 Danish astronomer Tycho Brahe discovers a supernova in constellation of Cassiopeia

1582 Pope Gregory XIII introduces the Gregorian calendar.

Classical Astronomy: 1600 to 1900

1603 German astronomer Johann Bayer publishes his star atlas Uranometria and introduces the Bayer designation of stars

1608 Dutch lensmaker Hans Lippershey invents the first practical telescope1609 Italian astronomer Galileo Galilei uses telescope to discover four

moons of Jupiter, craters of the moon and the Milky Way Galaxy

1609 - 1619 German mathematician and astronomer Johannes Kepler introduces three Laws of Planetary Motion

1610 Galileo Galilei discovers Saturn’s rings1656 Dutch astronomer Christian Huygens discovers Saturn's rings and

the fourth satellite of Saturn Titan1668 English mathematician Sir Isaac Newton builds the first reflecting

telescope

1675 Danish astronomer Ole Romer measures the speed of light1687 English mathematician Sir Isaac Newton publishes Principia

Mathematica1705 British astronomer Edmund Halley predicts the return of the comet

bearing his name

1758 German astronomer Johann Palitzsch confirms Halley’s 1705 prediction

1781 Sir William Herschel discovers Uranus1781 France’s Charles Messier discovers galaxies, nebula and star clusters1801 Italian mathematician and astronomer Giuseppe Piazzi discovers first

asteroid, Ceres

1842 Austrian mathematician and physicist Christian Doppler publishes hiswork on the Doppler Effect

1843 German astronomer Samuel Heinrich Schwabe describes the sunspot cycle

1846 German astronomer Johann Galle discovers Neptune1847 American astronomer Maria Mitchell becomes the first person to

discover acomet using a telescope

1860-63 Sir William Huggins uses spectral analysis of stars1872 American astronomer Henry Draper takes a first ever photograph of

stellar spectrum using the star Vega

1877 American astronomer Asaph Hall discovers Martian moons, Phobos and Deimos

Modern Astronomy: 1900 to Present

1905 Mount Wilson Observatory is built in California1905 German Physicist Albert Einstein introduces special Theory of

Relativity 1908 Danish astronomer Ejnar Hertzsprung describes giant and dwarf stars1908 American astronomer Henrietta Swan Leavitt discovers Cepheid

variables1916 German Physicist Albert Einstein introduces his general Theory of

Relativity1923 American astronomer Edwin Hubble proves other galaxies exist

outside the Milky Way galaxy

1927 Dutch astronomer Jan Oort calculates the center of the Milky Way Galaxy

1930 American astronomer Clyde Tombaugh discovers Pluto1931 American physicist Karl Jansky discovers cosmic radio waves1933 Astrophysicist Fritz Zwicky infers existence of dark matter1937 American electrical engineer Grote Reber builds the first radio

telescope1957 Russians launches man-made satellite Sputnik, 1958 United States launches first U.S. satellite, Explorer 11963 Quasars are detected1973 Astronomers make predictions of Great Attractor 1975 Vera Rubin announces the existence of dark matter 1986 Location of Great Attractor is found1990 Hubble Space Telescope put into orbit1994 Comet Shoemaker-Levy crashes into Jupiter1999 Chandra X-ray Observatory is put into orbit2006 Dark matter observed separate from ordinary matter

ANCIENT ASTRONOMERS AND DEVELOPMENT OF ASTRONOMY

ANCIENT TIMES

a) Stonehenge, on the Salisbury Plain in southern England, was built in stages from about 2800 BC to about 1075 BC to observe the sun and the moon, and thus bring regularity to the builder's calendar.

b) Big Horn Medicine Wheel, an arrangement of rocks resembling a 28-spoke wheel in the Big Horn Mountains of Wyoming, was used as a calendar by the Plains Indians from about 1500-1700 A.D.

c) The Caracol Temple on the Yucatan peninsula is a 1000-year-old astronomical observatory.

THE ASTRONOMY OF GREECE

Greek, astronomy was based on the astronomy of Babylon and Egypt, which was heavily influenced by astrology.

a) Plato (478-347 BC) argued that the reality we see is only a distorted shadow of the perfect ideal form. Further, he taught that the most perfect form was the circle.

b) Aristotle (384-322 BC) suggested two reasons to believe the Earth was round. First, when a ship came over the horizon, the mast was initially visible, then the deck, and then the entire ship. Second, he observed that the Earth's shadow on the moon during a solar eclipse was curved. Only an Earth which was curved could produce this. He also proposed a geocentric (Earth-centered) solar system.

c) Aristarchus (c. 200 BC) proposed a theory that the Earth rotated on its axis and orbited about the sun.

d)  Eratosthenes (c. 200 BC) devised a method for determining the Earth's circumference to within 5 percent of the currently accepted value.

e) Hipparchus (c. 150 BC) discovered precession and made the first catalog of stellar magnitudes.

f)  Ptolemy

1. Claudius Ptolemacus (Ptolemy) (c. 100 AD) lived and worked in the Greek settlement of Alexandria (now Egypt). He ensured survival of Aristotle’s geocentric universe theory by fitting it to a sophisticated mathematical model.

2. Ptolemy found that simple spheres were not enough to account for the motions of the planets. Planets sometimes move faster, sometimes slower, and occasionally appear to slow to a stop and move backward over a period of days or months. This is called retrograde motion. He accounted for this motion by placing the planets on small circles (epicycles) that moved along larger circles (deferents).

3. His work was published in 140 AD in what is now known as the Almagest.

PIONEERS OF ASTRONOMY

a) COPERNICUS

1. Nicolas Copernicus (1473-1543) lived and worked in what is now Poland. Because of his long and abiding relationship with the Christian Church, he hesitated to publish his revolutionary ideas in astronomy, so he distributed an unsigned pamphlet in 1507, which outlined his hypothesis of a heliocentric (sun-centered) solar system.

2. Copernicus worked on his book, De Revolutionibus, over a period of many years. It was published in 1543, when he realized he was dying.

3. The Copernican system explained retrograde motion without epicycles, and was elegant and simple compared to the Ptolemaic system.

b) TYCHO BRAHE

1. Tycho Brahe (1546-1601) was a Danish nobleman. He developed new and better instruments for viewing the stars, sun, moon, and planets. (Telescopes had not yet been invented.)

2. Brahe published his results in what are now called the Rudolphine Tables (after his patron, Holy Roman Emperor Rudolph II). To assist him, he hired other mathematicians and astronomers, including Johann Kepler.

c) KEPLER

1. Johann Kepler (I 571-1630) was born in what is now southern Germany. Ten days before Brahe died, in 1601, he asked that Kepler be made imperial mathematician. Upon Brahe's death, Kepler inherited his records.

2. Using Brahe's tables of the positions of the planets, Kepler was able to deduce his three laws of planetary motion:

The orbits of the planets are ellipses with the sun at one focus. A line from the planet to the sun sweeps over equal area in equal time. A planet's orbital period squared, is proportional to its average distance from the

sun cubed, where P is the period in years, and A is the distance in AU. One AU is the distance from the earth to the sun, and is equal to 93 million miles. A2 =P3

3. Kepler's laws are empirical (based on observations). They do not describe the causes of the motion; they only predict where the planets will be in the future.

d) GALILEO

1. Galileo Galilei (1564-1642) was born in Pisa, Italy. Galileo was the first scientist to make systematic use of the telescope in looking at the heavens.

2. Galileo's discoveries with the telescope include - The moon was not smooth; it had valleys and craters. This conflicted

with the notion that all heavenly bodies were perfect spheres. The Milky Way was made up of thousands of stars too dim to be seen

with the unaided eye. The discovery of Jupiter's moons lent credence to the Copernican

model, as it was now recognized that objects other than the earth could have moons orbiting about them. These Galilean moons are Io, Europa, Ganymede, and Callisto, all satellites of Jupiter.

Galileo later observed that the sun had sunspots and rotated with a period of 25 days.

Galileo saw that Venus passed through phases similar to those of the moon. That meant it orbited around the sun, not the Earth.

3. Galileo published two major works, Sidereus Nuncius and Dialogue Concerning the Two Chief World Systems. The publication of the second of these created a storm of controversy. He was interrogated four times by the Inquisition, and in 1633 he was forced to recant his views of the heavens. Upon recanting, Galileo was put under house arrest until his death in 1642.

e) ISAAC NEWTON

1. Isaac Newton (1642-1727) was born in the English village of Woolsthorpe. In 1665-1666, when Black Plague closed Cambridge where he was studying, he returned to Woolsthorpe, and there derived his famous three laws of motion. These laws of motion were found to work for objects in the heavens, as well as objects on Earth, thereby making Newton the first astrophysicist. His laws of motion are:

A body continues in motion in a straight line at constant speed, or remains at rest, unless it is acted upon by some external force.

A body's change of motion is proportional to the force on it and the direction of the force, F=ma, where F=Force, m=mass, and a=acceleration.

When one body exerts a force on a second, the second body exerts an equal and opposite force upon the first.

2. Newton distinguished between an object's mass, which is how much matter it contains, and its weight. A person who is on the moon is attracted by the moon's gravity less than that same person will be attracted to the Earth by Earth's gravity. That person's mass is the same in both places, but the weight is different. Weight is a force, mass is the amount of matter.

3. Newton determined that for the planets to orbit the sun in elliptical trajectories, they must be subject to a force that decreases proportional to the square of their

distance from the sun. In addition, the force must be proportional to the masses of the sun and the planet. In equation form, this is stated by F=GMm/r(2)

4. In the above formula, F is the mutual force of attraction between the planets, G is the universal gravitational constant, 6.67X10-11m2/kg s2, r is the distance between the sun and the planet, M is the mass of the sun, and m is the mass of the planet. This is the Law of Universal Gravitation because we can extend this equation to any two objects, in the universe. For example 'M' could be the mass of Jupiter, while 'm’ could be the mass of its satellite Europa. Therefore all massive objects are gravitationally attracted to all other massive objects in the universe.

ASTRONOMY AND SPACE TIMELINE

1. Approximately 15 Billion Years Ago: - The Big Bang occurred an estimated 15 billion years ago. The universe began

with a cataclysm that created space and time, as well as all the matter and energy the universe will ever hold.

2. Immediately After The Big Bang: - One millionth of a second after the Big Bang, the universe continued to expand

but not nearly as quickly. It became less dense and cooler. Gravity emerges. Matter forms. Building block particles of quarks, leptons, photons, and neutrinos, form. The universe is now about the size of a melon. Quarks combine to form protons and neutrons. Protons and neutrons form the nuclei of all atoms. Protons and neutrons combine to form the atomic nuclei of  hydrogen, helium and lithium.

3. 10,000 Years After The Big Bang: Radiation Era: - Most energy was in the form of radiation -- different wavelengths of light, X rays,

radio waves and ultraviolet rays. As the universe expanded, these waves of radiation were stretched and diluted.

4. 300,000 Years After The Big Bang: Matter Domination Era: - The average temperature had cooled to a mere 5000 degrees Fahrenheit. The

energy in matter and the energy in radiation were equal. But as the universe continued to expand, the effects of the stretching of the light waves continued driving them into lower and lower energy, while the matter continued outward largely unaffected. Electrons could now remain in orbit around atomic nuclei. These hydrogen and helium atoms would eventually form the fuel for the stars.

5. 300,000,000 Years After The Big Bang: Stars and Galaxies Form: - The force of gravity began to affect the irregularities in the density of the gaseous

matter. As the universe continued to expand more rapidly, pockets of gas formed, becoming more and more dense. Within these pockets, stars ignited, and as they formed, groups of them became the earliest galaxies.

6. 5 Billion Years Ago: Our Solar System Forms: - Our sun formed within a cloud of gas in a spiral arm of what we now call the

Milky Way Galaxy. A huge cloud of gas and debris surrounded this new star gave birth to planets, moons, and asteroids.

7. 3.8 Billion Years Ago: Life Appeared: - The Earth cooled and an atmosphere formed. Microscopic cells began to form,

which were neither plant nor animal.

8. 700,000,000 Years Ago: Animals Appeared:

- Mostly flatworms, jelly fish and algae. 130 million years later large numbers of creatures with hard shells suddenly appear.

9. 200,000,000 Years Ago: Mammals Appeared: - These early mammals evolved from some reptile who had begun developing

mammalian traits.

10. 65,000,000 Years Ago: Dinosaurs Became Extinct: - An asteroid or comet crashed into the northern part of the Yucatan Peninsula in

Mexico. This catastrophic event brought an end to the long age of the dinosaurs, providing mammals with a chance to expand their ranges.

11. 600,000 Years Ago: Homo Sapiens Emerged: - The early ancestors of the human species evolved from apes somewhere in what

is now Africa

12. 170,000 Years Ago: Supernova 1987A Exploded: - A star, in what is now known as the Large Magellanic Cloud, exploded. It was a

blue supergiant 25 times more massive than the Sun.

13. 8000BC: The Maya make astronomical constructions14. 4000BC: Egyptians institute the 365 day calendar.15. 2680 BC: The Great Pyramid at Giza completed.16. 2300BC: Chinese astronomers start to observe the sky.17. 2296BC: A comet is observed for the first time by the Chinese18. 1860 BC: The Construction of Stonehenge.19. 1800BC: Babylonians begin to keep observational records20. 1600BC: Chaldean astronomers identify the zodiac21. 763BC: Solar eclipse observed and recorded by Babylonians22. 624BC: Thales of Miletus was born.23. 585BC: Thales of Miletus predicted a solar eclipse.24. 547BC: Thales of Miletus died.25. 500BC: Pythagoras suggests that the Earth is a sphere and not flat, as had been

previously assumed26. 440 BC: Greek philosopher Leucippus and Democritus, his student present the

concept that all matter consists of fundamental particles called atoms. (Atom comes from the Greek word meaning "indivisible.")

27. 365BC: Chinese spot first moons of Jupiter with the naked eye28. 350 BC: Aristotle writes Meteorologica, the first book on weather.29. 300 BC: Euclid, a Greek from Alexandria, writes Elements, introducing geometry

(which means "land measurement").30. 270BC: Aristarchus says that the Sun is at the center of the Solar System; this is

generally dismissed31. 240BC: What would later become known as Halley's comet is observed by the

Chinese

32. 212 BC: Archimedes calculates the area of circle, defines the principles of the lever, the screw, and buoyancy.

33. 194 BC: Eratosthenes calculates the size of Earth.34. 120 BC: Hipparchus of Rhodes (161 BC-122 BC, ) Defines the cosmos by latitude

and longitude; and makes triangular measurement of celestial navigation. 35. 127: Alexandrian astronomer and mathematician Ptolemy (Claudius Ptolemaeus)

publishes Almagest, in which he catalogued 1,022 stars - the previous known number of stars being 850. This was the primary astronomy text for 14 centuries.

36. 1473:Copernicus born in Poland. Nicolas Copernicus born in Poland.37. 1514: Astronomer Nicolas Copernicus suggests that the earth moves around the

sun.38. 1543: Copernicus publishes De Revolutionibus Orbium Caoelestium (The

Revolutions of the Heavenly Spheres), the theory that earth revolves around the sun, while on his deathbed.

39. 1546: Tycho Brahe born in Denmark.40. 1552: Books on Geography and Astronomy are burned in England because people

thought they contained magic.41. 1564: Galileo Galilei born in Italy.42. 1572: Tycho Brahe observes a supernova in Cassiopeia constellation.43. 1583: Galileo Galilei demonstrates that successive beats of a pendulum always take

place in the same length of time, regardless of the distance through which it swings.44. 1590: Microscope invented by Dutch spectacle maker Zacharias Janssen. Galileo

Galileiexperiments with falling objects.45. 1593: Galileo Galilei invents a water thermometer.46. 1596: Johannes Kepler publishes Mysterium cosmographicum.47. 1598: Tycho Brahe describes his experiments in astronomy.48. 1608: Hans Lippershey invents the telescope49. 1609: Galileo Galilei improves the telescope.50. 1609: Kepler publishes Brahe's calculation of the orbit of Mars. Kepler publishes his

first two laws of planetary motion.51. 1610: Galileo discovers Jupiter's 4 largest moons.52. 1613: Galileo publishes work on sunspots.53. 1619: Kepler publishes De cometis and Harmonice mundi, in which he announces

his third law of planetary motion.54. 1632: Galileo publishes Dialogo sopra I due massimi sistemi del mondo, supporting

Copernicus' view that the planets circled the sun.55. 1633: Inquisition forces Galileo to recant his belief in Copernican theory.56. 1642: Galileo dies.57. 1655: Dutch mathematician Christiaan Huygens develops a new method for grinding

telescope lenses, making a more powerful telescope, and discovers the rings and one moon of Saturn.

58. 1656: Christiaan Huygens invents a pendulum clock and discovers that Saturn's "handles" are in fact rings.

59. 1659: Anglo-Irish physicist and chemist Robert Boyle develops an air pump for creating vacuums, confirms Galileo's view that bodies fall in a vacuum at the same rate, regardless of weight; discovers that sound does not travel in a vacuum.

60. 1660: Robert Hooke of London claims he invented and applied the hairspring to the balance wheel. However, the invention is widely credited to Christiaan Huygens and Abbé d'Hautefeuille who simultaneously developed the use of a hairspring with the balance wheel in 1674.

61. 1664: Isaac Newton experiments with gravity. The Great Red Spot on Jupiter is observed by Robert Hooke.

62. 1666: Isaac Newton develops calculus (fluxions). Cassini discovers the polar ice caps on Mars.

63. 1668: Isaac Newton invents a reflecting telescope.64. 1669: Isaac Newton in England and Gottfried Wilhelm Leibrniz in Germany

determine the principles of calculus at the same time. (The name is derived from the Latin word for pebble, referring to the use of pebble for counting.) Robert Hooke observes that the star Gamma Draconis has a parallax of 30 seconds of arc.

65. 1675: Leibniz determines integral and differential calculus. Christian Huygens patents the pocket watch. Foundation of the Royal Greenwich Observatory.

66. 1678: Christiaan Huygens discovers the polarization of light.67. 1680: First publication of "Old Moore's Almanack", which later becomes known as

"Vox stellarum".68. 1682: Edmond Halley discovers Halley's comet.69. 1687: Isaac Newton describes the theory of gravity. The era of modern physics is

inaugurated by the publication of his Mathematical Principles of Natural Philosophy, commonly called the Principia'. It was published in Latin and did not appear in English until 1729.

70. 1688: Newton constructs the first reflecting telescope.

71. 1701: Swedish astronomer Anders Celsius devises the centigrade temperature scale.

72. 1705: Edmund Halley predicts that the comet spotted in 1682 will return in 1758.73. 1754: The heliometer, a device designed to measure the diameter of the sun, is

invented by John Dollond. It is also used to measure distances between stars.74. 1757: John Campbell invents the sextant.75. 1758: Dolland invents a chromatic lens. As predicted by Edmund Halley, the 1682

comet returns, and is thereafter named Halley's Comet.76. 1762: James Bradley publishes a star catalogue, containing the measured positions

of 60,000 stars.77. 1781: William Herschel discovers Uranus and recognises star systems outside our

galaxy.78. 1796: Pierre Laplace develops the theory of the origin of the universe.79. 1798: Laplace predicts the existence of black holes.80. 1801: Thomas Young publishes proof of the principle of interference of light,

supporting the wave theory of light. The first asteroid is discovered when Giuseppe Piazzi identifies Ceres.

81. 1820: The Royal Astronomical Society is founded.82. 1838: Friedrich Bessel makes the first measurement of the distance of a star from

the Earth, calculating the distance of 61 Cygni to be approximately 6 light years away; the true value is later calculated as approximately 12 light years.

83. 1840: John Draper makes the first daguerreotype image of the Moon.

84. 1846: The 8th planet, Neptune, is discovered by Johann Galle.85. 1849: The first US astronomical publication is instigated: the Astronomical Journal.86. 1850: William Bond takes the first photographic image of a star (Vega).87. 1865: Jules Verne publishes From Here to the Earth, mentioning the exact velocity

that the cannon shot the three travelers to the moon (an object must have a velocity of seven miles a second to escape the Earth's gravity).

88. 1866: Great Leonid meteor showers.89. 1887: AA Michelson and EW Morley experimentally demonstrate the constancy of

the speed of light.90. 1895: Konstantin Tsiolkovsky publishes a series of papers describing space flight.91. 1900: Max Karl Ernst Ludwig Planck, in a lecture to the German Physical Society,

announces that matter absorbs heat energy and emits light energy discontinuously, giving birth to quantum mechanics.

92. 1903:Orville Wright launches first powered flight in history, flying at Kitty Hawk for 12 seconds - 4 flights were made on 17 December. Earlier that year, Russian physicist Konstantin Tsiolkovsky claimed, with complex mathematical theories that man will one day travel in space and occupy planets. Konstantin Eduardovich Tsiolkovsky publishes The Investigation of Outer Space by Means of Reaction Apparatus.

93. 1904:Discovery of interstellar matter by Johannes Hartmann.94. 1905:Albert Einstein publishes "theory of relativity."95. 1906:An explosion at Tunguska, Siberia, is attributed to comet fragments.96. 1915:Discovery of Proxima Centauri, the nearest star to the Earth (except the Sun).97. 1919:International Astronomical Union founded.98. 1924:Edwin Hubble proves that galaxies are systems independent of the Milky Way.99. 1930:Clyde Tombaugh discovers the 9th planet, Pluto.100. 1931:Karl Jansky invents radio astronomy101. 1939:Frank J Whittle invents the jet engine. Robert Watson-Watt invents radar.102. 1945: Radar contact is established with the Moon. Arthur C Clarke proposes

communications satellites in geosynchronous orbit above the Earth - by 1965 his visionary ideas become reality.

103. 1947: Chuck Yeager breaks the sound barrier in the Bell X-1 rocket plane.104. 1948:The Hale reflector telescope is installed at the Mount Palomar observatory

in California.105. 1949:Rocket testing ground is established at Cape Canaveral.106. 1951:First space flight by living creatures when US sends 4 monkeys into the

stratosphere.107. 1955:The Jodrell Bank telescope is completed.108. 1957:USSR launches the Sputnik 1 satellite into space.109. 1958 NASA founded.110. 1959:First pictures of far side of the moon by Luna III.111. 1961: Yuri Gagarin the first man in space. Alan B. Shephard Jr is the first

American in space.112. 1962:John Glenn becomes first American to orbit earth in space. The first X-ray

source is discovered in Scorpius.113. 1963:Velentina Tereshklova becomes first woman in space in Vostok 6. First

quasar discovered.

114. 1965:Soviet astronaut Alexei Leonov makes the first space walk.115. 1966: Star Trek debuts on NBC. Neil Armstrong and David Scott makes the first

space docking in Gemini 8. Luna IX probe lands on the Moon, while Venera III makes a landing on Venus.

116. 1967:Bell and Hewish discover the first pulsar117. 1969:Neil Armstrong is the first man on the moon followed by Buzz Aldrin.118. 1970:Apollo 13 forced to abort Lunar Mission when oxygen tank explodes. Crew

managed safe return to Earth.119. 1971:The Russians launch Salyut I, the first orbital space station.120. 1975:Soviet Soyuz 19 docks with Apollo 18. Venera IX makes a landing on

Venus and relays pictures of the planet back to the Earth121. 1976:Viking I lands on Mars.122. 1977:Star Wars debuts. Rings around Uranus discovered. The Voyager deep

space probes are launched.123. 1978:Pioneer 1 and 2 reach Venus 1978 James Christy discovers Charon, a

moon of Pluto.124. 1979-1981:The Voyager spacecraft pass Jupiter and Saturn, relaying an

enormous amount of information back.125. 1981:Shuttle Columbia launched.126. 1982: Rings around Neptune discovered.127. 1983:Sally Ride is first US woman in space. Pioneer 10 becomes the first man-

made object to travel beyond the solar system.128. 1986:Soviet Union launches Mir space station. Space Shuttle

Challenger explodes, killing all aboard. Voyager 2 reaches Uranus, finding 6 new moons.

129. 1987:Supernova SN1987A flares up, becoming the first supernova visible to the naked eye since 1604.

130. 1989:Voyager 2 reaches Neptune, discovering a ring system and 8 moons.131. 1990:Hubble space telescope launched.132. 1991:Helen Sharman becomes the first British astronaut, on Soyuz TM-12.133. 1992: COBE satellite discovers ripples from the Big Bang. NASA launches the

SETI (Search for Extraterrestrial Intelligence) program.134. 1994: An asteroid passes earth at only 160 000km (100,000 miles). Hubble

Space Telescope finds evidence for a black hole at the centre of the M87 galaxy..

135. 1996:NASA scientist announce the discovery of proof of living organisms on a Mars meteorite in Antarctica.

136. 1997:First ever space funeral when Timothy Leary's ashes is launched into space. US space probe pathfinder lands on Mars. World's first university, where Aristotle and Socrates taught, is discovered in Athens.

137. 1998:Construction started on the International Space Station. Supernova observations suggest that the universe is expanding at an increased rate.

138. 2001: Evidence for a black hole at the center of our galaxy is found. Spacecraft NEAR Shoemaker safely lands on the asteroid 433 Eros, February 15. United States launched the Genesis mission to study solar wind particles.

139. 2002: First planet detected orbiting a giant star. Mars Odyssey achieves possible identification of significant amounts of frozen water.

140. ??: ??141. 100 Trillion Years After The Big Bang: The Stellar Era Ends: If the universe

continues to expand and does not collapse under its own gravity, it will slowly wither away. Right now, most of the energy in the universe is in the form of stars. That energy will slowly disperse until the age of stars is over.

142. 100 Trillion to 1037 Years After The Big Bang:The Degenerate Era: The majority of the universe's mass is now in the form of degenerate stars, ones that have blown up and collapsed into black holes and neutron stars, or have deteriorated into white dwarfs. Energy is no longer primarily generated by the stars, but from decay of protons and particle annihilation.

143. 1038 to 10100 Years After The Big Bang: Black Hole Era: Now that the decay of protons has ceased to be the dominating factor, the only stellar-like objects left are black holes of widely varying mass. They are starting to evaporate at an increasing speed.

144. 10100 Years After The Big Bang: Protons have all decayed and the black holes have evaporated. The only thing remaining are the waste products from the previous self-destructive processes. These are mostly photons of huge wavelengths, electrons, and positrons. Our universe has mostly dissipated.

145. Beyond 10100 Years After The Big Bang: The Big Crunch: One scenario for the end of the universe states that when the universe stops its expansion, it will ever so slowly at first, but gaining speed as it goes, will begin to collapse. Eventually, it will become an infinitely small point of infinite density and infinite temperature. Will it then begin the cycle all over again with another Big Bang? Who knows?

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