A Western History of Astronomy

Larry A. Maddox

A Western History of Astronomy

Larry A. Maddox

Greeks were among first active stargazers.Noted the changing sky.

Our name “planet” comes from the greek word for “wanderer”Observers were puzzled by the phenomenon of retrograde motion exhibited by the planets.

Retrograde motion of Saturn and Jupiter

Plato

1. There is certainty.

2. Mathematics gives us the power of perception.

3. Though the physical applications of mathematics may change, the thoughts themselves are eternal and are in another realm of existence.

4. Mathematics is thought and, therefore, it is eternal and can be known by anyone.

Plato's Four Points

Pythagoras

The Pythagorean Paradigm

1. The planets, Sun, Moon and stars move in perfectly circular orbits;

2. The speed of the planets, Sun, Moon and stars in their circular orbits is perfectly uniform;

3. The Earth is at the exact center of the motion of the celestial bodies.

Eudoxus (sorry, no picture)

Aristotle

Aristotle

Adopted cosmology of Eudoxus.Noted that southern stars get higher in the sky as one goes south.Noted that Earth cast a circular shadow during a lunar eclipse. From these observations, argued that Earth is spherical

Aristarchus

Broke with Greek religious tradition of geocentrism

“The fixed stars and the Sun remain unmoved”

“The Earth revolves about the Sun on the circumference of a circle” (quotes are from Archimedes, “The Sand Reckoner”)

Model is inferred from geometric arguments

Not accepted at the time, but precedent for Copernicus

Aristarchus

Hipparchus

Believed in pure observation.Examine precise positions of stars.Found the precession of the pole and the equinox.Gave us the modern magnitude system. Brightest stars are 1st magnitude. Faintest stars are 6th magnitude. Later found to be very (mathematically) regular in divisions.

Claudius Ptolemy

Motion on the Epicycle

And then, not much happenedfor a while...

Nicholas Copernicus

Tycho Brahe

Tycho's Inner Universe

Tycho

1572 noticed a “stella nova” in Cassiopeia. November 11, 1572 Remained in the sky for a few months. Published observations in Der Stella Nova On the night of discovery, required several verifications.

Johannes Kepler

Kepler

1604: observed another stella nova. Named star and dedicated next book for Tycho.

Kepler's Laws of Plantary Motion

1. The orbit of every planet is an ellipse, having the sun at one of its foci.

Kepler's Laws of Plantary Motion

2. If a line, called a radius vector, is supposed to be drawn from the sun to any planet, the areas described by this line, as the planet revolves in it orbit, are proportional to the times.

Kepler's Laws of Plantary Motion

3. The squares of the times of revolution of any two planets are proportional to the cubes of their mean distances from the sun.

Galileo

Observations of the Moon

And Venus

Galileo believed that Saturn was a “tri-form” planet.

Christian Huygens

Theorized that Saturn was surrounded bya ring of material that was separated from

the sphere of the planet.

18th Century, William Herschel discovered Uranus, a new planet beyond Jupiter. Barely visible with the unaided eye, Herschel made the observation with his telescope.

Early in the 19th Century Adams (English) & LeVerrier (French) independently calculated that there must be another planet beyond Uranus that was producing small gravitational disturbances in Uranus' orbit. First observed in 1846 by Hohan Galle, it was named Neptune. (It was actually spotted earlier by Challis in Cambridge, but Challis did not note his discovery until Galle reported his observation.)

1930 Clyde Tombaugh discovered Pluto.

1910 Harlow Shapley estimated the size of the Milky Way.

W. H.Pickering and Annie J. Cannon calculated the surface temperatures of the stars.

Einstein (1905) developed the Theory of Special Relativity, based upon the idea that light travels at the same speed in all frames of reference. Modified Newton's Theory of Gravity by developing the General Theory of Relativity (1916).

Cecilia Payne-Gaposchkin & Henry Norris Russell determined the composition of stars.

1929 Hubble & Milton Humason discovered that the Universe is expanding.

1938 Hans Bethe determined that the Sun's energy comes from thermonuclear fusion reactions.

1940s Karl Jansky (from Norman, OK) observed that the nucleus of the Milky Way and other celestial objects are strong sources of Radio Waves in 1931. Based on radar technology developed in WWII, Radio Astronomy becomes an active field in the late 1940s.

1948 Geroge Gamov developed the Hot Big Bang Theory of the origin of the Universe.

1950's chemical composition of the stars; stars build the heavy elements via nuclear fusion reactions, mapped out in a famous paper by Burbidge, Burbidge, Fowler & Hoyle.

1954 Radio Galaxies

1960-63 Quasars

1960s X-Ray &Infrared astronomy

1965 Arno Penzias and Robert Wilson from Bell Laboratories discovered the cosmic microwave background radiation remnant of the Big Bang.

1968 Jocelyn Bell (Burnell) & Anthony Hewish discovered Pulsars