Aristotle writes Metaphysics and Prior Analytics. Founded the school called the Lyceum
90 A.D. - 168 A.D.
Ptolemy writes the Almagest, a comprehensive treatise on the movements of the stars and planets. Developes the Ptolemaic System, Earth is at the center of the universe. Catalogues 48 constellations.
1473 - 1543
Copernicus publishes De Revolutionibus Orbium Coelestium ("On the Revolutions of the Heavenly Spheres"). Introduces the heliocentric solar system model.
1564 - 1642
Discovers the Galilean moons of Jupiter. Publishes "Dialogue Concerning the Two Chief World Systems", it supports the Copernican heliocentric model of the solar system.
1571 - 1630
Writes The First Law: Planets move in ellipses with the Sun at one focus. Publishes "Astronomia Nova" with the First Law, and the Second Law: The radius vector describes equal areas in equal times. Discovers The Third Law: The squares of the periodic times are to each other as the cubes of the mean distances. Publishes "Harmonices Mundi".
1625 - 1712
Discovers Saturn's moons: Iapetus, Rhea, Tethys and Dinoe. Cassini and Richer use the parallax method to determine the distance of Mars from Earth. Discovers a division in Saturn's rings called the Cassini Division.
1629 - 1695
Proposed that a thin, flat ring circled Saturn, discovered the moon Titan. Makes the first known drawing of the Orion Nebula. proposes a wave theory for light.
1642 - 1727
Publishes "Philosophiæ Naturalis Principia Mathematica", contains his 3 laws of motion and the universal law of gravitation.
1879 - 1955
Formulates his special theory of relativity, the laws of physics are the same everywhere, the speed of light is constant. Formulates his famous equation: E=mc2, where E is energy, m is mass and c is the speed of light. Publishes the theory of general relativity. Receives the Noble Prize.
1889 - 1953
Proposes a galaxy classification sysetm. Four classes: spirals, barred spirals, ellipticals and irregulars. Discovers that the universe is expanding at an astronomical rate, known as Hubble's Law.