History of Astronomers

500 BCE

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500 CE

1000 CE

1500 CE

2000 CE

Aristotle creates the geo- centric model referencing that the Earth is the center of the universe.

Aristotle says that the movement of stars and planets are perfectly circular.

Ptolemy believes the geocentric theory and states that planets must move on epicycles.

Ptolemy also believes that the model observed the paths of five planets including the sun and the moon.

Copernicus asserts that the Earth sits on its axis and rotates while orbiting the sun.

Copernicus rediscovers the Heliocentric theory where as the Earth is no longer the center of the universe.

He accounts of planetary retrograde motion.

Galileo builds a telescope for himself.

Makes observation that Jupiter has moons.

Galileo observes that the sun has imperfections and it rotates.

Discovers that Venus has phases.

Galileo states that the moon has mountains, valleys, and craters.

Brahe makes observations of a supernova.

Brahe observes a comet.

Brahe supports heliocentric model but personally believes the Earth was motionless and the center of our universe.

Brahe compiles information on planet Mars.

Kepler finds that planetary orbits are ellipses with the sun at one focus.

Kepler states that an imaginary line connecting the sun and planet sweeps out equal areas in equal time.

Kepler says square of period of planet's orbital motion is proportional to cube of semimajor axis.