Aristotle

• he was from Greece
• he was borned 384-332 BCE
• he thought everything was around the Earth
• the positions of the stars would change as Earth moves

ARISTARCHUS

PTOLEMY

• he was astronomer geograopher and mathematician
• 100-170 CE
• detailed geocentric model
• wheels-on-wheels
• try to explain retrograde motion

COPERNICUS

• 1473-1543
• his model is more basic and easy to understand
• his heliocentric model of copernicus was popular
• he changed a little of the ptolemy model

Kepler

• 15711-1630
• german mathematician and astronomer
• planets orbit around the sun at one focus
• planets move faster in the orbit when closer to the sun
• the distance of a planet from the sun to the time it takes to go once around its orbit

GALILEO

• 1564~1642
• he observed the moons Io, Europa
• the earth is not the only planet that can orbit
• venus went through phases similar to the phases of Earth

isaac newton

• 1642~1727
• laws of motion
• universal gravitation

EDWIN HUBBLE

• 1889~1953
• the recessional velocity
• telescope

GEOCENTRIC MODEL

• everything orbit around the Earth
• Earth is the cener of the univrse
• wrong

heliocentric model

• earth and other planets orbit around the sun
• sun is the center of the solar system
• right