ASTRONOMERS

GEOCENTRIC MODEL

• Earth is believed to be the central of the solar system
• All planets orbit around Earth

HELIOCENTRIC MODEL

• All of the planets revolve around the sun
• They all orbit the sun

ARISTOTLE

• 384-322 BCE
• Greek Philosopher
• Geocentric Model

ARISTARCHUS

• 310-230 BCE
• Greek Astronomer
• Tried to Measure the relative distances to the moon and sun
• Said that the Sun is the center of the solar system

PTOLEMY

• 100-170 CE
• Astronomer
• Created the wheels on wheels system
• Retrograde Motion

COPERNICUS

• 1473-1543
• First Modern Astronomer
• Heliocentric Model

KEPLER

• 1571-1630
• German Astronomer
• Kepler's 3 Laws

KEPLER'S LAWS

• Planetary orbits are ellipses with the sun at one focus
• Planets move faster in orbits when closer to the sun
• States the distance of a planet from the sun to the time it takes to go once in orbit

GALILEO

• 1564-1642
• Used telescopes to obverse different things in space:
• Sunspots & Supernova
• Phases of Earth and Venus' moon
• Jupiter's moons

NEWTON

• 1642-1727
• Law of Universal Gravitation

EDWIN HUBBLE

• 1889-1953
• American Astronomer
• showing that the recessional velocity of a galaxy increases with its distance from the earth, implying the universe is expanding.