ASTRONOMERS

ARISTOTLE

• 384-322BCE
• The moon, stars, Sun and planets orbited Earth.

ARISTARCHUS

• 310-230BCE
• He proposed a heliocentric model of the solar system
• He attempted to measure the distance to thr Sun and Moon

PTOLEMY

• 100-170ce
• Geocentric model
• A celestial body traveled at constant speed in a perfect circle
• "Wheel on wheels"

NICOLAUS COPERNICUS

• 1473-1543
• Perfect cirlces around the sun
• Heliocentric
• 1st step of modern systems

JOHANNES KEPLER

• 1571-1630
• Planets did not go in perfect circles. Kepler's laws:
• 1. Planetary orbits are elipses with the sun
• 2. Planets move faster when close to the sun
• 3. Planet to sun compared to time for one orbit

GALILEO

• 1564-1642
• Improvements to telescopes
• Earth was not only the object that could be orbited
• Venus phases

ISAAC NEWTON

• 1643-1727
• Gravitational forces pulling us down
• Gravity forcing the moons orbit
• Further developed the telescope

EDWIN HUBBLE

• 1889-1953
• Universe is expanding- Hubble's law
• Classification system for galaxies

GEOCENTRIC

• Earth is the center of the solar system

HELIOCENTRIC

• Earth and other planets orbit the Sun