Galileo’s Telescope

Aristotle’s Cosmology• Cosmology= study of the cosmos (universe)• The earth is the center of the universe• Planets, sun and moon revolve around the

earth.• Stars are fixed to a “crystal sphere” which

rotates around the earth.• Celestial objects (sun, moon, planets, stars)

are perfect and immutable (no change)

1st quarter 3 rd quarter

Lunar Landscape

• Mountains and valleys just like on earth.• Earth might not be unique• Moon was not perfect like a celestial object

should be

Medicean Stars

Moons of Jupiter

• “Stars” revolving around Jupiter• Other objects could have “moons”• Moons were not left behind• Here was something that did not revolve

around the earth!

Phases of Venus

Phases of Venus

• Predicted by Copernican system• Impossible in Ptolemy system

“Ears” of Saturn

• Now we know he saw the rings of Saturn

Sun spots

• Sun is not “perfect”• Sun rotates• Why can’t earth also rotate.

Milky Way- full of stars