•“Sidereus Nuncius”
(The Starry Messenger)
published in 1610 reporting:
•Moon isn’t “perfect”
(violating Aristotelian principles for heavens)
–Shows mountains and valleys
»Uses shadows to estimate heights
•Milky Way made up of myriad faint stars
–Doesn’t directly violate Aristotelian
principles, but suggests that a few simple phenomena can explain many features of the heavens
•Discovers 4 moons (Galilean Satellites) orbiting
Jupiter
–Violates idea that all motion is centered on the
Earth
–Shows that orbiting objects can “follow” a moving
body
–4 moons will also be seen to follow
Kepler’s 3rd law P2 µa3
(but with
a different proportionality constant)