Galileos earlier work
1590 Masses
fall at same rate heavier do not fall faster (unless affected by air resistance)
1604 Observes
a supernova, no parallax ή must be
beyond the Moon
Telescopes:
1609 Hears of
invention of telescope, which at that
point just use eyeglass lenses
Works out details of better lenses and lens placement, builds improved ones himself