perhaps the most valuable astronomical instrument ever produced.

These and other discoveries in dynamics may seem very obvious now; but
it is often the most every-day matters which have been found to elude
the inquiries of ordinary minds, and it required a high order of
intellect to unravel the truth and discard the stupid maxims scattered
through the works of Aristotle and accepted on his authority. A blind
worship of scientific authorities has often delayed the progress of
human knowledge, just as too much "instruction" of a youth often ruins
his "education." Grant, in his history of Physical Astronomy, has well
said that "the sagacity and skill which Galileo displays in resolving
the phenomena of motion into their constituent elements, and hence
deriving the original principles involved in them, will ever assure to
him a distinguished place among those who have extended the domains of
science."

But it was work of a different kind that established Galileo's popular
reputation. In 1609 Galileo heard that a Dutch spectacle-maker had
combined a pair of lenses so as to magnify distant objects. Working on
this hint, he solved the same problem, first on paper and then in
practice. So he came to make one of the first telescopes ever used in
astronomy. No sooner had he turned it on the heavenly bodies than he
was rewarded by such a shower of startling discoveries as forthwith
made his name the best known in Europe. He found curious irregular
black spots on the sun, revolving round it in twenty-seven days; hills
and valleys on the moon; the planets showing discs of sensible size,
not points like the fixed stars; Venus showing phases according to her
position in relation to the sun; Jupiter accompanied by four moons;
Saturn with appendages that he could not explain, but unlike the other
planets; the Milky Way composed of a multitude of separate stars.