In his own lifetime Galileo was the centre of violent controversy; but the scientific dust has
long since settled, and today we can see even his famous clash with the Inquisition in
something like its proper perspective. But, in contrast, it is only in modern times that
Galileo has become a problem child for historians of science.
The old view of Galileo was delightfully uncomplicated. He was, above all, a man who
experimented: who despised the prejudices and book learning of the Aristotelians, who put
his questions to nature instead of to the ancients, and who drew his conclusions fearlessly.
He had been the first to turn a telescope to the sky, and he had seen there evidence enough
to overthrow Aristotle and Ptolemy together. He was the man who climbed the Leaning Tower
of Pisa and dropped various weights from the top, who rolled balls down inclined planes,
and then generalized the results of his many experiments into the famous law of free fall.
But a closer study of the evidence, supported by a deeper sense of the period, and
particularly by a new consciousness of the philosophical undercurrents in the scientific
revolution, has profoundly modified this view of Galileo. Today, although the old Galileo lives
on in many popular writings, among historians of science a new and more sophisticated
picture has emerged. At the same time our sympathy fro Galileo's opponents ahs grown
somewhat. His telescopic observations are justly immortal; they aroused great interest at
the time, they had important theoretical consequences, and they provided a striking
demonstration of the potentialities hidden in instruments and apparatus. But can we blame
those who looked and failed to see what Galileo saw, if we remember that to use a telescope
at the limit of its powers calls for long experience and intimate familiarity with one's
instrument? Was the philosopher who refused to look through Galileo's telescope more
culpable than those who alleged that the spiral nebulae observed with Lord Rosse's
great telescope in the eighteen-forties were scratches left by the grinder? We can perhaps
forgive those who said the moons of Jupiter were produced by Galileo's spyglass if we
recall that in his day, as for centuries before, curved glass was the popular contrivance for
producing not truth but illusion, untruth; and if a single curved glass would distort nature,
how much more would a pair of them?