professor in Padua. In the middle of the page, on its own line was the word
“PERSPICILLI,” Galileo’s word for his telescope.
In the opening of the book, the forty-six-year-old Galileo describes how
his telescope came to be. Ten months earlier, in May 1609, Galileo
received word that a Dutchman had constructed a telescope with the aid of
lenses and a tube. After some thought, Galileo “finally determined to give
myself up first to inquire into the principle of the telescope, and then to
consider the means by which I might compass the invention of a similar
instrument, which a little while after I succeeded in doing, through deep
study of the theory of Refraction; and I prepared a tube, at first of lead, in
the ends of which I fitted two glass lenses, both plane on one side, but on
the other side one spherically convex, and the other concave.”^5
As will be seen time and again in this work, the breakthrough in an area
of science resulted from a tinkerer who relentlessly focused on the
problem at hand and physically involved himself in the manufacture of
tools, instruments, and measuring devices. The innovation that made
telescopes possible was first the development of clear glass in Murano and
the subsequent perfection of curved glass fabrication by the Dutch and
Germans. Galileo himself prepared the lenses, perfecting the size and
shape of each glass disk, turning a three-powered spyglass into a twenty-
times magnification tool suitable for celestial navigation. In all, he
fashioned over two hundred lenses, ending up with ten telescopes with
magnification of at least twenty times.^6
Realizing the functional military usefulness of his viewing instrument,
Galileo approached the Senate and Doge (chief magistrate) of Venice. In
the bell tower of Saint Mark’s Basilica in Venice, Galileo demonstrated the
superiority of using his telescope over the naked eye. On August 21, 1609,
a faraway ship was invisible to onlookers, but with his 12x telescope,
Galileo was able to show the Doge the potentially threatening vessel in the
Venetian Lagoon. Pleased with the promise of naval superiority based on
early detection of enemy warships, the Doge granted Galileo a handsome
salary and a mathematical professorship at the University of Padua.
Galileo spent eighteen years in Padua (1592–1610), including an
overlap of three years, between 1599 and 1602, in which he and
Englishman William Harvey were both at the university. In an Italian
university town at the turn of the 17th century, two men occupied the same
sphere; two giants of science who would be the first physicist,