Italian mathematician, astronomer, and
physicist. He developed the astronomical telescope and was the first
to see sunspots, the four main satellites of Jupiter, and the appearance
of Venus going through phases, thus proving it was orbiting the Sun.
In mechanics, Galileo discovered that freely falling bodies, heavy or
light, have the same, constant acceleration and that a body moving on
a perfectly smooth horizontal surface would neither speed up nor slow
Galileo's work founded the modern scientific method of deducing laws
to explain the results of observation and experiment (although the story
of his dropping cannonballs from the Leaning Tower of Pisa is questionable).
His observations were an unwelcome refutation of the ideas of Aristotle
taught at the (church-run) universities, largely because they made plausible
for the first time the heliocentric (Sun-centred) theory of Polish astronomer
Nicolaus Copernicus. Galileo's persuasive Dialogo sopra i due massimi
sistemi del mondo/Dialogues on the Two Chief Systems of the World 1632
was banned by the church authorities in Rome and he was made to recant
by the Inquisition.
Galileo was born and educated in Pisa, and in 1589 became professor
of mathematics at the university there; in 1592 he became a professor
at Padua, and in 1610 was appointed chief mathematician to the Grand
Duke of Tuscany. When tried for heresy in 1633, and forced to abjure
his belief that the Earth moves around the Sun, Galileo is reputed to
have muttered: 'Eppur si muove' ('Yet it does move'). He was put under
house arrest for his last years.
Galileo discovered in 1583 that each oscillation of a pendulum takes
the same amount of time despite the difference in amplitude. He invented
the thermometer and a hydrostatic balance, and discovered that the path
of a projectile is a parabola.
Galileo published De motu/On Motion 1590. Having made his own telescopes,
he published his first findings in Sidereus nuncius/The Starry Messenger
1610; the book was a sensation throughout Europe. He summed up his life's
work in Discorsi e dimostrazioni matematiche intorno a due nove scienze/Discourses
and Mathematical Discoveries Concerning Two New Sciences. The manuscript
of this book was smuggled out of Italy and published in Holland 1638.