Galileo Galilei was an Italian physicist, mathematician, astronomer, and
philosopher who played a major role in the Scientific Revolution.
1564
Galileo Galilei was born on 15 February in Pisa, Italy, the first of
six children of Vincenzo Galilei and Giulia Ammannati.
1581
Galileo went to college at the University of Pisa. He began his
studies as a medical student, but changed to Mathematics.
Drawing of pendulum clock designed
by Galileo Galilei
1583
During his student days at Pisa, Galileo conducted several
experiments with pendulums.
“…the period (the time in which a pendulum swings back and
forth) does not depend on the arc of the swing (the
isochronism).”
1589
Galileo obtains a teaching position in mathematics at the
University of Pisa.
•1590 While at the University of Pisa, Galileo disproved existing beliefs
that heavier objects fall faster than lighter ones:
“…all objects, regardless of their density, fall at the same rate in a
vacuum.”
1590
According to Vincenzo Viviani, Galileo’s first biographer, Galileo
demonstrated his conclusions by dropping weights from the
leaning tower of Pisa. This report has been doubted by historians.
Apollo 15 Commander Dave Scott
demonstrates that the mass of an object does
not affect the time it takes to fall, using a
hammer and a feather on the Moon. Click the
image to view the Google video.
Galilean Sector
1593
Galileo invents a water lifting machine, a pump driven by horses.
He receives a patent for the machine in 1594.
1597
Galileo invents a sector, a calculating instrument consisting of
two equal length rulers joined by a hinge. It was used to solve
practical mathematics problems in proportion, trigonometry,
multiplication and division.
A replica of the earliest surviving telescope
attributed to Galileo Galilei, on display at the
Griffith Observatory.
1607
Invents a thermoscope, a primitive thermometer that could
register variations in temperature.
1609
In early 1609 Galileo built a three-powered telescope based on
descriptions of Hans Lipperhey’s invention the previous year. By
fall of the same year he had developed an eight-powered
telescope.
Jupiter's four Galilean moons, in a composite image
comparing their sizes and the size of Jupiter. From
top to bottom: Io, Europa, Ganymede, Callisto.
1609
Using this higher-powered telescope, Galileo was the first to
observe lunar mountains and craters on Earth’s moon.
1610
In January of 1610, Galileo discovered four satellites in orbit
around Jupiter: Io, Europa, Callisto and Ganymede. Initially, he
named these Medicean stars after one of his patrons.
The phases of Venus
1610
Galileo was the first person to observe Saturn. Initially, he
mistook the rings for planets thinking it was a three-planet
system.
1610
Galileo observed that Venus exhibited a full set of phases similar
to that of the Moon. The heliocentric model of the solar system
developed by Nicolaus Copernicus predicted that all phases
would be visible.
1612
Galileo observed the Sun through his telescope and saw that the
Sun had dark patches on it (what we now call sunspots). He also
observed the motion of the sunspots indicating that the Sun was
rotating on an axis. More evidence of the Copernican heliocentric
model of the solar system.
1615
A Dominican friar Niccolo Lorini, who had earlier criticized
Galileo's view in private conversations, files a written complaint
with the Inquisition against Galileo's Copernican views.
1616
On orders of the Pope Paul V, Cardinal Bellarmine delivered to
Galileo an order not to "hold or defend" the idea that the Earth
moves and the Sun stands still at the centre. The decree did not
prevent Galileo from discussing heliocentrism hypothesis (thus
maintaining a facade of separation between science and that
church). For the next several years Galileo stayed well away from
the controversy.
Galilean Microscope
1624
Galileo develops a the first known microscope.
1632
Galileo’s book “Dialogue Concerning the Two Chief World
Systems” is published. It compares the Copernican (sun-centered)
theory of the solar system with the Ptolemaic (Earth-centered)
system.
1633
Galileo is summoned to face the Inquisition in Rome. He is
convicted of heresy and forced to publicly recant his support of
Copernicus. He was sentenced to life imprisonment but because
of his advanced age he was allowed to serve his term under
house arrest at his villa near Florence.
1642
Galileo died on January 8, 1642.
1992
Pope John Paul II expressed regret for how the Galileo affair was
handled, acknowledging the errors committed by the Catholic
Church tribunal that judged Galileo’s scientific positions.
The Vatican formally and publicly cleared Galileo of any
wrongdoing.