Galileo Galilei, a future astronomer and physicist, was born near
Pisa, Italy on February 15, 1564. The family moved to Florence in 1570.
Vincenzo Galilei, who was Galileo's father, had an important role in the
musical transition from medieval polyphony to harmonic modulation. Galileo
was taught by monks at Vallombrosa and then entered the University of Pisa
in 1581 to study medicine because his father wanted him to be a doctor.
He left the university without a degree in 1585 and turned to philosophy
and mathematics of Aristotle which became his interest at the university.
He also developed a distaste for authority. He then questioned Aristotle's
philosophy and scientific thought. Most of his questions about Aristotle
came from the logic of Nicolaus Copernicus, a Polish astronomer who died
just 31 years before Galileo was born.
For a time, he tutored privately
and wrote on hydrostatics and natural motions. Galileo discovered the law
of falling bodies and the parabolic path of projectiles. While in a cathedral,
he noticed that a chandelier was swinging with the same period as timed
by his pulse, regardless of its amplitude. He began to study the isochronism
of the Pendulum in 1581, as well as the motion of bodies. Using an inclined
plane, he showed that all bodies fall at the same rate. He also investigated
Cohesion, and concluded that a waterfall breaks when the weight of the
Water becomes too great, the same reason that Water pumps could only raise
water by 34 feet. He also investigated mechanics and the strength of materials.
In 1589 he became professor of mathematics at Pisa, where he is reported
to have shown his students the error of Aristotle's belief that speed of
fall is proportional to an objects weight, by dropping two objects of different
weights at the same time from the Leaning Tower of Pisa. As for Galileo's
interest in disproving Aristotle's Theory about falling objects, years
later he said that he had first thought about this during a hailstorm,
when he notice that both large and small hailstones hit the ground at the
same time. His contract was not renewed in 1592, because he contradicted
professors who liked Aristotle's philosohpy better. In the beginning of
1595, he preferrd the Copernican theory that the earth revolves around
the sun rather than Aristotle's theory that the sun revolving around the
earth. In Aristotle's theory, the earth does not move at all.
In August 1609 he built his first
telescope that is almost as powerful as the modern field glass. Only a
few months later in December, he made a telescope of 20 times magnification
which he used to discover mountains and craters on the moon. This went
against Aristotle's belief that bodies in space were smooth an perfectly
spherical. It wasn't long before Galileo began to make a series of startling
observations, including the discovery of innumerable stars never seen before,
mountains on the moon, and the four satellites of Jupiter, the movements
of which he carefully plotted from day to day. Galileo named the moons
of Jupiter the "medicean planets" -- in honor of his former student Cosmo
and the famous Medici family (royal family). thanks to which he was shortly
thereafter appointed Chief Mathematician and Philosopher to the Grand Duke
of Tuscany in Florence. and for pointing out that the Milky Way galaxy
was composed of many stars. Galileo observed the Supernova of 1604
and tried unsuccessfully to measure its parallax. According to Copernicus's
theory, the Earth 's motion must produce a parallax, but no such parallax
was found until Bessel. Galileo was the first person who used a telescope
to study the sky. He published his findings in his March 1610 publication,
The Starry Messenger. As he was gaining new fame and respect as a brilliant
scientist, he was freed from teaching duties so he could have time for
research and writing. In December 1610, he proved the Copernican system
which stated that the planets revolved around the central sun. He did this
by using his telescope to observe the phases of Venus. Since phases would
only be observed if Venus were always closer to the sun than to the
Earth which is how he proved it.
Galileo disputed with professors at Florence and Pisa over hydrostatics,
and he published a book on floating bodies in 1612. Soon after, 4 publications
were made opposing Galileo's "new physics". Galileo also proposed Galilean
relativity, which states that the same definitions of motion are valid
everywhere. The resultant Galilean Transformation is correct for
low speeds, but must be replaced by the Lorentz Transformation for
relativistic speeds.Galileo also said that motion is continuous and can
only be altered by the application of a Force . Galileo enunciated the
law of fall (which states that distance traveled is proportional to the
square of time) and the time law (which
states that velocity is proportional to time). He remained silent
on the subject for years, and started working on a method of determining
longitudes at sea by using his predictions of the positions of Jupiter's
satellites. Galileo was banned from discussing Copernican or his findings
in any way in 1616. In 1633, Galileo was arrested and was found guilty
of having published a heretical book. In the end, Galileo had no choice
but to repent and confess that he had gone to far. He was sentenced to
life in prison. The punishment was soon changed to permanent house arrest
because of Galileo's poor health and his age. His sentence was read at
all universities to try to frighten scholars of Copernican's logic. His
book Dialogue, which discussed Copernican relationship of tides
and physics, was ordered burned. The Catholic church did not allow the
book published again until 1835. After this, Galileo mostly stuck to studying
motion. In Leiden, he published his final book about motion and the principles
of mechanics. This publication lead Newton to the law of universal gravitation.
Galileo went blind before it was published and died in Arcetri, Italy on
January 8, 1642. Pope Urban VIII refused to forget his feud with Galileo,
and refused to permit his burial with a suitable monument -- instead, Galileo
was buried unceremoniously in the Church of Santo Croce, in Florence. Only
a few hundred years later were his remains moved to their present magnificent
tomb, opposite that of Michelangelo near the entrance to the church.
Galileo's most important contibution was his founding of
physics on precise measurement. Some historians call him the founder of
modern experimental science. He is credited with the invention of the thermometer.
Newton, the inventor of calculus, was born only a year after Galileo died
and used some of Galileo's ideas to become on of the greatest scientists.
Galileo's biggest struggle was freeing scientific inquiry from theological
interference. In October 1992, Pope John Paul II acknowledged the Vatican's
error in condemning Galileo and rehabitated him.
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