Pierre Gassendi was a
seventeenth-century French philosopher, scientist, and astronomer. He was born
on January 22, 1592 in the South of France, to a poor family. He developed a
clear adeptness for academics in his early life and went on to study at the
most sophisticated schools in France when he was only just a teenager. As he
grew older, he began branching out with careers, becoming a professor at Digne
and getting his doctorate in theology, and ended up joining the Catholic Church
as a priest.
His occupation as a priest is
actually rather ironic, as later in life most of his published findings were
those which opposed the general beliefs of the Church at that time. His
research actually supported the views of Johannes Kepler, but Gassendi was
careful to make sure his works did not obviously show this, or show that he
rejected most of the Copernican beliefs. He mainly practiced experimental
astronomy, and his studies reflected that he researched based on a heliocentric
view of the universe. However, since the heliocentric idea was not accepted by
the church at the time, Gassendi made sure not to include in his works that he
supported this view because of the empirical astronomy he practiced. So
needless to say, Gassendi was in a complicated situation, wanting to post his
full research but not wanting to go against the church that he was so dedicated
to.
Pierre Gassendi conducted several
astronomical experiments. He liked to spend most of his time observing the sky,
possibly even with telescope lenses personally given to him by Galileo. And like Galileo himself, Gassendi
recorded lengthy observations to benefit him in his studies. One of Gassendi’s
most important discoveries was his 1631 observation of the transit of Mercury
over the sun. With this observation, and the help of two small solar scales,
Gassendi was able to estimate the diameter of Mercury, which he assumed to be
around twenty arc seconds. This discovery turned out to be fairly controversial
among other scientists at the time, because Gassendi’s estimate was much
smaller than anyone had expected. Not only did it cause commotion from its
size, but his discovery also provided support for Kepler’s law of planetary
motion—the first known confirmation of this law, in fact. Other planetary
calculations that Gassendi made include finding out how to determine longitude
through reference to lunar eclipses. These important discoveries led to the
eventual calculations of the distances between planets and the Sun.
Another discovery he made was an observation of colorful
lights in the sky, which he named “aurora
borealis.” He studied and discovered the cause of this occurrence—it was a
high altitude reflection of sunlight on ice crystals. This realization is
important because even though it was uncovered by Gassendi in 1621, it was
still proven to be correct two centuries later.
Pierre Gassendi also did a lot of
work in the field of optics, between studying both vision and light. He and his
partner Peiresc were confused with the idea of inverted images, and concluded
that the retina must act as a mirror, which takes an upside-down, backwards
picture and reflects it into the picture that is actually viewed through the
eyes. In addition, in 1642 Gassendi decided to attempt to explain the visually
perceptible variations of the size of the moon and sun at certain times of the
day and night. He concluded it to the interaction of light behavior and the
workings of the human eye, with respect to the visual experience produced by
different kinds of light.
Pierre Gassendi died on October 24,
1655, in Paris. He was certainly one of the most controversial philosophers and
astronomers in the seventeenth century. He studied celestial motions that
differed what the Catholic Church was teaching, yet firmly stood by the Church
and tried not to make his views appear to be sacrilegious. He made many
important observations and discoveries that created a basis for later
astronomers’ discoveries. Many of his findings are still relevant today.
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