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Gal ileo

Galilei
10

(1564-1642)

"He will live forever in his writings,
even they are prohibited."
if

already proposed the 1609 he pointed his latest telescope
Sun to be the centre at the most conspicuous objects in
of the Universe. After the night sky. What he saw would
many years of mathe- change human knowledge forever.
matical
Among his observations were that:
calculations
Copernicus became 1. ) The moon was not a smooth
n the fourth century B.C., two convinced that the "heliocentric" celestial disk as had been supposed,
influential Greek philoso- explanation was, indeed, the right but its surface was marked by nume-
phers, Plato and his student and only one, but at first he made rous craters and jagged mountains.
J Aristotle, stated that the no attempt to make his ideas known. 2. ) The Milky Way was not a dia-
Earth was the centre of the Universe. Finally, after many years of delay his phanous mist but was made up
They said that the stars and planets disciples persuaded him to reveal his of "swarms of small stars placed
were carried around the Earth on a discoveries. The completed book was exceedingly close together".
series of changeless, perfect transpa- brought to Copernicus in May 1543 3. ) Jupiter was accompanied by four
rent spheres, arranged in the order as he lay on his deathbed. moonsthatrotatedaboutit,andthere-
(going outwards): Moon, Sun, Venus, fore it could not possibly be situated
Mercury, Mars, Jupiter, Saturn In July 1609, an early telescope of in a solid transparent sphere.
and then the fixed stars altogether. Dutch origin fell into the hands of a 4. ) Venus had phases just like the
Sometime during the second century Venetian monk and scholar named moon, and therefore had to be situa-
A.D., the Greek astronomer Ptolemy Paolo Sarpi. He thought that this ins- ted between the Earth and the Sun,
published a series of books now trument could be improved and he with Venus orbiting the Sun.
known as the Almagest in which he knew just the man to do it -- a pro- 5. ) Saturn consisted of three objects
said much the same thing. Although fessor at Padua University and ins- (the resolution of his telescope was
neither Plato, nor Aristotle nor Pto- trument maker called Galileo Gali- not good enough to distinguish Sa-
lemy were Christians, this "geocen- lei. About a month later Galileo had turn's rings), two of which disappea-
tric" viewpoint was adopted without made an improved version of the red from time to time (i.e. when the
question by Christianity and remai- telescope that magnified distant ob- rings were edge-on to the Earth).
ned a fundamental article of faith for jects nine times. He was the first per- 6. ) Finally, by projecting the Sun's
the next 2,000 years. That is to say, son to understand the way the lenses image on to a sheet of paper, he dis-
even though it had nothing what- functioned and to describe them in covered sunspots that indicated that
soever to do with religion in general mathematical terms. Instead of sel- it rotated about once a month.
and Christianity in particular, if you ling his remarkable instrument to It should be said that Galileo was not
disagreed with this point of view, his clientele, the astute Galileo pre- the only person who looked at the
you were a heretic who would be put sented it to the Doge of Venice as sky through a telescope, but he was
to death by burning at the stake! a gift. In return he was granted life the only one who gave a perfectly
tenure as a university professor. accurate explanation of what he saw.
At the end of the fifteenth cen- It was now clear that the Earth and
tury it became obvious to the Po- In the following months, he conti- the other planets revolved around
lish astronomer Copernicus that nued working on improved versions the Sun. Galileo had been convinced
something was profoundly wrong with of the telescope, finally making one of this for a long time but was reluc-
Ptolemy's system. He knew that that magnified thirty-two times. tant to express his opinion in case of
some early Greek philosophers had Around the beginning of December ridicule.

Sciences 43 1