Summary
The Renaissance set the stage for the astronomy
of the sixteenth century by engendering interest in the physical world and its
surroundings. By 1510 Leonardo da Vinci had
developed many theories on the creation of the universe and the functioning of
celestial bodies. In 1528, the French physician Jean Fernal made a calculation
of the size of the Earth correct to one percent.
However, these accomplishments are far overshadowed by those of Nicolas
Copernicus. Copernicus, a highly educated Pole, studied at university until
the age of 30, excelling in classics, medicine, law, theology, and painting, as
well as astronomy. He was not a practical astronomer, and only observed a
handful of eclipses and oppositions of planets. Rather, he was a student of
past observers and a theoretician. He studied the observed motions of heavenly
bodies in relation to the accepted geocentric Aristotelian system, which
placed the earth at the center of the solar system, with the sun and planets in
orbit. Copernicus' observations led him to conclude that there was something
wrong with the geocentric theory. He tested the hypothesis that the earth was
in fact in orbit around the sun against the records of observation and found
that this heliocentric theory was more feasible.
Copernicus' new scheme retained many of the aspects of the ancient theory. It
still assumed that the universe was spherical and finite, ending at the range of
the stars so distance that their movements could not be detected. It still
assumed that the motion of all heavenly bodies was perfectly circular.
Copernicus finished the description of his heliocentric theory in De
Revolutionibus Orbium Coelestium (On the Revolutions of Celestial Bodies) in
1530, though it went unpublished until 1543, just months before his death.
The next great astronomer, Tycho Brahe, a Dane, differed from Copernicus in
that he was, foremost, a practical astronomer who spent his time observing the
heavens. For 21 years, from 1576-1597, Tycho worked out of a laboratory
provided to him by the King of Denmark, systematically collecting observational
data, which he used to test and revise astronomical theories. His records were
far more extensive than any of his predecessors. Tycho set up a flawed, but
fairly viable (by his observations), model of the solar system in which the
Earth was central to the orbits of the moon and sun, and the sun was central to
the orbits of the remaining planets. Mathematically, this system worked out
identically to that suggested by Copernicus.
In 1584, Giordano Bruno, a renegade Italian monk, published three books
explaining his philosophy. They are: The Ash-Wednesday Supper,On
Cause, Principle, and Unity, and On the Infinite Universe and its
Worlds. Bruno argued therein that not only does the Earth move, but so does
the sun, and that there is no such thing as a point absolutely at rest in the
universe. He argued further that the stars whose movements could not be
detected were at vast, but varying distances from the solar system, and are the
centers of remote solar systems. He claimed that it was folly to maintain that
our planetary system was the center of the universe.
Bruno's conclusions were incompatible with the teachings of the Church, which
maintained that the universe was finite and therefore separate from its creator.
In 1600, Bruno was burned at the stake as a heretic. His work remained obscure
during most of his career, but influenced some disciples, such as William
Gilbert, whose work On the Magnet and Magnetic Bodies and Concerning that
Great Magnet, the Earth, a New Physiology was published in 1600, and
received high praise from future scientists.
