|
In Europe, the study of the solar system, and people's knowledge about the solar system was dominated by the doctrines of the Roman Catholic church. The Church's position was based on the Ptolemaic theory, developed by Claudius Ptolemy in 150 A.D. His theory was based on the thoughts of earlier Greek philosophers and stated that the Earth was the center of the universe and that the universe was a closed space surrounded by a spherical envelope beyond which there was nothing. Copernicus first published findings that the sun was the center of the universe in 1513 and the resulting Copernican view was outlawed by the Church. His book was banned in 1616 and was not removed from the Index of Banned Books until 1835. Galileo, Giordano Bruno, and Kepler also believed the Sun was the center of the universe. Galileo was imprisoned and Bruno was burned at the stake for their belief in and support of Copernicus' work. For the majority of Europeans the solar system was defined in a geocentric way, with Earth at the center and the planets: Moon, Mercury, Venus, Sun, Mars, Jupiter and Saturn orbiting around Earth.
 |
Around 250 B.C. Aristarchus of Samos became the first known person to place the Sun at the center of the solar system. Despite this, most people believed that the Earth was the center of the universe until the Copernican Revolution, which began in 1543 A.D. with the publication of De revolutionibus orbium coelestium, libri VI. Greek philosophers from 500-300 B.C. believed that the Earth alone contained imperfections while the rest of the "heavens" were perfect and unchanging. Heavenly bodies were also supposed to move in perfect circles, yet observations of the planets did not support this view. It wasn't under the 1300's and 1400's in medieval Europe that astronomers began considering the Earth as an integral part of the universe rather than as something separate from the other bodies which contained no imperfections and were composed of a material not found on Earth.
 |
The Copernican Revolution began in 1543, but the new ideas were not immediately accepted by most people. It took more observations, mathematical calculations and proofs, and repeated testing to convince people that Earth was not the center of the universe, and that our solar system was part of, not the center of, a larger universe. Copernicus' work was supported by Newton's theory of universal gravitation. Tycho Brahe's observations were an important first step in making Copernicus' theories acceptable. Tycho Brahe made precise measurements of the planetary motions, the Sun, the Moon and the stars from 1576-1597 , which became the foundation for Johannes Kepler's work. Tycho Brahe did not believe that the Sun was the center of the universe. His Christian views did not allow for this, rather, he felt that the planets rotated around the Sun which in turn rotated around Earth.
 |
Johannes Kepler and Tycho Brahe worked together beginning in 1600. Kepler used Brahe's extensive and accurate observations to create his own model of the universe. Kepler's model was also based on mathematics, and one of his first discoveries was that the orbit of Mars is an ellipse with the sun at one focus, and the speed of the planet in its orbit varying in a calculable way. This information was discovered in 1609 and is the basis of the first and second of Kepler's Three Empirical Laws. The first law states that the orbit of each planet is an ellipse with the Sun at one focus. The second law states that the radius vector to a planet sweeps out equal areas in equal intervals of time. Kepler formulated his third law in 1619; it states that the squares of the sidereal periods of the planets are proportional to the cubes of the semimajor axes (mean radii) of their orbits.
 |
Galileo was also active during this time period. His most important contribution towards astronomy occurred in 1609 when he created the astronomical telescope. With this instrument he discovered Jupiter's four largest moons and the stellar composition of the Milky Way. These discoveries proved that everything did not rotate around Earth. In 1632, he published Dialogue Concerning the Two Chief World Systems, which favored the Copernican viewpoint rather than the Ptolemaic. In 1633, he was forced by the Inquisition to renounce his beliefs and writings. Despite the acts of the Inquistion, Galileo's publication influenced others to think scientifically rather than philosophically.
Images courtesy of MacTutor History of Mathematics.
