Astronomers Essay Research Paper Part OneBrief Descriptions — страница 3

accepted. In 1530 he finished his great book, ‘Concerning the Revolutions of the Celestial Spheres’. His theory was in opposition to the teachings of the Roman Catholic church, and the book was not published for 13 years. Copernicus apparently received the first copy as he was dying, on May 24, 1543. The book opened the way to a truly scientific approach to astronomy. Such men as Galileo and Kepler were profoundly influenced by it. Galilieo (1564-1642) : Modern physics owes its beginning to Galileo, who was the first astronomer to use a telescope. By discovering four satellites of the planet Jupiter, he gave visual evidence that supported the Copernican theory. Galileo thus helped disprove much of the medieval thinking in science. In 1583 Galileo discovered the law of the

pendulum by watching a chandelier swing in the cathedral at Pisa. He timed it with his pulse and found that, whether it swung in a wide or a narrow arc, it always took the same time to complete an oscillation. He thus gave society the first reliable means of keeping time. In about 1609, after word from Holland of Hans Lippershey’s newly invented telescope reached him, he built his own version of the instrument. He developed magnifying power until on Jan. 7, 1610, he saw four satellites of Jupiter. He also saw the mountains and craters on the moon and found the Milky Way to be a dense collection of stars. Kepler (1571-1630) : This Renaissance astronomer and astrologer is best known for his discovery that the orbits in which the Earth and the other planets of the solar system

travel around the sun are elliptical, or oval, in shape. He was also the first to explain correctly how human beings see and to demonstrate what happens to light when it enters a telescope. In addition, he designed an instrument that serves as the basis of the modern refractive telescope. Kepler’s great work on planetary motion is summed up in three principles, which have become known as “Kepler’s laws”: (1) The path of every planet in its motion about the sun forms an ellipse, with the sun at one focus. (2) The speed of a planet in its orbit varies so that a line joining it with the sun sweeps over equal areas in equal times. (3) The squares of the planets’ periods of revolution are proportional to the cubes of the planets’ mean distances from the sun. These laws

removed all doubt that the Earth and planets go around the sun. Later Sir Isaac Newton used Kepler’s laws to establish his law of universal gravitation. 31e