Guthrie Rowe, age 15, of Chester, Pa. for his question:
WHAT ARE KEPLER'S LAWS?
Kepler's laws are three laws concerning the motion of planets formulated by a great German astronomer named Johannes Kepler early in the 17th century.
Kepler based his laws on planetary data collected by the Danish astronomer Tycho Brahe, to whom he was an assistant. The proposals broke with a centuries old belief based on the Ptolemaic system advanced by the Alexandrian astronomer Ptolemy, in the second century A.D. and the Copernican system put forward by the Polish astronomer Nicolaus Copernicus, in the 16th century, that the planets moved in circular orbits.
According to Kepler's first law, the planets orbit the sun in elliptical paths, with the sun at one focus of the ellipse.
The second law states that the areas described in a planetary orbit by the straight line joining the center of the planet and the center of the sun are equal for equal time intervals; that is, the closer a planet comes to the sun, the more rapidly it moves.
Kepler's third law states that the ratio of the cube of a planet's mean distance, from the sun to the square of its orbital period, is a constant that is the same for all planets.
These laws played an important part in the work of the 17th. zentury English physicist, astronomer and mathematician Sir Isaac Newton. The laws are important for the understanding of the orbital paths of the moon, the natural satellite of the earth, and the paths of the artificial satellites launched from the earth.
Kepler was born in 1571 and studied theology and classics. He then held the chair of astronomy and mathematics at the University of Graz in Austria from 1594 until 1600, when he became the assistant to Brahe in his observatory near Prague.
On the death of Brahe in 1601, Kepler assumed his position as imperial mathematician and court astronomer to Rudolf II, Holy Roman emperor.
One of Kepler's major works during the period he was court astronomer to Rudolf II was the publication of "New Astronomy," the great culmination of his painstaking efforts to calculate the orbit of Mars.
In 1612 Kepler became mathematician to the states of Upper Austria. While living in Linz, he published his "Harmony of the World," the final section of which contained another discovery about planetary motion.
In 1621 he published "Epitome of Copernican Astronomy" which brought ail of his discoveries together in a single volume. It became the first textbook of astronomy to be based on Copernican principles, and for the next three decades it was a major influence in converting many astronomers to the theories of Copernicus.
Kepler's last major work, published in 1625, was based on Brahe's data.
Kepler also made contributions in the field of optics and developed a system of infinitesimals in mathematics, which was a forerunner of calculus.
Kepler died in 1630 in Regensbserg ,Germany.