Kepler, Johann
Johann (1571-1630), a German astronomer. A native of Wurtemberg. He appears to have been educated at the expense of the reigning duke and to have been an apt mathematician and an ardent supporter of the Copernican system. In 1601 he was engaged as an assistant by Tycho Brahe at Prague, whom he shortly succeeded. Kepler inherited Tycho's observations and a series of records kept during many years. The details of Kepler's life are not pleasing. He was the son of an unhappy marriage in poverty. He himself married twice. His first wife was a woman of temper. His second wife he chose from eleven women whose characteristics he has left on record. His services fell in the troublous times of the Thirty Years' War, and Kepler himself died while waiting on the emperor, trying to collect a pittance of salary long overdue. In contrast with these unpleasing details are the importance of Kepler's laws:
1. Every planet moves in an ellipse which has the sun as one of its foci.
2. The radius vector of a planet moves over equal areas in equal times.
3. The squares of the periodic times of the planets are proportional to the cubes of their mean distances from the sun.
The first law may be understood by consulting the article on ELLIPSE. According to the second law, lines drawn from the sun to any two points in a planet's path a month apart inclose equal areas, which means that the line drawn from the sun to the planet shifts faster when the planet is in the part of its path nearer the sun.
According to the third law, a planet that is four times as far from the sun as another would require eight times as long to go around once, or at one-ninth of the distance it would require one-twenty-seventh as long to complete a revolution.
Kerguelen (kerg'e-len) Land, or Desolation Land, an Antarctic island at the southern border of the Indian Ocean. It is about 100 miles in length and half as wide. It is composed chiefly of volcanic rocks, rising to a height of 2,500 feet. It has a barren, desolate appearance. Its cliffs and headlands are occupied by numerous sea fowl. There are no land animals. The vegetation is scanty. The island was annexed by France in 1893. There are now a few settlers. The island is remarkable chiefly as the only known home of a cruciferous plant known as the kerguelen cabbage. It is intermediate between lettuce and cabbage. It grows abundantly. The heads abound in a yellow oil. When boiled and served at table, the so-called cabbage is a remedy for scurvy, the scourge of sailors. Before the art of canning made it possible to carry a supply of fresh vegetable food, ships in that part of the world made calls at Kerguelen Land to obtain a supply of the cabbage. See Scurvy