Sun

the center of our solar system. It is one of the fixed stars. It is the source of the earth's light and heat. We are at an average distance of 92,900,000 miles from the sun. Astronomers think that future measurements cannot change this estimate materially. The distance is so great that figures give a very small idea. A railroad train, running at an ordinary speed of thirty miles an hour, would require 350 years to reach the sun. Some one has said that, were it possible for a child to touch the sun with the tip of its finger, it would die of old age before the sensation of pain could run along the nerves of the arm to the child's brain.

The diameter of the sun is about 109 times that of the earth, or 866,500 miles. If the sun's center were at the center of the earth, the orbit of the moon would be little more than half way from the center of the sun to its circumference; that is to say, the moon's entire path would be within the sun, nearly half way to its center. The average weight of the sun is about 1.4 times as great as that of water. Were the entire weight of the sun suspended, a steel rod 3,000 miles in diameter would be required to support it. A child weighing seventy-five pounds on the surface of the earth would weigh a ton on the surface of the sun. Like the earth, the sun turns on its axis. Each revolution requires 25.35 of our days.

A very interesting subject of study is the occurrence of dark spots on the surface of the sun. Very possibly they are craters in the sun's atmosphere, caused by tremendous gaseous explosions. A cyclonic disturbance or sun-spot visible in 1905 was thought to cover 5,000,000,000 square miles. An examination of solar light by means of the spectroscope indicates that at least thirty-six chemical elements are present. Most of the metals, including iron, nickel, copper, zinc, silver, tin, and lead have been identified. Hydrogen and carbon are present, and some indications of oxygen have been found. Chlorine, sulphur, phosphorus, and nitrogen are thus far supposed to be wanting.

Figures fail to convey an adequate idea of the amount of light and heat emitted by the sun. Some idea of the heat may be had by a statement that the tropical sun will melt an inch of ice an hour, and that the heat received during the year is enough to melt a layer of ice 177 feet thick all over the earth's surface. Professor Young of Princeton indorses the statement that, were the sun itself frozen solid to a depth of 64 feet, the heat emitted would melt such a crust in one minute.

See Arcturus; Star; Spectroscope; Seasons; Light