Great Inventions and Discoveries

by Willis Duff Piercy

Sir Isaac Newton

The operation of this law of gravitation pointed the way to the discovery of the planet Neptune, which is considered the greatest triumph of mathematical astronomy since the days of Newton. Prior to the discovery of Neptune, Uranus was the outermost known planet of the solar system. It was noticed that Uranus was being pulled out of its proper path. It was being tugged away by some strange force beyond the edge of the known planetary system. As the result of a skilful and laborious investigation, Leverrier, a young French astronomer, wrote in substance to an assistant in the observatory at Berlin: "Direct your telescope to a point on the ecliptic in the constellation of Aquarius in longitude 326°, and you will find within a degree of that place a new planet, looking like a star of the ninth magnitude, and having a perceptible disk." Leverrier did not know of the existence of such a planet. He calculated its existence, location, and mass from the fact that some such body must be there, to account for the disturbance caused to Uranus. The telescope in the Berlin Observatory was directed to the place designated by Leverrier, and on the night of September 23, 1846, in exact accordance with his prediction and within half an hour after the astronomers had begun looking, Neptune was discovered within less than one degree from the exact spot where Leverrier had calculated it must be. Such are the triumphs of the human mind. Such are the failures of nature to hide her secrets from the inquiry of man, even behind untold millions of miles.

According to the principles of gravitation as unfolded by Newton, the power of attraction decreases directly as the square of the distance between the sun and a planet. Neptune, being on the outer rim of the system and hence farthest away from the sun, moves in its orbit around the sun more sluggishly than any other planet. Life such as we know it on the earth could not exist on Neptune; it would be too cold. The light and heat from the sun on Neptune are only one nine hundredth part of what we get on the earth. But even so, the sunlight falling upon Neptune is equal in power to seven hundred of our full moons. It was thought that Uranus was the last planet of the solar system until Neptune was found. Whether Neptune is the last, or whether other worlds are roaming around beyond it, is not known.

Ptolemy, who was one of the most celebrated astronomers of earlier times, was born in Egypt about a century and a half after Christ. According to the Ptolemaic system of astronomy, which Ptolemy expounded but did not originate, the earth was considered the center of the universe, and around it the other planets and the sun were believed to revolve. A passage in the Bible in which Joshua commanded the sun to stand still indicates that the old Hebrews believed the sun circled around the earth. The Ptolemaic theory did not account for all the facts observed by astronomers, but for nearly fifteen centuries it held practically universal sway over the belief of men, until another thinker set the matter right.

Nicholas Copernicus was born in Prussia, February 19, 1473. He studied mathematics, medicine, theology, and painting, but his greatest achievements were in astronomy. He made holes in the walls of his room, through which he might observe the stars. Copernicus did not believe in the theory of Ptolemy that the earth was the center of the universe, but held that the solar system had for its center the sun, and that around it the planets, including the earth, revolved. In working out this belief, which science has subsequently shown to be correct, he laid the foundations of the modern system of astronomy.

The book in which Copernicus expounded his theory was begun in 1507 and was completed in 1530. He could not be induced to publish it, however, until shortly before his death. On May 24, 1543, he lay dying in Frauenburg. A few hours before his death, when reason, memory, and life were slipping away from him, the first printed copy of his book was borne to Frauenburg and placed in the great astronomer's hands. He touched the book, looked at it for a time, and seemed conscious of what it was. Quickly afterward he lapsed into insensibility and was gone.

Johann Kepler, who was born in Germany in 1571, contributed several important facts to astronomy. He studied the motions and laws of the celestial bodies. Copernicus taught that the planets revolved around the sun in circular orbits, but Kepler discovered that their paths are ellipses. He also found that the nearer the planets are to the sun the faster they travel. Kepler's discoveries were embodied in three great laws of astronomy known as Kepler's laws. These furnished the foundation for Newton's discoveries and are the basis of modern astronomy. Kepler died in November, 1630.

Many of the wonderful discoveries that have been made in the field of astronomy could not have been possible without the telescope, the most important instrument used by astronomers. The first part of the word is the same Greek adverb meaning "afar," found in telegraph and telephone; the last part is derived from a Greek verb meaning "to see." The telescope, therefore, is an instrument for seeing objects that are far off. It is a long tube With lenses so arranged as to make objects appear much larger than they would to the naked eye. The telescope was invented by a Dutch optician named Hans Lippershey about three hundred years ago. The Italian scientist Galileo, who was born at Pisa in February, 1564, heard of the invention, began studying the principles upon which it depends, and greatly improved it. Galileo was the first to use the telescope for astronomical purposes. With it he discovered the satellites of Jupiter, the spots on the sun, and the hills and valleys of the moon.