Chapter 8 ASTRONOMICAL DISCOVERIES AND INVENTIONS

"When I consider thy heavens, the work of thy fingers, the moon and the stars, which thou hast ordained, what is man, that thou art mindful of him?" The Hebrew psalmist feels the insignificance of man compared with the infinitude of the heavens. Victor Hugo expresses the opposite thought: "There is one spectacle grander than the sea-that is the sky; there is one spectacle grander than the sky-that is the interior of the soul."

There is nothing more dignified, more sublime, more awful, than a contemplation of the heavens. In point of grandeur, astronomy may be regarded as king of the sciences. It is also their patriarch. Thousands of years before the birth of Christ the priests of Chaldea, from the tops of their flat-roofed temples, studied the stars and laid the foundations of the science of astronomy. The heavens, with their teeming, whirling, circling congregation, obeying laws that have no "variableness neither shadow of turning" do, indeed, "declare the glory of God."

From the earliest times the stars were supposed to influence for good and ill the lives of men. There were supposed to be stars of good luck and of bad omen. The cool, calculating Cassius tells Brutus,

"The fault, dear Brutus, is not in our stars,

But in ourselves, that we are underlings."

When you look up into the heavens at the flickering dots of light which we call the stars, you are looking at worlds, many of them far larger than our earth. They seem small because of vast distances from us. Our own solar system, great as it is, in comparison with the celestial universe is but a clod in an acre. At the center of our system is the sun, a huge ball of fiery matter 93,000,000 miles from the earth, and as large as 330,000 worlds like ours. Circling around the sun like maddened horses around a race course are eight planets. These planets, with the sun and some comets, constitute our solar system; our system, for how many solar systems there are in space no one knows. These planets, in their order outward from the sun, are Mercury, Venus, our Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. Of these, Mercury is the smallest and Jupiter is the largest. The following table shows some interesting facts about the planets:

Name Diameter in miles Number of planets required to equal sun in size Distance from sun in millions of miles Time required for one revolution around sunin days Velocity in orbit, miles per hour

Mercury 3,008 5,000,000 36 88 107,012

Venus 7,480 425,000 66 225 78,284

Earth 7,926 332,260 92 365? 66,579

Mars 4,999 3,093,500 141 687 53,938

Jupiter 88,439 1,048 483 4,332 29,203

Saturn 75,036 3,502 886 10,759 21,560

Uranus 30,875 22,600 1,783 30,687 15,202

Neptune 37,205 19,400 2,794 60,127 12,156

The moon is 240,000 miles from the earth, and it would require nearly 24,500,000 moons to equal the sun in size. Other planets have moons, some of them several. If you lived on the planet Mercury, your annual birthday would come around about once in three of our months. If you had your home out on the border land of the solar system, on the planet Neptune, you would have a birthday once in about 165 years, as we count time on the earth. It will be observed that the closer the planet is to the sun, the faster it travels in its orbit. This fact is due to the power of gravitation toward the sun. This strange influence drives the planets around the sun, and the nearer the planet is to the sun the greater is the power and consequently the faster the revolution. The law of gravitation was discovered by Sir Isaac Newton.

Newton was born in 1642 in Lincolnshire, England. His father was a farmer, and the farmhouse in which the son was born is still preserved. He was educated at a grammar school in Lincolnshire, and later entered Trinity College, Cambridge, from which he was graduated in 1665. Early in life he displayed a great liking for mathematics. Within a few years after he entered college, he had mastered the leading mathematical works of the day and had begun to make some progress in original mathematical investigation.

Newton's great life work-the achievement which insured to his name a place among the immortals-was suggested to him by accident. As the story goes, while he was walking one day in a garden, he saw an apple fall from a tree. He speculated upon the reasons for its falling, and ultimately concluded that the same force which causes an apple to fall from a tree holds the heavenly bodies in their places. Further investigation brought him to the unfolding of this general law of gravitation: "Every body in nature attracts every other body with a force directly as its mass, and inversely as the square of its distance." This law is the greatest law of nature. It is the central fact of the physical universe, the cement of the material world, the mighty, mystic shepherdess of space, that keeps the planets from wandering off alone. It is this awful, silent power reaching out from the enormous mass of the sun, that lashes the planets in their furious race, and yet holds them tightly reined in their orbits.

Newton was one of the greatest mathematicians, scientists, and thinkers in the history of the world. He died at Kensington, England, on March 20, 1727, and was buried in Westminster Abbey, with the illustrious dead of Great Britain.

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.

Galileo

At the present time the largest telescopes in the world are made and owned in America. The largest is the Yerkes telescope, belonging to the University of Chicago and located on the shores of Lake Geneva, Wisconsin. Microscopes, opera glasses, and other magnifying instruments depend upon the same principles as the telescope.

One of the most astounding of man's tools is the spectroscope, an instrument used for analyzing light. Through a knowledge of chemistry scientists can establish scientific relations between different substances and the light which they emit. By analyzing the light from the heavenly bodies with the aid of the spectroscope, and comparing this result with the light sent out from different known kinds of matter, man can stand on this little flying speck of matter we call the earth and discover of what substances the stars are made.

One of the most interesting questions arising in a study of the heavenly bodies is whether or not any of them besides the earth are inhabited. Is there any good reason for supposing that our pigmy planet, so insignificant compared with many celestial bodies, is the only one containing life? On the other hand, life such as we know it could not exist on some of the other planets. Mercury would be too hot; Neptune too cold. Climatic conditions on Mars are most nearly like those of the earth. Within recent years the telescope has revealed on the surface of Mars a number of peculiar, regular lines. Many scientists hold that these are artificial canals or irrigation ditches, and that the planet must be inhabited. The theory does not seem at all unreasonable. But the most that can be safely said is that if any of the other planets are inhabited, the most likely one is Mars.