Galileo

(1564–1642)

Sometime in the year 1583, repairs were going on in the cathedral of an old Italian city called Pisa; and, accidently, a workman had set swinging a great lamp which was suspended from the high roof of the building. People came into the church and knelt for a few minutes to say their prayers and then went out without noticing that the lamp kept on swinging to and fro.

A young man about eighteen years of age came into the church. He noticed the swinging lamp; and he also thought that it took just the same time to make each of its swings.

With his right hand he clasped his left wrist. He knew that the times between pulse beats are practically equal. So, feeling his pulse and watching the swinging lamp, he was trying to measure the one by the other.

The young man who watched the swinging lamp was Galileo; and he found that its motions were equal in duration.

Before his time no pendulum had ever swung in a clock. No clock with a pendulum had been thought of. But after Galileo published his great discovery that pendulums made their swings in equal periods of time, a man named Huygens (Hi' genz) made a pendulum clock.

It was found that pendulums about a yard long make each swing in a second; and so, at first, clocks were made with pendulums which beat seconds.

From Galileo's watching the swinging lamp, all our clocks may fairly be said to have been invented.

The father of Galileo hoped that his son would become a physician; but the young man liked to study mathematics, and his father permitted him to follow the bent of his genius.

Not long after graduating at the university, and when not quite twenty-five, Galileo was made professor of physics. He taught his classes about pumps and machinery, why smoke rises in the air, why birds' wings enable them to fly, and why fishes' fins send them through the water.

Nobody in Europe at that time knew much about such matters. There were no steam engines; no railroad trains were in existence; no steamers were crossing the seas.

People knew very little about such simple things as the falling of stones and feathers, and pieces of iron and lead. Even learned men thought that two pounds of lead would fall twice as fast as one pound, one hundred pounds one hundred times as fast, and so on.

One day Galileo asked some of his friends to climb with him the leaning tower of Pisa. This tower is one of the famous buildings of Europe. The odd thing about it is that it does not stand up straight like the tower or spire of a church, but leans over, as some of our trees do.

Some of Galileo's friends stayed at the foot of the tower; some went to the top. Heavy and light things were carried up and dropped from the summit of the tower; and one pound of iron reached the ground at the same instant as did a piece that weighed ten pounds.

While Galileo was professor at Pisa the people of Europe who watched the heavens saw a new star in the sky.

"Have you seen the new star? What do you think it is?" were questions that everybody was asking. Some thought it was only a meteor; but Galileo said, "No! It must be a star, because a meteor would surely be moving, and that star seems still." He gave three lectures upon it and people went by hundreds to hear him.

Galileo, like everybody else, could look at the star only with the naked eye. He tried to contrive something that would show both it and the other stars more plainly. He had seen spectacles. His grandfather wore a pair. He had somewhere read that if two eyeglasses are placed one above the other, things seen through them will appear nearer and larger.

Galileo and his telescope

Some bright man in Holland fixed an eyeglass at one end of a tube and another like it at the other end; and so made the first telescope.

Galileo had heard about this. He bought a piece of lead pipe and fixed a glass at either end. His telescope magnified only three times; but it made things look nearer and larger.

He was as pleased with it as a child with a new toy. Wealthy and noble Venetians looked through it with wonder; just as when you look through a microscope at the point of a needle you are surprised to see how blunt it is.

Then Galileo used stronger lenses. His second telescope magnified eight times; and a third was made which magnified thirty times.

He looked at the moon; and he saw what no human being had ever seen before. There are mountains on the moon. He saw their bright tops and the shadows which they threw.

Then he looked at the planet Venus. She no longer looked like the other stars; but sometimes she seemed to be round like the full moon, sometimes horned, like the old and new moons.

Galileo showing the heavenly bodies through the telescope

With his naked eye Galileo counted only six stars in the Pleiades. People long years before had seen seven; and it was believed that one had been lost. Galileo looked one bright night and his telescope showed him forty. He looked at the Milky Way and found that its whiteness is the dim light of millions of stars so far away that they seem as small as the finest dust.

He then made a fourth and larger telescope, and turned it upon the farthest away of the known planets. Jupiter, like Venus, seemed no more a star. It was round like the moon at the full.

But another and greater wonder appeared. Close to the edge of Jupiter's disk were three tiny stars. Two were seen on the east side of the planet and one on the west. They were Jupiter's moons.

Galileo watched on another night and found that instead of three there were four. We now know that there are seven.

He told the other professors in the university what he had seen, and the news quickly spread. The newly-found moons were called planets, just as our own moon was; and so it seemed that Galileo had made the number of planets eleven, instead of seven.

One of the professors was so angry that he would not even look through the telescope. Another man said, "The head has only seven openings—two eyes, two ears, two nostrils and one mouth, and how can there be more than seven planets?"

Galileo had an old friend called Kepler, who was the greatest astronomer then living. Galileo wrote to him, "Oh, my dear Kepler, how I wish we could have one good laugh together. Why are you not here? What shouts of laughter we should have at their glorious folly!"

About sixty years before this, Copernicus had printed a book in which he said that the earth was not still, as people thought, but that it was all the time moving round the sun.

Galileo did not at first believe this, and said in one of his letters that it was "folly." Then he saw that it was probably true; and when he looked through his telescope at the planets he became certain of it.

Milton visiting Galileo at Florence.

When people said that the system of Copernicus was contrary to the teaching of the Scriptures, Galileo tried to explain the sense in which the passages in the Bible are to be taken. He was then accused of teaching what would do harm to religion, and was summoned to Rome His trial took place in 1616 and he promised to give up his opinions concerning the Copernican system.

But his enemies still pursued him, and in 1633 Galileo was again accused of heresy and of breaking the promise he had made in 1616. The main part of the charge was that Galileo had denied that God is a personal being and that miracles are not miracles at all. As to breaking the promise he had made in 1616, Galileo admitted that he had felt proud of his arguments in favor of the Copernican system and in one of his books he had made out rather a strong case for it. He denied, however, having expressly taught the Copernican system. Unfortunately Galileo did not tell the truth in thus denying what he had taught, and he was sentenced to an indefinite term of imprisonment.

The imprisonment was not severe, although Galileo complained of it. He was to remain with an old friend and disciple; but at the end of six months he was permitted to return to his home near Florence.

His friends were allowed to visit him; but he was not allowed to go outside the gate to visit them. This was sad for him; but sadder still was the loss of his sight; for his eyes had seen more of the glory of the heavens than all the millions of eyes that had ever looked at the stars since the world began.

He died in 1642 and his body was interred in the Cathedral of Santa Croce.