For centuries the laws of mechanics as laid down by the Greek Aristotle had been accepted without much dispute by the civilized world. But a spirit of new thought and investigation was now rising in Europe, and more especially in Italy. Galileo determined to study the laws of mechanics by experiment, and not, as so many earlier scientists had done, by argument or mere theoretical opinions. Therefore he undertook to establish definitely the laws relating to falling bodies.
Aristotle, almost two thousand years before, had announced that if two bodies of different weights were dropped from the same height the heavier would reach the ground sooner than the lighter, according to the proportion of their weights. Galileo doubted this, and decided to try it. Accordingly he assembled the teachers and students of the university one morning about the base of the famous Leaning Tower of Pisa. He himself climbed to the top, carrying with him a ten-pound shot and a one-pound shot. He balanced them on the edge of the tower and let them fall together. They struck the ground together. As a result of this experiment Galileo declared three laws in relation to falling bodies. He said that if one neglected the resistance of the air, or in other words supposed the bodies to fall through a vacuum, it would be found, first, that all bodies fall from the same height in equal times; second, that in falling the final velocities are proportional to the times; and third, that the spaces fallen through are proportional to the squares of the times.
The first of these laws was shown by his experiment on the Leaning Tower. To show the others he built a straight inclined plane with a groove down its centre. A bronze ball was free to move in the groove with the least possible friction. By means of this he showed that no matter how much he inclined the plane, and so changed the time, the ball would always move down it according to the laws he had stated.
But in disproving the accuracy of the old laws of Aristotle the young scientist had raised a hornet’s nest about his ears. The men of the old school would not believe him, a conspiracy was set on foot against him, and finally the criticism of his new teachings grew so severe that he was forced to resign his position, and move to Florence.
In spite of his wide-spread reputation no school or university was ready to welcome the young scientist. He was known as a man of a very original turn of mind, and therefore one who would be apt to clash with those who clung to their belief in the old order of thought. At last, however, he succeeded in obtaining the chair of Professor of Mathematics at the University of Padua, then one of the greatest seats of learning in Italy. Here again he showed the great scope of his knowledge, and wrote on military architecture and fortifications, the laws of motion, of the sphere, and various branches of mechanics. He invented a machine for raising water, and was granted a patent which secured him his rights in it for twenty years, and he also produced what he called his Geometrical and Military Compass, but what was later commonly known as the Sector.
Galileo’s fame as a teacher had now spread widely throughout Europe, and students began to flock to Padua to study under him. He had a large house, where a number of his private pupils lived with him, a garden, in which he delighted, and a workshop. Here he experimented on his next invention, that of the air thermometer. One of his friends, Castelli, wrote of this in a letter many years later, dated 1638. “I remember,” he writes, “an experiment which our Signor Galileo had shown me more than thirty-five years ago. He took a small glass bottle about the size of a hen’s egg, the neck of which was two palms long, and as narrow as a straw. Having well heated the bulb in his hand, he inserted its mouth in a vessel containing a little water, and, withdrawing the heat of his hand from the bulb, instantly the water rose in the neck more than a palm above its level in the vessel. It is thus that he constructed an instrument for measuring the degrees of heat and cold.”
In 1604 the attention of all the astronomers of Europe was attracted by a new star which suddenly appeared in the constellation Serpentarius. Galileo studied it, and shortly began to lecture on the comparatively new science of astronomy. Formerly he had taught the old system of Aristotle to his classes, now, after a searching investigation, he declared his belief in the contrary conclusions of Copernicus. This study led him on and on. He became interested in the magnetic needle, and its use as a compass in navigation. Columbus’ discovery of its changing its position according to its relation to the North Pole took place on his first voyage to America, and reports of this had reached Padua. All educated men were rousing to the fact that the age was fertile with new discoveries in every branch of knowledge, and Galileo and those who were working with him gave eager heed to each month’s batch of news.
Mere chance is said to have brought about the making of the first telescope. The story goes that an apprentice of Hans Lipperhey, an optician of Middleburg, in Holland, was, one day in October, 1608, playing with some spectacle lenses in his master’s shop. He noticed that by holding two of the lenses in a certain position he obtained a large and inverted view of whatever he looked at. He told Master Hans about this, and the optician fixed two lenses in a tube, and looking at the weathercock on a neighboring steeple saw that it seemed much nearer and to be upside down. He hung the tube in his shop as a curious toy, and one day the Marquis Spinola examined it and bought it to present to Prince Maurice of Nassau. Soon a number of Hans Lipperhey’s scientific neighbors were trying to make copies of his tube, and before very long reports of it were carried to Italy. The news reached Galileo while on a visit to Venice in June, 1609. This is his account of what followed, taken from a letter written to his brother-in-law Landucci, and dated August 29, 1609.
Galileo’s Telescope