Galileo
Galileo saw a chandelier swinging gently to and fro and he wondered why. Thousands had witnessed the same thing since the beginning of man, but few contemplated the phenomenon thoughtfully, as he did. Apples had dropped for ages, but Newton (if the apple story is true) was one of the relatively few to wonder why. Primitive men learned early in their lives that some things were heavy and other things were lighter. This downward force, which we term gravitation, was utilized in many ways even by early races. There is nothing spectacular in the force of gravity. Being commonplace and universal in man’s experience there is little wonder that it did not interest or was not even recognized by many persons as a great fundamental natural property of the Earth and of matter. So much more credit is due to those who did give their attention to it.
These discussions do not aim at historical treatment so no attempt will be made to go back to the first person who devoted study to this or that phase of physical science. In fact, it would be impossible in most cases to find a record of the first person. However, as a matter of interest and as an aid in presenting the various subjects somewhat in perspective, some of the early contributors of noteworthy data and analyses will usually be included.
Galileo (1564-1642) was born on the day of Michelangelo’s death. One might fancy that this signified the passing of the sceptre from art to science, for science was destined to receive a great impetus from this remarkable man. While still a youth he discovered the regularity of the vibration of a pendulum by observing the swinging of the cathedral lamp of Pisa. He set to work and found that the vibration of a pendulum varies as the square root of its length. He recognized the utility of the pendulum as a timing device, but it remained for Huygens (1673) and others to perfect its use in clocks.
Shortly after his first observations of the pendulum, Galileo conducted his famous experiments on falling bodies dropped from the leaning tower of Pisa. By showing that the velocity of descent was independent of weight, he upset the idea which had prevailed for centuries that the velocity was proportional to weight. Many who saw his objects of unequal weights, dropped simultaneously from the same height, strike the ground at the same time, still did not believe that Aristotle (384-322 B. c.) and his followers were in error. When we contemplate that civilization had been progressing for many thousand years, it is difficult to believe that only 400 years ago Galileo was for the first time proving before an audience, which for a time was still to remain skeptical, the law of falling bodies. To us this is a simple law, but Galileo, in proving by experiment and placing in proper mathematical relation to other factors the acceleration of a falling body, made a contribution to physical science comparable to all the work of the philosophers who preceded him.
He also studied the motion of projectiles under the two forces, the projecting force and that of the earth’s attraction. Then Galileo turned his attention more to the heavenly bodies. Learning of the telescope invented in Holland, he constructed one for himself and began a series of noteworthy observations. He discovered the sun-spots, the satellites of Jupiter, the rings of Saturn, and the mountains and other markings of the Moon. What fascination there must have been to gaze upon these marvels that had been hidden from man’s eyes for so long!