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Saturday, February 26, 2011


Long time ago a Greek, Democritus, said that all things in a vacuum fall at the same speed. He had not got a vacuum, but he was right. The air makes a difference. If a heavy weight and a piece of paper fall together through the air, the heavy weight reaches the ground first. The air has some resistance, and it makes the paper fall slowly, but if there was no air, the paper would fall quickly.
Aristotle said that heavy things fall faster than light things, but he was wrong.

Most of the later scientists believed Aristotle. This remained true until the time of Galileo, the Italian scientist. Galileo (1564-1642) did not believe him. He went to school at Vallombrosa, which is a place near Firenze (Florence) Italy. He tried to learn science there, but he did not like it. He went to the university of Pisa to continue his studies.

There is a famous tower at Pisa. It does not stand straight up but leans a little more each year. Some scientists believe that it will soon fall down.
Galileo climbed to the top of the leaning tower and from there he dropped two weights. One of them was heavier than the other, but they reached the ground at the same moment. The scientists who were watching were very surprised. This did not agree with Aristotle’s rule.
Galileo believed that scientists ought always to make experiments. He said that they ought not only to sit in universities and talk, they ought to do something. They ought to watch the results of their experiments, and describe them honestly. Then they could learn more about science.
Many people of that time believed that the earth never moved. The other planets and the sun appeared to move round the earth, and they believed that the earth was the centre of the universe. Ptolemy had taught this many years before, and it appeared to be true. Nobody knew then that the earth was an unimportant planet.
Copernicus (1473-1543) was an astronomer and a scientist who had studied the planets and the stars. His ideas were new. He said that the earth moved round the sun, and that it was not the centre of everything. He put these ideas into a book, but he hid the book. Nobody could read it until Copernicus died.
Many years later Galileo read it and believed it. He said that the earth was moving round the sun, and this made a lot of people angry. They believed that the earth was too important to move. They said that it must be centre of the universe. Galileo got into trouble and he had to say that he was wrong, but he knew that he was right.
Galileo made many other experiments, and also made some telescopes. When pointed a telescope at the moon, he saw some hills there. He also saw some of the millions of stars in the universe more than anyone had ever seen. He thanked God, who let him see these wonderful things. 

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