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Christopher Columbus has gone down in history as the man who discovered America.

He was looking for a way of getting to the East by sailing west.

It was hard for him to get help for this journey.

He was laughed at by most people when he said he could go this way to India because the earth was round.

This is the sort of ship Columbus sailed in.

He made use of a half-hour sand glass for measuring time at sea.

Through all the long month the glasses on Columbus's three ships had to be turned every half-hour as the sand ran out.

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People living in America were named Indians by Columbus because he thought he had got to India when he discovered America.

He went back to spain without knowing than he had found a new continent.

He knew nothing of the life that had been going on in North and South America for thousands of years or of the two great peoples,

the Aztecs and the Incas,who had been living there-

the one in Mexico, the other in Peru-for centuries.

It is now thought that in 1500 the population of the Americas was about 30 million,

and that the first of these "Indians" had come from Asia themselves.

There may have been a land bridge between Asin and alaska across which they could have come.

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Thirty years after Columbus discovered America, the ship of Magellan, a sailer of Portugal,

was the first to make its way south of South America and on round the world through the Indian Ocean and past the Cape of Good Hope back to Europe.

Magellan himself died on one of the Philippine Islands on April 27 (in) 1521.

When a ship sailed out to the west and come back home from the east three years later people could see that the earth must be round.

This proved that the earth was round.

It was proof enough for most people.

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But is was harder to take in idea that the earth might be moving round the sun,

as Copernicus of Poland, 1473-1543, said it was.

Very few people had make any sense of the writings of Copernicus by the time the died in 1543,

twenty-one years before Galileo and Shakespeare were born.

Few people could read or write in those days.

It was Galileo who made the first telescope,through which he could watch the stars and look into the ideas that Copernicus and others had been working upon.

Through his telescope the stars seemed more than thirty times as near,

and he could see not only the mountains of moon but spots on the face of the sun,

and the motion of the moons moving round the planet Jupiter.

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Galileo could let people look through his telescope but he could not make most of them see the picture of the universe that was becoming clear in his mind.

He could not do that any more than copernicus had been able to do it.

People's ideas were changing, but not as quickly as his.

Galileo was put in prison for saying that the ideas written down by Ptolemy fifteen hundred years before did not make sense to him.

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Newton,who was born the year than Galileo died, took the new line of thought much farther.

Like Galileo,he became a great watcher and recorder,asking the question "how" more than "why and" answering by measuring and recording and comparing and proving.

Even more than Galileo,he saw the universe as part of a great machine,

and he was able to put into words great natural laws-accounts of its workings.

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He was able to do this only because he was carried forward on the shoulders of such men as Galileo, Kepler and Copernicus.

With their work before him he could think out new ideas about the weights of things and their motions.

His Law of Gravitation says that all things in the universe have an attraction for one another.

It was only by standing on Newton's and other scientists' shoulders that Einstein was able to get his picture of the universe and work out new ideas about time and space and energy.

Their work made it possible for him to see farther into the laws of the universe than they could.

Younger scientists in their turn are developing new ideas made possible by Einstein.

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The thinking of scientists has become clearer and truer as their instruments have become better.

Galileo made one of the first microscopes as well as the first telescope,

and by the middle of the seventeenth century this new instrument had opened up another world, a world of things too small for our eyes by themselves to see.

The microscope made possible the discovery of the cell structure of all living things.

Even the human body could be pictured now as a great machine with millions upon millions of working parts, each part a cell.

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Together with all this new knowledge of the cell structure of plants and animals,

the microscope opened up a world of living beings so small that people had no idea such thing were possible.

It was surprise to the scientist to see that in a drop of water there might be thousands of living things of many different sorts moving about and taking in food.

With the invention of such instruments as the microscope and telescope,people found themselves walking between two strange new words:

one too far off and great,

the other too near and small for anyone but the scientist to know much about or do much about.

As science developed, thinking people came to feel less and less at home in the universe.

They had enough knowledge to become conscious of the need for more.

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Our bodies can be looked upon as machines which are kept going by fuel.

As food is burned up in the body cells it gives us heat and other sorts of energy.

All through our lives-from birth to death- we must be supplied with energy.

Even when we are sleeping we are using up some food to keep our bodies warm.

Our lungs and heart keep on working.

Some animals sleep through the cold winter weather: snakes, for example.

When they are asleep,their rate of breathing and pulse rate and temperature go down, and less food is needed.

Only animals that can store enough fat in their bodies to keep them alive through the winter can sleep through the months when food is hard to get.