VOICE ONE:

This is Steve Ember.

VOICE TWO:

And this is Sarah Long with the VOA Special English program,Explorations. Today we tell about a scientist who changed the way weunderstand the universe, Albert Einstein.

VOICE ONE:

In the year Nineteen-Oh-Five,Albert Einstein published some important papers in a Germanscientific magazine. They included one of the most importantscientific documents in history. It was filled with mathematics. Itexplained what came to be called his "Special Theory of Relativity."Ten years later he expanded it to a "General Theory of Relativity."

Albert Einstein's theories of relativity are about the basicideas we use to describe natural happenings. They are about time,space, mass, movement, and gravity.

VOICE TWO:

Albert Einstein was born in Ulm, Germany, inEighteen-Seventy-Nine. His father owned a factory that madeelectrical devices. His mother enjoyed music and books. His parentswere Jewish but they did not observe many of the religion's rules.

Albert was a quiet child who spent much of his time alone. He wasslow to talk and had difficulty learning to read.

When Albert was five years old, his father gave him a compass.The child was filled with wonder when he discovered that the compassneedle always pointed in the same direction -- to the north. Heasked his father and his uncle what caused the needle to move.

Their answers about magnetism and gravity were difficult for theboy to understand. Yet he spent a lot of time thinking about them.He said later that he felt something hidden had to be behind things.

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Albert did not like school. The German schools of that time werenot pleasant. Students could not ask questions. Albert said he feltas if he were in prison.

One story says Albert told his Uncle Jacob how much he hatedschool, especially mathematics. His uncle told him to solvemathematical problems by pretending to be a policeman. "You arelooking for someone," he said, "but you do not know who. Call him X.Find him by using the mathematical tools of algebra and geometry."

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Albert learned to love mathematics. He was studying the complexmathematics of calculus when all his friends were still studyingsimple mathematics. Instead of playing with friends he thought aboutthings such as: "What would happen if people could travel at thespeed of light?"

Albert decided that he wanted to teach mathematics and physics.He attended the Federal Polytechnic Institute in Zurich,Switzerland. He graduated with honors, but could not get a teachingjob. So he began working for the Swiss government as an inspector ofpatents for new inventions. The job was not demanding. He had a lotof time to think about some of his scientific theories.

VOICE ONE:

From the time he was a boy, Albert Einstein had performed what hecalled "thought experiments" to test his ideas. He used his mind asa laboratory. By Nineteen-Oh-Five, he had formed his ideas intotheories that he published.

In one paper he said that light travels both in waves and inparticles, called photons. This idea is an important part of what iscalled the quantum theory.

Another paper was about the motion of small particles suspendedin a liquid or gas. It confirmed the atomic theory of matter.

The most important of Albert Einstein's theories published thatyear became known as his "Special Theory of Relativity." He said thespeed of light is always the same -- almost three-hundred-thousandkilometers a second. Where the light is coming from or who ismeasuring it does not change the speed. However, he said, time canchange. And mass can change. And length can change. They depend onwhere a person is in relation to an object or an event.

VOICE TWO:

Imagine two space vehicles with a scientist travelling in eachone. One spaceship is red. One is blue. Except for color, bothspaceships are exactly alike. They pass one another far out inspace.

Neither scientist feels that his ship is moving. To each, itseems that the other ship is moving, not his. As they pass at highspeed, the scientist in each ship measures how long it takes a beamof light to travel from the floor to the top of his spaceship, hit amirror and return to the floor. Each spaceship has a window thatlets each scientist see the experiment of the other.

VOICE ONE:

They begin their experiments at exactly the same moment. Thescientist in the blue ship sees his beam of light go straight up andcome straight down. But he sees that the light beam in the red shipdoes not do this. The red ship is moving so fast that the beam doesnot appear to go straight up. It forms a path up and down that lookslike an upside down "V".

The scientist in the red ship would see exactly the same thing ashe watched the experiment by the other scientist. He could say thattime passed more slowly in the other ship. Each scientist would becorrect, because the passing of time is linked to the position ofthe observer.

Each scientist also would see that the other spaceship wasshorter than his own. The higher the speeds the spaceships weretravelling, the shorter the other ship would appear. And althoughthe other ship would seem shorter, its mass would increase. It wouldseem to get heavier.

The ideas were difficult to accept. Yet other scientists didexperiments to prove that Einstein's theory was correct.

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Ten years after his paper on the special theory of relativity,Albert Einstein finished work on another theory. It described whathe called his "General Theory of Relativity." It expanded hisspecial theory to include the motion of objects that are gainingspeed. This theory offered new ideas about gravity and the closerelationship between matter and energy. It built on the ideas aboutmass he had expressed in Nineteen-Oh-Five.

Einstein said that an object loses mass when it gives off light,which is a kind of energy. He believed that matter and energy weredifferent forms of the same thing. That was the basis of his famousmathematical statement E equals m-c squared (energy equals masstimes the speed of light squared). This statement or formulaexplained that a great amount of energy could come from a smallpiece of matter. It explained how the sun could give off heat andlight for millions of years. This formula also led to the discoveryof atomic energy.

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In his general theory ofrelativity, Einstein said that gravity, like time, is not always thesame. Gravity changes as observers speed up or slow down. He alsosaid that gravity from very large objects, such as stars, could turnthe path of light waves that passed nearby. This seemedunbelievable. But in Nineteen-Nineteen, British scientists confirmedhis theory when the sun was completely blocked during a solareclipse. Albert Einstein immediately became famous around the world.

In Nineteen-Twenty-One, he won theNobel Prize in Physics. It was given to him, not for his theories ofrelativity, but for his discovery of the law of the photoelectriceffect. This scientific law explained how and why some metals giveoff electrons after light falls on their surfaces. The discovery ledto the development of modern electronics, including radio andtelevision.

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Albert Einstein taught in Switzerland and Germany. He leftGermany when Adolph Hitler came to power in Nineteen-Thirty-Three.Hemoved to the United States to continue his research. He worked atthe Institute for Advanced Study in Princeton, New Jersey. Einsteinbecame a citizen of the United States in Nineteen-Forty.

VOICE ONE:

Einstein was a famous man, but you would not have known that bylooking at him. His white hair was long and wild. He wore oldclothes. He showed an inner joy when he was playing his violin ortalking about his work. Students and friends said he had a way ofexplaining difficult ideas using images that were easy tounderstand.

Albert Einstein opposed wars. Yet he wrote to President FranklinRoosevelt in Nineteen-Thirty-Nine to advise him that the UnitedStates should develop an atomic bomb before Germany did.

Einstein spent the last twenty-five years of his life working onwhat he called a "unified field theory." He hoped to find a commonmathematical statement that could tie together all the differentparts of physics. He did not succeed.

Albert Einstein died in Nineteen-Fifty-Five. He was seventy-sixyears old.

VOICE TWO:

This Special English program was written by Marilyn Christianoand produced by Paul Thompson. This is Sarah Long.

VOICE ONE:

And this is Steve Ember. Join us again next week for anotherExplorations program on the Voice of America.