CONSIDERING THAT Albert Einstein was one of the greatest scientific geniuses of all time, some of the facts of his early years seem quite unbelievable.

He did not learn to speak until 3. He hated school; one of his teachers told him he would never amount to anything, and at 15 he dropped out. At 16 he took the entrance exam for the Polytechnic Institute in Zurich, and failed.

There is, however, another side to the story. At about 5 he was given a magnetic compass by his father, and when he saw its needle in the grip of a mysterious, invisible force, he was filled with a sense of awe and wonder that never left him. At 12 he came upon a geometry textbook that utterly fascinated him; he spoke of it as "the holy geometry book" and cherished it all his life.

What he hated about German schools was their rigid, oppressive discipline and their emphasis on learning rote (he had a poor memory for words). He taught himself calculus and read about science with intense excitement. Although he failed the entrance examination at the Polytechnic Institute, his performance in mathematics and physics was impressive, and ultimately he was permitted to enroll.

Einstein attended lectures only occasionally, preferring to perform experiments and study the writings of great scientists. This was an ideal way for a genius to study, but caused a serious problem when examination time arrived. Luckily his friend Marcel Grossmann had taken superb lecture notes and allowed him to study them. Without those notes he might have failed.

Cramming for the final exam was so distasteful to Einstein that for a year he lost all interest in science. He antagonized his professors and as a result was unable to obtain an academic position. After bitter years of temporary teaching jobs, he managed, with Grossmann's help, to obtain a position in the Swiss patent office in Berne. There his genius burst into flower.

THE YEAR 1905 would have been memorable in the annals of science even if Einstein had produced only his paper "On the Electrodynamics of Moving Bodies," in which he presented what we now call the special theory of relativity.

But he made other major contributions; in those days there were outstanding scientists who still doubted that atoms existed, but they could doubt no longer when predictions in another of Einstein's 1905 papers were verified experimentally.

Then, too, there was a momentous paper, only three pages long, in which he showed that energy has mass according to his famous formula, E = mc2 -- that is, energy equals mass times the speed of light squared. (Two years later he realized this formula also showed that mass is a reservoir of colossal amounts of energy.)

Perhaps his most remarkable and certainly his most revolutionary paper, the first of his 1905 papers, argued that we should think of light as particles even though overwhelming evidence suggested that light consisted of waves. Five years earlier the great German physicist Max Planck had introduced a new concept, the quantum, an idea so revolutionary that not even Planck believed in it; what Einstein did was to take the quantum seriously and apply it to light.

In 1913, when some of the greatest German scientists wanted to offer Einstein a prestigious positon in Berlin, they spoke glowingly to the authorities of his accomplishments and apologized for his idea of particles of light. But Einstein had found a surprisingly simple mathematical formula for the photoelectric effect, which is used today by television cameras to convert light into electricity.

About the time of the invitation to Berlin, the American physicist Robert Millikan began a difficult experiment to show once and for all the falsity of Einstein's photoelectric formula. The experiment took two years. To Millikan's surprise, the photoelectric formula was in precise agreement with the experiment, and he published the results with enthusiasm. When Einstein received the 1921 Nobel Prize in physics, his photoelectric formula was the only one of his achievements specifically mentioned in the citation.

MY OWN FIRST meeting with Einstein remains vivid in memory. In fear and trembling, I knocked on his door at the Institute for Advanced Study in Princeton, N.J., hoping to ask about some ideas in relativity that I had been working on. When I entered I found him sitting in a comfortable chair smoking a pipe, sloppily dressed, hair unruly, with papers on his lap. He smiled and asked me to write my equations on the blackboard. "Please go slowly," he said. "I do not understand things quickly."

At once all my fears vanished. He asked me penetrating questions, many of which I had not thought of, and he did it without making me feel stupid. It was as if we were partners looking at an idea from all sides.

Einstein, like Isaac Newton, found sublime simplicity in the universe. He looked primarily for beauty in the laws of the universe. He said that in evaluating a scientific theory, he asked himself whether he would have made the universe that way if he had been God. This he did to arrive at his general theory of relativity.

One of the basic principles of his 1905 theory was that uniform motion is relative: If we are in a closed, windowless vehicle that is moving uniformly we cannot detect its motion by ay experiment we take inside it. Einstein felt it was inartistic that only uniform motion should be relative. God would not have made the universe in so clumsy a way. The trouble was that non-uniform motion is detectable: When a train suddenly speeds up or slows down the passengers have to hold on tightly.

Einstein studied the facts and saw to his joy that it was indeed possible to regard all motion as relative. For the passengers in the train the effects of the acceleration or deceleration could be thought of as gravitational, and with this insight Einstein was on his way to a new theory of gravitation.

EINSTEIN WAS working on his General Theory of Relativity in Berlin when World War I broke out in 1914. Having been for some time a Swiss citizen, he was able to devote himself to his work, and in 1915 he presented his General Theory of Relativity. One of his basic predictions was that light rays would be found to be bent by gravitation.

British scientists had no direct communication with Germany, but the Cambridge astronomer and physicist Arthur Stanley Eddington, a Quaker and pacifist, obtained details of Einstein's new theory through scientists in Holland. He was fascinated with its beauty. In the midst of war, an expedition was mounted to test the bending of light rays during an eclipse of the sun that was to occur in 1919. It was carried out after fighting had ceased but with the war still not ended. The eclipse observations agreed with Einstein's prediction.

The British put aside their strong anti-German feelings and announced the results at a special meeting of the Royal Society of London and the Royal Astronomical Society. It was clear to the scientists in the crowded hall that Newton's theory of gravitation, which had held sway for 250 years, must yield to the theory perfected in enemy Berlin. Almost overnight Einstein became world famous.

With fame came responsibilities. He knew his name carried weight, and he spoke out in the cause of peace and freedom and human rights. Having himself experienced anti-Semitism and seen its devastating effect on less fortunate Jews, he gave his support to Zionism and helped to raise funds for the construction of the Hebrew University in Jerusalem.

In Germany, envy and his being a Jew led to attacks on his theories and even threats to his person. When the Nazis seized power in 1933, they confiscated his savings and accused him of treason. Luckily he was outside Germany at the time. He never returned.

Instead he became a professor in Princeton, N.J., at the newly created Institute for Advanced Study. There he spent the rest of his days, continuing his search for a way to link gravitation and electromagneticism in a single unified theory while speaking out as boldly as ever against both foreign and domestic threats to freedom.

In early August 1939, with the world on the brink of World War II, Einstein wrote to President Franklin D. Roosevelt, alerting him to the alarming possibility of an atomic bomb being made out of uranium and pointing to the ominous fact that the Nazis had stopped the sale of uranium from mines in conquered Czechoslovakia.

The letter took 10 weeks to reach the president, and by then the war had started. Moreover, the letter turned out to have very little effect. Serious work on the atomic bomb by the Allies did not begin until two years later, and then only after the urgings of scientists in embattled Britain. These scientists -- chiefly refugees from Nazi Germany -- demonstrated that an atomic bomb was frighteningly possible. Its development was carried out in the United States to avoid interruption by air raids.

When Einstein wrote his letter to Roosevelt he had been afraid that the Nazis would develop the bomb first and with it impose their dictatorship on the world. When the United States dropped atomic bombs on Japanese cities he was horrified, and on learning that the Nazis had not done any major work on the bomb, he said that if he had known it at the time he would not have sent the letter to Roosevelt.

Most of us will never fully understand the complex ideas that Albert Einstein gave the world. But we can glimpse the outlines of his genius and imagine its awesome dimensions. To appreciate Einstein on the centennial of his birth is to celebrate the potential of the human mind .