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Einstein's solution of this dilemma was characteristically bold. "Light," he said, "is both corpuscles and waves." A light ray is a shower of energy particles called "photons" whose energy increases with the wave frequency of the light.
Out of this simple but daring idea developed the supremely important knowledge that energy comes in small, discontinuous "quanta" analogous to the atoms of matter and the electrons of electricity.
Gravitation and Starlight. "Special Relativity," though it stood many rigorous tests, was not accepted at once. For ten years Einstein worked, extending his theory to cover more varied "frames of reference." In 1915, he published his "General Relativity." It explained the force of gravitation itself, which Newton had merely pointed out.
Here was a chance for a final, convincing test. According to Einstein, light carried energy. Therefore it had mass. Therefore rays of light from a star should be bent by a definite amount when they passed through the strong gravitational field near the sun. A convenient solar eclipse provided the opportunity to test the theory. Star images near the rim of the blacked-out sun were displaced by almost exactly the amount which Einstein predicted, proving that their rays had been bent.
From that day, Relativity was the basic law of the universe. Einstein's photons, too, grew into the head-splitting Quantum Mechanics, which teaches that all matter is nothing but waves, crossing and interacting! Little by little, both theories have worked their way into nearly all branches of science.
The end of the physical revolution which Einstein started is not yet in sight. Perhaps it will stop itself—suddenly—in mid-development under the impact of that equation, E = mc2, which inspired the nuclear physicists to turn small bits of matter into world-shaking energy.
If the atom bomb blasted the last popular skepticism about Einstein's genius it also blasted man's complacent pride in the power of unaided intellect. At the very moment that it was finally mastered, matter was most elusive and most menacing.
The fateful mind behind the bomb was born into the world it was to change so greatly, at Ulm, Germany, in 1879.
Einstein's father was an unsuccessful merchant turned unsuccessful electrical engineer.
The boy was painfully shy, introsoective, and so slow in learning to speak that his parents feared he was subnormal. At school he was a poor student. But he learned to improvise on the piano, and used to make up religious songs which he would hum in his own room where no one could hear him.
At 13, Albert was reading Kant's Critique of Pure Reason. Soon he discovered Schopenhauer and Nietzsche.
In 1895, Einstein took the entrance examinations for the Polytechnicum in Zurich, Switzerland. He failed, but got in a year later. At Zurich he completed his formal scientific education, became fast friends with the Austrian Socialist leader, political assassin and physicist, Friedrich Adler.
After graduation Einstein became a Swiss citizen, later married the Serbian mathematician, Mileva Marech, by whom he had two sons.