The world has lost a shy and kindly man, sweet-natured and intensely human, and for a long time now will be taking stock of what resulted from his three quarter-centuries of living. Most of what he did, woven into the mesh of all future civilization, came about from the long, long thoughts of a youth of twenty-six. Like Newton, Einstein finished his greatest work before the age of thirty.
They are saying that such minds come on the human scene only once in a hundred years, but this is an understatement. Not since that earlier youth invented the calculus and discovered the law of universal gravitation, nearly three hundred years ago, has so lofty a peak of intellectual achievement even been approached. It is futile to argue whether Einstein's was the Everest and Newton's the lesser Himalaya of a mind, or vice versa; in my opinion, with which some would disagree, one must go beyond Galileo and even Archimedes to find Einstein's match, back to the days when the world of speculation was very young indeed. The peaks that rose from the plain of thought when intellectual adventure was new are hard to measure, and it may well have been easier to reorient the ideas of men when there were fewer of men or ideas. The violence Einstein wrought on the common run of thought has been only approached by others. He reared his structures on a massif left by many minds, but his influence on the reasoning and actions of mankind is likely in the end to make men think of a few only as his peers.
It was more than youth that gave young Einstein such willingness to plunge off in new directions to explain phenomena that had defied explanation in previous terms, but youth played an important role. 1905 was his great year of fruition. Max Planck had in 1901 come to the conclusion that it was impossible to explain the emission of light waves by atoms and molecules in terms of any conceivable adaptation of the classical theories of physics. So much of red light, so much of green, such an intensity of blue in the mixture—the ratios were known to depend mainly on how hot was the luminous object emitting them, whether sun or electric are. Planck had pointed out that only by assuming the existence of discrete packets of energy, the quanta or photons of light that we all now accept as real, could the observed distribution of energy from a hot glowing object be explained. Few were prepared to believe so radical a concept, until Einstein came forward with a new theory of the photoelectric effect, in which quanta appeared again as essential to an understanding of energy. Today the photoelectric effect, in which electrons are struck from metal plates by incoming light waves, is basic to many of our most common instruments: exposure meters, vacuum tubes to open doors for baggage-laden travelers, pickup tubes for television cameras. Einstein showed that to explain the basic phenomenon it was necessary again to assume that light came in tiny packets. Thus he got Planck's Quantum Theory off to a good start.
Soon he did violence to preconceptions again. He started thinking about certain inconsistencies in the explanation of specific heats. When an atom or a molecule vibrates, any person of common sense would suppose that it does so by an amount depending on the energy communicated to it, as a tree vibrates in the wind or a bell rocks when rung. This idea is correct for objects of ordinary size, but Einstein showed that ultramicroscopic objects vibrate with only certain amounts of energy, refusing to accept a change unless a definite increase in energy is communicated to them, so that they change their vibrating energy in discrete jumps. What a thrill of discovery he must have had when he found that using the quantum idea again cleared up the discrepancies!
That the basic action of energy is quantized, it has recently been pointed out by Schrodinger, probably explains how the hereditary genes can remain the same over the ages yet be susceptible to mutations when struck by a cosmic ray or any other unusual bundle of excessive energy. To explain the panorama of organic evolution one must have a gene which is very stable, yet capable of rapid change on occasion. The horseshoe crab, for example, has remained essentially the same for 160 million years, during which time its gene molecules have reduplicated themselves, millions of times. How can the gene, a molecule composed of many thousands of atoms, under the ceaseless buffetings of the atoms surrounding it remain stable enough to assemble inert matter into the bodies of horseshoe crabs identical with their ancestors of past ages? Easy, says Schrödinger, if you follow Einstein and the experimenters who have proved that his ideas were right. For at the temperatures at which living creatures exist, the vibrations that come in from other atoms jiggle the gone molecules effectively only seldom, because their energy acceptance is quantized. But subject them to high temperatures, or to mustard gas, or to cosmic rays, and an atom is easily knocked out of place so that a change is induced in the gene which results in production of a creature of slightly different characteristics. Thus a mutation can result, giving nature an occasional new opportunity for improving by selection, with the resulting great sweep of organic evolution.
These great assists to the Quantum Theory of light were only two of Einstein's early papers; the third, his greatest break-through of the boundaries of knowledge, was his 1905 paper on Special Relativity. Only a few scientists paid much attention to it for a dozen years, and for a time fewer than a dozen, were able to understand its mathematics. By 1917 it had been extended, verified, and accepted, and with the Quantum Theory it now forms one of the great twin bastions of modern physics, and indeed of all science.
By 1907 Einstein's greatest work was done, though he was still to do enough of importance to bring an outstanding reputation to any run--of-the-mine theoretical physicist. His short paper on General Relativity made a great splash in the popular press when it appeared in 1916, especially after it and his earlier theory were verified by measurements on such things as his prediction of a bending of light rays by the gravitational field of the sun and his explanation of the advance of the perihelion of the planet Mercury.
From this time onward Einstein's work, though occasionally sending a sharp shaft of light to illuminate a dark spot in physics, declined in importance. His work on the Brownian movement, that flea-like jumping of small flakes of mica or carbon that can be observed as they are pushed about by the molecules of a liquid in which they are suspended, published in 1926, was merely an excellent theoretical investigation by a highly qualified physicist. His contribution to the Bose-Einstein Statistics was even more important, but in the same category, and could have been made by any one of a dozen living physicists.
In his later years, while a professor at the Institute for Advanced Study in Princeton, Einstein occupied himself in the search for a unified field theory. Of the three basic forces of the universe, the electrical, magnetic, and gravitational forces which account for all physical phenomena, the first two are known to be related, and it seems probable to many physicists that all will ultimately be found to be expressions of a single basic force. The papers that Einstein published on this subject seem not to have been directly fruitful, though his thoughts will surely serve as a basis on which others can build in the urge for seeking a unifying principle behind all life. Many experts believe that he was not even on the right track in this work. Some felt that he became increasingly traditional as he aged; others that he had struck such a high mark in his youth that he was unable to excel it except by attempting the almost impossible.