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 arc. 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 Schrödinger, 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.
Thus the Quantum Theory and Relativity, both basic to our modern understanding of the universe, benefited by Einstein's thought. To the first was only one contributor of many, however, and the names of Planck, Bohr, Heisenberg, Dirac, de Broglie, Schrödinger, Pauli, and many others must be joined with his. But Relativity is Einstein's alone, and it will stand as his enduring monument.
The basic arguments of Relativity are not difficult to comprehend, though the detailed mathematical argument lies in a field so uncommon that it was familiar to only a few trained mathematicians when the theory first appeared. Einstein had a pleasant and full-fledged gift of humor, which he used to fob off laymen who wanted a simple explanation of Relativity, saying, "When you sit with a nice girl for two hours, you think it's only a minute. But when you sit on a hot stove for a minute, you think it's two hours. That's relativity." This has, of course, nothing to do with his theory, but only with what the world well knew before he lived: that many things are relative. Closer to the truth was the statement he approved: "There is no hitching post in the Universe—so far as we know." His great feat was analogous to breaking with such obvious observations as that bullets shot from a moving gun have a different velocity than those from a gun at rest, for their motion relative to the gun and to an observer must both be measured. Such common sense when applied to light waves led to contradictory results, and his great genius lay in having both the willingness and the ability to see what had to be assumed to make things come out as they are observed. By being so apparently foolish as to assume that light moves at a constant speed relative to all observers, no matter how they are moving relative to one another, Einstein picked up the thread of truth again and led the whole baying field of scientists, their tattered Aether in shreds, off in a new direction.
The passing of Einstein gives us a chance to stop and think how it felt to have been alive while one of the authentic great minds of all history was doing its work. All of his reputation is deserved, but on a basis rather different from that commonly supposed. The intelligent man in the street is likely to say that Einstein was the world's greatest mathematician. This is correct enough, but in truth it misses the mark. He was, to be sure, a natural lover of mathematics, and taught himself from books at an early age more mathematics than any person but one in a million ever learns. However, there have been and are many greater mathematicians than he. Instead, he was that priceless rarity, an intuitive thinker who was able to assemble and grasp great generalities, and manipulate them into view for the world of men. He knew what he wanted to do, and when he did not have the mathematical tools himself, he knew where to turn for help. For mathematical help he turned to specialists. Much of Relativity is based on the work of Lorentz and of Poincaré.
It is not the feat of working out a theory so difficult to understand as the basic tenets of Relativity that excites our admiration, so much as the ability of a man to dash in so radical a direction to pick up the vanished thread of truth. Truth travels a variably curved path, and scientists tend to travel in straight lines in the direction in which the thread pointed when they last had hold of it. Then they need an Einstein, who goes in quite unreasonable directions and finds the thread again.
Einstein could be very, very wrong. In fact he gloried in the willingness to be so, as a mark of the true scientist; for probing in the dark for truth is bound, as he pointed out, to bring ninety-nine fruitless gropings for one successful grasp. But he could be wronger than most, for his mental reach was greater.
Einstein was always a kindly professor, and did human acts which endeared him to many. I treasure my only letter from him, received as an anonymous minor wartime government official in charge of a certain scientific field in which he made an invention. While doing his greatest thinking, Einstein had worked in the Swiss Patent Office, and he was patent-conscious all his life. One of his patents was for a camera in which the size of the lens stop was automatically adjusted by the light from the scene to be photographed as it fell on a photocell attached to the camera. But Einstein was primarily a theorist, and was likely to overlook important details that often bar such devices from practicality. So it was with the device he submitted to the government in wartime, an automatic instrument for navigators, quite correct in theory, but incapable of reduction to practice because of the unfortunate presence of friction.
Einstein became in the last two decades a familiar figure on the Princeton campus in his wrinkled sweater, his long white hair straggling out from under his formless stocking cap. The isolated college community in its village was an ideal place for him; his duties were to sit and think, and to help young scientists to think while they sat and listened to his discussions. He was always a most stimulating thinker, though far from what would be called a good speaker.
Typical of Einstein is the story of the popular lecture he was finally prevailed upon to give, for it shows his incapability of behavior that was not genuine. He had been asked many times to speak to a certain audience, but had always begged off on the basis that he had nothing to say. Finally, however, the pressure became so great that he was forced to accede. Came the evening of the lecture, and amidst applause Dr. Einstein was led to the front of the stage and introduced. For a few moments, he looked out at the audience, tongue-tied and silent. Finally he could stand it no longer and, smiling sheepishly, said, "I find that I have nothing to say," and returned to his seat.
Much of his shyness sprang from the fact that the things that occupied his mind would not have interested a casual listener. He was a simple, friendly man, of utter modesty, truly uninterested in worldly honors, and worried by the adulation heaped upon him. His latest entry in American Men of Science does not even mention the Nobel Prize he won in 1921, although it does mention a lesser prize. He had humility in its truest form, and the greatest need of his later years sprang from his desire for protection from a prying and inquisitive public.
Was Einstein naive? By ordinary standards he often seemed so, but he had the naiveté of a Parsifal, the innocence so dangerous to falsity, a cutting sword that slices the draperies from sham. Many of his friends regretted his stand in advising scientists to refuse to testify before congressional committees, and his half-jesting and misunderstood comment that, the way scientists are treated today, if he had had it to do all over he might well have become a plumber. He did not expect his dicta to be taken with such seriousness by so many.
He was a great lover of mankind and an internationalist. He was an intense Zionist, and although he would have been called irreligious by many, was deeply religious in the highest sense, with a profound conviction of the unity of nature and of the presence of purpose in the universe. But he did not concern himself with personal salvation or the details of creeds and isms. Although he lent himself, as the scientist most likely to catch the ear of a busy statesman, to the efforts of others to bring to the attention of President Roosevelt the possibility of the release of nuclear energy, he had no stomach for instruments of warfare and was a profound lover of peace.
A newspaper headline that I saw on the day he died, "His Theory Paved the Way for Atom Bomb," would lave saddened him. While true in word, it is a distortion of the truth. It would be equally true, and almost as relevant, to say that the submarine Nautilus resulted from the discovery made by Archimedes when he sprang from his bath shouting "Eureka!" Einstein's great law of the equivalence of matter and energy, which sprang from his 1905 Theory of Special Relativity, without a doubt is one of the most basic discoveries made, and will be remembered long after atom bombs have been outmoded or outlawed. The concept that matter and energy are interconvertible strikes directly to the core of the universe, probably exceeds in grandeur any other picture the field of physical science. He exercised the most profound influence on the future cogitations of philosophers, and though his ideas of causality have lately been the subject of controversy between himself and such great physicists as Bohr, and much misunderstood by ordinary thinkers, they cut the solid earth out from under the placid concepts of the nineteenth century and substituted a more tenuous but more realistic picture.
No one regretted more than Einstein the close association of his great theory with atomic bomb and instruments of warfare, yet he realized that this was a normal part of human evolution and that man must grow with his universe. His new directions of thought were filled with meaning for the coming races of mankind, and will lead men into new fields of awareness, new challenges of attainment, and new realizations of human destiny.
Such a combination of intellectual abilities as his comes not more than a few times in a millennium; we are distinguished to have lived while such a giant walked the earth.