THE PATHOS OF SCIENCE LIES IN ITS DOUBLE NATURE: The scientist is at once free and strictly confined, individual but ultimately subsumed. This double role begins when the apprentice scientist starts the long and exacting effort to master the findings of that formidable (and always growing) army of predecessors. The energy of the young scientist, the intense interest, busy labor, and excitement of possible discovery naturally block off presentiments of eventually being an old lion in winter—and fortunately so, for the sake of science. Trying to make any sort of advance is strenuous enough without also contemplating being ultimately dislodged. Physics sees itself as a self-erasing discipline, concerned only with the leading edge of research.
Those no longer on the leading edge—whether a few years behind, or centuries—no longer have an independent existence, as, say, Shakespeare and Rembrandt continue to have. Einstein was at the leading edge until 1926, but thereafter became like those he himself had once helped supplant. One might say that scientists have two careers, the living one of progress and discovery, and the posthumous one—and in certain ways, the posthumous career can begin before death occurs.
Needless to say, science never advances very neatly. The time-lines of discovery move at very different speeds, and often in odd directions. While Einstein brought relativity to consummation in 1905, clarity about the atom progressed in fits and starts. The electron was discovered inside the atom in 1897; radioactive matter in 1896; the quantum in 1900. In 1911, Rutherford found the atomic nucleus; in 1913, Bohr showed that the stability of the atom required a quantum explanation. Quantum mechanics arrived in 1925. The physics of the nucleus began to catch up only in the 1930s.
One scientist can be trumped very quickly by a new advance—consider Schrödinger, who thought his wave equation of 1926 had rid physics of the plague of quantum mechanics, only to find he had been co-opted within a year. Newton was dead two centuries before his theory was supplanted. Some discoveries are tied not to an individual, but to a team, or are a mosaic of findings, supplanted bit by bit. Older scientists begin to harvest the limitations science set on them when they entered the fray, as if a custodianship.
Every advance costs an earlier achievement's demotion or displacement. Einstein revered Galileo, Newton, Maxwell, Lorentz, and Planck even as his findings dislodged each of them. He turned Newtonian gravitation into a special case of general relativity; used the Maxwellian field concept to supplant Newtonian mechanics; used Maxwell to radically revise older views of space and time, including Maxwell's own; routed the ether principle, which Lorentz clung to; transformed Planck's quantum concept from a “black body” concept into the vast new subject of quantum theory. (The reader can choose other verbs.) If he had succeeded as hoped with unification, the list would be much longer, beginning with a fundamental revision of what electromagnetism and quantum theory mean.
As the cutting edge advances, those once in the forefront of research are left behind. This can scarcely be lamented, since science would otherwise not keep advancing. Even a Newton or an Einstein will be dislodged. Homer, Bach, Botticelli—never. Science in this sense is one of the strangest human enterprises, imposing a limitation known nowhere else in thought or art.
None of this was lost on Einstein. His sharp and humorous sense of how he came to be regarded as a “petrified object” was part of his realism about what would happen to his—and everyone else's—place in science. If physics cannot be based on the field concept, he wrote to his old friend Besso in 1954, then “nothing remains of my entire castle in the air, gravitation theory included, [and of] the rest of modern physics.”1 Even if the field theory holds, it will be modified.
There are countless studies of genius and creativity, but the decline of great scientists is a largely uncharted subject. Some preliminary sifting is needed. If one asks why Einstein ceased being the Einstein who revolutionized physics, a few explanations have become familiar. First and expectedly, his gifts are said to have faded as he grew older. As this happened, the young man's strengths became the older man's handicaps. In the Swiss patent office and in Berlin, he was a loner, unusually stubborn, fiercely independent, self-isolated—all this was an instinctual wisdom about how to protect and fulfill his great gifts. But later, the stubbornness hardened into an obstinate clinging to fixed ideas; the self-isolation ignored new findings that could challenge his preconceptions; he became inflexible as his younger self never was. In this view, too, he was the victim of his own early success. General relativity—that single-handed triumph against all odds and cautious advice—made him overconfident that the same method could handle the new problem. His triumphant experience “seared” him, said Abraham Pais, a colleague of Einstein at Princeton. It kept him persisting, decade after decade, despite setbacks that should have warned him off.
Yet one may wonder. A quite different picture of the older Einstein also exists. Mathematical ability proverbially weakens early, but the aging Einstein kept his prowess. Peter G. Bergmann, one of his younger mathematical assistants in the 1930s, recalled:
[What] impressed me—and remember that I was very young and Einstein in his fifties—was his tremendous creativeness… his sheer inventiveness of new approaches, of new mathematical tricks.2
Mathematics is not, however, the indispensable gift for a theoretical physicist—rather, physical intuition: the inner sense, judgment, hunch, perceptive inspiration, or however one names the inner gyroscopic instinct insisting that Nature supports this idea but not that one—and, of course, turns out to be right. In 1918, when (as noted earlier) Einstein rejected Hermann Weyl's unifying of gravity and electromagnetism as not corresponding to reality, Weyl made a telling remark: “The criticism,” he replied to Einstein, “very much disturbs me, of course, since experience has shown that one can rely on your intuition.”3 Everyone thought the same, and rightly so: Everything Einstein had done since the age of twenty-six demonstrated it. It is why he could often proceed without benefit of laboratory experiments, using only his “thought experiments.”
Did this supreme gift desert him in his later years? The American relativist John Wheeler of Princeton, who knew Einstein well from the 1930s, emphatically thinks not. In 1954, Wheeler hypothesized a “geon”—“a gravitating body made entirely of electromagnetic fields”—and sent his paper to Einstein for comment. Einstein, then seventy-five, thought about it awhile and said he doubted that a geon was stable; it took the much younger Wheeler several years to realize that Einstein was right.4 Einstein's intuition, Wheeler said, was as “amazing” as always.
But even if all Einstein's powers did flag suddenly and disastrously, this explanation is still too limited. The outcome of any scientific career depends as much on what others accomplish: New discoveries can throw logs across the path, raise perplexities, find powerful new explanations. Einstein hugely admired Lorentz, and Lorentz was hardly bereft of his great powers in 1905, mainly because the young Einstein dismissed the ether to which Lorentz was so committed. Einstein revered Newton even more, but he wrote:
Newton, forgive me: you found the only way which in your age was just about possible for a man with the highest powers of thought and creativity. The concepts which you created are guiding our thinking in physics even today, although we now know they will have to be replaced by others farther removed from the sphere of immediate experience, if we aim at a profounder understanding of relationships.5
What Newton did, what Einstein did after him, was possible only because science is a collective and cumulative enterprise.
The eighteenth-century poet Alexander Pope proclaimed: “God said, Let Newton be! and all was light.” Newton preferred a more sober view. In 1675, he wrote to Hooke:
You defer too much to my ability in searching into this subject. What Descartes did was a good step. You have added much…. If I have seen further it is by standing on the shoulders of giants.6
Science, said Robert Oppenheimer, is cumulative in “a quite special sense.” Its findings are defined in terms of the objects and laws and ideas that were the science of its predecessors. What Galileo or Faraday did is, for working physicists, not history to be learned, but tools to be used: the physicist's very language, subject, definitions, rules, instruments, and foundations.
Einstein used these tools freely in search of his quest for unity. Still, he never believed that Nature can be made to yield her secrets given enough brute force (say, accelerators) and ingenuity. Einstein spoke instead, in a Goethean vein, of the “implacable smile of Nature,” at once benign and mocking towards human efforts to fathom her mysteries. It may be that these efforts will always fall short, since Nature stands beyond. To those with eyes to see, the implacable smile foretells ultimate failure; any lifting of the veil is triumph enough. The smile, however, also bespeaks a benign posture, evidenced in what Einstein said was the ultimate mystery: that the universe is intelligible, and we can partake of that knowledge—and of that nobility. As he once said, “Nature conceals her secret through her essential nobility, not out of cunning.”7
For Einstein, the defeat that science visits on its practitioners seemed as impersonal as the order of the universe. Most scientists probably agree, in principle. But the daily life of science is simply not geared to Einstein's exalted attitude. Intense competitiveness spurs the scientist to produce that extra surge of energy, labor, and intense concentration needed. It can spill over into unseemly scuffles for fame and prizes. Few work on the rarefied mountain-tops of theory as Einstein did, commanding the grand view—the field is parceled instead into specialties and subspecialties, with teams of researchers instead of the lonely pioneer. By 1929, Dirac had made one extraordinary discovery after another; that year, he nonetheless wrote to Niels Bohr that quantum mechanics “will ultimately be replaced by something better, (and this applies to all physical theories).”8
The pathos of science does not always abide in the future. Often it doesn't wait, but invades the present as pressure, anxiety, doubt, or envy. Rivals may snatch away priority; someone else's research can devastatingly derail years of effort; or the supplanting future can appear in the here and now in the shape of an Einstein or Feynman, discouragingly quick, fertile, original; or invincibly sure-handed like Fermi or Rutherford. When the young Pauli and Heisenberg became Max Born's assistants at Göttingen, the older Born had such a presentiment. He said he couldn't match their genius.
If science is present-oriented, it also requires sustenance. It is vulnerable to the demands of its benefactors, whether the emergent German state on the cusp of World War I or the triumphant postnuclear United States.
Finally, the pathos can be shattering. Paul Ehrenfest, Einstein's beloved friend, committed suicide because he felt unable to keep up with the flood of new data and conundrums. His sense of being supplanted knotted unbearably and was—said Einstein—why he killed himself.
Einstein was also supplanted, but he was not shattered. In his old age, he became the ever more kindly, grandfatherly figure. He never considered his failing quest to be a tragedy. If many of his colleagues did, it was because he rejected quantum mechanics, the most vital new branch of physics. His last thirty years provoked steady and often unbridled opposition from cherished friends. Shortly before he died, Einstein wrote to Niels Bohr about banning nuclear weapons, but he couldn't resist teasing his old friend: “Don't frown like that,” Einstein's letter began, “this is not about quantum mechanics.” Einstein must have known that his personal quest for a unified theory had failed. In the end, belief trumped established science and yet left room for humor.
David Lindley, in his critical study The End of Physics, suggests that we have reached the end of what can be verified:
What restrains the theorist from becoming wholly carried away by the attractions of some mathematical theory is the need to make predictions with it and to test them against the hard realities of the real world. But as, during this century, experiments in fundamental physics have become harder to do, more costly, and more consuming of time and manpower, this restraining empirical influence has been weakened.
Lindley believes that Einstein's general theory of relativity inaugurated a tendency to view “experimental verification [as] something of an afterthought.”9 Even its most fervent proponents acknowledge that superstring, the most encompassing of the string theories, is nearly impossible to test, even indirectly.10 The same was said of early atomic theories; but by the time Russell visited Einstein and his friends in 1943, experiment was catching up to quantum physics. Einstein and Russell would spend the rest of their lives trying to wrest the atom from the industries of war.
What did the four great men speak of when they met at 112 Mercer Street? We will never know, of course. But speculation as to the topics is quite possible. They probably spoke little of the war: As Russell said, they were all in accord politically. Russell and Einstein disagreed over German war reparations, Einstein unable to forgive his former homeland. The doings of Los Alamos were sufficiently shrouded to have afforded little meat, although Pauli and Einstein were aware of the goings-on. Einstein and Pauli had just collaborated on a paper that touched on unified field theory and, despite their differences over quantum mechanics, found common ground—even suggesting, according to Pauli's biographer Charles Enz, an idea strikingly similar to the strings of string theory.11 Gödel was writing his critique of Russell's mathematical logic for the Living Philosophers volume, but it is unlikely, given Gödel's taciturn nature and Russell's distance from his early work, that much was said of it.
Russell, however, may have listened attentively and probed deeply. His Human Knowledge was in the planning stages; its subject, the nature of scientific knowledge. In it, Russell would begin modestly and conclude even more modestly. “To discover the minimum principles required to justify scientific inferences is one of the main purposes of this book,” he wrote in the Introduction. Having attempted to do so, he concludes, “[A]ll human knowledge is uncertain, inexact, and partial. To this doctrine we have not found any limitation whatever.”