einstein

Was Infeld right? Was tenacity the characteristic feature of Einstein’s genius? To some extent he had always been blessed by this trait,
especially in his long and lonely quest to generalize relativity. There was also ingrained in him, since his school days, a willingness to sail against
the current and defy the reigning authorities. All of this was evident in his quest for a unified theory.
But even though he liked to claim that an analysis of empirical data had played a minimal role in the construction of his great theories, he had
generally been graced with an intuitive feel for the insights and principles that could be wrested from nature based on current experiments and
observations. This trait was now becoming less evident.
By the late 1930s, he was becoming increasingly detached from new experimental discoveries. Instead of the unification of gravity and
electromagnetism, there was greater disunity as two new forces, the weak and the strong nuclear forces, were found. “Einstein chose to ignore
those new forces, although they were not any less fundamental than the two which have been known about longer,” his friend Abraham Pais
recalled. “He continued the old search for a unification of gravitation and electromagnetism.” 61
In addition, a menagerie of new fundamental particles were discovered beginning in the 1930s. Currently there are dozens of them, ranging from
bosons such as photons and gluons to fermions such as electrons, positrons, up quarks, and down quarks. This did not seem to bode well for
Einstein’s quest to unify everything. His friend Wolfgang Pauli, who joined him at the Institute in 1940, quipped about the futility of this quest. “What
God has put asunder,” he said, “let no man join together.” 62
Einstein found the new discoveries to be vaguely disconcerting, but he felt comfortable not putting much emphasis on them. “I can derive only
small pleasure from the great discoveries, because for the time being they do not seem to facilitate for me an understanding of the foundations,” he
wrote Max von Laue. “I feel like a kid who cannot get the hang of the ABCs, even though, strangely enough, I do not abandon hope. After all, one is
dealing here with a sphinx, not with a willing streetwalker.” 63
So Einstein beat on against the current, borne back ceaselessly into the past. He realized that he had the luxury to pursue his lonely course,
something that would be too risky for younger physicists still trying to make their reputations. 64 But as it turned out, there were usually at least two or
three younger physicists, attracted by Einstein’s aura, willing to collaborate with him, even if the vast majority of the physics priest-hood considered
his search for a unified field theory to be quixotic.
One of these young assistants, Ernst Straus, remembers working on an approach that Einstein pursued for almost two years. One evening,
Straus found, to his dismay, that their equations led to some conclusions that clearly could not be true. The next day, he and Einstein explored the
issue from all angles, but they could not avoid the disappointing result. So they went home early. Straus was dejected, and he assumed that
Einstein would be even more so. To his surprise, Einstein was as eager and excited as ever the next day, and he proposed yet another approach
they could take. “This was the start of an entirely new theory, also relegated to the trash heap after a half-year’s work and mourned no longer than its
predecessor,” Straus recalls. 65
Einstein’s quest was driven by his intuition that mathematical simplicity, an attribute he never fully defined though he felt he knew it when he saw
it, was a feature of nature’s handiwork. 66 Every now and then, when a particularly elegant formulation cropped up, he would exult to Straus, “This is
so simple God could not have passed it up.”
Enthusiastic letters to friends continued to pour forth from Princeton about the progress of his crusade against the quantum theorists who
seemed wedded to probabilities and averse to believing in an underlying reality. “I am working with my young people on an extremely interesting
theory with which I hope to defeat modern proponents of mysticism and probability and their aversion to the notion of reality in the domain of
physics,” he wrote Maurice Solovine in 1938. 67
Likewise, headlines continued to emanate from Princeton on purported breakthroughs. “Soaring over a hitherto unscaled mathematical
mountain-top, Dr. Albert Einstein, climber of cosmic Alps, reports having sighted a new pattern in the structure of space and matter,” the
distinguished New York Times science reporter William Laurence reported in a page 1 article in 1935. The same writer and the same paper
reported on page 1 in 1939, “Albert Einstein revealed today that after twenty years of unremitting search for a law that would explain the mechanism
of the cosmos in its entirety, reaching out from the stars and galaxies in the vastness of infinite space down to the mysteries within the heart of the
infinitesimal atom, he has at last arrived within sight of what he hopes may be the ‘Promised Land of Knowledge,’ holding what may be the master
key to the riddle of creation.” 68
The triumphs in his salad days had come partly from having an instinct that could sniff out underlying physical realities. He could intuitively sense
the implications of the relativity of all motion, the constancy of the speed of light, and the equivalence of gravitational and inertial mass. From that he
could build theories based on a feel for the physics. But he later became more reliant on a mathematical formalism, because it had guided him in
his final sprint to complete the field equations of general relativity.
Now, in his quest for a unified theory, there seemed to be a lot of mathematical formalism but very few fundamental physical insights guiding him.
“In his earlier search for the general theory, Einstein had been guided by his principle of equivalence linking gravitation with acceleration,” said
Banesh Hoffmann, a Princeton collaborator. “Where were the comparable guiding principles that could lead to the construction of a unified field
theory? No one knew. Not even Einstein. Thus the search was not so much a search as a groping in the gloom of a mathematical jungle
inadequately lit by physical intuition.” Jeremy Bernstein later called it “like an all but random shuffling of mathematical formulas with no physics in
view.” 69
After a while, the optimistic headlines and letters stopped emanating from Princeton, and Einstein publicly admitted that he was, at least for the
time being, stymied. “I am not as optimistic,” he told the New York Times. For years the paper had regularly headlined each of Einstein’s purported
breakthroughs toward a unified theory, but now its headline read, “Einstein Baffled by Cosmos Riddle.”
Nonetheless, Einstein insisted that he still could not “accept the view that events in nature are analogous to a game of chance.” And so he
pledged to continue his quest. Even if he failed, he felt that the effort would be meaningful. “It is open to every man to choose the direction of his
striving,” he explained, “and every man may take comfort from the fine saying that the search for truth is more precious than its possession.” 70
Around the time of Einstein’s sixtieth birthday, early in the spring of 1939, Niels Bohr came to Princeton for a two-month visit. Einstein remained
somewhat aloof toward his old friend and sparring partner. They met at a few receptions, exchanged some small talk, but did not reengage in their
old game of volleying thought experiments about quantum weirdness.
Einstein gave only one lecture during that period, which Bohr attended. It dealt with his latest attempts to find a unified field theory. At the end,
Einstein fixed his eyes on Bohr and noted that he had long tried to explain quantum mechanics in such a fashion. But he made clear that he would
prefer not to discuss the issue further. “Bohr was profoundly unhappy with this,” his assistant recalled. 71
Bohr had arrived in Princeton with a piece of scientific news that was related to Einstein’s discovery of the link between energy and mass,
E=mc 2 . In Berlin, Otto Hahn and Fritz Strassman had gotten some interesting experimental results by bombarding heavy uranium with neutrons.
These had been sent to their former colleague, Lise Meitner, who had just been forced to flee to Sweden because she was half Jewish. She in turn