einstein

ather than (or in addition to) expanding. In such a case, the relationship between space and time could become, mathematically, mixed up. “The
existence of an objective lapse of time,” he wrote, “means that reality consists of an infinity of layers of ‘now’ which come into existence
successively. But if simultaneity is something relative, each observer has his own set of ‘nows,’ and none of these various layers can claim the
prerogative of representing the objective lapse of time.” 8
As a result, Gödel argued, time travel would be possible. “By making a round trip on a rocket ship in a sufficiently wide curve, it is possible in
these worlds to travel into any region of the past, present and future, and back again.” That would be absurd, he noted, because then we could go
back and chat with a younger version of ourselves (or, even more discomforting, our older version could come back and chat with us). “Gödel had
achieved an amazing demonstration that time travel, strictly understood, was consistent with the theory of relativity,” writes Boston University
philosophy professor Palle Yourgrau in his book on Gödel’s relationship with Einstein, World Without Time. “The primary result was a powerful
argument that if time travel is possible, time itself is not.” 9
Einstein responded to Gödel’s essay along with a variety of others that had been collected in a book, and he seemed to be mildly impressed but
also not totally engaged by the argument. In his brief assessment, Einstein called Gödel’s “an important contribution” but noted that he had thought
of the issue long ago and “the problem here involved disturbed me already.” He implied that although time travel may be true as a mathematical
conceivability, it might not be possible in reality.“It will be interesting to weigh whether these are not to be excluded on physical grounds,” Einstein
concluded. 10
For his part, Einstein remained focused on his own white whale, which he pursued not with the demonic drive of Ahab but the dutiful serenity of
Ishmael. In his quest for a unified field theory, he still had no compelling physical insight—such as the equivalence of gravity and acceleration, or the
relativity of simultaneity—to guide his way, so his endeavors remained a groping through clouds of abstract mathematical equations with no ground
lights to orient him. “It’s like being in an airship in which one can cruise around in the clouds but cannot see clearly how one can return to reality, i.e.,
earth,” he lamented to a friend. 11
His goal, as it had been for decades, was to come up with a theory that encompassed both the electromagnetic and the gravitational fields, but
he had no compelling reason to believe that they in fact had to be part of the same unified structure, other than his intuition that nature liked the
beauty of simplicity.
Likewise, he was still hoping to explain the existence of particles in terms of a field theory by finding permissible pointlike solutions to his field
equations. “He argued that if one believed wholeheartedly in the basic idea of a field theory, matter should enter not as an interloper but as an
honest part of the field itself,” recalled one of his Princeton collaborators, Banesh Hoffmann. “Indeed, one might say that he wanted to build matter
out of nothing but convolutions of spacetime.” In the process he used all sorts of mathematical devices, but constantly searched for others. “I need
more mathematics,” he lamented at one point to Hoffmann. 12
Why did he persist? Deep inside, such disjunctures and dualities—different field theories for gravity and electromagnetism, distinctions between
particles and fields—had always discomforted him. Simplicity and unity, he intuitively believed, were hallmarks of the Old One’s handiwork. “A
theory is more impressive the greater the simplicity of its premises, the more different things it relates, and the more expanded its area of
applicability,” he wrote. 13
In the early 1940s, Einstein returned for a while to the five-dimensional mathematical approach that he had adopted from Theodor Kaluza two
decades earlier. He even worked on it with Wolfgang Pauli, the quantum mechanics pioneer, who had spent some of the war years in Princeton.
But he could not get his equations to describe particles. 14
So he moved on to a strategy dubbed “bivector fields.” Einstein seemed to be getting a little desperate. This new approach, he admitted, might
require surrendering the principle of locality that he had sanctified in some of his thought-experiments assaulting quantum mechanics. 15 In any
event, it was soon abandoned as well.
Einstein’s final strategy, which he pursued for the final decade of his life, was a resurrection of one he had tried during the 1920s. It used a
Riemannian metric that was not assumed to be symmetric, which opened the way for sixteen quantities. Ten combinations of them were used for
gravity, and the remaining ones for electromagnetism.
Einstein sent early versions of this work to his old comrade Schrödinger. “I am sending them to nobody else, because you are the only person
known to me who is not wearing blinders in regard to the fundamental questions in our science,” Einstein wrote. “The attempt depends on an idea
that at first seems antiquated and unprofitable, the introduction of a non-symmetrical tensor ... Pauli stuck his tongue out at me when I told him about
it.” 16
Schrödinger spent three days poring over Einstein’s work and wrote back to say how impressed he was. “You are after big game,” he said.
Einstein was thrilled with such support. “This correspondence gives me great joy,” he replied, “because you are my closest brother and your brain
runs so similarly to mine.” But he soon began to realize that the gossamer theories he was spinning were mathematically elegant but never seemed
to relate to anything physical. “Inwardly I am not so certain as I previously asserted,” he confessed to Schrödinger a few months later. “We have
squandered a lot of time on this, and the result looks like a gift from the devil’s grandmother.” 17
And yet he soldiered on, churning out papers and producing the occasional headline. When a new edition of his book, The Meaning of
Relativity, was being prepared in 1949, he added the latest version of the paper he had shown Schrödinger as an appendix. The New York Times
reprinted an entire page of complex equations from the manuscript, along with a front-page story headlined “New Einstein Theory Gives a Master
Key to Universe: Scientist, after 30 Years’ Work, Evolves Concept That Promises to Bridge Gap between the Star and the Atom.” 18
But Einstein soon realized that it still wasn’t right. During the six weeks between when he submitted the chapter and when it went to the printers,
he had second thoughts and revised it yet again.
In fact, he continued to revise the theory repeatedly, but to no avail. His growing pessimism was visible in the lamentations he sent to his old
friend from the Olympia Academy days, Maurice Solovine, then Einstein’s publisher in Paris. “I shall never ever solve it,” he wrote in 1948. “It will be
forgotten and must later be rediscovered again.”Then, the following year: “I am uncertain as to whether I was even on the right track. The current
generation sees in me both a heretic and a reactionary who has, so to speak, outlived himself.” And, with some resignation, in 1951: “The unified
field theory has been put into retirement. It is so difficult to employ mathematically that I have not been able to verify it. This state of affairs will last for
many more years, mainly because physicists have no understanding of logical and philosophical arguments.” 19
Einstein’s quest for a unified theory was destined to produce no tangible results that added to the framework of physics. He was able to come up
with no great insights or thought experiments, no intuitions about underlying principles, to help him visualize his goal. “No pictures came to our aid,”
his collaborator Hoffmann lamented. “It is intensely mathematical, and over the years, with helpers and alone, Einstein surmounted difficulty after
difficulty, only to find new ones awaiting him.” 20
Perhaps the search was futile. And if it turns out a century from now that there is indeed no unified theory to be found, it will also look