Walter Isaacson - Einstein - His Life and Universe

By now the siren song of a unified theory had come to mesmerize Einstein. “Over it lingers the marble smile of nature,” he told Weyl. 8On his steamer ride through Asia, he polished a new paper and, upon arriving in Egypt in February 1923, immediately mailed it to Planck in Berlin for publication. His goal, he declared, was “to understand the gravitational and electromagnetic field as one.” 9

Once again, Einstein’s pronouncements made headlines around the world. “Einstein Describes His Newest Theory,” proclaimed the New York Times. And once again, the complexity of his approach was played up. As one of the subheads warned: “Unintelligible to Laymen.”

But Einstein told the newspaper it was not all that complicated. “I can tell you in one sentence what it is about,” the reporter quoted him as saying. “It concerns the relation between electricity and gravitation.” He also gave credit to Eddington, saying, “It is grounded on the theories of the English astronomer.” 10

In his follow-up articles that year, Einstein made explicit that his goal was not merely unification but finding a way to overcome the uncertainties and probabilities in quantum theory. The title of one 1923 paper stated the quest clearly: “Does the Field Theory Offer Possibilities for the Solution of Quanta Problems?” 11

The paper began by describing how electromagnetic and gravitational field theories provide causal determinations based on partial differential equations combined with initial conditions. In the realm of the quanta, it may not be possible to choose or apply the initial conditions freely. Can we nevertheless have a causal theory based on field equations?

“Quite certainly,” Einstein answered himself optimistically. What was needed, he said, was a method to “overdetermine” the field variables in the appropriate equations. That path of overdetermination became yet another proposed tool that he would employ, to no avail, in fixing what he persisted in calling the “problem” of quantum uncertainty.

Within two years, Einstein had concluded that these approaches were flawed. “My article published [in 1923],” he wrote, “does not reflect the true solution of this problem.” But for better or worse, he had come up with yet another method. “After searching ceaselessly in the past two years, I think I have now found the true solution.”

His new approach was to find the simplest formal expression he could of the law of gravitation in the absence of any electromagnetic field and then generalize it. Maxwell’s theory of electromagnetism, he thought, resulted in a first approximation. 12

He now was relying more on math than on physics. The metric tensor that he had featured in his general relativity equations had ten independent quantities, but if it were made nonsymmetrical there would be sixteen of them, enough to accommodate electromagnetism.

But this approach led nowhere, just like the others. “The trouble with this idea, as Einstein became painfully aware, is that there really is nothing in it that ties the 6 components of the electric and magnetic fields to the 10 components of the ordinary metric tensor that describes gravitation,” says University of Texas physicist Steven Weinberg. “A Lorentz transformation or any other coordinate transformation will convert electric or magnetic fields into mixtures of electric and magnetic fields, but no transformation mixes them with the gravitational field.” 13

Undaunted, Einstein went back to work, this time trying an approach he called “distant parallelism.” It permitted vectors in different parts of curved space to be related, and from that sprang new forms of tensors. Most wondrously (so he thought), he was able to come up with equations that did not require that pesky Planck constant representing quanta. 14

“This looks old-fashioned, and my dear colleagues, and also you, will stick their tongues out because Planck’s constant is not in the equations,” he wrote Besso in January 1929. “But when they have reached the limit of their mania for the statistical fad, they will return full of repentance to the spacetime picture, and then these equations will form a starting point.” 15

What a wonderful dream! A unified theory without that rambunctious quantum. Statistical approaches turning out to be a passing mania. A return to the field theories of relativity. Tongue-sticking colleagues repenting!

In the world of physics, where quantum mechanics was now accepted, Einstein and his fitful quest for a unified theory were beginning to be seen as quaint. But in the popular imagination, he was still a superstar. The frenzy that surrounded the publication of his January 1929 five-page paper, which was merely the latest in a string of theoretical stabs that missed the mark, was astonishing. Journalists from around the world crowded around his apartment building, and Einstein was barely able to escape them to go into hiding at his doctor’s villa on the Havel River outside of town. The New York Times had started the drumbeat weeks earlier with an article headlined “Einstein on Verge of Great Discovery: Resents Intrusion.” 16

Einstein’s paper was not made public until January 30, 1929, but for the entire preceding month the newspapers printed a litany of leaks and speculation. A sampling of the headlines in the New York Times, for example, include these:

January 12:

“Einstein Extends Relativity Theory / New Work Seeks to Unite Laws of Field of Gravitation and Electro-Magnetism / He Calls It His Greatest ‘Book’ / Took Berlin Scientist Ten Years to Prepare”

January 19:

“Einstein Is Amazed at Stir Over Theory / Holds 100 Journalists at Bay for a Week / BERLIN—For the past week the entire press as represented here has concentrated efforts on procuring the five-page manuscript of Dr. Albert Einstein’s ‘New Field of Theory.’ Furthermore, hundreds of cables from all parts of the world, with prepaid answers and innumerable letters asking for a detailed description or a copy of the manuscript have arrived.”

January 25 (page 1):

“Einstein Reduces All Physics to One Law / The New Electro-Gravitational Theory Links All Phenomena, Says Berlin Interpreter / Only One Substance Also / Hypothesis Opens Visions of Persons Being Able to Float in Air, Says N.Y.U. Professor / BERLIN—Professor Albert Einstein’s newest work, ‘A New Field Theory,’ which will leave the press soon, reduces to one formula the basic laws of relativistic mechanics and of electricity, according to the person who has interpreted it into English.”

Einstein got into the act from his Havel River hideaway. Even before his little paper was published, he gave an interview about it to a British newspaper. “It has been my greatest ambition to resolve the duality of natural laws into unity,” he said. “The purpose of my work is to further this simplification, and particularly to reduce to one formula the explanation of the gravitational and electromagnetic fields. For this reason I call it a contribution to ‘a unified field theory’... Now, but only now, we know that the force that moves electrons in their ellipses about the nuclei of atoms is the same force that moves our earth in its annual course around the sun.” 17Of course, it turned out that he did not know that, nor do we know that even now.

He also gave an interview to Time, which put him on its cover, the first of five such appearances. The magazine reported that, while the world waited for his “abstruse coherent field theory” to be made public, Einstein was plodding around his country hideaway looking “haggard, nervous, irritable.” His sickly demeanor, the magazine explained, was due to stomach ailments and a constant parade of visitors. In addition, it noted, “Dr. Einstein, like so many other Jews and scholars, takes no physical exercise at all.” 18