Einstein (75 page)

But Einstein offered no proof of this creed, one that seems belied by modern particle physics.
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Nor did he ever fully explain what, exactly, he meant by mathematical simplicity. Instead, he merely asserted his deep intuition that this is the way God would make the universe. “I am convinced that we can discover by means of purely mathematical constructions the concepts and the laws connecting them with each other,” he claimed.

It was a belief—indeed, a faith—that he had expressed during his previous visit to Oxford, when in May 1931 he had been awarded an honorary doctorate there. In his lecture on that occasion, Einstein explained that his ongoing quest for a unified field theory was propelled by the lure of mathematical elegance, rather than the push of experimental data. “I have been guided not by the pressure from behind of experimental facts, but by the attraction in front from mathematical simplicity,” he said. “It can only be hoped that experiments will follow the mathematical flag.”
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Einstein likewise concluded his 1933 Oxford lecture by saying that he had come to believe that the mathematical equations of field theories
were the best way to grasp “reality.” So far, he admitted, this had not worked at the subatomic level, which seemed ruled by chance and probabilities. But he told his audience that he clung to the belief that this was not the final word. “I still believe in the possibility of a model of reality—that is to say, of a theory that represents things themselves and not merely the probability of their occurrence.”
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Back in 1917, when Einstein had analyzed the “cosmological considerations” arising from his general theory of relativity, most astronomers thought that the universe consisted only of our Milky Way, floating with its 100 billion or so stars in a void of empty space. Moreover, it seemed a rather stable universe, with stars meandering around but not expanding outward or collapsing inward in a noticeable way.

All of this led Einstein to add to his field equations a cosmological constant that represented a “repulsive” force (see page 254). It was invented to counteract the gravitational attraction that would, if the stars were not flying away from one another with enough momentum, pull all of them together.

Then came a series of wondrous discoveries, beginning in 1924, by Edwin Hubble, a colorful and engaging astronomer working with the 100-inch reflector telescope at the Mount Wilson Observatory in the mountains above Pasadena, California. The first was that the blur known as the Andromeda nebula was actually another galaxy, about the size of our own, close to a million light years away (we now know it’s more than twice that far). Soon he was able to find at least two dozen even more distant galaxies (we now believe that there are more than 100 billion of them).

Hubble then made an even more amazing discovery. By measuring the red shift of the stars’ spectra (which is the light wave counterpart to the Doppler effect for sound waves), he realized that the galaxies were moving away from us. There were at least two possible explanations for the fact that distant stars in all directions seemed to be flying away from us: (1) because we are the center of the universe, something that since the time of Copernicus only our teenage children believe; (2) because
the entire metric of the universe was expanding, which meant that everything was stretching out in all directions so that all galaxies were getting farther away from one another.

It became clear that the second explanation was the case when Hubble confirmed that, in general, the galaxies were moving away from us at a speed that was proportional to their distance from us. Those twice as far moved away twice as fast, and those three times as far moved away three times as fast.

One way to understand this is to imagine a grid of dots that are each spaced an inch apart on the elastic surface of a balloon. Then assume that the balloon is inflated so that the surface expands to twice its original dimensions. The dots are now two inches away from each other. So during the expansion, a dot that was originally one inch away moved another one inch away. And during that same time period, a dot that was originally two inches away moved another two inches away, one that was three inches away moved another three inches away, and one that was ten inches away moved another ten inches away. The farther away each dot was originally, the faster it receded from our dot. And that would be true from the vantage point of each and every dot on the balloon.

All of which is a simple way to say that the galaxies are not merely flying away from us, but instead, the entire metric of space, or the fabric of the cosmos, is expanding. To envision this in 3-D, imagine that the dots are raisins in a cake that is baking and expanding in all directions.

On his second visit to America in January 1931, Einstein decided to go to Mount Wilson (conveniently up the road from Caltech, where he was visiting) to see for himself. He and Edwin Hubble rode in a sleek Pierce-Arrow touring car up the winding road. There at the top to meet him was the aging and ailing Albert Michelson, of ether-drift experiment fame.

It was a sunny day, and Einstein merrily played with the telescope’s dials and instruments. Elsa came along as well, and it was explained to her that the equipment was used to determine the scope and shape of the universe. She reportedly replied, “Well, my husband does that on the back of an old envelope.”
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The evidence that the universe was expanding was presented in the popular press as a challenge to Einstein’s theories. It was a scientific drama that captured the public imagination. “Great stellar systems,” an Associated Press story began, “rushing away from the earth at 7,300 miles a second, offer a problem to Dr. Albert Einstein.”
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But Einstein welcomed the news. “The people at the Mt. Wilson observatory are outstanding,” he wrote Besso. “They have recently found that the spiral nebulae are distributed approximately uniformly in space, and they show a strong Doppler effect, proportional to their distances, that one can readily deduce from general relativity theory without the ‘cosmological’ term.”

In other words, the cosmological constant, which he had reluctantly concocted to account for a static universe, was apparently not necessary, for the universe was in fact expanding.
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“The situation is truly exciting,” he exulted to Besso.
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Of course, it would have been even more exciting if Einstein had trusted his original equations and simply announced that his general theory of relativity predicted that the universe is expanding. If he had done that, then Hubble’s confirmation of the expansion more than a decade later would have had as great an impact as when Eddington confirmed his prediction of how the sun’s gravity would bend rays of light. The Big Bang might have been named the Einstein Bang, and it would have gone down in history, as well as in the popular imagination, as one of the most fascinating theoretical discoveries of modern physics.
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As it was, Einstein merely had the pleasure of renouncing the cosmological constant, which he had never liked.
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In a new edition of his popular book on relativity published in 1931, he added an appendix explaining why the term he had pasted into his field equations was, thankfully, no longer necessary.
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“When I was discussing cosmological problems with Einstein,” George Gamow later recalled, “he remarked that the introduction of the cosmological term was the biggest blunder he ever made in his life.”
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In fact, Einstein’s blunders were more fascinating and complex than even the triumphs of lesser scientists. It was hard simply to banish the term from the field equations. “Unfortunately,” says Nobel laureate Steven Weinberg, “it was not so easy just to drop the cosmological constant, because anything that contributes to the energy density of the vacuum acts just like a cosmological constant.”
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It turns out that the cosmological constant not only was difficult to banish but is still needed by cosmologists, who use it today to explain the accelerating expansion of the universe.
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The mysterious dark energy that seems to cause this expansion behaves as if it were a manifestation of Einstein’s constant. As a result, two or three times each year fresh observations produce reports that lead with sentences along the lines of this one from November 2005: “The genius of Albert Einstein, who added a ‘cosmological constant’ to his equation for the expansion of the universe but then retracted it, may be vindicated by new research.”
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Einstein’s house in Caputh near Berlin

Einstein wanted some solitude for his fiftieth birthday, a refuge from publicity. So in March 1929 he fled once again, as he had during the publication of his unified field theory paper of a few months earlier, to the gardener’s cottage of an estate on the Havel River owned by Janos Plesch, a flamboyant and gossipy Hungarian-born celebrity doctor who had added Einstein to his showcase collection of patient-friends.

For days he lived by himself, cooking his own meals, while journalists and official well-wishers searched for him. His whereabouts became a matter of newspaper speculation. Only his family and assistant knew where he was, and they refused to tell even close friends.

Early on the morning of his birthday, he walked from this hide-away, which had no phone, to a nearby house to call Elsa. She started to wish him well on reaching the half-century mark, but he interrupted.
“Such a fuss about a birthday,” he laughed. He was phoning about a matter involving physics, not the merely personal. He had made a small mistake in some calculations he had given to his assistant Walther Mayer, he told her, and he wanted her to take down the corrections and pass them along.

Elsa and her daughters came out that afternoon for a small, private celebration. She was dismayed to find him in his oldest suit, which she had hidden. “How did you manage to find it?” she asked.

“Ah,” he replied, “I know all about those hiding places.”
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The
New York Times,
as intrepid as ever, was the only paper that managed to track him down. A family member later recalled that Einstein’s angry look drove the reporter away. That was not true. The reporter was smart and Einstein, despite his feigned fury, was as accommodating as usual. “Einstein Is Found Hiding on His Birthday” was the paper’s headline. He showed the reporter a microscope he had been given as a gift, and the paper reported that he was like a “delighted boy” with a new toy.
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From around the world came other gifts and greetings. The ones that moved him the most were from ordinary people. A seamstress had sent him a poem, and an unemployed man had saved a few coins to get him a small packet of tobacco. The latter gift brought tears to his eyes and was the first for which he wrote a thank-you letter.
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Another birthday gift caused more problems. The city of Berlin, at the suggestion of the ever-meddling Dr. Plesch, decided to honor its most famous citizen by giving him lifelong rights to live in a country house that was part of a large lakeside estate that the city had acquired. There he would be able to escape, sail his wooden boat, and scribble his equations in serenity.

It was a generous and gracious gesture. It was also a welcome one. Einstein loved sailing and solitude and simplicity, but he owned no weekend retreat and had to store his sailboat with friends. He was thrilled to accept.

The house, in a classical style, was nestled in a park near the village of Cladow on a lake of the Havel River. Pictures of it appeared in the papers, and a relative called it “the ideal residence for a person of creative intellect and a man fond of sailing.” But when Elsa went to inspect
it, she found still living there the aristocratic couple who sold the estate to the city. They claimed that they had retained the right to live on the property. A study of the documents proved them right, and they could not be evicted.

So the city decided to give the Einsteins another part of the estate on which they could build their own home. But that, too, violated the city’s purchase agreement. Pressure and publicity only hardened the resolve of the original family to block the Einsteins from building on the land, and it became an embarrassing front-page fiasco, especially after a third suggested alternative also proved unsuitable.

Finally it was decided that the Einsteins should simply find their own piece of land, and the city would buy it. So Einstein picked out a parcel, owned by some friends, farther out of town near a village just south of Potsdam called Caputh. It was in a sylvan spot between the Havel and a dense forest, and Einstein loved it. The mayor accordingly asked the assembly of city deputies to approve spending 20,000 marks to buy the property as the fiftieth birthday gift to Einstein.