The Perfect Theory (20 page)

Penrose immediately took to Kerr's result. He spent hours discussing the discovery with his new colleagues at Austin, rephrasing the new spacetime in his own way. Like Sciama, Schild was taken by Penrose's way of seeing things. Penrose's mathematical insight and diagrams shed a completely new light on Kerr's solution. Kerr submitted his remarkably simple and powerful result to the
Physical Review Letters,
the American journal that only a few years before had considered banning the publication of anything related to relativity. It was instantly accepted and published in September 1963, just a few months before the Texas Symposium was to take place in Dallas. There he could present his result to the astrophysicists.

Afraid that Kerr's presentation might be too dry and mathematical, Schild tried to convince Penrose to present the new solution instead of Kerr. Penrose would have none of it; it was Kerr's baby. Schild's concerns were not entirely unfounded. When Kerr went to the podium to make his presentation, half of the participants left the hall. Kerr was young and unknown, a relativist among a gang of astrophysicists who had better things to do at that moment. Kerr spoke to the remaining, desultory crowd, and, as Penrose recalls,
“They didn't pay much attention to him.” Very few people understood the point of Kerr's result, the first big step in making Schwarzschild's solution more general, more real, and more useful to astrophysicists. Kerr wrote a short note for the conference proceedings, but the person charged with summing up the main results of the symposium left him out entirely. It was still too much general relativity for the astrophysicists to accept.

 

There wasn't a single Soviet physicist at the first Texas Symposium. Much of the precious intellectual power of Soviet physics had been taken up with the Soviet nuclear project, leaving little time or attention for general relativity. However, just as a new generation of relativists emerged from the Manhattan Project in the United States and radar in the United Kingdom, many of the Soviet nuclear scientists would eventually lead a revival of general relativity in the Soviet Union in the 1960s.

The Soviet nuclear project was late getting started. During the Second World War, precious resources had been drained from the Soviet machine on the Soviet German front, which prevented Joseph Stalin from putting his men to work on the bomb. Starting in 1939, following John Wheeler and Niels Bohr's paper that discussed the copious release of energy from the nuclear fission of heavy elements, scientific papers on nuclear fission in the West seemed to have dried up. To the Soviets, it was as if Western research into nuclear fission had ground to a halt. In 1942, when a Soviet physicist, Georgii Flerov, wrote to Stalin and alerted him to this strange state of affairs, Stalin became suspicious. He guessed that the Americans were working on a bomb, and he realized he had to get in the game. Once the war ended, Stalin plundered his own scientific elite to set up a bomb project. The team included Lev Landau and Yakov Zel'dovich.

Lev Landau had suffered under the wave of persecutions during the great terror of the late 1930s. His stint in prison had left him a deeply bitter man, profoundly disillusioned by the regime, yet at its mercy. Landau had already become legendary, with a raft of discoveries to his name spanning from quantum mechanics to astrophysics. He had created a school of physics and a following of brilliant disciples who would be tried to the limit of their intellectual abilities just to be allowed to work with him. In fact, to be accepted as one of Landau's protégés, aspirants had to pass a series of eleven punishing exams, known as
“Landau's Theoretical Minimum,” set and overseen by Landau himself, a process that could take up to two years. Only a few made it through the barrier and were able to work with the great man himself.

Yakov Zel'dovich, a Belorussian Jew just a few years younger than Landau, had been a precocious student. He became a lab assistant at seventeen, gained a doctorate at twenty-four, and rapidly became one of the Soviet authorities on combustion and ignition. It was inevitable that he would be roped into developing the bomb, and he did so with flair. From 1945 until 1963, Zel'dovich took part in the construction of the first Soviet atomic bomb, dubbed “Joe-1” by the Americans when they detected its explosion in August of 1949, and then worked on its successor, the “superbomb.” The Soviet Union had caught up with the Americans and become a nuclear power.

While Zel'dovich was passionate about the nuclear project, Landau, still smarting from his ordeal in the Lubyanka and nursing a profound hatred for Stalin, had been coerced into taking part. And while Zel'dovich greatly admired Landau, Landau was less charitable toward his colleague and the nuclear project as a whole. When Zel'dovich attempted to enlarge the Soviet nuclear bomb project, Landau called him
“that bitch.” When Stalin died, he said to a colleague, “That's it. He's gone. I'm no longer afraid of him, and I won't work on [nuclear weapons] anymore.” Nevertheless, for their contribution to the Soviet bomb project, both men were awarded the Stalin Prize and the Hero of Socialist Labour medal a number of times. Landau went on to win the Nobel Prize in 1962.

In the mid-1960s, Zel'dovich's star was still rising, but Landau was incapacitated, laid low by a car crash that left him a shell of the man he once was, unable to do physics. Landau's protégés carried on in his stead; they were the first Soviets to go after singularities in spacetime. The two young men, Isaak Khalatnikov and Evgeny Lifshitz, who had both undergone the rigors of an education with Landau, were well prepared to tackle the intricacies of Einstein's theory to look at what happens when matter collapses under its own gravity.

Oppenheimer and Snyder had built their solution around a simple approximation, a perfectly symmetric sphere of stuff collapsing inward. The perfect symmetry had initially bothered people like Wheeler, who saw it as too much of an idealization. The surface of the Earth is covered with irregularities: huge mountains and deep oceans and valleys. What if a collapsing star was similarly uneven? Could the irregularities and imperfections distort the collapse so much that parts of the surface would fall in far more quickly than others, rebound, and make their way out again? If that was so, singularities might never form.

The Russians addressed this question by loosening the symmetries Oppenheimer and Snyder had enforced. In Khalatnikov and Lifshitz's calculation, spacetime could twist and churn in each direction in a different way. Imagine looking face-on at the seething mass of stuff, a massive star, for example, as it implodes, collapsing inward toward its center. In general, you would expect it to appear lopsided. The top and the bottom bits of the blob might collapse more quickly than the sides, so quickly that they might bounce right back out before the sides of the blob had time to collapse. Instead of everything falling inward, inexorably forming the singularity, there would always be some part moving outward, holding spacetime up. Only if the collapse was set up just so, perfectly symmetric around the center, would everything fall in at
exactly
the same time, allowing the singularity to form. Khalatnikov and Lifshitz's paper, published in the Soviet journal
Soviet Physics,
came to the striking conclusion that in realistic situations singularities
never
formed. Schwarzschild's and Kerr's solutions were abstractions that should never form in nature. Einstein and Eddington, it appeared, had been right all along.

Soviet scientists were occasionally allowed to attend meetings in the West. The Third Meeting on General Relativity and Cosmology, the successor of the Chapel Hill meeting, was held in London in 1965, with over two hundred relativists in attendance. When Khalatnikov presented his results there, all those relativists paid close attention. While it was evident that Einstein's theory had taken off in the Soviet Union, it was difficult for Western scientists to tell exactly what was going on. Translations of the main Soviet journal,
Soviet Physics,
were always delayed.

Penrose sat quietly and listened to Khalatnikov's presentation. He knew they were wrong but thought it would be “undiplomatic” to speak out.
“You couldn't really prove anything doing it the way they did it,” he says. “There were simply too many assumptions. They couldn't rule out singularities like that.” In fact, Penrose could prove that singularities
always
formed, contrary to Khalatnikov's claim. Penrose's results were completely general because he had used his own new methods of looking at spacetime.

Since his first encounter with Sciama at the Kingswood restaurant in Cambridge almost ten years before, Penrose had developed his diagrams into a set of rules for how to think of light, or anything for that matter, propagating through spacetime. He could take an arbitrary spacetime, and from looking at some of its most basic properties and what kind of stuff it contained, he could get a definitive sense of what would happen to it, whether it would collapse to a point or explode out to infinity. When he applied his rules to the problem of gravitational collapse, what Wheeler called “the issue of the final state,” the outcome was inevitable: singularities. Penrose wrote up his paper, “Gravitational Collapse and Spacetime Singularities,” and submitted it to
Physical Review Letters.
As he summarized in his paper,
“Deviations from spherical symmetry cannot prevent spacetime singularities from arising.” Almost half a century later, it is still a masterpiece of concision, clarity, and rigor: a perfect paper in just under three pages, with a brief explanation of the problem, the mathematical toolkit and the proof in a small paragraph, all illustrated with one of Penrose's signature diagrams.

When Khalatnikov gave his presentation, Penrose had already submitted his paper. It was about to be accepted and would be published in December of that year, but his techniques were unfamiliar to most of the relativists in the audience, especially the Russians. When Charles Misner, one of John Wheeler's students, stood up and challenged Khalatnikov with Penrose's result, it was a lost battle. Suspicious of Penrose's result, the Russians refused to accept that there might be an error in their own approach. “I hid in the corner,” Penrose recalls. “It was too embarrassing.”

But Penrose was right. What became known as his singularity theorem had far-reaching consequences. It meant that if general relativity was correct, the Schwarzschild and Kerr solutions, those strange spacetimes with singularities at their centers, had to exist in the universe. They weren't merely mathematical constructs. Einstein and Eddington were wrong. Four years later, Khalatnikhov and Lifshitz admitted defeat. In 1969 they looked at their calculations again, this time with one of their students, Vladimir Belinski. To their dismay, they found a mistake. While in 1961 they had thought that the collapse that leads to the formation of a singularity was too special and unnatural to occur in the real world, with Belinski they found quite the opposite. In their own way they confirmed Penrose's theorem: singularities always formed. They humbly published their results in the West, publicly acknowledging their mistake.

Penrose had proved the inevitability of singularities in gravitational collapse and answered Wheeler's question about the final state. Deeper confirmation would soon follow.

 

Martin Ryle may have failed in his first attempts to dismantle Cambridge's steady-state orthodoxy through his initial radio source measurements, but his data was improving. In 1961, when he released the 4C Catalogue of radio sources, most of the radio astronomers agreed that many of the problems with the previous data had been fixed. But the end of the steady state would begin with the theory's own adherents.

Dennis Sciama was a strong advocate of Hoyle's steady-state theory. He was also fascinated by quasars and assigned one of his students, Martin Rees, the task of looking at Ryle's new measurements in different ways. Rees took a simpler and much cleaner approach than Ryle's technique of plotting the number of quasars as a function of flux. Instead, Rees took a subset of thirty-five quasars with measured redshifts and divided it up into three slices. One slice exhibited low redshift, corresponding to quasars close to Earth in time and distance. The second slice contained quasars with medium redshifts, and the final slice was made up of objects with high redshifts viewed in the distant past.

Rees's idea was simple but remarkably clever. In the steady-state model, in which the universe does not evolve over time, each slice should have approximately the same number of quasars. Instead, Rees found almost no quasars in the most recent slice. Almost all of them were in the farthest slice. In other words, the number of quasars seemed to have changed with time—there were more in the past—and so the universe couldn't be in a steady state. The plot told it all—the steady-state universe didn't work.
“It was really that plot that converted Dennis,” Rees recalls. From then on Sciama believed in Lemaître's theory, or the Big Bang as Hoyle had called it in his lectures, and whatever that entailed.

The final nail in the coffin of the steady-state theory came from across the pond in New Jersey. Arno Penzias and Robert Wilson had been working on an antenna at Holmdel, one of the telecommunications sites belonging to Bell Labs. They wanted to retrofit the antenna, a huge horn that captured radio waves, and use it to measure the galaxy. To accurately map out the structure of the Milky Way, they first needed to determine the precision of their instrument. So they used the antenna to stare at nothingness and check how well they could see it.

But what they saw wasn't nothing. Penzias and Wilson were definitely seeing or, to be more precise,
hearing
something: a low, soft hiss streaming out of empty space. No matter how they adjusted their instrument, they couldn't get rid of it. These two men had inadvertently stumbled upon a relic from the early universe, a fossil of the Big Bang.