The Perfect Theory (19 page)

Fowler and Hoyle proposed that the radio stars were indeed stars, but not like any other stars. These stars would be
superstars,
with masses of a million or a hundred million suns like ours, so immense that they could produce tremendous amounts of energy during their lifetimes. And their lifetimes were short, for they burned up their energy so quickly that they would rapidly collapse in a brief, violent death. With their superstars, Hoyle and Fowler pushed the rules for understanding stars developed by Eddington well into the realm of the general theory of relativity. Einstein's theory beckoned.

 

In the oppressive heat of the summer of 1963, a small group of relativists gathered in Dallas, Texas. They sat around the pool drinking martinis and discussing the strange, heavy objects that Maarten Schmidt had unlocked. They were an international bunch in Dallas for, as one of them put it,
“American scientists outside of geophysics and geology would rarely deign to settle there. To most the region seemed to be as magnetic as Paraguay.” But Texas was to become an unlikely center for relativity, a shift driven mainly by the efforts of a hard-talking, gregarious Viennese Jew named Alfred Schild.

Schild had an itinerant childhood and youth, a product of the turmoil of the 1930s and 1940s. He was born in Turkey and lived in England as a child. Like Bondi and Gold, he was interned in Canada, where he studied physics under Leopold Infeld, one of Einstein's disciples, and wrote a thesis on cosmology. He had been at the meeting in Chapel Hill in 1957, taking part in the excitement of general relativity's next phase, and that year he was recruited to take up a professorship at the University of Texas at Austin.

Texas was a backwater when Alfred Schild arrived in Austin, but it was phenomenally rich from the oil income that was flowing through the local economy. Schild was able to cajole the university to put the oil money to good use, letting him set up his own Center for Relativity. With the air force keen to tap into the potentially magical powers of gravity, there was no shortage of money. And while the mathematicians at Austin looked down on Schild's work, the physicists were willing to take him in.

Schild went looking for talent, and he definitely had a knack for finding it. The group of young relativists he assembled from Germany, England, and New Zealand transformed Austin, Texas, into an obligatory stopping point for any relativist worth his salt. Schild didn't stop in Austin. In Dallas, the newly created Southwest Center for Advanced Studies was looking for young faculty to boost the
“science starved south,” so Schild stepped in. Schild told them to invest in relativity, and so they did, hiring the center's very own international group to build up the ranks of Texan relativity.

That July afternoon, the Texan relativists lounging by the pool cooked up a scheme that would bring the world to Texas to discuss relativity. It wouldn't just be another Chapel Hill, small and freewheeling. This time they would bring in a whole new crowd, the astronomers, and try to rope them into thinking about Einstein's theory by hosting a meeting focusing on radio stars, the “quasi stellar radio sources.” With Schmidt's measurements of the previous March, it was clear that these strange objects were too massive and too distant to be treated using the old Newtonian laws of gravity. These were the big things that Chandra and Oppenheimer had alerted everyone to, the stars that would be too big to withstand the pull of gravity, and where general relativity could play such a dramatic role. In the invitation letter they sent out, the organizers proposed that
“energies which lead to the formation of radio sources could be supplied through the gravitational collapse of a superstar.” The relativists called their meeting the Texas Symposium on Relativistic Astrophysics. It was to be held in December of 1963 in Dallas.

 

The first Texas Symposium on Relativistic Astrophysics was almost canceled. President John F. Kennedy had just been assassinated in Dallas, and conference goers were simply too scared to come to Dallas and run the risk of being shot. The Dallas relativists asked the mayor to reach out to potential attendees individually and assure them of the city's safety. It worked. Over three hundred people turned up in Dallas to hear the latest about radio stars and what could be made of them. Among the crowd was Robert Oppenheimer, who had discouraged work on general relativity at the institute in Princeton. He was intrigued by these new radio stars, for they were, as he described them,
“incredibly beautiful . . . spectacular events of unprecedented grandeur.” He commented on how the meeting resembled those in quantum physics almost two decades before “when all one had was confusion and lots of data.” For him, it was an exciting time.

The meeting went on for three days, with astronomers and relativists alike debating the import of the strange “quasi stellar radio sources” in Ryle's 3C Catalogue. One of the meeting's attendees starting calling them “quasars,” which was quicker and easier to pronounce. For the relativists, these quasars seemed so massive and so concentrated that Schwarzschild's weird solution, and Oppenheimer and Snyder's calculation, had to be taken into account if any sense was to be made of the data. The astronomers and astrophysicists found the quasars so bizarre and mysterious that they started paying attention to what the relativists were saying. Maybe, just maybe, general relativity had to be brought into the picture to make any sense of these new discoveries.

At Dallas, more than ten years after he had started working on general relativity, John Wheeler was present and ready to say his piece. The big unanswered question on his mind was what he called “the issue of the final state.” He wanted to find out what happens at the endpoint of gravitational collapse. He still found it impossible to believe Oppenheimer and Snyder's prediction that singularities formed, and he was convinced general relativity would play an integral role in explaining why they wouldn't. Despite his prejudice, he felt duty-bound to explain all the possibilities and enlist his audience in his pursuit of the final state. Before his talk, Wheeler picked up a piece of chalk and meticulously filled a blackboard with his elaborate pictures and equations illustrating what he had been thinking about for almost a decade. On the board were plots showing how he thought a star would collapse under its own weight and how general relativity predicted the star's inexorable movement toward its final fate. Scattered around were equations, bits of Einstein's field equations, summaries of quantum physics, a hodgepodge of brilliance that helped him lay out his results of the past ten years. More than anything, Wheeler's talk was an apologia of general relativity arguing that it should be taken seriously by any right-minded astrophysicist.

For many of the astronomers the results were too fanciful, and one of the attendees recalled
“utter disbelief” on the face of “a distinguished participant.” Yet others marveled that the universe had finally caught up with Wheeler. It seemed the general theory of relativity that he had been thinking about for so long now actually had relevance and might be of use to understand the new radio observations.

In a description of the meeting,
Life
magazine said, “The scientists, having stretched their imagination to a point that once would have embarrassed science fiction writers, were hardly less mystified than they were before they began their talks . . . so fantastic is the nature of radio sources that no bets were ruled out.” During the after-dinner speech, Thomas Gold summed up the extraordinary turn of events that they were witnessing at the symposium: “Here we have a case that allowed one to suggest that the relativists with their sophisticated work were not only magnificent cultural ornaments but might actually be useful to science! Everyone is pleased: the relativists who feel they are . . . suddenly experts in a field they hardly knew existed; the astrophysicists for having enlarged . . . their empire by the annexation of another subject—general relativity.” He ended on a cautious note, saying, “Let us all hope that it is right. What a shame it would be if we had to go and dismiss all the relativists again.”

With his incredible vision and persistence, John Wheeler had overseen the resurrection of Einstein's moribund theory. By devoting his fearsome intellect and creativity to training a new generation of brilliant young relativists, and supporting the new centers that were scattered throughout the country, he had nurtured a new and vibrant community that could think deeply about gravity. Finally, the data had been obliging, and with astronomers, physicists, and mathematicians ready to tackle the big questions, the Texas Symposium heralded a new era. General relativity was back.

Chapter 8

W
HILE MOST OF
the audience listened to John Wheeler's presentation at the 1963 Texas Symposium with incomprehension, one young mathematician watched enthralled as Wheeler lectured in front of his carefully prepared blackboard of equations and plots.
“Wheeler's talk made a real impression on me,” Roger Penrose recalls. And even though Wheeler stubbornly refused to accept the existence of singularities, he was, in Penrose's mind, asking the right question: Could these singularities be an essential ingredient of general relativity? Wheeler's talk at the Texas Symposium heralded the start of a decade that would be dubbed the “Golden Age of General Relativity” (by one of Wheeler's own students, Kip Thorne), and Roger Penrose would be one of the brilliant thinkers to see it through.

Penrose has spent his life playing with spacetime: cutting it up, gluing it back together, pushing it to its limits. He sees things differently, possessing a mathematician's gaze enhanced by a more visceral understanding of space and time. His drawings, known as Penrose diagrams, unwrap spacetime and reveal its oddest properties. They visualize what happens to light as it zooms past the Schwarzschild surface, how light behaves as you follow it back to the Big Bang, and even how space and time can be stretched to look like the frothy surface of the sea.

Penrose was still an undergraduate, studying mathematics in London, when he first felt the pull of general relativity. He taught himself the basics using a book by Erwin Schrödinger aptly called
Space-Time Structure.
But what really set him thinking about the details were Fred Hoyle's lectures proselytizing about his steady-state theory. There was something fascinating but also odd about the universe that Hoyle was describing—it didn't fit with Penrose's understanding of relativity. He decided to pay a visit to his brother Oliver, also a mathematician, who was studying for a PhD in Cambridge. He thought Oliver could help him understand this strange theory that so appealed to him.

Cambridge in the 1950s, despite the staid atmosphere of centuries-old cloisters and the stifling rituals of the colleges and university, was becoming an exciting place. Paul Dirac, an English physicist who had played a crucial role in showing that the quantum theories of Heisenberg and Schrödinger were one and the same, gave brilliant, exquisitely crafted lectures on quantum mechanics. Hermann Bondi lectured on general relativity and cosmology and, with Fred Hoyle, actively promoted their steady-state universe. And then there was Dennis Sciama.

Penrose and his brother met at the Kingswood restaurant in Cambridge to discuss Fred Hoyle's radio lectures. Penrose simply couldn't understand Hoyle's claim that in the steady-state model, galaxies would speed up and away so quickly that at some point they would disappear over a cosmic horizon. He recalls thinking that something else ought to happen, something he could show with his diagrams. Oliver pointed over to another table and said,
“Well, you can ask Dennis. He knows all about it.” He walked Roger Penrose over to Dennis Sciama and introduced them. They hit it off immediately.

Sciama was only four years older than Penrose but was already embroiled in Einstein's theory with a passion that he would pass along to a string of students and collaborators over almost fifty years. He had done a stint at the Institute for Advanced Study in the year before Einstein died. In one of his few conversations with Einstein, Sciama had boldly, and somewhat rashly, declared that he was there to
“support the ‘old Einstein' against the new.” Einstein had laughed at his impudence. Sciama had studied with Paul Dirac, to the extent that such a thing was possible, and had become seduced by the work of Hoyle, Bondi, and Gold. Yet while he was a staunch believer in the steady-state universe, he paid attention to what the radio astronomers were finding. The results coming out of Ryle's group down the road intrigued him. He could see how they might sink Hoyle's model.

That evening in the Kingswood, Penrose explained to Sciama why galaxies wouldn't disappear from sight. They would get dimmer and, from a distance, would appear to freeze in time, just as Oppenheimer and Snyder had shown would happen with an imploding star as its surface passes through the Schwarzschild horizon. Sciama saw the spark in Penrose's eyes and loved his fresh approach to looking at spacetime. They would be friends for the next fifty years.

Penrose eventually moved to Cambridge to pursue a PhD in mathematics, but he remained beguiled by the mathematical oddities he'd found in the geometry of spacetime. He desperately wanted to understand them better. When he finished his PhD, he took the plunge and decided to work on general relativity. He spent the next few years roaming the world, working with Wheeler in Princeton, Hermann Bondi in London, and Peter Bergmann in Syracuse. He finally joined Schild's Austin, Texas, group in the autumn of 1963.

 

Texas was the hot spot for general relativity, and researchers there were flush with funding. “We didn't really ask where the money was coming from or why anyone thought it was worthwhile to spend all that money on relativity,” Penrose says. “I always felt there must be some mistake.” One of Penrose's colleagues was a young New Zealander named Roy Kerr. Kerr had spent long days in the Texas heat and humidity grappling with Einstein's field equations, trying to find more complex, more realistic solutions. He had come up with an elegant set of equations that corresponded to a simple geometry for spacetime. Kerr's solution could be seen as a more general form of Schwarzschild's geometry. While Schwarzschild described a spacetime that was perfectly symmetric around a point, the point where the infamous singularity would lie, Kerr's solution was symmetric around a line that cut through the whole of spacetime. It was as if he had set Schwarzschild's solution spinning on an axis, twisting and tugging spacetime around it. If he wanted to retrieve Schwarzschild's original solution, all he had to do was stop his solution from spinning.