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As has happened many times in the history of science, just when we finally are able to cozy up to an idea like the big bang that initially was hard to like, let alone understand, another even more mind-bending one comes along. Steinhardt and Turok, cosmologists at Princeton and Cambridge, respectively, present their case that string theory gives a more complete account of our origins; in this account, the big bang came about through the collision of two membrane-thick strings called "branes." Our universe sits on one brane, which floats parallel to the other, unseen one. Every few trillion years, the two branes approach each other; when they collide, a flash of radiation annihilates everything in both, kick-starting the creation process all over again. According to the authors, this solves certain problems with the standard big bang theory, such as inflation, dark matter and dark energy. General readers will be able to follow the authors' clearly laid out, equation-free arguments. Their new theory has little chance of being confirmed experimentally in the foreseeable future, but many who eventually embraced the big bang will doubtless find the notion of cyclic universes and parallel worlds attractive. Illus. (June 5)Copyright 2007 Reed Business Information
He was moving through a new order of creation of which few men ever dreamed. Beyond the realms of sea and land and air and space lay the realms of fire, which he alone had been privileged to glimpse. It was much too much to expect that he would also understand.
—Arthur C. Clarke, 2001: A Space Odyssey
Two boys sit in darkened cinemas, one in London and one in Miami, set to watch Stanley Kubrick's movie 2001: A Space Odyssey. It is 1968, a year of worldwide conflict and turmoil: Vietnam, the arms race, political assassinations, student protests, and rebellions. But all this is forgotten as the film sweeps the boys along in a glorious tale of science, space, and the future.
The boy in Miami witnessed firsthand the awesome power of technology to annihilate or inspire. Six years earlier, from his home near Homestead Air Force Base, he watched missiles being prepared for a strike on Cuba, knowing that his family and community would be obliterated if the looming crisis led to a nuclear exchange. Then, as the crisis subsided, he became galvanized by John F. Kennedy’s promise to send a man to the Moon by the end of the decade. He emerged from these early experiences optimistic about the power of technology to improve the future and fascinated by all things scientific. He kept logbooks of every manned mission and traveled often to Cape Canaveral to observe the launches. He turned the family garage into a laboratory with large stocks of chemicals and biological specimens. And he headed to the Everglades at night, avoiding the city lights and fending off mosquitoes, to take a peek at the heavens through his telescope.
The boy in London was a refugee from South Africa, where his parents had been imprisoned for resisting the oppressive apartheid regime. But he too was optimistic, having seen the determination of people like Nelson Mandela to build a better future. Upon his parents’ release, the family had left South Africa for Kenya and then Tanzania, new countries full of natural wonders—the Serengeti’s wild animals and the Olduvai Gorge, home of the earliest humans. Under the hot African sun the boy had learned mathematics and science from spirited young teachers. He’d built electric motors, made explosions, and watched ant lions for hours. In 1968 his family had moved to England for the sake of the children's education, arriving in time to watch the Apollo moon landings on TV.
As young children, both boys had acquired their passion for science from their fathers. Each night, the father in America told stories to his little boy of Marie Curie, Louis Pasteur, and other great discoverers. The father in Africa patiently explained the Pythagorean theorem and spoke of the great achievements of ancient Greek science. Their words were like water on seeds, feeding insatiable curiosities. How does the world work? How did it start out? Where is it headed? The boys asked the same questions that have gripped people from every society, every culture, every religion, and every continent since civilization began.
Kubrick’s film speaks of a time in the foreseeable future when people will devote their skills and resources to uncovering the secrets of the universe. A space mission is dispatched to investigate a powerful signal emanating from one of Jupiter’s moons. Technology, in the form of the computer HAL, threatens to end the mission, but human ingenuity and adaptability win out. A lone surviving astronaut arrives to find a giant monolith, appearing like a solid rock two thousand feet high. As he approaches, he realizes that it’s actually the opening of an infinite shaft, drawing him into a transdimensional trip through hyperspace and revealing the creation and the future of the universe. Watching the film, neither boy realizes how prophetic this story might be.
A Real Space Odyssey
Fast–forward to the real 2001: rather than a lone astronaut, a worldwide community of cosmologists engaged in an intense effort to understand the beginning of the universe. The two of us, now grown, are thrilled to be among them. The boy in Miami, Paul Steinhardt, is now a professor of mathematical physics at Princeton University. The boy in London, Neil Turok, is a professor of physics at Cambridge University in England. Each of us, following his own path, has pursued his dream of becoming an explorer of the universe, albeit with paper and pencil instead of a rocketship. Three years have passed since the two of us joined forces on a risky venture to investigate a new, transdimensional view of space and time that challenges the conventional history of the universe.
Cosmologists celebrate 2001 as the year the U.S. National Aeronautics and Space Administration (NASA) launched a satellite mission from Cape Canaveral to investigate not the black monolith of Kubrick’s film but a thin, dark layer of space at the outermost edge of the visible universe. The mission is called WMAP (pronounced “W-map,”), which stands for Wilkinson Microwave Anisotropy Probe. On board is a bank of highly sensitive detectors designed to gather some of the ancient light emitted from the dark layer nearly 14 billion years ago, at a time when the first atoms were just beginning to form. Every 2.2 minutes, the satellite spins once around its axis, and every hour the axis itself traces out a circle. From the combination of motions, light from a narrow ring on the sky is collected. Over the course of six months, the entire satellite keeps shifting, until the detectors have covered the entire sky. The sequence will be repeated every six months until enough light has been gathered to make a detailed portrait of the infant universe. (WMAP is a follow–up to the pioneering NASA satellite launched in 1989 called COBE, the Cosmic Background Explorer, which had made an initial low–resolution image of the early universe; in 2006, the leaders of the COBE team, John Mather at the NASA Goddard Space Flight Center and George Smoot at the University of California at Berkeley, were awarded the Nobel Prize in Physics.)
Nineteen months after the WMAP launch, in February 2003, mission head Charles Bennett and his team had collected and analyzed sufficient light to announce their initial findings at NASA’s Washington headquarters, in a press conference broadcast throughout the world. One of us watched in an auditorium at Princeton University, overflowing with what seemed like everyone in town, from mailroom clerks to middle–school students, drawn by rumors of a great new discovery. The other was in a similarly packed lecture room in Cambridge, England. The sense of anticipation was tremendous, each crowd aware that its understanding of the origin and evolution of the universe would hinge on what the WMAP team had found.
At last, Bennett and his team unveiled the image that had emerged after a yearlong exposure. Just like the fictional astronaut peering into the monolith, the WMAP satellite had gazed into the primordial layer and obtained the first clear view of the infant universe. What the greatest thinkers in history—from Plato to Newton to Einstein—could only speculate about was suddenly there for all to see, bringing humanity closer to answering the ultimate question: Where did it all come from?
At the end of the broadcast, world-renowned astrophysicist John Bahcall summarized the sentiments of the scientists watching: “Every astronomer will remember where he or she was when they first heard the WMAP results. For cosmology, the announcement today represents a rite of passage from speculation to precision science.” Bahcall’s point was that not only are the measurements marvelously accurate, but they are also in astonishing agreement with what cosmologists had been expecting.
By the time of the WMAP announcement, most scientists had come to accept a cosmological theory known as the inflationary model of the universe. In scientific discussions, “model” is often used to mean “theory,” especially cases where the idea includes aspects that are qualitative or incomplete. The inflationary model, as the term is used today, refers to a combination of three concepts: the hot big bang model, developed in the early twentieth century; the inflation mechanism, introduced in the 1980s; and the dark energy hypothesis, added in the 1990s.
In this picture, the big bang itself is not explained. It is simply imagined that space and time emerged somehow. Next, it is assumed that just after the bang, a small region of the universe underwent a dramatic process called inflation, during which it expanded a googol (10 raised to the 100) times or more within a billionth of a billionth of a trillionth (10 raised to the negative 30) of a second. Once this period of inflation ended, the energy causing the inflation was transformed into a dense gas of hot radiation. The gas cooled and the expansion slowed, allowing atoms and molecules to clump into galaxies and stars. This picture of an inflationary universe was originally conceived in the 1980s and is now presented in many textbooks. However, recent astronomical discoveries have led to a major amendment to the story—that 9 billion years after the big bang, a mysterious force called dark energy took over and started to accelerate the expansion again. In the standard picture, the expansion of the universe will accelerate forever, turning all of space into a vast and nearly perfect vacuum.
Both of us had been cosmologists for over two decades by the time of the WMAP announcement, and each had played a part in building the case for the leading view of the universe. In the 1980s, Paul was one of the architects of the original inflationary theory. A decade later, he and his Princeton University colleague Jeremiah Ostriker were among the first to incorporate dark energy into the big bang model. They showed that, assuming a particular mixture of matter and dark energy today, it is possible to tie together the leading ideas about the early and late history of the universe in a way consistent with all the available astronomical evidence. Neil was a leader in exploring, testing, and ruling out numerous competing notions. By showing how these alternatives failed, he helped to build the current consensus. He also predicted, on the basis of the inflationary model, a key feature of the pattern of the ancient light, which WMAP’s portrait of the infant universe would later confirm.
As the two of us watched the WMAP press conference on our respective sides of the Atlantic, we were enthralled by the achievement. We both knew Bennett and most of the WMAP team personally and were overjoyed by their success. We took pride in the fact that the inflationary model, to which we had each contributed, had scored a major victory. In addition to WMAP, the model now fits an enormous range of measurements—the clustering of galaxies, the distribution of infrared radiation and X–rays, the expansion rate of the universe and its age, and the abundances of the elements—to within 10 percent or better. To have a theory that can so accurately describe events occurring billions of years ago is a stunning success; the best forecasting models cannot describe tomorrow’s weather with nearly as much certainty. Fortunately, compared to the Earth’s atmosphere, the conditions in the early universe are uncomplicated, and the physical laws that govern them are remarkably simple to analyze.
Yet even as we enjoyed this great step forward, we had misgivings about how the results were being portrayed as a final proof of the inflationary model. Certainly, the precise agreement between theory and observation was impressive. It was very tempting to proclaim that the big questions in cosmology were now answered. But was it really time to declare victory?
Cosmology, the study of the origin and evolution of the universe, has some unique limitations that call for a high degree of caution. Scientists cannot perform direct experiments on the universe, and they cannot travel back in time. The best they can do is gather indirect information about the history of the universe through painstaking observations of distant objects that emitted their light a long time ago and try to piece together a logical account. But the evidence is uneven, with highly detailed information about some epochs and little or no information about others. Even if one story fits all the available evidence well, there is always the possibility that another story might fit just as well, or better. Sometimes, as with Clarke and Kubrick’s astronaut, a closer look will reveal that the original idea is wrong. Just as the giant monolith proved different when viewed from up close, more precise snapshots of the embryonic universe could, in the foreseeable future, lead to an entirely different explanation of the origin and evolution of the cosmos.
The chances of a dramatic shift in perspective did not seem so far–fetched. We were keenly aware that the inflationary model was not the complete and convincing picture it was sometimes portrayed to be. A number of flaws and untested predictions remained. More important, because of our own recent work, we knew of another possible explanation for the WMAP findings, one every bit as accurate as the inflationary model but based on a very different version of cosmic history.
This book will describe this more ambitious alternative, known as the cyclic model. According to this picture, the big bang is not the beginning of space and time but, rather, an event that is, in principle, fully describable using physical laws. Nor does the big bang happen only once. Instead, the universe undergoes cycles of evolution. In each cycle, a big bang creates hot matter and radiation, which expand and cool to form the galaxies and stars observed today. Then the expansion of the universe speeds up, causing the matter to become so spread out that space approaches a nearly perfect vacuum. Finally, after a trillion years or so, a new big bang occurs and the cycle begins anew. The events that created the large–scale structure of the universe today occurred a full cycle ago, before the last big bang.
The cyclic model accounts for the WMAP results and all other current astronomical observations with the same accuracy as the inflationary model, but the interpretation it offers is drastically different. From the cyclic view, the WMAP image is nearly as strange as Clarke’s monolith. The image literally takes all of us on a transdimensional journey to view events ranging from before the big bang to the distant future.
From the Hardcover edition.
Posted March 1, 2008
This was an excellent book. Although it was at times difficult to wrap my head around, the idea proposed: a cyclic universe and its compenents, was worth the effort. The authors' genuine joy for the subject matter comes through in a such a way that you too will share their excitement and wonder for the history of the universe.
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