he stunning success of the book took everybody by surprise. The author, a quiet, even demure physics professor named Alex Vilenkin, has become an instant celebrity. His talk show engagements have been booked solid six months in advance. He has hired four bodyguards and has moved to an undisclosed location to avoid paparazzi. His sensational bestseller, titled
Many Worlds in One
, describes a new cosmological theory that says that every possible chain of events, no matter how bizarre or improbable, has actually happened somewhere in the universe—and not only once, but an infinite number of times!
The consequences of the new theory are mind-boggling. If your favorite football team did not win the championship, don’t despair: it did win on an infinite number of other earths. In fact, there is an infinity of earths where your team wins every single year! If your discontent goes beyond football and you are completely fed up with how things are, again Vilenkin’s book has something to offer. According to the new theory, most places in the universe are nothing like our Earth and are even ruled by different laws of physics.
The most controversial aspect of the book is the claim that each of us has an infinite number of identical clones living on countless earths scattered throughout the universe. Much sleep has been lost over this issue. People feel their unique identities have been stolen. So attendance at psychoanalysts’ offices has doubled, and sales of the book have soared. Using his theory, Vilenkin also predicted that on some earths his book would be a phenomenal success. But to be fair, he had to admit there were infinite others where it would be a complete flop …
We live in the aftermath of a great explosion. This awesome event, called somewhat frivolously “the big bang,” occurred some 14 billion years ago. The whole of space erupted in a hot, rapidly expanding fireball of matter and radiation. As it expanded, the fireball cooled down, its glow steadily subsided, and the universe slowly descended into darkness. A billion years passed uneventfully. But gradually, galaxies were pulled together by gravity, and the universe lit up with myriads of stars. Planets revolving about some of the stars became home to intelligent creatures. Some of the creatures became cosmologists and figured out that the universe originated in the big bang.
Compared with historians and detectives, the great advantage cosmologists have is that they can actually see the past. Light from remote galaxies takes billions of years to reach our telescopes on Earth, so we observe the galaxies as they were in their youth, when their light was emitted. Microwave detectors pick up the faint afterglow of the fireball, yielding an image of the universe at a still earlier epoch, prior to the formation of galaxies. We thus see the history of the universe unfolding before us.
This wonderful vision, however, has its bounds. Even though we can trace the history of the cosmos to less than a second after the big bang, the bang itself is still shrouded in mystery. What triggered this enigmatic event? Was it the true beginning of the universe? If not, then what came before? There is also a fundamental limit to how far we can see into space. Our horizon is defined by the maximum distance light could have traveled since the
big bang. Sources more distant than the horizon cannot be observed, simply because their light has not yet had time to reach Earth. This leaves us wondering what the rest of the universe is like. Is it more of the same, or could it be that distant parts of the universe differ dramatically from our cosmic neighborhood? Does the universe extend to infinity, or does it close in on itself, like the surface of the Earth?
These are the most basic questions about the universe. But can we ever hope to answer them? If I claim that the universe ends abruptly beyond the horizon, or that it is filled with water and inhabited by intelligent goldfish, how can anyone prove me wrong? Cosmologists, therefore, focus mostly on the observable part of the universe, leaving it to philosophers and theologians to argue about what lies beyond.
But if indeed our quest must end at the horizon, wouldn’t that be a great disappointment? We may discover scores of new galaxies and map the entire visible universe, just as we mapped the surface of the Earth. But to what end? Mapping our own galaxy could serve a practical purpose, since we may want to colonize it some time in the future. But galaxies billions of light-years away are not likely prospects for colonization. At least not in the next few billion years. Of course, the appeal of cosmology is not in its practical utility. Our fascination with the cosmos is of the same nature as the feeling that inspired ancient creation myths. It is rooted in the desire to understand the origin and the destiny of the universe, its overall design, and how we humans fit into the general scheme of things.
Cosmologists who do rise to the challenge of the ultimate cosmic questions lose all their advantage over detectives. They can rely only on indirect, circumstantial evidence, using measurements made in the accessible part of the universe to make inferences about the times and places that cannot be observed. This limitation makes it much harder to prove one’s case “beyond a reasonable doubt.” But because of remarkable recent developments in cosmology, we now have answers to the ultimate cosmic questions that we have some reason to believe.
The worldview that has emerged from the new developments is nothing short of astonishing. To paraphrase Niels Bohr, it may even be crazy enough to be true. That worldview combines, in surprising ways, some seemingly contradictory features: the universe is both infinite and finite,
evolving and stationary, eternal and yet with a beginning. The theory also predicts that some remote regions have planets exactly like our Earth, with continents of the same outline and terrain, inhabited by identical creatures, including our clones, some of them holding copies of this book in their hands. This book is about the new worldview, its origins, and its fascinating, bizarre, and at times disturbing implications.