Alex Vilenkin. Vilenkin was born in Ukraine, in the former Soviet Union, where, after obtaining an undergraduate degree in physics, he held a job as a night watchman in a zoo. In 1976 he immigrated to the United States, and in little more than a year he managed to earn a Ph.D. in physics. Vilenkin now teaches at Tufts University near Boston, where he is also director of the Tufts Institute of Cosmology. He is known for wearing dark glasses during seminars, Anna Wintour–like, supposedly because of the sensitivity of his eyes to light.
When Vilenkin talks about the universe arising from “nothing,” he means it quite literally, as I learned from chatting with him a few years ago. “Nothing is nothing!” he insisted to me, with some vehemence. “Not just no matter. It’s no space. No time. Nothing.”
But how could a physicist even define a state of sheer nothingness? Here is where Vilenkin showed ingenuity. Imagine spacetime as the surface of a sphere. (Such a spacetime is called “closed,” since it curves back on itself; it is finite, even though it has no boundaries.) Now suppose that this sphere is shrinking, like a balloon that is losing its air. The radius grows smaller and smaller. Eventually—try to imagine this—the radius goes all the way to zero. The surface of the sphere disappears completely, and with it spacetime itself. We have arrived at nothingness. We have also arrived at a precise definition of nothingness: a closed spacetime of zero radius. This is the most complete and utter nothingness that scientific concepts can capture. It is mathematically devoid not only of stuff but also of location and duration.
With this characterization in hand, Vilenkin was able to do an interesting calculation. Using the principles of quantum theory, he showed that, out of such an initial state of nothingness, a tiny bit of energy-filled vacuum could spontaneously “tunnel” into existence. How tiny would this bit of vacuum be? Perhaps as little as one hundred-trillionth of a centimeter. But that, it turns out, is good enough for cosmogonic purposes. Driven by the negative pressure of “inflation,” this bit of energetic vacuum would undergo a runaway expansion. In a couple of microseconds it would attain cosmic proportions, issuing in a cascading fireball of light and matter—the Big Bang!
So the transition from Nothingness to Being, as imagined in the Vilenkin scenario, is a two-stage affair. In the first stage, a tiny bit of vacuum appears out of nothing at all. In the second stage, this bit of vacuum blows up into a matter-filled precursor of the universe we see around us today. The whole scheme would appear to be scientifically irreproachable. The principles of quantum mechanics, which govern the first stage, have so far proved to be the most reliable principles in all of science. And the theory of inflation, which describes the second stage, not only has been a conceptual success since it was introduced in the early 1980s, but also has been triumphantly confirmed by empirical observations—notably, by the patterns of background radiation left over from the Big Bang that have been observed by the COBE satellite.
So Vilenkin’s calculations appeared to be sound. Yet, in chatting with him, I had to confess that my imagination bridled at his scenario of creation from nothing. Surely, the bubble of false vacuum out of which the cosmos was born had to come from somewhere. So, rather impishly, he told me to picture the bubble forming in a glass of champagne—and then to subtract the champagne.
Even with this image in mind—a not-altogether persuasive one—I remained perplexed. A champagne bubble forms in the course of time. But Vilenkin’s bubble that appears out of nothingness is a bubble of spacetime. Since time itself (along with space) is created in the transition from Nothing to Something, this transition can’t very well take place in time. It seems to unfold logically rather than temporally. If Vilenkin is right, nothingness never had a chance: the laws of physics eternally ordained that, with some appreciable probability, there would be a universe. But what gives ontological clout to these laws? If they are logically prior to the world, where exactly are they written down?
“If you like,” Vilenkin told me, “you can say they’re in the mind of God.”
Perhaps, I thought after talking with Vilenkin, this is the best that science could do. It could show that the laws explaining how things happen within the world also explain why there should be a world at all—and hence,