Alexander Vilenkin has a disconcerting tendency to smile when he talks about the end of our universe. I’m careful to say our universe because according to Vilenkin, the Director of Tufts’ Institute of Cosmology, what most people think of as the universe is really only a drop in the ocean, or more precisely, a quantum bubble nucleation in the eternally propagating ocean of false vacuum. I sat down with Professor Vilenkin in his office to discuss where everything came from, where everything’s going, what the previous sentence means and which zoo animals are most susceptible to being eaten by thieves. He had all the answers. During the course of the interview, Professor Vilenkin and I were instantaneously annihilated an infinite number of times. Sometimes Vilenkin didn’t even flinch.
In 1973, Alexander Vilenkin was a fallen physics student looking for a job in Kharkov, Ukraine. Two years earlier he had graduated from a prestigious university and had been accepted to a number of graduate programs in physics. He planned to accept an invitation from the professor who had supervised his undergraduate thesis to continue their work together in graduate school. But somewhere along the line, Vilenkin had found a way to agitate the KGB (the former USSR’s state security and intelligence agency). He was informed that the open graduate position, along with the open positions at all the other schools he had applied to, had been unexpectedly eliminated. Even the fact that Vilenkin’s father was a professor at the school he planned to attend didn’t make a difference. Vilenkin recalled, “My father was not a very practical man. He did not know who to bribe.”
To this day, Vilenkin still doesn’t know exactly what he did to get blacklisted (“The KGB never tells you why they do these things.”) On top of eliminating his graduate position, the KGB also took an opportunity to reevaluate Vilenkin’s military exemption status. Vilenkin had been excused from conscription due to a childhood bout with polio, but once he was on the state’s radar, they decided it was time to double check.
He spent the next two years in “non-combat troops,” a physical labor detail that, according to Vilenkin, the USSR assigned primarily to soldiers with criminal records, people who couldn’t be trusted with weapons. After the army, Vilenkin realized that his standing with the government would prevent him from getting “any decent job,” so he assessed the skills he had to offer and landed a job as a night watchman for a concession stand at a zoo in Kharkov. “The main quality that they were looking for was that one shouldn’t be a complete drunkard, because there was some wine in the kiosk,” said Vilenkin. In the wayward years following his days as a promising physics undergraduate, Vilenkin never lost sight of his true passion. Whenever he could, he spent his nights in the kiosk studying.
“Some friends of mine came to the zoo at night to discuss physics but the difficult part was that my colleagues, the other night watchmen, their idea of a well-spent night was to get drunk. So they would come to the kiosk and say, ‘Sashkoa [the Ukrainian diminutive for Alexander], do you have a ruble? If we each have a ruble we can get something.’ Of course, in Russia, to refuse to drink with somebody is the greatest insult, so you cannot do such a thing.”
Soon Vilenkin was promoted from his post at the concession kiosk to one of the night watchmen for the zoo proper. He never saw any action in the line of duty, but his position was no mere formality. Apparently, zoo animal theft in Kharkov was a persistent problem. “It was a pretty hopeless enterprise. There was a single rifle there that only one of the guys knew how to shoot, and the zoo was large so occasionally things would disappear. People would steal a swan, for example. A swan, you probably could eat a swan, but they would steal an eagle” said Vilenkin.
When Vilenkin wasn’t studying physics or contending with the pressures of Russian social etiquette, he sometimes wandered the zoo grounds and commiserated with the down-and-out captives. “It wasn’t like the zoos in the U.S. where they have these spacious habitats. There they were in these little cages and they were in pretty sad condition, so I would go around and talk to these poor animals. There were animals who would come to you if you would come to them, deer for example, and bears.”
If it seems improbable that we live in a world where paradigm-shaking cosmologists get their start petting caged bears in the moonlight for minimum wage, then maybe it is. After Vilenkin emigrated to the U.S. in 1976 and got his Ph.D. from SUNY Buffalo just one year later, he began to formulate a bold theory about the origin and nature of the universe, a theory that asserts that there are actually an infinite number of worlds where Vilenkin never got the job as a night watchman. There are also an infinite number where he did and an infinite number where he saved the eagle.
Vilenkin speaks with the kind of soft-‘i’-as-hard-‘e’, palatalized Eastern European accent that makes you almost believe him when he says things like, “We are having this exact conversation in an infinite number of other places in the universe but those places are very, very far away.”
The theory is called eternal inflation and although it remains on the avant-garde of promising cosmological models (the avant-garde of cosmology being a contender for the weirdest of all the avant-gardes), Vilenkin first came up with the idea almost thirty years ago. It arose as a natural corollary to the slightly more modest in scale but still startling theory of cosmic inflation, a theory originated in 1979 by a close friend of Vilenkin’s, the M.I.T. physics professor and theoretician, Alan Guth.
Before Guth proposed cosmic inflation, the familiar Big Bang theory had very little to say about the “bang” itself. It provided a satisfying account of the evolution of the early universe immediately following its fiery initiation, but it didn’t even attempt to explain what caused the “bang” or where any of the matter that “banged” came from in the first place. “It was the theory not of the bang but of the aftermath of the bang,” said Vilenkin Guth’s theory of cosmic inflation faced down the “bang.” He proposed that the observable universe was birthed by the exponential expansion and subsequent decay of what Vilenkin refers to as “a peculiar material which is called false vacuum.”
This is where, as they often do, things get hairy for the layman, but the skeleton of the idea can be understood by anyone who has blown up a balloon or baked a loaf of raisin bread. The theory hinges on the fact that gravity, like Dr. Jekyll, has a foil. This repulsive gravity has the same effect on space that blowing up the balloon has on the latex or putting the raisin bread in the oven has on the bread. It causes space itself to expand, repelling everything in it away from everything else in much the same way that the baking bread expands and pushes apart the raisins. The “peculiar material called false vacuum,” which might be roughly described as a bit of space with some energy stuffed inside of it, turns out to be a prime purveyor of repulsive gravity. And what is perhaps easier to understand than a false vacuum’s essence is its consequence, which can be briefly summed up as everything getting very big very quickly. According to Vilenkin and Guth, this is exactly what happened at our universe’s inception. “In a fraction of a second, a region which was subatomic in size, less than an atom, was exploded to dimensions much bigger than the observable universe,” said Vilenkin.
The physics community quickly embraced cosmic inflation because it solved a few persistent problems that the convention al Big Bang theory couldn’t address, such as why our universe has a uniform temperature (matter stuffed into a region a billionth the size of a proton would quickly reach a thermal equilibrium) It also explained where the matter we observe today came from. According to Vilenkin, a region of false vacuum tends to decay to a lower energy state by the same sort of probability that governs the decay of a radioactive element to a stable one, and when it stabilizes to a true vacuum, marking the end of the inflationary epoch, it releases its latent energy in a fireball of matter, providing the same expanding soup of hot matter postulated by the conventional Big Bang theory.
Today, most physicists accept some form of cosmic inflation and a number of its predictions have been observationally confirmed to a very high accuracy. Vilenkin’s theory of eternal inflation concerns itself with some of inflation’s wider and weirder implications.
Vilenkin is thin with silver hair, peaking eyebrows and a baseline smirk. He looks like he could be Carl Sagan’s drug dealer. It’s not clear if he has always looked this way or if you start to take on the appearance when you stare at infinity for a living.
As he eagerly devoured the equations of cosmic inflation in the early eighties, Vilenkin began to realize that a region of rapidly expanding false vacuum would propagate at a far faster rate than it decayed. In other words, by the time one region of false vacuum probabilistically decayed into a true vacuum, setting off a big bang in the process, there would already be another vast region of false vacuum around it, which would then precipitate more big bangs. “The big bang was not a unique event in the history of the universe. Multiple bangs went before it and countless big bangs will occur in the future in remote parts of the universe. Each of these big bangs creates a small bubble. This bubble rapidly expands and inside it we have galaxy formation and all that stuff. We live in one of these bubbles,” said Vilenkin.
The repercussions of this universe-as-marshmallow-in-microwave model are staggering. One of the most bizarre is that every conceivable possibility of how the events in one of these bubble universes can unfold must be repeated an infinite number of times. If you can imagine it, it can and will and is and has happened, always. Vilenkin has proven mathematically that although the false vacuum will continue to expand indefinitely, creating new bubble universes forever, there is a vast but finite limit to the number of ways in which matter can arrange itself in one of these bubbles, so on an eternal scale, every permutation will recur eternally. What this means in practice is that in an infinite number of bubble universes, Bill Murray will unexpectedly fall to earth from an overhead airplane killing you instantly before you finish reading this sentence. According to the Director of Tufts’ Institute of Cosmology, one of only few people in the world who supposedly really understands the most sophisticated physical equations humankind has yet achieved, that statement is actually true.
The realization that every snowflake is not technically special in the face of eternity isn’t exactly uplifting. Naturally, Vilenkin’s first reaction to his breakthrough was existential dread. “I was pretty depressed about it because of the loss of uniqueness. My thought was that we humans are not good or bad, but if you could think of our civilization as unique, then you could say that it has to be cherished as a work of art without making a value judgment. But eternal inflation tells you that it’s not,” said Vilenkin.
He has since come to terms with the idea, and he maintains that even though “we do not have significance on the scale of the entire universe,” we can probably still help ourselves to a hearty measure of idiosyncrasy in our own bubble. “Indications are that it takes some very unlikely event to trigger the origin of life so it could well be that in the entire visible universe we are the only place where this happened, the closest billion light years. In this picture,” said Vilenkin, “we are not that insignificant. We are responsible for quite a bit of real estate, and whether or not we screw it up, on that depends the future of the visible universe.”
Until recently, eternal inflation was thought to be totally speculative, an interesting possibility that had no hope of ever being proved or disproved by direct evidence. For this reason, many physicists dismissed the idea as fantastical and pointless. However, there is now reason to believe that if Vilenkin is correct, he may see evidence for his theory within his lifetime. Although most bubble universes will never come in contact with one another because the false vacuum between them is expanding at a rate far faster than they are expanding within the false vacuum, every once in a while a bubble will nucleate very close to the boundary of a pre-existing one. When this happens the bubbles can collide and, depending on the difference between their vacuum energies, one bubble will either bump into the other and then retreat or it will encroach on the other’s territory, annihilating everything it engulfs as it expands. If the former situation (call it the bump-and-retreat) happened somewhere near the visible horizon of our own pocket of the universe, it would leave a distinctive, perfectly circular fingerprint in the Cosmic Microwave Background, or CMB (a ubiquitous haze of thermal radiation left over from the big bang that is most luminous in the microwave spectrum.) And if one or more of these fingerprints, which will appear as cold spots in the CMB, is located it will provide compelling evidence for Vilenkin’s theory.
The search is already underway. Four candidates have been located by the Wilkinson Microwave Anisotropy Probe, an orbiting satellite launched in 2001 that was designed to probe the CMB, and Vilenkin is hopeful that the Planck satellite, a spacecraft launched in 2009 that is studying the CMB at an even higher resolution, will help to settle the nature of the potential collision marks.
Unfortunately, Vilenkin also finds time to speculate about the evil twin of the bump-and-retreat collision, namely the breach-and-destroy. When I ask Vilenkin about his bet for the ultimate fate of our own cozy corner of the universe, he tells me that he imagines that if we last long enough, then one day we will all be randomly annihilated by a surprise bubble nucleation before Bill Murray can even land on our heads.
Of course, the probability of something like that happening at any given moment is exceedingly slim, but according to eternal inflation, for any given moment, there are an infinite number of universes where that precise instant is doom. Vilenkin takes obvious delight in this bleak absurdity. As he explained the idea, he was careful to remind me that “it may be coming already.” Just to be sure, I clarified, “So in an infinite number of universes it will happen in the next second?”
He responded, “Absolutely.” For a moment then, we sat in silence in the afternoon light, staring at each other and awaiting our deaths. But it turned out that we were in one of the lucky infinities.