[Editor’s note: This is the second of three parts. This article is about experiments, to be soon conducted at Brookhaven National Laboratory, which some say could end all life as we know it. Everything in the following article is true.]
[Read part one]
Black Holes, Stranglets and Lower Vacuum States
The unprecedented energy levels that make RHIC potentially groundbreaking is what make it theoretically dangerous. The first hazard to make it to the popular press last summer was an accidental black hole—a catastrophe we can, but dare not, conceptualize: The whole world would be sucked into Long Island. As it turns out, an unwanted black hole is the least of our worries. The Review investigates several other possible RHIC-induced “exotic phenomena”: a ravenous “strangelet” that would eat the Earth, and a transition to a lower vacuum state, which, if triggered, would destroy the universe at the speed of light. (None of these “phenomena,” unfortunately, will bring back the dinosaurs.)
Exotic indeed. Although the black hole seems to be a public favorite, Hallman says “it doesn’t even pass the laugh test.” RHIC is powerful, but not that powerful. It is 10 million billion times too weak to create a black hole, and its 2.4-mile ring is much too small. (It would have to be about as big as the galaxy with current technology.)
The strangelet scenario, although very improbable, is harder to rule out. “This one,” says Hallman, “you can’t absolutely say no to.” Strange matter is a type of matter containing strange quarks, particles so named because the researchers who first encountered them in the 1950s had a hard time interpreting their properties. Physicists have wondered for some time if there could be a hypothetical configuration of strange matter that would be more stable than ordinary matter, thereby converting everything it encountered into more of itself. According to the Review, this quantum King Midas, “if [it] did exist and could be produced at RHIC…would be extremely dangerous.”
But not as dangerous as a lower vacuum state. In this scenario, RHIC’s collisions could potentially trigger the collapse of the vacuum that makes up the universe. If a collapsed vacuum sounds counter-intuitive, it’s because the term vacuum is somewhat of a misnomer. The vacuum of space is actually a highly structured medium that, according to Piet Hut, an astrophysicist at Princeton’s Institute for Advanced Study, “can exist in various states or phases, much like the liquid, solid and vapor phases of water.” In an article published in 1980, Steven Coleman and Frank De Luccia suggested that our vacuum might only be sort of stable. As the universe cooled and fell to a stable energy state, they proposed, it could have settled into a “false vacuum”—a point where it was locally stable, but not at its lowest energy level. (This would be somewhat like a pen rolling down a desk top and settling in a groove half way down; it is locally stable in that groove, but if pushed, it would fall further.) In this state, the universe would be a disaster waiting to happen: If a bubble of “real vacuum”—the vacuum at a lower energy level—formed, it could trigger a collapse of the false vacuum at the speed of light.
In the lower vacuum state, we would disappear. Matter as we know it could not exist; there would be no electrons, protons or neutrons—none of the particles that we are made of. Coleman and De Luccia wrote that this would be the “ultimate ecological catastrophe.” When asked, Piet Hut said, “words fail me to describe what this would mean. It would be incredible.” In 1982, Piet Hut and Martin Rees published a paper in which they studied the problem of whether a lower vacuum state could be triggered by a new generation of particle accelerators. They concluded that it was unlikely, because many billions of naturally occurring cosmic ray collisions in inter-stellar space produce similar or greater energy collisions than those in accelerators, and none of them have yet triggered a vacuum instability. The fact that we are still here, they argued, is proof that these experiments will be safe. And the evidence keeps mounting: Since Hut and Rees’s study, new particle accelerators like the Tevatron at the Fermilab complex in Illinois have operated for years, yielding important new scientific discoveries without any apocalyptic mishaps.
The authors of the Review used a similar argument to dispel fears of ravenous strangelets. The thousands of trillions of high energy collisions that have occurred on the moon’s surface have not turned our lone satellite into a ball of strange matter. In fact, for each of the “speculative disasters,” calculations or empirical comparisons yield astronomical safety factors, which means that the danger is so small that, according to Tim Hallman, “the word infinitesimal does not even do it justice.” Robert Jaffe, one of the authors of the Review and the world’s leading expert on strangelets, says that the probability is negligible. “It’s like worrying that water is suddenly going to flow uphill,” he said. “It’s not impossible, but it’s incredibly improbable.”
[Part three will appear on Monday.]