Big debate over a ‘Little Big Bang’

Big debate over a ‘Little Big Bang’

Real-life quest for quarks sparks science-fiction speculation

By Alan Boyle
MSNBC

Sept. 21 — Some have made it out to be a “mad scientist” story: Using an experimental particle collider, researchers are planning to create an exotic kind of matter they believe existed a millionth of a second after the Big Bang. But in this case, the scientists are really mad — about the doomsday talk that has overshadowed the experiment itself.


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THE EXPERIMENT, which is to take place at Brookhaven National Laboratory’s new $600 million Relativistic Heavy Ion Collider in New York, aims to smash gold nuclei together at 99.95 percent of the speed of light — creating temperatures of more than a trillion degrees. That’s 10,000 times hotter than the sun, says Tom Ludlam, RHIC’s associate project director.
“Under those conditions, neutrons and protons in the atomic nuclei would literally melt into a plasma of quarks,” he said. “It’s a thermodynamic phase transition, like water changing from a solid to a liquid, or a liquid to a gas when it boils.”
Physicists say that the neutrons and protons within ordinary matter are actually built up from combinations of quarks, particles that were first postulated in the 1960s. The quarks are bound together through the exchange of particles whimsically dubbed gluons. Thus, the object of Ludlam’s 15-year quest at Brookhaven is to create a brew called quark-gluon plasma.
“The quark-gluon plasma exists for just a flash of time,” he said — in fact, for only a billionth of a trillionth of a second.

The Relativistic Heavy Ion Collider will zap beams of atomic nuclei at nearly the speed of light around a 2.4-mile-wide ring - visible at upper left in this aerial photograph.

Cosmologists believe that the universe as we know it began billions of years ago in a cataclysm popularly known as the Big Bang, and that in the first millionth of a second after that Big Bang, the entire cosmos was contained in an ultradense, ultrahot dollop of quark-gluon soup.
But physicists have never actually seen such a brew.
“Part of the motive (for doing the experiment) is in fact to confirm that such a state of matter exists, by discovering it,” Ludlam said. “As far as we know, it doesn’t exist in the present universe, although it could exist in the centers of very dense stars.
“But the real motivation is to look at this phase transition from ordinary matter to this deconstructed plasma, and then back again. And then try to answer the question of why is it that there are these preferred configurations of quarks, and could there in fact be other configurations. ... It opens up a vast new realm of exploration for people who do nuclear physics.”

SCIENCE FICTION
The magnitude of the mystery is the prime factor behind the collider’s allure — and behind the “mad scientist” angle as well. Last year, the concept behind RHIC (pronounced “rick”) spawned a science-fiction novel titled “Cosm,” in which the collider produces what turns out to be a strange new cosmos. Ludlam was even written into the plot as a minor character.
“To be honest, I haven’t read the book,” Ludlam confessed. But he said others have told him everything turns out all right. “At least the world didn’t get destroyed.”
This year, however, the tales involving RHIC have had a different twist: It all started with a letter published in July’s issue of Scientific American, asking whether the creation of a quark-gluon plasma could possibly create a black hole. Frank Wilczek of Princeton’s Institute for Advanced Study replied that “dangerous surprises seem extremely unlikely.” But he also referred to a speculative scenario involving something called “strangelets.”


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Strangelets would contain “strange” quarks — which are somewhat heavier and less understood than the garden-variety “up” and “down” quarks that make up ordinary protons and neutrons. If a series of highly unlikely conditions apply, strangelets could in theory gobble up ordinary matter, and it’s that scenario that has captured the attention of physicists as well as the popular press.
Most notably, The Sunday Times of London headlined its story "Big Bang Machine Could Destroy Earth.” Other media outlets reported on the black-hole-strangelet brouhaha in terms that made some scientists see red. Brookhaven’s director, John Marburger, issued two news releases downplaying the concerns — but also asked a panel of scientists to investigate the potential risks.
“There is a series of unlikelihoods that you’d have to string together like a Rube Goldberg invention,” said Robert Jaffe, director of the Center for Theoretical Physics at the Massachusetts Institute of Technology, who headed up the panel. “But if you strung them up all together, you’d end up with what could be a dangerous situation.”

STRANGE SCENARIOS
Jaffe said while strangelets could exist within the cores of supermassive stars, it would be far more difficult — “pretty damn near impossible,” to use a technical term — to create tiny bits of strange matter within RHIC.
And even if strangelets were created within RHIC, they would not necessarily be destructive.
“The most likely scenario is that a strangelet would have a positive charge, but a small charge,” Jaffe said. In that case, strangelets would be admittedly bizarre but basically harmless — for example, something like grossly overweight helium atoms.

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The danger would arise only if the strangelet nuclei happened to carry a negative charge. The strangelet lumps would attract ordinary nuclei and consume them like so many dots in a Pac-Man game.
“It would kind of burp a few times, and after readjustment it would have a negative charge again,” Jaffe said. “It would eat more, and burp and capture, and burp and capture to the point that it has eaten all the matter around it.”
Is such a scenario possible? To weigh that question, the panel of scientists considered the analogous natural phenomenon of cosmic-ray collisions.
“If strangelets could be made in RHIC, they also would have been made in cosmic rays,” Jaffe explained.
The physicists determined that about a trillion cosmic-ray collisions per second were occurring on the moon at energies sufficient to create strangelets. That compares with a half-trillion collisions over RHIC’s anticipated 10 years of operation, Jaffe said. Yet, the scientists saw no evidence of any lasting effect that could be traced to strange matter.

“The fact that planets and stars have not been converted to strange matter is evidence that this Rube Goldberg string does not exist,” Jaffe said. “Cosmic rays basically rule out this possibility. Our conclusion is that there’s no reason to fear for any safety concern at RHIC.”

ALL SYSTEMS GO
And so, although the draft report is yet to be released, the plans for RHIC appear to be on track: The 2.4-mile-wide collider ring will be dedicated as scheduled at an Oct. 4 ceremony — during which Brookhaven spokeswoman Mona Rowe says the local high school’s cheerleaders will perform an interpretation of quark-gluon interactions. And the collisions are likely to begin in December or January.
“Whenever a big new machine turns on that reaches to yet higher energies in these collisions of elementary particles, there’s always speculation about these disaster scenarios,” Ludlam said. “Especially now, with millennium fever starting to set in, the effect is a little bit more pronounced.”
Jaffe said the controversy also plays off an age-old clash of philosophies.
“There’s a tone in the messages that I’ve received, that scientists are playing God,” he said. “I think scientists have been guilty in the past of being Faustian, of hungering for too much knowledge. But actually, these experiments, and the whole tone of modern science, are much more circumspect.
“In contrast, the idea that we could do something that could disrupt the fabric of the universe is actually rather Ptolemaic,” he said, referring to the ancient view that Earth was at the center of the cosmos. “Everything doesn’t revolve around us.”



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