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- NEW YORK - Researchers
in New York say they are just days away from a milestone in physics: the
first particle collisions within the most powerful machine of its kind.
Scientists say the experiment eventually will generate a state of matter
that existed a millionth of a second after the Big Bang. And even before
the first collision' the experiment has generated a legal and scientific
debate worthy of a movie plot.
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- The experiment' which is to take place at Brookhaven
National Laboratory,s $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 would be 10,000 times hotter than the sun.
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- "Under those conditions, neutrons and protons in
the atomic nuclei would literally melt into a plasma of quarks. It's a
thermodynamic phase transition' like water changing from a solid to a liquid,
or a liquid to a gas when it boils, said Tom Ludlam, associate project
director for RHIC. (The acronym is pronounced like "rick.)
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- 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.
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- In the first millionth of a second after the universe,s
beginning, the entire cosmos consisted of this ultradense, ultrahot brew,
scientists say. But they have never observed this brew in the current universe
" although a less powerful collider experiment at CERN in Switzerland
may have provided <link
evidence of its existence last year.
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- Brookhaven's experimenters expect to create tiny bursts
of quark-gluon plasma for only a billionth of a trillionth of a second.
Then the plasma would coalesce again into ordinary matter, Ludlam said.
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.
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- "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.
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- SCIENCE FICTION
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- The magnitude of the mystery is the prime factor behind
the collider,s allure " and the controversy as well. Last year, physicist
Walter Wagner wrote a <link
letter to Scientific American' asking whether the creation of a quark-gluon
plasma might create a globe-gobbling black hole.
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- That particular doomsday scenario " as well as another
involving a catastrophic transition in the nature of empty space "
has been shown to be without foundation. But in his answer to Wagner,s
letter, Frank Wilczek of Princeton's Institute for Advanced Study 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
start consuming ordinary matter, turning the entire Earth into a sphere
of strangeness.
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- It's this scenario that has captured the attention of
physicists and the press.
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- For example, The Sunday Times of London headlined its
story <link
Big Bang Machine Could Destroy Earth. Chicago Sun-Times columnist Zay
N. Smith regularly publishes <link
"Defcon alerts about RHIC,s status. And Wagner, the author of
that Scientific American letter, filed federal lawsuits in San Francisco
and New York aimed at stopping the collisions at RHIC by court order.
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- Brookhaven's director, John Marburger, issued <link news releases
downplaying the concerns " but also asked a panel of scientists to
investigate the potential risks.
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- Last September, the panel ruled out even the worst-case
scenario for a strangelet doomsday.
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- "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.
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- The panelists said that even if RHIC were able to create
strangelets, the evidence indicates that they couldn't persist long enough
to cause trouble. And even if strangelets did somehow persist' they wouldn't
necessarily be dangerous.
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- "The most likely scenario is that a strangelet would
have a positive charge, but a small charge, Jaffe told MSNBC.com when the
report was released. In that case, strangelets would be admittedly bizarre
but basically harmless " for example, something like grossly overweight
helium atoms.
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- But if stable strangelets carried a negative charge,
that would create a "dangerous situation' Jaffe acknowledged. Tiny
lumps of strange matter would attract ordinary nuclei and consume them
like so many dots in a Pac-Man game.
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- "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.
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- Could this actually happen? The panelists argued that
if such a scenario had any validity, cosmic-ray collisions already should
have created enough strange matter to be detected.
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- "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.
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- MILESTONE IMMINENT
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- In the wake of such reassurances, RHIC was formally dedicated
last October. Since then' Ludlam and his colleagues have been fine-tuning
every element of the system, including two collider rings that are each
more than 2 miles in circumference, and four detectors looking for signs
of the quark-gluon plasma.
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- "There was beam acceleration in both rings simultaneously
for the first time this morning, Ludlam told MSNBC.com on Tuesday. "It's
getting very close to the point where we,ll be able to start actively steering
the beams in those first collisions.
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- The initial collisions could come anytime in the next
two or three weeks, he said.
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- "It's really not something where you,re going to
see an announcement saying that we have all our ducks in a row, and tomorrow
we,re going to push the button. It really doesn't happen that way, he said.
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- For the first few months of experimentation' Ludlam said,
collisions would proceed at an energy level of 70 billion electron volts
per nucleon. That's seven times more energetic than the CERN collisions,
he said. Eventually, the energy levels are due to reach 100 billion electron
volts.
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- Wagner, meanwhile, is continuing with his legal challenge.
In an interview with MSNBC.com, Wagner argued that the Brookhaven experiment
opened the way for scenarios that were "qualitatively different from
those involving cosmic rays. In a follow-up e-mail message, he complained
that the risks of creating a world-gobbling strangelet were being understated
so that the experiment could proceed.
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- "I disagree with that philosophy, as it places the
future of all humanity at risk, just for the benefit of a very few, he
said.
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- Wagner,s New York lawsuit was dismissed last week on
a technicality. In San Francisco, Wagner,s requests for a restraining order
have been turned down repeatedly, but the case is still on the docket.
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- Ludlam said the doomsday debate hasn't affected the efforts
at Brookhaven.
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- "It's just one of those things that certainly does
capture the imagination of people, even some people who feel they have
some understanding of the science and feel compelled to take strong measures,
he said. "But in fact' this has been looked at very thoroughly by
people who understand and know how the science of these collisions works.
... You can always invent scenarios, but in fact these are really not scientifically
valid scenarios.
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