"Here is where the action takes place. This is where we effectively try to turn the clock back 14 billion years. Right above your head, about 13½ feet in the air."
Looking up, I try to imagine the events Tim Hallman is describing—atoms of gold colliding at 99.99 percent the speed of light; temperatures instantly soaring to 1 trillion degrees, 150,000 times hotter than the core of the sun. Then I try to picture a minuscule five-dimensional black hole, which, depending on your point of view, may or may not have formed at that same spot over my head. It's all a little much for an imagination that sometimes struggles with the plot of Battlestar Galactica.
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Particles unleashed by the high-energy |
I'm standing in a Battlestar-scale room at Brookhaven National Laboratory in Upton, New York, where Hallman and about 1,200 other physicists labor away as latter-day demiurges. Here in the middle of Long Island, they are re-creating the opening microseconds of the universe's existence, the time when the first particles of matter—of everything—appeared.
The building we're in straddles a small segment of the Relativistic Heavy Ion Collider, or RHIC (pronounced "Rick"), an ultrapowerful particle accelerator with a 2.4-mile circumference. For nine months of the year, a 1,200-ton detector as big as a house fills most of the room. But technicians have hauled the detector to an adjoining hangar-size area for maintenance, leaving me and Hallman free to amble just below the spot where a new form of matter exploded into being during the accelerator's recent runs. New, that is, in that it hasn't existed since the very beginning of time, or by the transcendently precise reckoning of physicists, since 10 millionths of a second after the Big Bang, 13.7 billion years ago.
That was the last time particles called quarks and gluons—the most fundamental constituents of matter—roamed free in the cosmos, and it was a brief run. After just a hundred-millionth of a second, all the universe's quarks combined in triplets—held together by gluons—to form protons and neutrons. They have been locked inside the hearts of atoms ever since, until RHIC set them loose once again.
When the gold nuclei collide in the accelerator, they explode in a fireball just a trillionth of an inch wide. Inside that nanoscale fireball, temperatures exceed a trillion degrees, mimicking conditions in the immediate aftermath of the Big Bang. The nuclei literally melt back into their constituent quarks and gluons. Then, 50 trillionths of a trillionth of a second later, the fireball cools, just as the infant universe did as it expanded, and the quarks and gluons merge once again to form protons and neutrons.
With these experiments, Hallman and his Brookhaven colleagues are discovering something extraordinary about the early universe. The quarks and gluons that coursed through the newborn cosmos—and considerably more recently, through RHIC—took the form not of a gas, as physicists expected, but of a liquid. For a few instants, a sloshing soup of quarks and gluons filled the universe.
"I like to say that our theory of the early universe is now all wet," says Bill Zajc, a physicist at Columbia University and the leader of one of the experimental teams at RHIC.
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In the circular tunnel at RHIC (above), |
He might have added that the theory is full of holes, little black ones from the fifth dimension, because it turns out that in a strange mathematical sense, the quarks and gluons at RHIC are equivalent to microscopic black holes in a higher-
dimensional space. Understanding just why that is so involves navigating a labyrinth of strange, heady, and heretofore seemingly unrelated theories of physics. In addition to challenging the conventional model of how the universe behaved in its earliest instants, the RHIC data also provide the first empirical support for a theory so enthralling it once had physicists dancing at a major conference. Moreover, the accelerator's results hint that string theory—the much-
ballyhooed "theory of everything," which has lately come under attack as being little more than a fanciful, if elegant, set of equations—may have something to say about how the universe works after all.
Before the physicists at Brookhaven could begin their pursuit of quarks, gluons, and hyperdimensional holes in space-time, they first had to prove that they wouldn't destroy the planet in the process. The doomsday risk never really existed, but making that clear to a worried public occupied the time of some of the world's leading physicists (see "Could a Man-Made Black Hole Swallow Long Island?" opposite page).
Once the doubts about Earth's safety had been laid to rest, the physicists at Brookhaven fired up their $500 million accelerator for the first time, in the summer of 2000. For Nick Samios, it was the culmination of two decades of work. Samios, who is now director of the RIKEN-BNL Research Center, headed Brookhaven from 1982 until 1997 and was the driving force behind the effort to build RHIC. "I'll tell you a story," he says over lunch at Brookhaven's staff cafeteria, leaning forward. The story's principals are Stalin; his chief of secret police, Lavrenty Beria; and Igor Vasilyevich Kurchatov, a leading Soviet nuclear physicist. "Stalin and Beria are discussing the Soviet Union's first atomic-bomb test. 'Who gets the award if the test is a success?' Beria asks Stalin. 'Kurchatov.' So then Beria asks, 'Who gets shot if it doesn't work?' 'Kurchatov.' I feel like Kurchatov. Anyone else could disassociate themselves from the project. I couldn't."
One gamble Samios and his colleagues made 20 years ago was to trust in Moore's law, first formulated in 1965 by one of Intel's founders, which holds that computing power doubles roughly every 18 months. The type of accelerator Samios wanted to design would generate a petabyte of data—a million gigabytes—during each run, a rate that would fill the hard drive of one of today's typical desktop PCs every few minutes. In 1985 there were no computers that could handle anything close to that. But the "if we build it, the computers will be there" strategy paid off, and Samios's dream of a Big Bang machine became a reality.
To re-create the immediate aftermath of the Big Bang, RHIC reaches higher energies than any other collider in the world. Unlike most accelerators, which smash together simple particles like individual protons, RHIC accelerates clusters of hundreds of gold atoms—with 79 protons and neutrons in each gold nucleus—to 99.99 percent the speed of light. In the resulting multiatom collisions, a melee of tens of thousands of quarks and gluons is released. They in turn form thousands of ordinary particles that can be tracked and identified.
"The physics at RHIC is complicated," Samios says with a touch of understatement. "Two big nuclei are hitting each other. Physicists are used to calculating a proton hitting a proton. We're hitting 200 nucleons with 200 nucleons [a nucleon is a proton or neutron]. With each collision we get thousands of particle tracks coming out. We had to build detectors that could count all of them. People weren't used to that. They were used to counting 50 in a collision.
"We hoped that RHIC would make great discoveries. We hoped that we'd break nuclei into quarks—the early universe was quarks and gluons, and then it cooled off and you got protons and us. We've done that. The question is–Is there something new going on? And the answer is yes."
