Scientists Cook Up Hottest 'Soup' Ever

THE GIST:

• The hottest-ever matter is created in a laboratory -- 4 trillion degrees Celsius.
• The "soup" of highly energized subatomic particles is believed to have existed for a microsecond after the Big Bang.
• Scientists don't know why the so-called "quark-gluon plasma" is a liquid and not a gas.

Using a particle accelerator to smash together gold particles, scientists momentarily generated the hottest temperature in a lab -- 4 trillion degrees Celsius -- as much heat as what filled the universe for a fraction of a second after the Big Bang explosion.

The searing temperature -- 250,000 times hotter than the center of the sun -- melted protons and neutrons into an oddly near-perfect liquid of subatomic particles known as quark-gluon plasma. This highly energized form of matter is believed to have existed for ten-millionths of a second after the universe's birth. It then cooled and condensed to form the protons and neutrons that comprise matter today.

"Our present understanding of the history of the universe says that these temperatures were reached first about a microsecond after the Big Bang. Even higher temperatures were believed to exist earlier," said Steven Vigdor, with the Relativistic Heavy Ion Collider, a 2.4-mile circumference atom smasher at the Department of Energy's Brookhaven National Laboratory.

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The experiment is intended to test models simulating the early universe in an attempt to understand how it came into existence and evolved.

The measurement itself was extremely difficult to make, added Barbara Jacak, a physicist with Stony Brook University.

"The plasma only lives for a billionth of a trillionth of a second so we can't stick a thermometer in it," she said.

Instead, scientists use photons of high-energy light to make the measurement.

The experiment also verified the asymmetrical nature of quark-gluon plasma, replicating conditions believed to be responsible for the universe's existence.

"If the universe was symmetrical, the Big Bang would have produced equal amounts of matter and antimatter, which would have annihilated each other, leaving only radiation," said Dmitri Kharzeev, a theorist at Brookhaven. "The universe would be a very desolate place."

Follow-up studies are planned to help scientists learn more about the quark-gluon plasma, including why it is a liquid, not a gas. Magnetic fields are believed to play a role.

The research was unveiled this week at the American Physical Society meeting in Washington D.C. Details will be published in Physical Review Letters.