The Littlest Big Bang

Scientists are building ultra-cold systems that mimic the most extreme edges of the universe. Can these analogues help solve the big bang’s mysteries?

By James Owen Weatherall Posted 05.07.2008 at 3:30 pm 9 Comments

King of Cold: Richard Haley at the Lancaster Low Temperature Laboratory. Jonathan Worth

Hawking’s calculation was a breakthrough. Ever since the laws of quantum mechanics were unraveled in the 1920s, physicists had been trying to combine these laws of the very small with Einstein’s theory of gravity. (Nearly a century on, they still are—that quest, among others, is what drives string theorists.) Hawking didn’t create a quantum theory of gravitation, but his calculation was one of the first that applied quantum mechanics to a gravitational system, and it remains the most famous.

Yet for now, Hawking radiation is just a theoretical supposition, an educated guess at what happens near the horizon of a black hole. The difficulty is that the signal from Hawking radiation is extremely weak. No one has been able to see Hawking radiation coming out of a black hole, although some hope that a gamma-ray satellite to be launched this month will detect it.

But there may be another way. When Unruh noticed that the equations for sound near a waterfall were the same as for light near a black hole, he checked whether Hawking’s calculation also applied to the waterfall. And sure enough, dumb holes, too, should emit particles by a process akin to Hawking’s.

Unfortunately, it’s almost as hard to observe Hawking radiation from a dumb hole as from a black hole. A waterfall’s edge is a warm, busy place, and the tiny temperature bump that would come from Hawking radiation would be overwhelmed by all the activity. According to Unruh, managing to pick out the Hawking radiation in a dumb hole is possible, “but doing it would require such an effort, I doubt it will be done for a while.”

Yet dumb holes aren’t the only black hole stand-ins around. Once Unruh pointed out the mathematical analogy between fluid dynamics and black holes, other theorists began to notice connections as well. In 2000, Ulf Leonhardt, a professor at the University of St. Andrews in Scotland, published a paper in the journal Physical Review Letters describing a system in which light, rather than sound waves, would be sucked into an artificial black hole. Two years later, he showed how it could be tested in the laboratory. Once more, the world of quantum analogues would dip into the ultra-cold.

Stop Light, Then Spin

Black-hole equivalents happen when you satisfy one simple condition: Your fluid must flow faster than the waves that travel through it. Light would seem to be a bad choice of wave, because it is very fast and fluids are comparatively slow. But that’s not always the case in an exotic form of matter called a Bose-Einstein condensate.

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9 Comments

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fromagesfondus

05/08/08 at 10:10 am

This quandtum stuff is very interesting but remains very confusing to me. Good article though,

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jmnowell

05/09/08 at 1:02 am

I think you mean 0.0003 K above absolute zero. At about 4 K, liquid helium has a boiling point well below 0.0003 F, which is around 255 K, where it would only exist in its gaseous state.

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Toomanytoys

05/09/08 at 12:15 pm

In the article, the author writes: "The trouble is in the details—no one knows why it happened, nor quite how. It takes an awful lot of energy to make a universe accelerate, and pretty powerful brakes to get it to slow down again."

The answer is simple. God did it. He knows why and how it happened.

Just kidding! I would be a fool to try to explain science with religion or try to support religion with science.

Religion is "Faith".

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pernicious

05/09/08 at 1:39 pm

could someone please explain to me how it is they "watched" this process as stated in the article? also, as i understand it, wouldn't their observation of the experiment actually change the results and also render it different from the true Big Bang which one can only assume was absent of the "observer"?

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paulkruger

05/09/08 at 2:15 pm

Imagine the original big bang as a tiny singularity and look at it today. Then imagine an experiment like this gone wrong.

A new "little bang" as a singularity. Of course that would fit in the space of this little gadget. But how big and how fast would it grow if the results were similar to the real thing?

Obvious lack of mass aside...this could make for a chilling SciFi story, right?

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philbert

05/09/08 at 4:54 pm

jmnowell said:
> I think you mean 0.0003 K above absolute zero. At about 4 K, liquid helium has a boiling point well below 0.0003 F, which is around 255 K, where it would only exist in its gaseous state.

0 °F is about 255 K, as you say. Absolute zero is 0 K, or about -460 °F. So 0.0003 °F above absolute zero is still very nearly -460 °F.

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librtyship

05/09/08 at 6:43 pm

Yes things do get more and more complex the deeper we go. For instance Darwin theory seemed pretty reasonable as individual live cells in the body were assumed to be litle gelatinous globs. Now it has been discovered that they contain millions of intricate tiny components which means that each one is a complete tiny factory, then all these cells make up a human body which is an organizm of mind boggling complexity which renders the theory of evolution totally invalid and has to lead to the conclusion that life is created by an extremely high intelligence that we really can't grasp with our limited mental capabilities, then we also have all the other wonders of the universe to ponder, yes Toomanytoys had the right answer, all of these marvels were indeed the handiwork of God and he understands us and understands all else in the universe as he is the creator.

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pastkev

05/09/08 at 10:17 pm

It would be really nice to hear about evidence without the spin of religious atheists. Atheism is just as much a religion as anyone who believes in God. Atheism is based on faith and cannot be proved.

It is fine to have a worldview, but please keep your worldview out of the science, it has no place in real science and is offensive to those interested in the facts to have to hear your worldview about them.

Evidence is evidence, let it speak for itself and leave your religious worldview to discuss with your friends who will probably think you are smart; the rest of us do not care.

As he said in Dragnet, just the facts please.

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Alex R.

05/16/08 at 6:27 pm

"Evidence" is a very twistable term to use, as it can go more than one way.

Atheism is like a religion! It implies faith in supposed "evidence", does'nt it?