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

A Bose-Einstein condensate forms when all the atoms in a gas cool down to their lowest possible energy state. These atoms then “condense” into a single mega-atom that behaves as an enormous quantum particle. Bose-Einstein condensation occurs only at a fraction of a degree above absolute zero, a temperature so cold that nearly everything comes to a stop.

Under the right conditions, that includes light. In 1999, physicist Lene Hau of Harvard University slowed light down to a moderate walking pace as it passed through a Bose-Einstein condensate. Two years later, she slowed it to a stop.

What’s more, rotating a Bose-Einstein condensate creates a regular pattern of vortices—localized quantum-mechanical waterfalls. According to Leonhardt, these quantum waterfalls should act like black holes for slow light, just like Unruh’s dumb holes would for sound. Hawking’s telltale temperature increase should be easy to catch when you’re perched just above absolute zero.

So far, no one has successfully performed Leonhardt’s proposed light experiment. But he has since shown how to create other black-hole analogues using easier experimental setups. As this magazine went to press, results from the first of these experiments were set to be announced.

Ultimately, though, what’s the point? Hawking’s calculation is about real black holes warping the fabric of spacetime. He never said anything about slow light or waterfalls. According to Unruh, observing analogue Hawking radiation would “strengthen one’s faith in the validity of his prediction.” On the other hand, if we didn’t see Hawking radiation, “it would mean that we seriously misunderstood something in the fluid situation,” he says, “and would lead to the strong worry that we had misunderstood something analogous in the black-hole case.”

Either way, quantum analogues can’t provide final proof that this or that theory of the universe is correct. But until scientists figure out how to see a black hole up close, or how to turn back the clock and study inflation, analogues offer a terrestrial way for experimenters to study them. As physicists push the boundaries of their understanding further and further away from everyday experience, the importance of experimental evidence becomes ever more acute—just as the necessary experiments become more difficult, or even impossible. Analogue systems are one way to fill in the gap, to check that physicists’ theories indeed make sense.

Deciphering the systems that we can see, prod, and fiddle with will always be easier than understanding the ones we can’t. Luckily, it sometimes happens that we can use relatively familiar cases as models for the more exotic. As Unruh puts it, “Analogy is not identity. But analogy can sometimes be a very good guide.”

James Owen Weatherall is a Ph.D. student at the Stevens Institute of Technology and at the University of California at Irvine.

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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?