Black holes not black after all

May 12, 2008

International scientists have used flowing water to simulate a black hole, testing Stephen Hawking's theory that black holes are not black after all.

The researchers, led by Professor Ulf Leonhardt at the University of St Andrews and Dr Germain Rousseaux at the University of Nice, used a water channel to create analogues of black holes, simulating event horizons.

An event horizon is the place in the channel where the water begins to flow faster than the waves. The scientists sent waves against the current, varied the water speed and the wavelength, and filmed the waves with video cameras. Over several months the team painstakingly searched the videos for clues. They wanted to see whether the waves show signs of Stephen Hawking's famous prediction that the event horizon creates particles and anti-particles.

Professor Ulf Leonhardt, from the School of Physics and Astronomy, explained, "It is probably impossible to observe the Hawking radiation of black holes in space, but something like the radiation of black holes can be seen on Earth, even in something as simple as flowing water."

Black holes resemble cosmic drains where space disappears like water going down a plughole. Space seems to flow, and the closer one gets to the black hole, the faster it flows. At the event horizon space appears to reach the speed of light, so nothing, not even light, can escape beyond this point of no return.

The experiments were carried out at the Genimar laboratory near Nice which houses a 30-metre-long water channel with a powerful pump on one end and a wave machine on the other. The normal business of Genimar is testing the environmental impact of currents and waves on coasts or the hulls of French submarines, but the scientists turned the machinery to testing black holes.

The team demonstrated that something as simple and familiar as flowing water might contain clues of the mysterious and exotic physics of black holes. In a forthcoming paper in New Journal of Physics, the scientists report observed traces of "anti-waves" in their videos.

Professor Leonhardt continued, "Flowing water does not create anti-particles, but it may create anti-waves. Normal waves heave up and down in the direction they move, whereas anti-waves do the opposite.

"We definitely have observed these negative-frequency waves. These waves were tiny, but they were still significantly stronger than expected. However, our experiment does not completely agree with theory and so much work remains to be done to understand exactly what happens at the event horizon for water waves."

Source: University of St Andrews

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User comments : 7

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thales
1.3 / 5 (4) May 12, 2008
How does this make black holes not black? Do virtual particles have a non-black color? Do "anti-waves" have a non-black color? In summary: what the crap?
Lord_jag
3 / 5 (3) May 12, 2008
uh... i think black holes are considered "black" because no energy that can be detected is emmitted. If there are any particals including the wierd ones expelled, then they can be detected on something making them non-black over all spectrums.
Ragtime
May 12, 2008
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Ragtime
May 12, 2008
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brant
2.3 / 5 (3) May 12, 2008
"However, our experiment does not completely agree with theory and so much work remains to be done to understand exactly what happens at the event horizon for water waves."

YOUR THEORY IS BROKEN!!!!!

How stupid do you have to be.... Ding ding, LIGO the non gravity wave detector.... Looking for non existent entities..

I have never said that about science before, but its definitely getting there...
WolfAtTheDoor
3.4 / 5 (5) May 13, 2008
I agree this seems a little obtuse. Not that I think I'm smarter than these guys or anything, but you're dealing with two completely different systems that are not governed by the same forces. I don't see how anything meaningful can come out of it.
bobwinners
1 / 5 (2) May 13, 2008
Just one comment: Space doesn't move. Matter moves, energy moves. Space is where this takes place. It is infinite.
Soylent
3 / 5 (1) May 13, 2008
Just one comment: Space doesn't move. Matter moves, energy moves. Space is where this takes place. It is infinite.


Spoken like a true classical physicist.

May I direct you to the theory of general relativity which is now very well entrenched and has succesfully made many, very accurate predictions and welcome you to the 20th century.

Space is no longer regarded as a static scene on which 'actors' play out, it is an active participant. Curvature in spacetime tells matter how to move and matter tells spacetime how to curve.

It's not at all known whether the universe is infinite; it's not even known if the universe is simply connected.
Alexa
May 13, 2008
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Alexa
May 13, 2008
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googleplex
5 / 5 (1) May 13, 2008
Some people might mock such a simplistic anologue to black holes.
Let me tell you that I modelled a nuclear reactor in my backyard using potatoes instead of neutrons. Sure enough when I passed the nuclear cross section threshold I achieved critical Mash!

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