Creation Of A Sound Singularity

There has been quite a lot of news to kick off the week about an experiment designed to create an analogous model of a black hole and then observe hawking radiation being emitted from it. Use the link to The Brilliant Cosmos to learn more about black holes in general. Hawking radiation is the idea that at the edge of the event horizon, right on the brink between a possible escape and certain doom, a pair production occurs from no energy, a quantum fluctuation. Often both particles fall back into the black hole and suffer effective annihilation and since the beginning and end total energy is the same the universe doesn’t care. But occasionally the two particles will have the energy to escape the black hole; however only one of these particles will be heading in the right direction to escape. The other will fall back into the black hole as its partner rushes off into space. But now the universe has a problem: since a particle has just flown off with a kinetic energy and won’t be annihilated, the total energy won’t be zero. Unless of course the other particle has a negative energy and since this particle fell into the black hole the black hole suffers a reduction in its energy. This loss is called evaporation and the released particle Hawking radiation.

Now the experiment that everyone has been getting excited about uses a very condensed Bose-Einstein condensate, at a standard low temperature, to create a system where sound could not escape. Any of these acoustic vibrations get trapped and muffled to nothing in the condensate and so this area represents the black hole but one of sound not light. But near the surface, small vacuum fluctuations produce mechanical waves , in essence sound, which has now been detected. Hawking radiation has never been observed but this parallel radiation fits many of the mathematical predictions and proves that this radiation follows a classic thermal distribution. There is still some uncertainty on how similar this experiment is to a real black hole but the possibility of performing observations on a mathematically identical system is very alluring.

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