In a Bose–Einstein condensate no one can hear you scream!

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ok perhaps not as catchy as “in space no one can hear you scream!” but its a pretty apt description of the work of a number of condensed matter physisits who have recent created the worlds first acoustic black hole. Now I know what you are thinking … it was the same thought I had as soon as I heard about this work : acoustic black hole + coldplay = a better world for us all. In my head its like those flying flat prison things from superman … but we let out the brutal superhuman dictator and replace him with the far greater evil of coldplay

Seriously though this is some really cool stuff. As we all know in our current theory of gravity, matter and energy bend space and time around it and in turn light and matter will move along the contours of this curvature. In a black hole the density of the matter/energy doing the warping of space time is so great that light (and everything else) is unable to escape from that region. Now what you might not have known (I certainly didn’t!) is that it turns out that in a certain state of matter, known as a Bose-Einstein condensate, the equations which govern the paths of sound through the matter are the same as those which govern how light travels along the curvature of space. This throws up an pretty intriguing idea: could we create within a Bose-Einstein condensate a region from which no sound can escape? A form of  coldplay prison acoustic black hole?

Well it turns out that not only is the answer a resounding “hell yeah!” but some scientists form the Israel Institute of Technology, in Haifa have done just that. They created a region within the Bose-Einstein condensate which had a  supersonic flow, that is the material which makes up the condensate is moving faster than sound. Within this region little packets of sound called phonons (an analogous version of photons but for sound instead of light) can never escape this region. Its sort of like running on one of those flat escalators that you get at airports, if its moving faster than you can run you can never get off it. The border between the supersonic region and the rest of the condensate then acts like an event horizon in regular black holes.

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