Sonic black hole

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A sonic black hole is a type of artificially produced phenomenon utilizing an ultra-low temperature Bose-Einstein condensate in which sound waves are trapped in certain areas of a moving fluid behind a sonic event horizon. The speed of sound in these conditions is very low.

An event horizon for sound waves occurs wherever there is a surface through which a fluid flows at the local speed of sound, the flow being subsonic on one side of the surface and supersonic on the other. Inside the horizon, the background flow speed is greater than the local speed of sound, and so sound waves are inexorably dragged inwards. A sonic event horizon is completely analogous to those appearing in general relativistic black holes in the sense that sonic perturbations cannot propagate through this surface in the outward direction.

The purpose of creating sonic black holes is to learn more about gravitational black holes as the equations describing sound waves in a fluid are the same as the ones describing light propagation in a gravitational field. The observations from such experiments could help to resolve some of the conflicts between general relativity and quantum theory.