Thursday, October 28, 2010

Event horizons: try this at home

How to Make a White Hole in your Kitchen Sink
WiredScience: That ring of water in your kitchen sink is actually a model white hole... Liquid flowing from a tap embodies the same physics as the time-reversed equivalent of black holes. When a stream of tap water hits the flat surface of the sink, it spreads out into a thin disc bounded by a raised lip, called the hydraulic jump... If the water waves inside the disc move faster than the waves outside, the jump could serve as an analogue event horizon. Water can approach the ring from outside, but it can't get in.

'The jump would therefore constitute a one-directional membrane or white hole,' wrote physicist Gil Jannes and Germain Rousseaux of the the University of Nice Sophia-Antipolis in France in a study on ArXiv... 'Surface waves outside the jump cannot penetrate in the inner region; they are trapped outside in precisely the same sense as light is trapped inside a black hole.' The analogy is not just surface-deep. The math describing both situations is exactly equivalent... 'The concept of horizons is not limited to relativity.'...

'This is a brilliant experiment: Kitchen-sink physics is turned into a black-hole analogue,' commented Ulf Leonhardt, a physicist at the University of St. Andrews in Scotland who works on making analogue black holes in fiber-optic cables. 'Germain Rousseaux and his team used sophisticated equipment and did very careful measurements, but at its heart, the experiment is based on a simple idea everyone can understand and try at home.'

Image source here.