Kitchen sink experiment simulates exotic white holes

David Shiga - Expensive particle colliders are not the only way to explore far-out physics. It seems that water gushing from a tap and hitting a sink behaves like a white hole – the theoretical opposite of a black hole.

A black hole is a dense concentration of mass surrounded by an extremely powerful gravitational field. Nothing that falls within a certain radius surrounding it, known as the event horizon, escapes. A white hole is the opposite: its event horizon allows things to escape but prevents anything from entering. However, so far white holes only exist in theory, so cannot be studied observationally.

When water hits the bottom of a sink, it flows outwards in all directions. At a certain distance from the point where the water hits the sink, the outgoing liquid rapidly decelerates and piles up before continuing its outward flow, creating a ring-like ridge.

Physicists have previously suspected that any ripples that might arise beyond the ridge and travel towards it should not be able to get past the ridge. This is because at the ridge the water flows outwards at the maximum speed that ripples could travel inwards, so the ripples would make no forward progress, like a runner on a treadmill. This makes the ridge behave like a white hole event horizon.

Now this has been experimentally confirmed by Germain Rousseaux of the University of Nice in France and colleagues. ...

via Kitchen sink experiment simulates exotic white holes - physics-math - 19 October 2010 - New Scientist.