Black Holes in the Bathtub
Scientists observe Hawking radiation in unexpected materials
If you stuck your hand inside a black hole recently created in a Canadian laboratory, you wouldn’t get sucked in like a string of spaghetti. You’d just get wet.
This black hole exists in a water tank, its forces afflicting water waves rather than unsuspecting space travelers. Technically this bathtub version is a white hole, an inverted black hole that keeps waves out rather than sucking them in. But the white hole can serve as an analog because it shares an important feature with astrophysical black holes — an imaginary boundary that emits an unusual kind of radiation.
Black holes are notorious for sucking matter in, but physicist Stephen Hawking proposed in 1974 that a signal of their existence, now called Hawking radiation, would also leak out. In the bubbling quantum vacuum surrounding a black hole, particle-antiparticle pairs pop into existence. An electron, for example, and its partner, the positron, would emerge from the vacuum and then burst into a flash of energy after colliding an instant later. But if one particle slipped inside the black hole, forever trapped, the other particle would whiz away.