This is scientific American's 60 second science.

I'm Christopher Intagiyata.

Black holes got their name because light can't escape them,

beyond a certain radius called the event horizon. But in 1974 Stephen Hawking proposed that quantum effects at the event horizon might cause black holes to be not completely black.

Hawking said that pairs of particles should be created at the event horizon.

Jeff Steinhauer, a physicist at the Israel Institute of Technology.

One particle exits the black hole and travels away perhaps to Earth

and the other particle falls into the black hole. Ideally we could just study

those exiting particles which make up the so-called

hawking radiation, but that signals too weak. We can't see it against the

universe's own background radiation. So Steinhauer built a model of a black hole instead, which traps

not photons, but phonons. Think of them as sound particles, and it traps them using a gas of

rubidium atoms flowing faster than the speed of sound.

And that means that phonons, particles of sound, trying to travel against the flow,

are not able to go forward, they get swept back by the flow.

Like, it's like someone trying to swim against a river

which is flowing faster than they can swim.

The phonon trying to go against the flow is analogous to a photon trying to escape

a black hole.

Steinhauer doesn't actually pipe sound particles into the device. He doesn't need to. He

merely created the conditions under which quantum effects predict their appearance.

So the two swimmers can come into existence simultaneously without anybody supplying energy to create them.

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