Fake black hole proves famous theory

After simulating a black hole, scientists have confirmed that Hawking radiation is limited but constant – just as physicist Stephen Hawking predicted.

Black holes are objects in space in which gravity is so intense that not even light can escape. But English physicist Stephen Hawking predicted that black holes spontaneously emit a limited but constant quantity of light, which was named Hawking radiation.

Now Israeli scientists have confirmed his theory using a lab-simulated black hole. The artificial black hole simulated the conditions around a black hole by collecting a cloud of 8000 rubidium atoms. To simulate light, the scientists used sound waves. Rubidium atoms travel faster than the speed of sound – so the sound waves could not escape the rubidium cloud, and in this way the scientists could simulate an event horizon. In a black hole, the event horizon is the point from which nothing can escape – not even light. But outside the simulated event horizon, the gas could travel slowly, and sound waves were able to escape.

Scientists chose the name ‘event horizon’ because they cannot observe what happens on the other side. In a real black hole, Hawking radiation is formed from pairs of photons – light particles; one particle falls into the black hole, the other one escapes. The Israeli scientists observed the same thing with their sound waves. They identified sound-wave pairs and examined their behaviour 97,000 times over a period of 124 days.

The conclusion was that the sound waves left the simulated black hole at a constant rate – just as Stephen Hawking predicted for light in real black holes.