In 1974 Stephen Hawking postulated that black holes should give off a trickle of particles, or radiation, from their outer boundaries. The finding established Hawking’s reputation as a brilliant scientist and set the stage for his highly visible public profile, which includes provocative best-selling books and guest appearances on The Simpsons . In the midst of all the celebrity, the original theory of Hawking radiation, as the black hole phenomenon is known, has almost been forgotten, at least by the general public. The faint emission has never been detected from a real black hole, and researchers have not been able to produce the effect in the lab.
A few years ago a group of scientists in Italy decided to try a new approach to test Hawking’s thesis. They used a piece of glass to re-create a black hole’s “event horizon”--the point of no return beyond which even light is too slow to escape, where Hawking believes the radiation would arise. Alongside ordinary matter and light falling into a black hole, he reasoned, ought to be particles popping in and out of existence. Quantum mechanics dictates that such short-lived particle pairs arise even from empty space; in most corners of the cosmos, those pairs quickly disappear together back into the vacuum. But at an event horizon, one particle may be captured by the black hole, leaving the other free to escape as radiation.
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