Monday, September 27, 2010

Physicists confirm Hawking radiation in lab

In recent years, the ability to create laboratory analogs has become a popular way to examine theory that can't be directly observed in nature.

Last week, I blogged about how the properties of a vacuum might play a dramatic role in the evolution of relativistic stars, in the blog I talked about how the study authors said we wouldn't be able to directly detect Hawking Radiation in the universe. Now, it seems some clever physicists from the University of Milan have found a way to detect Hawking Radiation after all: sort of. The physicists say they've observed the radiation in a clever lab analogy with a so-called white hole, which is often thought of as the inverse of the black hole.

Normally, when an antiparticle-particle pair form they release their energy immediately and mutually annihilate. Hawking radiation proposes that when the pair starts to cross over the event horizon of a black hole, one photon can be sucked in while the other is released. Because the free photon can't return to the vacuum from which it came, it "becomes real" and gains energy at the expense of the black hole. This process causes the black hole to gradually lose mass.

It's clear why such an effect would be difficult to observe in the cosmos, but a white hole can also create an event horizon and provide an earthly test. Instead of sucking light inside it like a black hole, a white hole causes light waves to come to a complete stop. In the research, which is set to be published in the journal Physical Review Letters, the Milan physicists were able to create a white hole by firing ultrashort infrared laser pulses through fused silica glass.

They say the measurements they made of their gravitational analog confirm what physicists have long predicted would happen in theory and "demonstrates a spontaneous emission of photons." They also claim they were able to distinguish the effect from other causes for photon emissions.

If confirmed, such a finding would demonstrate that Hawking radiation should indeed have a major impact on the endstate of our universe.

Check out the preprint posted to the arXiv.

No comments:

Post a Comment