One of the weirdest things about black holes is that they are thought to evaporate over time, due to an effect named Hawking radiation after the renowned physicist who postulated its existence.
While the nearest black hole is light years away and the titanic gravitational forces within make it impossible to observe directly, a new report in the journal Nature describes a possible analog for Hawking radiation that can be created on earth.
University of Saskatchewan theoretical high-energy physicist Masoud Ghezelbash specializes in the physics of black holes, gravitation, supersymmetry and M-Theory. We asked him for his views.
Q: Is this a valid model?
A: The idea of dumb hole (which is the sonic analog of a black hole) dates back almost 35 years ago by William Unruh of the University of British Columbia. In a dumb hole, the speed of phonons (the quanta of sound waves that are analog to photons) is less than the speed of fluid in which the sound waves propagate. So, there is a region of fluid that these phonons are bounded to and cannot escape from (similar to what happens in a black hole that photons are trapped by intense gravitational field of the black hole).
Q: What can this model tell us about Hawking radiation?
A: Similar to a black hole, one can define the concepts of horizon, surface gravity as well as temperature and Hawking radiation from a dumb hole. Although they are very similar to black holes from the viewpoint of fundamental underlying physical concepts such as horizons, by no means can experimental detection of Hawking radiation from black holes be explained and replaced by detection of Hawking radiation from dumb holes.
Q: What are the most pressing questions for physics related to Hawking radiation? Will this model help answer them?
A: The detection of Hawking radiation from a black hole (especially from more massive black holes) is much more difficult than detection of radiation from a dumb hole that is made in laboratory. So, in general, the detection of Hawking radiation from dumb holes is a great step to pursue the detection of Hawking radiation from actual black holes.
The problem with detecting Hawking radiation is that the radiation is very weak for normal-sized black holes. In fact by increasing the mass of black hole, the intensity of Hawking radiation drops significantly. Hawking radiation is strong enough to be detected only for micro black holes that may be formed in the Large Hadron Collider.
Professor Ghezelbash is available to speak to the media on the subject of Hawking radiation, black holes, gravitation and associated topics.