jonquil
September 29, 2010, 8:49pm
1
And this is an ultrafast laser pulse that makes a desktop black hole glow, thus proving the existence of Hawking radiation and paving the way for Stephen Hawking to win a Nobel Prize. How the wheel of fortune turns, eh…
arstechnica.com/science/news/201 … mments-bar
The eerie glow is called Hawking radiation, and physicists have been hunting it for decades. In 1974, Stephen Hawking calculated that, rather than gobbling up everything in their path and giving nothing back, black holes can radiate like the heating element in a toaster.
But astrophysical black holes, the ultradense gobs of mass that lurk at the centers of galaxies and are left behind when stars collapse, radiate too dimly to be seen. So instead of looking at real black holes, a group of physicists led by Francesco Belgiorno of the University of Milan, Italy, created a miniature analog by shooting short pulses of intense laser light into a chip of glass. The results will appear in Physical Review Letters.
“This is an extremely important paper,” said physicist Ulf Leonhardt of the University of St Andrews in Scotland, who built an artificial black hole in a phone line in 2008. “The experiment confirms that Hawking radiation can exist in principle.”
The basic idea behind Hawking radiation is that the quantum vacuum is not actually empty. Instead, it is a roiling mess of virtual particles and anti-particles that constantly pop into existence and eliminate each other when they meet. If one member of the particle/anti-particle pair is created on the wrong side of an event horizon—the edge of a black hole beyond which not even light can escape—the particles can never meet to destroy each other. An observer outside the black hole would see a perpetual stream of real particles.
jonquil
September 29, 2010, 11:37pm
3
Tab:
Good find.
Yes, this is very awesome. Next step, find out if the photons are entangled. It also means there’s a GUT in sight.
Farsight
September 30, 2010, 5:56pm
4
It isn’t really vindicated I’m afraid, there’s an element of hype to this story. Ever heard of Unruh? Have a read of this:
physics.princeton.edu/~mcdon … 008_03.pdf
“Recently Leonhardt [6,8] has suggested that slow light systems could be used to create such an analog, but that approach has been criticized by one of us [10]. In this paper, we look in more detail at the use of slow light in such an analog, and try to understand in what sense slow light could be used to create an analog for black holes, and why, despite that analog, it will not create the thermal radiation characteristic of the Hawking process”.
jonquil
October 1, 2010, 2:34am
5
This article describes and discusses the desktop black hole experiment, and it also provides an assessment of the problem in trying to analogize it to actual black holes with gravitational fields.
newscientist.com/article/mg2 … -hole.html
Some of the photons they detected were due to the infrared laser interacting with defects in the glass. This generates light at known wavelengths, for example between 600 and 700 nanometres. But mysterious, “extra” photons also showed up at wavelengths of between 850 and 900 nanometres in some runs, and around 300 nanometres in others, depending on the exact amount of energy that the laser pulse was carrying. Because this relationship between the wavelength observed and pulse energy fits nicely with theoretical calculations based on separating pairs of virtual photons, Belgiorno’s team concludes that the extra photons must be Hawking radiation (Physical Review Letters, in press).
Not everyone is ready to agree. Adam Helfer at the University of Missouri in Columbia says the term Hawking radiation is best reserved for actual black holes with gravitational fields. “There is a parallel between them to a certain extent, [but] the laboratory experiments, interesting as they are, do not really bear on the very deep problems which are special to black holes.” These revolve around how to fully marry gravity and qauntum mechanics when describing these objects.