LEGO Hawking

October 07, 2008

Is there any limit to the creative potential of LEGOS? Via Talk like a Physicist, I stumbled upon Brick Shelf's whimsical series of photographs featuring a LEGO model of astrophysicist Stephen Hawking. Author of the bestselling A Brief History of Time, Hawking has appeared on Star Trek and The Simpsons, gone weightless in NASA's "vomit comet," and indulged his penchant for making small wagers with his fellow physicists on the outcome of various theories. Most recently, he bet $100 that the Large Hadron Collider wouldn't find the elusive Higgs boson -- mostly because he thinks it'd be more interesting that way.

Hawking isn't betting on what amounts to an LHC long shot: that the collider will produce mini-black holes, which will evaporate within fractions of a second, thereby proving something he predicted at least a decade ago, called "Hawking radiation." There's a less than 1% chance this will happen, which is why Hawking told the New York Times, I'm not holding my breath." But if it did, he'd stand to win more than a small wager; he'd likely snag a Nobel Prize.

The premise of Hawking radiation is that black holes aren't as black as they seem. They can and do emit radiation, and this in turn causes black holes to lose mass over time, eventually winking out of existence. How fast this happens depends on the black hole's mass: the greater the mass, the more slowly it evaporates, and the smaller the mass, the more quickly it evaporates. Mini-black holes would be the size of subatomic particles, and thus would evaporate in fractions of a second.

But the reason we get Hawking radiation in the first place is because of a quirk of quantum mechanics. (Is there anything but quirks in quantum mechanics?) See, empty space isn't really empty. It is teeming with virtual pairs of particles (matter and antimatter, i.e., having the same mass but opposite charges) that spontaneously pop into existence, and just as quickly annihilate into radiation. It happens on such a short time scale that they can't be observed or measured directly, so in this way, the laws of energy conservation aren't violated.

Ah, but if a virtual particle pair pops into existence near a black hole, there's a pretty good chance that one half of the pair will fall in, while the other half is emitted as radiation. Energy appears to come from nothing. That's why, Hawking explained, the mass of the black hole must decrease ever so slightly in response to account for that sudden emission of energy. This happens over and over until, voila! The black hole evaporates completely.

Only time will tell if Hawking wins or loses his bet, or snags that Nobel Prize. He lost a prior bet on a technicality -- ironically stemming from his own pioneering work on Hawking radiation In 1991, he wagered 100 pounds sterling -- plus an article of clothing "embroidered with a suitable concessionary message" -- with two Caltech physicists that naked singularities could not exist. Most physicists believe singularities lie at the heart of black holes, but they are "clothed," that is, hidden from direct observation beyond the event horizon. A naked singularity wouldn't have that safeguard, known as "cosmic censorship."

But if black holes radiate energy and decay over time -- and all signs thus far indicate that they do -- then the protective event horizon must also evaporate over time. So the singularity at the center could be exposed oh-so-briefly at the very moment the black hole winks out of existence. Hawking graciously conceded the bet, although the message on the T-shirt he presented to his colleagues wasn't exactly concessionary. It read, "Nature abhors a naked singularity."

That Nature can be such a prude.

Photos: LEGO Hawking images from Brick Shelf, via Talk Like a Physicist.

Comments

[Lab Lemming]

Who wins if the Higgs is discovered by some other experiment?

[Brian Hodges]

Just when I think black holes can screw with my mind anymore than they already do, you go and post something like this. Holy cr** how does this universe even exist. Astronomy is the ultimate head trip and anyone who isn't constantly blown away (to quote Bohr) hasn't understood a thing.