Archive for September, 2013

S0701: The Hofstadter Insufficiency

September 26, 2013

This is the long awaited moment for fans of The Big Bang Theory.  The show has returned for another season with all new episodes.  Or is it the even longer-awaited return of The Big Blog Theory, giving you “the science behind the science”?

Our season opens with Leonard at sea. He left his girlfriend and his friends to go on a scientific expedition. Conveniently for the story, he left on a research vessel to the North Sea where no one could visit him.   But as we see, that story posed an inconvenient problem for the science….

smart alecks
I know that some of you were thinking, “Hey, there are no icebergs in the North Sea”. This map shows they are not unheard of. (See the marker above the “a” in “Britain”.)

Scientists, even physicists, of nearly every stripe at some point find themselves doing “field work”.  I have traveled with my physics students to Arctic and Antarctic research stations for weeks and even months at a time.  We’ve also gone several thousand feet underground into pure salt mines.  We go to factories we never would have known existed to check on the critical parts of our detectors — the latest being one that could stamp out 12 foot by 5 foot circuit boards on what amounted to a giant hydraulic panini press.  Other physicists and astrophysicists travel to mountaintops to build and use telescopes. Physicists go just about anywhere you can and maybe can’t imagine.   If you thought a career in science was purely an office job, you are missing some data.  The life of science can be a life of adventure.

Even if not going into a remote location, or even out-of-doors, many scientists travel to national laboratories for their data. Perhaps my most dangerous assignment of all was back when I was still a graduate student.   I worked in decaying old trailers on site of the Fermi National Accelerator Laboratory, complete with dead racoons on the roof, overflowing toilets,  and with (being physicists) nobody-knew-what growing behind the paneling and carpets.  Luckily, nobody contracted cholera.

Back to Leonard.  Conducting field work on a research vessel is not uncomon.  Actually, one of my former Ph.D. students is now a researcher at the Naval Research Lab who goes to sea often with instruments he built.  A research vessel on the North Sea was a perfect way for the writers to send off Leonard out-of-reach over the summer break.

But then we had a problem.  Leonard was working with Stephen Hawking, the physicist whom Penny calls the “dude who invented time”.   More specifically, Hawking is one of the world’s leading experts on Black Holes and the physics that governs them, Einstein’s Theory of General Relativity.   But there are no black holes to visit by a research vessel at sea.   Nothing beyond Newton’s laws of physics are required to understand the sea.  So maybe it was hopeless, what could Stephen Hawking possibly care about any research project Leonard would be conducting in the North Sea.  Oceanography and marine biology could not be farther from General Relativity.   But luckily there was one thing that fit the bill.

Nobody can visit a black hole, nor is anyone ever likely to.  But theories must be challenged with data to find out which, if any, are right.  It turns out that the mathematics of general relativity have something in common with the mathematics of fluid flows.   One of Hawking’s famous predictions is that the previously held idea that nothing ever escapes a black hole had a loophole, they could eventually evaporate through a process conveniently called Hawking radiation.  Because the process is quantum mechanical, it carries hope that it might lead us to the elusive theory of gravity that is also fully consistent with quantum mechanics.

Nobody has ever seen this radiation, but over thirty years ago William Unruh realized that supersonic fluids shared  some mathematics in common with black holes. Specifically, he showed that  the same arguments that led Hawking to predict radiation from black holes lead one to predict a certain spectrum of sound waves to be emitted from supersonic fluids.  Even many of the quantum effects are there, with units of sound waves called phonons, in analogy to units of light being called photons. Decades later, Leonard is putting this to the test on the research vessel.   Tune in to find out if the results were “promising” or not.

Now the biggest problem.  The script coordinator asked me how to pronounce Unruh.  But I’d never met him.  I asked several of my theoretical colleagues who were of course sure of the answer, as theorists always are.  But the problem was each was sure of a different pronunciation.    In desperation, I knew I would have to contact Professor Unruh.   I admit I was a bit nervous.    I considered calling his answering machine at 4 in the morning hoping he would say his name.  But since he’s a physicist there was a good chance he would be in his office.  So I asked him.   For the record it is UN-roo and he is very nice.

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