Tuesday, 29 December 2009

Black Holes are Rude (in French)

Image of the planet Uranus, outline of France, and a black hole, superimposedEnglish-language physics textbooks (before the mid-1970's) tend to give the impression that everyone had agreed that black holes couldn't radiate. It was supposed to be mathematically proved. Done deal.

But there's a slight geographical cultural bias. Not all countries' research communities adopted the idea of the perfectly-non-radiating black hole with the same enthusiasm. The French theoretical physics community in particular seemed not to like black holes very much at all.

And this was probably at least partly because in French, the term for "black hole" – "Trous Noir" – is slang for "anus".

Now, imagine what that must do to a serious talk on black hole theory delivered in French. To have to give a 45-minute lecture on how things that disappear into a black hole can't be retrieved, including topics like the proof that that "black holes have no hair", and its relationship to the hairy ball theorem. How the heck do you teach this subject without your students snickering?

So the French approach circa 1960 seemed to be to hunker down and wait for the new fashion to blow itself out (err...), after which normality could be restored. And it happened. The Wheeler black hole got assassinated by Stephen Hawking in the 1970's with his presentation on Hawking radiation.

But the English-speaking physics community kept using the term "black hole", even though technically, horizon-bounded objects under QM were now known NOT to be black holes in the Wheeler sense of the word. They weren't black, or holes. Maybe we kept the phrase because we didn't want to admit we'd screwed up, maybe we kept it because of the historical habit of physicists to completely ignore the literal meanings of words when it suits them, and maybe ... we simply liked upsetting the French.

Thanks to Hawking radiation, if you teach black hole theory in French you now have the unenviable job of addressing a room full of students on the subject of black hole emissions, and hoping that nobody thinks its funny to start making quiet comedic fart noises at comically appropriate moments.

Perhaps the smart thing to do is to take this opportunity to come up with a whole new name for a "QM black hole". Call it something like an "Etoile Hawking" (a "Hawking Star"). It's two extra syllables, but it solves the problem.

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