Yay! My sabbatical request went through, so I'm free to be with Lisa while she's in Europe from January to June next summer!
So here is my schedule from now until next summer:
Whew! Sounds like fun, but also lots of work! But I'll have plenty of time to rest after I'm dead...
Some forgotten history: Edison made the first commercially viable incandescent light bulb in 1879... but street lights were introduced in Paris in 1878. They didn't use incandescent lights. They used 'carbon arc lamps', generating light with a continuous electric spark!
The arc lamp was invented by the chemist Humphrey Davy back in 1809: he connected two wires to a battery, and used charcoal strips as electrodes, making a spark that could light up the room. But the arc lamp only became practical after the generator was invented. Arc lighting came to Paris in June 1878 as part of an exposition, and soon it found its way to London and the US as well.
But there was a problem. The arc made a constant humming noise. It was really annoying! So in 1899, in London, a young engineer named William Duddell was asked to find a solution.
He discovered that by changing the voltage he could vary the pitch of the sound. This didn't solve the problem... but at this point Duddell got distracted and had a cool idea. By attaching a keyboard, he was able to play music on an arc lamp.
Watch the video above to see the idea in action... not with a keyboard, alas, but using an arc as a speaker.
In fact a German engineer named Simon had a similar idea a year before, and called it the 'singing arc'. But I think Duddell was the first to play music with it. It was one of the first electronic instruments! Not the first — but that's another story, for another day.
For a while, Duddell toured England demonstrating the singing arc. Scientists even speculated about the possibility of playing music over London's street lights!
Sadly, the idea sputtered out and died. But the great mathematical physicist Henri Poincaré wrote several papers on this problem. Forgotten until recently, they appeared in the now-obscure journal La Lumihre ilectrique, and weren't included in his collected works. He also gave five lectures on this topic in 1908, where he showed that the oscillation of the arc is an example of a limit cycle: a solution of a differential equation that settles down to a periodic orbit.
I found out about this story from a nice new book:
• Jeremy Gray, Henri Poincaré: A Scientific Biography, Princeton U. Press, Princeton, 2013.
I got extra details from here:
• This Month in Physics History - December 20, 1900: Nature reports on William Duddell's 'musical arcs'.
Some serious steampunk fans should build a singing arc controlled by a keyboard. It would be perfect for the right sort of rock group.
© 2013 John Baez
baez@math.removethis.ucr.andthis.edu