A Very Cloudy Few Days in Paris

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Take a look at Feb. 25 and you can see the weather front move in with increasing cloudiness. It looks to take about a day and a half to move into the city completely. There is a slight break the afternoon of the 27th, but the 28th, the 29th (1896 was a leap year) and Sunday, March 1 were all cloudy, all day long.

Becquerel had no sun after he set up his experiments, so he put them in the drawer. But he still had no sun on the first of March, so he had no experiment. Remember, he thought he needed strong sunlight to get things going. Why did he develop those plates?

In fact, look at the record all the way through to March 5th. Every day was mostly cloudy. It was just a gloomy, cloudy time as winter was moving slowly into spring. So why didn't Becquerel let the plates just sit around for a sunny day. Why'd he develop them on Sunday, March 1. What's so special about that day?

Becquerel's Reason for Being in the Lab on Sunday

At the 50 year celebration of the discovery, Becquerel's son Jean suggested that his father was simply being thorough. He planned to use new plates for new experiments, so why not develop the old?

Also in 1946, G.E.M. Jauncey suggested "impatience after waiting four days for the sun to shine." And, Imight add, the seeming prospect for no sun in the near future either.

Alfred Romer has suggested "simple thrift . . . or an overriding curiosity."

Another person has even suggested (in print, mind you) that it was pure luck.

Lawrence Badash, a science historian at UC Santa Barbara, first suggested in 1966 what the ChemTeam thinks is the real reason he developed those plates. Becquerel was scheduled to speak the next evening (Monday, March 2) to the French Academy and he needed some results to discuss. Since the plates had been exposed to some diffuse, indirect sunlight before winding up in the drawer, Badash conjectures that Becquerel might have been looking for a connection between the intensity of the image and the intensity of the phosphorescence.

What Becquerel found, of course, was that there was no connection between sunlight and the radiation coming out of the uranium crystals. So, I guess, he did wind up with something to talk about the next evening.

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