Linkdump: July 2010

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Why is this?

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Flaw in the calculator:

1 Celsius = 274.15 Kelvin

Apparently, the calculator converts to Kelvin, gets 274.15, adds 1, then reports the results as 275.15 Celsius. Same problem if adding any two Celsius temps. On the other hand, adding temperature isn't really a logical operation, so I'm not sure we can totally blame the calculator.

Similar flaw in Fahrenheit conversion.

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I wouldn't call it a flaw in the calculator, I would call it a flaw in our grammar concerning it. The idea "1 degree C" could mean two very different things: Either a temperature of 1 degree C, or a temperature *difference* of 1 degree C. Google is absolutely correct (pun fully intended), if you use the proper definition of a degree celsius. But, if you're *adding* temperatures, in the normal usage, you *probably* mean adding a temperature *difference* to an absolute temperature. (In everyday use, one rarely adds either two temperature differences or two absolute temperatures.) Here's a tougher yet example: Suppose that it's 0 degrees C outside. Then, suppose that some day later, it's twice the temperature-- so, for example, a gas piston at ambient pressure and temperature has doubled in volume. But, 2 * 0 =0. So.... is it still zero degrees outside-- the same temperature -- or is it twice as hot?

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I don't think it's THAT weird to want to add temperatures. It doesn't seem far out to have an empirical relationship for some temperature, say something like melting temperature Tm = 500K + A*P + B*P^2, where P is pressure, and A would have units of degrees/pressure, etc.

And your Capcha is way too hard :(

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Buried in the comments on the liquid nitrogen page is this link:

http://www.wpi.edu/news/19989/nitro.html

Apparently liquid nitrogen is not safe for human consumption.

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There are a lot of neat things on Corante's blog, even if you can't follow most of his bread-and-butter organic-chemistry stuff.

I've paid homage to him on a couple of occasions:
http://dansdata.blogsome.com/2007/03/17/why-is-that-ultracentrifuge-walking-down-the-hall/

http://dansdata.blogsome.com/2008/03/05/ill-take-things-that-burn-asbestos-for-100/

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