Saturday, December 11, 2010

What's My Temperature?

I was watching "How it's Made" last night, and the topic was thermometers. It's a complicated process of welding glass tubes. The crux of the issue is in calibrating the thermometers.
They pull the air out of the tubing with a vacuum, and fluid is left inside. The thermometers travel down a conveyor of chilled alcohol. A heat gun drives the liquid up tubing. They then plunge the thermometers into a bath of ice-water to calibrate the freezing point. A notch is made in the glass where the liquid is.
They are next set into a bath of liquid set at 200 degrees Fahrenheit. Another scratch is made in the glass at that point, and the two marks are aligned on a grid and set to a calibration scale.
My question: How did they make the first thermometer? If they had to place it in a bath of water at 200 degrees Fahrenheit to calibrate it, how did they know what 200 degrees Fahrenheit was without a thermometer?
This whole temperature thing sounds like a big scam.
How cold is it, really?

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