27 January 2010

I'm Burned Up About How We Measure Freezing



The temperature here when I woke up this morning was zero. Zero as in no degrees. The temperature tonight may be ten degrees less than zero. Ten degrees less than no degrees.

That makes no sense. It's like saying "I have one beer, so I'll drink two of them and then I'll have less than zero beers". Or "There are zero gallons of gasoline in the tank of my car, so I'll drive another thirty miles and it will have less than zero gallons."

Zero should mean zero. Zero as in none, bupkus, nada, zip or zilch. Zero as in "I have zero chance of beating Lebron James to the basket with my killer slam dunk."

Fahrenheit is a lousy way to measure most temperatures, that's the problem. When Daniel Gabriel Fahrenheit (1686–1736) figured out his temperature-measuring scale, he determined the point at which water freezes, the point at which water boils, and divided the difference between the two into 180 increments. Hence 212-32=180.

Problem is, the Fahrenheit scale doesn't match the physics of the world, hence the negative temperatures on its scale. It runs out of degrees while there are a lot of degrees remaining.

Centigrade or Celsius isn't any better. It has negative temperatures, on a different scale, just like Fahrenheit. Worse, the Celsius increments are further apart, so temperatures are fractional, as in 23.6 degrees.

Paging William John Macquorn Rankine, please pick up the courtesy phone.

Rankine had the bright idea to make zero actually equal zero. His scale sets zero °R as equal to absolute zero, or −459.67 °F. The Rankine scale increments are identical to the Fahrenheit scale. Water freezes at 492°R. It boils at 672°R. And there are no negative degrees.

See, it all makes perfect sense. And it's a balmy 480°R here as I write this.

Where's my Coppertone?

7 comments:

  1. Relax and discover your inner Kelvin.

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  2. With that kinda heat, you'd better have another beer to go with that Coppertone.

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  3. El Pollo Real - Since you are a scientist, why is Kelvin scale better than Rankine degrees?

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  4. El Pollo Real - Since you are a scientist, why is Kelvin scale better than Rankine degrees?

    Because the French said so. :)

    Lord Kelvin (William Thompson) was the first to propose the need for an absolute temperature scale, i.e. one that had the coldest temperature possible as zero. He advocated that it be demarcated in units the same size as the Celsius temperature scale. Rankine came along later and adapted the notion of an absolute scale in units the same size and compatible with the Fahrenheit scale. Thus IMO, the Rankine sacle is a bit too derivative of Kelvin's original thoughts and work.

    Perhaps a more interesting question is why did Celsius win out over Fahrenheit for the normal, everyday scale of temperatures in the first place? Fahrenheit units are smaller than Celsius units, so they render more precision to a quoted measurement. I'm afraid that the question is related to why did the English set of measurements give way to metric system (except in our most exception of nations)? Here are some collected thoughts on that topic that are more extensive than I can come up with: Link

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  5. Did you know that Scotland was the hotbed of thermodynamics in the mid-19th century? Kelvin, Rankine, and a personal hero, James Clerk Maxwell

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  6. Scotland? Well, they probably needed an accurate means to measure the temperature of haggis while it was cooking.

    Underdone haggis would be just slightly more awful than properly cooked haggis.

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