Thanks for that nice bit of thermometer history, Nat. Quite interesting!
You mentioned two temperatures, in passing, regarding the Celsius temperature
scale. Of course, we realize that those are not the definition points for the
Celsius scale today and have not been for quite some time. Today we use,
effectively, 0.01 °C (triple point of water) and -273.15 °C ("absolute zero"
in common parlance).
Here's another interesting bit. The original scale used by Celsius put the 100
at the melting temperature of freshly fallen snow and the 0 at the boiling
point of water on a "fair" day. Why? I don't know. I use a picture of his
original thermometer in my classes and I've posted it here before.
Jim
On Friday 29 July 2005 17:32, Nat Hager III wrote:
> Might be interesting to someone...
>
> Nat
> 2005 The Buffalo News
> Buffalo News (New York)
>
> May 8, 2005 Sunday
> FINAL EDITION
>
> SECTION: SCIENCE/ENVIRONMENT; NATURE WATCH; Pg. I6
>
> LENGTH: 728 words
>
> HEADLINE: BOILING, FREEZING AND THE FAHRENHEIT THERMOMETER
>
> BYLINE: By Gerry Rising
>
> BODY:
>
>
> We have come to accept some rather strange numbers as part of our culture.
> Thus, on the Fahrenheit scale, which we still use in this country, we have
> 32 degrees as the temperature at which water freezes and 212 degrees as the
> temperature at which it boils. Why those particular numbers? Are they just
> two more values to make school science tests difficult?
>
> Clearly, the Celsius scale, with water freezing at 0 degrees and boiling at
> 100 degrees, is easier to remember, but my concern here is not promotion of
> the metric system. It doesn't need my support. Rather, I will explore the
> history that led to those numbers on the Fahrenheit scale. I was led to
> this history by a former student, Dipendra Bhattacharya, now a professor at
> Clarion University of Pennsylvania. He was asked why those numbers were
> chosen and passed on the question to me. I found the answer in H. Arthur
> Klein's 1974 book, "The World of Measurements," and I summarize his answer
> here.
>
> Turn back the calendar over 300 years, and you will find that there were
> very few instruments for measuring temperature. Then in about 1700, Danish
> astronomer Ole Roemer, already famous for his proof that light travels at a
> finite speed, not instantaneously as had been believed, turned his
> attention to this problem.
>
> Roemer constructed rudimentary thermometers much like those we use today:
> glass tubes in which alcohol expanded. He was then faced with the problem
> of how to associate a scale with the rising liquid.
>
> A few years earlier Italian scientist Carlo Rinaldi had proposed that any
> scale should reflect the freezing and boiling points of water, but Roemer
> thought that two other temperatures should be taken into account. These
> were our body heat and the lowest temperature of a mix of water and ice he
> could attain in his laboratory. He reached this lower temperature by adding
> salt to the mixture.
>
> So now Roemer had four scale points. He chose 0 degrees to represent that
> "lowest" temperature and 60 degrees to represent boiling. Why he chose 60
> is unclear, but it is a number that appears in minutes and seconds of time
> and in angle measure. In his rudimentary scale this gave Roemer 7.5 degrees
> for ice freezing and 22.5 degrees for body temperature.
>
> Enter German scientist Daniel Gabriel Fahrenheit. He adapted the idea of
> Ismael Boulliau to use quicksilver, which we now know as mercury, in his
> higher quality thermometer tubes. As Klein says, "Had it not been that his
> thermometers were so sound and practical, the Fahrenheit scale that he
> devised for them would never have become widely known. As it is, and rather
> ironically, too, Fahrenheit is famous today chiefly because of that same
> peculiar and highly illogical scale, whereas many of his more substantial
> contributions to scientific measurement are seldom mentioned."
>
> Taking advantage of the greater accuracy of his mercury thermometers,
> Fahrenheit decided to expand the Roemer scale by multiplying its values by
> four. Thus his four scale points were: 0 degrees, low; 30 degrees, ice; 90
> degrees, body temperature; and 240 degrees, boiling.
>
> Those are, of course, far nicer values than those he finally adopted.
> Unfortunately, he found that they didn't quite serve, and he began to
> tinker with them. First, he found the body temperature too low and he
> changed it from 90 to 96 degrees, as accurate as he could make it but still
> not the 98.6 degrees we use today. This change, however, raised the
> freezing point of water to 32 degrees, its present value and the answer to
> the first part of our problem.
>
> The boiling point, too, had to be changed. It had not been all that
> accurately placed on the Roemer scale because the alcohol used in
> thermometers boils at a lower temperature than water.
>
> So Fahrenheit had to adjust his scale one more time. He reduced his 240
> degrees to 212 degrees to fit with his other measures, finally arriving at
> the three scale points that continue to determine for us Fahrenheit
> temperatures: 32 degrees, water freezing; our corrected 98.6 degrees, body
> heat, and 212 degrees, water boiling -- all at sea level, of course. That 0
> degrees that provided the scale's starting point is long forgotten.
>
> Klein calls the Fahrenheit scale bizarre, and I cannot disagree. One
> defender, however, notes that for weather, it serves quite well, our
> expected temperatures ranging approximately between 0 and 100.
>
> e-mail: [EMAIL PROTECTED]
>
> GRAPHIC: Associated Press We measure the outdoor temperature using the
> Fahrenheit scale.
>
> LOAD-DATE: May 10, 2005
--
James R. Frysinger
Lifetime Certified Advanced Metrication Specialist
Senior Member, IEEE
http://www.cofc.edu/~frysingj
[EMAIL PROTECTED]
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