I remember being told this by my science teacher, Mr. Rockwell, way back in high school. Mr. Fahrenheit needed a way to calibrate his thermometers. What he used was a glass of ice, and his body temperature. He would put the new thermometer in a glass of ice water. Where the mercury would settle he would mark as 32 degrees. Why, I will get to in a minute. He would then put the thermometer under his arm pit. This would give him his axial (I think that is the term) body temperature, which is a bit lower than taking it orally. He would mark this as 96 degrees. Why? Because there are 64 units between 32 and 96. I will wait while you do the math. Now to mark the rest of the units on the thermometer he only needed to measure the difference between his two marks and make a new mark halfway between. This would be 64 degrees. Dividing in half again he would have 48 and 80 degrees. He could keep dividing by two until he had the unit numbered from 32 to 96. He would then measure the distance between 32 and 64, then make a mark this distance below 32. That would be 0 degrees. Now he could again keep dividing the distance between 0 and 32 in half until he had a mark for each degree. The reason for 32 marks below freezing is that is as cold as he ever expected he would have to measure something.
So the real reason that water freezes at 32 degrees Fahrenheit, and axial body temperature is 96 degrees is so there are 64 divisions between them. Making marking the degrees in between much easier.
I remember reading long ago that Fahrenheit chose his zero point as the coldest temperature measured outside of where he worked in the year he was developing his scale, and 100º was the warmest it got. Years later I found climate data suggesting that it rarely gets as warm as 100º or as cold as 0º in whatever city it was that he was working in.
I thought it was the freezing and boiling point of whatever medium he originally used as his liquid. (It wasn’t mercury; might have been an alcohol derivative–I can imagine an alcohol mix boiling at 100° F and freezing at 0° F, that sounds about right.
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I understood that 100 was set by the body temperature of his wife who had a bit of a high body temperature. The zero was ice mixed with equal parts salt.
100 was set as normal human body temp. 0 was the lowest temp he could get in the lab- using salted ice. He figured then there would be little need for “below zero” as temps would rarely get that low. And that 100 would be easy to remember, and get. Thus- since he, as the inventor, set the standards at 0 and 100- it is the other folks who are/were wrong at giving body temp as 98.6. However, since he also gave a few other marks, such as freezing or boiling of water, folks fixated on those as the “standards”- however- they are wrong. Incidentally, the centigrade/Celcius scale is no more “metric” than the Fahrenheit one- the French just picked that Cetigrade scale as the English used the F one.
That is also why they put the “meter” at 39", instead of a yard- to spite the English. One of the reasons why the metric system is not as useful as it could have been- is that so much of it was done to spite the English. The “english” foot/pound system, while mathematically wierd, had units that were useful in everyday life. A Meter is a bit too big. A gram is to small. They had to “back-engineer” the “hectare” and the “metric ton” to get some useful units to measure land & large wieghts, and a “square kilometer” is too big for everyday usage- and saying “a thousand kilograms” is a bit unwieldy.
Metre was picked in an attempt to have a standard unit based upon something measured frequently, the earth.
Here, I found a convenient page (one of many) explaining how it was created, and what the units are. You might find it useful… http://www.hlalapansi.demon.co.uk/Metric/
Mathematically weird is precisely why the metric system was created. It is mathematically standard. It was not an anti-english plot. It would be simply impossible to stay close to all english measurements, since they varied too much.
Personally, I think the system is quite elegant.
1 cubic centimetre of water at STP weighs one gramme. This makes a lot of rough calculations easy, given how much is water.
This same water marks 0 and 100 on the Celsius temperature scale. 1 degree is very very close to the triple point of water.
A litre is roughly a kilogramme of water.
If you don’t like saying tonne or metric tonne, then use the original notation as it was intended. Say “megagram”. There are units above 10[sup]3[/sup] you know… Personally I use from deca,kilo,mega,giga,tera, and peta going up, and deci,centi,milli,micro, and nano going down. That’s enough for comp. sci. (and the unit names have been slightly adapted ) although I suspect engineers and scientists on this board probably use stuff like femtoseconds fairly commonly.
Hectare I’ve never heard of. Is it 1/10th of a kilometer, a hectometer?
Metric isn’t going to go away simply because it is flexible as well as standard. If we’re going to have the “metric is unnatural debate” all over again, you’re going to have to find a unit that can’t be named easily. Yes, decimetre is more wordy then, say, a foot. But you’re going to have to expect some wordiness in a standard system of measurement.
Er. My bad, should stick to the units I’m intimately familiar with.
The triple point of water is just a little over 0, .01 actually.
Faulty memories of chemistry class…
Kber- I disagree- it is my opinion that they wanted a length measurement AROUND, but greater tha a yard- and found out you get get there by taking 1 millionth of the circumference of the earth, or whatever. Since there was no way to get any measurement of the earths circunference or diameter to within a mile or so- they were taking a guess anyway. They simply had no way to precisely measure it in those days. And " the earth" measured frequently? How many times have YOU gone out with a giant tape to measure the Earth?
True- they could not have stayed close to ALL the english measures- but not by coincidence- they did to several.
They could have simply made “meter=yard” and it would have been just as “scientific”. Then a cc still could have equaled a gram, etc.
The problem was when they selected the “base”- the circumference of the earth- is a very silly base. It DOES change, and it was impossible to measure precisely. Note that now they use a std of a 15 place or so % of the speed of light. They COULD have selected something which was a round number.
A hectare is 10000 sq meters. However- there is no prefix for 10000. So- in order to have a usable measure of land area- they made one up.
What, are you kidding? Eratosthenes was able to measure the circumference to within a few hundred miles more than 2,000 years ago with little more than sticks and shadows. By the time the French were developing the metric system, the tools for measuring a portion of arc on a terrestrial meridian were, to say the least, somewhat more advanced.
Nonsense. Scientists as far back as Newton knew that there was polar flattening taking place, and were working on calculating its severity (which amounts to around 1/300, or a difference of around 26 miles).
Disagree with you both. One more, and we can get this moved to GD.
The meter was the length of the so-called “second” pendulum,
which took one second to swing from side to side. That is why the acceleration of gravity is so close to pi squared. (g=9.81 m/s^2, and pi^2=9.87)
However, they wanted a standard that was more, uh, rigid. The pendulum period changes with altitude and latitude, so they searched around until they discovered that 1/40000000 of the circumference of the earth would be very close. Plus, they could get government funding for a scientific expedition to measure it.
A) Cecil’s column gives the full Fahrenheit story. Why clutter up the board with urban myths?
B) The Metric System was developed by the French, who weren’t bloody well using the English system in the first place!
C) Which “foot/pound” system? The English foot? The American foot? (They weren’t the same until both were adjusted to a compromise value, defined as exactly 0.3048 meters.) The English avoirdupois pound? The English Troy pound? The American avoirdupois pound? The American Troy pound? And which ton? The American ton of 2000 American avoirdupois pounds, or the English ton of 2240 English avoirdupois pounds? (Actually, I’m still oversimplifying the mess.)
Do you know what an “acre” actually is? It’s an area of land one chain wide by one furlong long. How much is a furlong? 10 chains. What’s a chain? 4 rods. What’s a rod? 25 links. What’s a link? 7.92 inches. (That’s in America. The English system has an intermediate unit of “1 perch”, which is 1/4 of an acre.)
By the way, the pound isn’t a unit of mass (comparable to a kilogram). It’s a unit of force (comparable to a newton). The “English” unit of mass is a “slug”, roughly 15 kilograms. Or, if you like, you can use the “pound-mass”, (something under half a kilogram), in which case you can use the “poundal” (a bit more than an ounce) as your unit of force.
Pld Yes- the Greeks could do it within a couple hundred MILES. The French could, AFAIK do it within 10 miles or so. Currently- the meter is based aupon the speed of light- measured down to TEN (10) significant figures. The French could not even get within an order of magnitude of that. Thus- they “base” they picked- could not, and still is not measured “precisely”- as ten sigfig is what they ask for.
Cecil’s original article goes into great and circumstantial detail about the origin of the Fahrenheit scale. So why jump in with a half-digested version of something remembered as having been retailed by a schoolteacher (a class rarely expert on anything except the watered-down and politically-correct dregs of psychology, sociology and anthropology taught s.v. “Education”, and especially unlikely to be expert in cross-discipline fields like the history of science), as though Cecil had never bothered to answer the question in the first place?
John- read the very first line- “researchers have gone to their grave trying to figure out what Fahrenheit was up to.” Thus, how F actually came up with his numbers is not really known. My Upper div Physics prof actually did his PhD on temp scales- so i accept his reasoning. Not that cecil is wrong, per se- but there is a certain amount of guesswork involved.
John, does that English ton predate the metric system? It looks to me like somebody’s trying to match a metric ton, but with numbers that come out reasonably close to round in the avoirdupois system.
As for the precision of the measurement of the Earth, how precisely is the length of the King of England’s arm measured? I’d say that the French had the advantage on that one.
A) The “King of England’s arm” story – which I don’t offhand remember the truth of – was only how the single national standard yard was set, by one particular measurement of one particular king on one particular day. (Previously, every town had had a standard yard, pound, etc.,.) The Metric system in this regard is no better or worse; the practical standards by then were metal bars for all systems, and, after a few decades based on wavelengths of specific spectral emission lines (the orange line of Krypton 86 is the one I remember), the standard is now based on the speed of light. But it’s always been a question of using a standard that is precisely measured and precisely copied, using available instruments and tools.
Using the size of the Earth to set the standard was just a reflection of period thinking, the same that established a ten-day week and attempted to establish a ten-hour day. Down with everything older than us! was the cry; those of us in our late 40’s and early 50’s will recall something along the same lines.
That the Metric System came out better than the rest is largely an historic accident. Decimal scaling helps, but I suspect the real reason is that it was an effective international standard in the days when many countries still didn’t have decent national standards; this led to its universal adoption by scientists.
B) The traditional ton antedates the Metric System. The rough equivalence of the various tons and the tonne is a coincidence.
This is straight from Cecil’s answer on the subject of why freezing in 32 and body temperature 96.
“Then, for reasons nobody has ever been able to fathom, he multiplied all the numbers by 16/15, making 32 freezing and 96 body temperature. Boiling point for the time being he ignored altogether.”
So Cecil is saying, he does not know why 32 was picked as the freezing temperature and 96 for body temperature. I’m only passing on information I heard which makes a lot of sense. (At least to me.) If you are going to make a scale, it is nice to have everything in powers of two. (64 degrees between freezing and body temperature. 32 between 0 and freezing.) Then to mark off individual degrees, you just keep dividing the distance between your marks by half until you get the accuracy you desire.
Go back to the figures of 30 and 90 which Cecil mentions. (These are the figures multiplied by 16/15 referred to above.) Half way between them would be 60 degrees. So far so good. Half way between 30 and 60 would be 45 degrees. Again so far so good. But, halfway between 45 and 30 would be 37.5 degrees. And each half from here on out makes it even worse. Of couse, Fahrenheit could have measured the distance between 45 and 30 on his scale and figured out what 1/15 of it would be, then mark individual degrees that way. But what a pain!
It works a lot easier using my system. Halfway between 32 and 96 is 64 degrees. Halfway between 32 and 64 would be 48 degrees. Halfway between 32 and 48 would be 40 degrees. Halfway between 32 and 40 would be 36 degrees. Halfway between 32 and 36 would be 34 degrees. And finally, halfway between 32 and 34 would be 33 degrees. By starting with 32 and 96 you can mark all the way down to individual degrees without doing anything more than measuring the distance between two points on your thermometer and dividing that length in half. Heck, you can even continue on and mark 1/2 degrees, 1/4 degrees etc, if you wanted to.
Seems a simple and easy way to mark his thermometer to me.
And finally, can anyone else come up with a reason to use 32 for freezing besides the convenience of it being 2 to the fifth power?
Here is a good history of the standardization of the meter. I found this quote:
“However, the first prototype was short by 0.2 millimeters because researchers miscalculated the flattening of the earth due to its rotation.”
This suggests two things: 1) That the French were aware of the flattening of the earth, they just didn’t get the amount exactly right. 2) Their calculation of “one ten-millionth of the length of the meridian through Paris from pole to the equator” was only off by (correct me if I’m wrong) 0.02%. If that’s just a “guess” then it’s a pretty damn good one.
Also as for the metric system not being “as useful as it could have been”, I disagree completely. The utility of the metric system is vasty superior to the English system not because of the accuracy of the intended base units, but because of its flexiblity. Is there an efficient way to describe the diameter and mass of a single hydrogen atom using English units? I’d love to hear it if there is.
Additionally, I have seen no indication that the French instituted the SI to spite the English, even in part.
You really should provide some cites to back up your claims, Dan.
) although I suspect engineers and scientists on this board probably use stuff like femtoseconds fairly commonly.