CELSIUS TEMPERATURES ANOTHER MODERN NUISANCE!
On the par with the annual headache of seasonal “daylight savings” time changes, such as in the our just completed “spring ahead, fall back” clock maneuvers which just irritates everyone and seems to do nothing positive*— is the other irritant: Celsius vs Fahrenheit temperature fiasco. Celsius or what is it good for?
We all know you can convert irritating Celsius to Fahrenheit with the 5/9 vs 9/5 fraction then adding or subtracting 32 degrees for some reason..and then come out with some answer of how you will feel today or tomorrow. You might, after some matematical suffering, be able to answer that question. Do I need that long winter underwear or muffler today? Or is it too hot?
I don’t want to have to go though these mental mathematical gyrations every time, I just want to know what underwear to wear. That’s why I like Fahrenheit!!
In 1754 a German instrument maker Daniel Fahrenheit began making glass thermometers using mercury rather than the tinted alcohol previously used by earlier instrument makers. He constructed a thermometer composed of a thin wand of hollow glass tubing which ended in a bulb. The bulb contained the bulk of the mercury. When the bulb end was plunged into cold water the mercury would contract and the level in the thin glass wand would sink, when placed against warm skin heated the mercury expands and drives the thin line of mercury up the wand. It was interesting to observe, but Fahrenheit had other ideas for its practical use.
To be useful he would need to standardize his thermometer scale, but to what?
If he could establish some standard temperatures these set temperatures could be used to calibrate his instrument. but what should he use?
Fahrenheit lived in a time when the human body set the standards for measurement. The human foot (was a standard of distance or length), the yard (the length of a standard arrow measured from tip of index finger to anchor point on the chin), the mile (mille passus—or 1000 human paces), and even the great scientist Galileo (1564-1642) used his regular thumping pulse to investigate gravity by timing the speed of a ball rolling down an inclined plane.
Fahrenheit followed suit by simply slipping his new glass and mercury thermometer under his shirt, placing the bulb deep into the hairy pit of his underarm. He let it remain in place for a few minutes..indeed the silvery strand of mercury ran up the glass wand and remained at one point along the glass rod.. He could clearly see the glass wand sticking out from his crumpled up shirt and he confirmed that it remained unmoving! It was stabilized at body temperature! That was his first and very useful standard. With a fine thin file he scratched a line where the silvery line of mercury ended.
That one point would be useful if only comparing his arm pit temperature to others…but he had dreams..he had more advanced uses for his new instrument. With another “standard”—a low temperature— he could create a scale of equal graduations along the glass wand and make useful temperature observations of air or water based on how high above or below human body temperature this medium was.
In those long off days..with no refrigeration, no “dry ice” and nothing but frozen lake water —ice—from a local “ice house”. These were sturdy wood outbuildings packed with big blocks of ice laboriously cut from a frozen lake at the the height of winter, then stored in a building constructed with thick walls stuffed with insulating sawdust to keep the ice from melting away though much of the spring and a part of the summer.
Like others of his time he did know that by mixing ice and salt ( he used ammonium chloride, or sometimes plain sea salt) one could achieve temperatures colder than that of the ice itself. (Why this occurs is another interesting story for another blog). Fahrenheit used this salt and ice method to achieve his “low point temperature” assuming that -as far as he knew, this “salt ice mix low point” was as cold as things could get, and for this reason put a little scratch mark on the glass tube where the top of thin silvery mercury line lay well below the human body temperature on the upper part of the glass tube.
He now had a glass with a bulb filled with mercury that had two reference points on it. One high, human arm pit temperature, and the lowest temperature known at the time—a maximized ratio of ice and salt bath as his low temperature
Fahrenheit simply divided the distance along the glass wand into one-hundred equal increments. He liked multiples of ten a dividing things into hundreths so the top point became “100”, and the low point “0”.
As a result, using the Fahrenheit scale human body temperature is about 1000F and Fahrenheit’s 1754 salt ice temperature of “lowest” temperature occurs at 00F. It just so happens that freezing of pure water occurs at 320F. Fahrenheit was aware that a mix of ice and water —no salt—does occur at around 30 0F on his scale.
The 100 0F standard based on human body temperature (actually 98.6 0F) is what made Fahrenheit’s thermometer and his scale useful and so popular. Human comfort levels can easily be calculated without a lot of busy calculations. This means that outdoor temperature at 20 0F clearly indicated to the observer, outside air temperature is almost 80 increments below your body temperature, a great deal of heat will be drawn from your body under those circumstances. While 110 0F means outside (or inside air) is ten degrees higher than your body temperature. Under those circumstances you will struggle to keep comfortable. Your body is the guideline from which you have a comparison.
The human body—unlike that of your canine pets—cools itself by evaporation of water (perspiration, sweat) from the surface of the skin. The system is very efficient, particularly in a dry climate. Each thimbleful (1 ml) of water that evaporates from your skin carries away about 540 calories. Outside temperatures must be cool enough (and the humidity of the air low enough) to permit that very necessary evaporation to occur. If no evaporation occurs the human body heats up rapidly. If the air is exceptionally dry evaporation rate from the body increases and this has a strong cooling effect. Wearing a wet tea shirt is an example—one feels very cold very quickly in wet clothes—evaporation is at work.
Comfort levels in homes are set most people are comfortable at temperatures which in winter hover around 70F (74-78 F), while summer indoor temperatures are generally set again about 70F (or 72-80 F). While optimal sleep temperatures are lower hovering about 65F (60-72F).
Humidity is a big factor and most recommend humidity levels between 20% to 60% for optimal comfort.
But if you get caught in Europe and want to get a real human related feel of the temperature outside—do the numbers thing.
30C can be converted to a close estimate of degrees F by multiplying by 2 and adding 32. Since there are 100 gradations between boiling and freezing on the Celsius scale but close to 2 times as many (180) between those same two points on the Fahrenheit scale. 212F boiling -32F freezing =180 increments. Fahrenheit degrees are almost two times larger. 180 vs 100 is 9/5ths —that’s where the 9/5ths comes from.
30 0C equals 86 0F
So 300F X 2= 60, 60+32 is about 92 0F That is only a rough estimate to tell you it’s hot in Paris today, don’t wear the long underwear! But not its not exact!!
A refinement for 30 0C is to multiply by 2, then subtract 10% from the product, then add the 32!
Thus 30 x 2 =60, 10% of 60= 6, 60-6=54, 54 + 32 = 86 0F Correct!
Here again: 24C =75.2 °F
24x2=48, 10% of 48= 4.8, 48-4.3= 43.7, 43.7+32 = 75.7, not 75.2 but close enough for a quick mental calculation.
(As I write this I notice that I have one more clock— the oven clock—has yet to be turned ahead…for “spring ahead”, while my automobile clock didn’t have to be changed at all, it remained on Eastern Savings Time all year long, causing confusion and late arrivals all winter long.)
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