Celcius, Centigrade, Farenhiet, Kelvin

[Johnny7oak]

Ok... so why centigrade is used in trek, and why not used in our 21st century.

so in the 50's I think they had a conference that officially set Centigrade to start at an offset to compensate for freezing temperature to be zero... it was there by 0 @ freezing temperatures (or 32 degrees Fahrenheit) Although this was beneficial for us to use the renamed nomenclature to Celsius,

My theory is that Centigrade is generic to Celsius on earth, as is mass in regards to weight on earth...

Anyways, astronomy(and other sciences such as chemistry) uses Kelvin when regarding temperatures too large or significantly too small.

The centigrade: could be better used on star trek... because the pressure/volume of a world might freeze water at a different setting, and although kelvin could be used it would be easier to relate to away teams... for thermal/environment needs and for science officers relaying samples of space ice... such that 0 is 0 and could be used in comparisons in later calculations that perhaps the off-set become necessary, and with planets thermal freezing point offset in some sort of new arbitrary planet side temperature units.

 

[Idran]

There's a few errors in this: Degrees Celsius and degrees centigrade are the same thing, the centigrade scale was just renamed to the Celsius scale in 1948. Both are used interchangeably both in real life today and on Star Trek. Weight isn't just a generic form of mass on Earth, the two are interchangeable only in a lay sense and scientifically weight is never treated as interchangeable with mass. There's also no reason to care about having a different scale for different planets, because the behavior of water at different temperatures and pressure is extremely well understood. Extremely well understood. (Yes, there are 18 different phases of ice.)

Also, Kelvin isn't used because of temperatures that are too large or small, it's used because degrees Celsius are a relative measurement in the sense that they only measure a relative change in temperature, while Kelvin is an absolute measurement in the sense that it measures an absolute change in temperature; 30 degrees Celsius isn't twice as hot as 15 degrees Celsius, while 30 Kelvin is twice as hot as 15 Kelvin. (In fact, that's why the official units are "degrees Celsius" and "Kelvin" respectively; the Celsius scale measures degrees of temperature, but the Kelvin scale measures temperature.)

 

[Nebusj]

Without taking away your accomplishment in working through the Original Post well enough to answer its major points, I did have a comment on your second paragraph ...

Also, Kelvin isn't used because of temperatures that are too large or small, it's used because degrees Celsius are a relative measurement in the sense that they only measure a relative change in temperature, while Kelvin is an absolute measurement in the sense that it measures an absolute change in temperature; 30 degrees Celsius isn't twice as hot as 15 degrees Celsius, while 30 Kelvin is twice as hot as 15 Kelvin.

I'm not sure I can agree that's a fair explanation for where and when Celsius is used versus Kelvin. It seems to me the difference in use comes from cultural differences. Celsius was created to measure the temperature of, well, ordinary human-scale environments, from Western-European Weather through to common cooking temperatures. It's still used in those contexts, since measuring those things requires numbers that aren't too big or strange.

Kelvin grew from several scientifically-minded threads. One was the desire to have a way of talking about temperature that was independent of the method used to measure temperature. One was the recognition that the expansion and contraction of gasses implied there should be an Absolute Zero. One was the development of statistical mechanics and the recognition links between energy and entropy and temperature (which is hard to keep separate from the behavior of gasses, yes).

Happily we can relate Kelvin and Celsius readings easily. But Kelvin grew to meet some particular needs, mostly in physics and astronomy and engineering, and it's stayed popular in those fields. Celsius developed to meet other needs, mostly in what we might call the normal-living-environment world, and it's stayed popular where those are the most important needs.

 

[Idran]

Fair points; I might have misstated or overstated some there. I think it's still an important distinction from a scientific perspective that Celsius is a relative scale while Kelvin is an absolute scale, but you're right that Celsius does have important advantages outside the scientific field related to where it came from.

(A bit of semi-related temperature scale trivia: the very original Fahrenheit scale actually had its own practical advantages behind why it was developed. Fahrenheit's idea was to take a variation of an earlier scale so as to put 64 units between two easily-measured points, freezing (32) and body temperature (96), to make it easy to mark off degrees on an unmarked measuring device without a ruler by just taking successive halves. That feature just got ruined later when they redefined it based on freezing and boiling (approximately 212 originally, exactly 212 afterwards) since those two were more reliable than body temperature, which bumped average body temperature up to 98. )

 

[lpetrich]

Fahrenheit - Wikipedia states

There exist several accounts of how he originally defined his scale. The lower defining point, 0 °F, was established as the temperature of a solution of brine made from equal parts of ice and salt. Further limits were established as the melting point of ice (32 °F) and his best estimate of the average human body temperature (96 °F, about 2.6 °F less than the modern value due to a later redefinition of the scale).

The Celsius or centigrade scale has the freezing and boiling points of water as its initial reference points. This eventually had to be clarified by specifying sea-level pressure, since water's boiling point goes noticeably downward at lower pressures. Water's freezing point goes upward, but by a very tiny bit.

This eventually led to using absolute zero and the triple point of water, where all three phases coexist, with the water having the Standard Mean Ocean Water (SMOW) isotopic composition.

Absolute zero came from thermodynamics and statistical mechanics. The Celsius scale referred to absolute zero is the Kelvin scale, while the Fahrenheit scale referred to absolute zero is the Rankine scale (yes, there is such a thing).

The General Conference on Weights and Measures (French initials: BGPM) is planning on fixing Boltzmann's constant, a constant that relates temperature and energy, thus turning that constant into a units factor. BGPM has already fixed the speed of light in a vacuum, and it also intends to fix Planck's constant and some other such constants.

 

[Idran]

Fahrenheit - Wikipedia states

Right, but if you go from the intro paragraph to the History section, you see this:

According to a letter Fahrenheit wrote to his friend Herman Boerhaave,[9] his scale was built on the work of Ole Rømer, whom he had met earlier. In Rømer's scale, brine freezes at zero, water freezes and melts at 7.5 degrees, body temperature is 22.5, and water boils at 60 degrees. Fahrenheit multiplied each value by four in order to eliminate fractions and increase the granularity of the scale. He then re-calibrated his scale using the melting point of ice and normal human body temperature (which were at 30 and 90 degrees); he adjusted the scale so that the melting point of ice would be 32 degrees and body temperature 96 degrees, so that 64 intervals would separate the two, allowing him to mark degree lines on his instruments by simply bisecting the interval six times (since 64 is 2 to the sixth power).[10][11]

To sum up, Fahrenheit himself said that he basically just multiplied the Rømer scale (which was the one that actually used a brine mixture as the definition of 0) by 4 and then nudged the two points I mentioned to different nearby degree marks because it made it easier to mark a thermometer.