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Celsius at least has a family of units that mesh with it precisely. To heat one cubic centimetre of water up 1°C takes 1 Joule. It also essentially weighs 1 gra

Celsius at least has a family of units that mesh with it precisely. To heat one cubic centimetre of water up 1°C takes 1 Joule. It also essentially weighs 1 gram at normal temperatures. How many BTUs does it take to heat up one cubic foot of water by one degree Fahrenheit?

posterboy 10y ago
I thought Kelvin would be the appropriate unit for temperature differences, deg. Celsius be only used for absolute values.
freeone3000 10y ago
It takes one BTU to heat one pound of water, one pint, one degree Fahrenheit. The units may be arbitrary, but they still line up.
- david-given 10y ago
  Is that a US or a UK pint?
- astrodust 10y ago
  Yeah, but a pound of water is not a cubic foot. A pint has nothing to do with inches.
  - ars 10y ago
    That has nothing to do with temperature. You can keep metric and use Fahrenheit with very little change. And you got your units wrong anyway: "To heat one cubic centimetre of water up 1°C takes 1 Joule" - you mean 1 calorie, not 1 Joule. Change Celsius to Fahrenheit and only calorie changes, and since it's anyway not part of SI it makes little difference. Joule is the main energy unit, and it's not tied to Celsius at all. I totally get the arguments for metric - except for temperature. For temperature Fahrenheit is the better scale. Look here: https://en.wikipedia.org/wiki/International_System_of_Units#/media/File:SI_base_unit.svg https://en.wikipedia.org/wiki/International_System_of_Units#... And notice how Kelvin stands alone - it's not tied to any other unit. It can be replaced with almost no impact.
    - averagewall 10y ago
      A difference in temperature has the same numerical value in both degrees C and K. Often differences in temperature are all we're interested in so C is often interchangeable with K. If you use Fahrenheit, then you lose that easy relationship unless you also use Rankine for absolute temperature. But nobody, not even Americans, has even heard of Rankine so it would be a far bigger challenge to get anyone to use that than just Fahrenheit alone. Perhaps an even more elegant unit for temperature would be thermal energy per degree of freedom per particle, which would be joules in SI. I'm not sure if that's really correct tho.
      - ars 10y ago
        > A difference in temperature has the same numerical value in both degrees C and K. I know, I used them basically interchangeably in my post. > unless you also use Rankine If people used Fahrenheit more often they would use Rankine more often as well (and yes, I was aware of it before this discussion). > which would be joules in SI Joules is a unit of energy, not temperature. You need to multiply by entropy to get temperature. It would be one thing if the unit for temperature was based on the SI units, fine. But it's not - it's completely arbitrary, and since that is the case you might as well use the more usable Fahrenheit. If I were doing it I would redefine it such that 1 joule of energy applied to 1 gram of water = 1 new-degree. (Right now it's 4.2 joules.) That would make the temperature scale less coarse, which is good. Then make absolute zero -1000 new-degrees.
        averagewall 10y ago
        Isn't temperature an energy scaled by the Boltzmann constant? That means it's proportional to the energy of something. Why not just use that energy directly instead of converting it to another unit? That's what I means about using Joules for temperature - divide kelvins by Boltzmann's constant Why on earth would you make absolute zero anything other than 0? That's the major problem of Fahrenheit and the reason Celsius is not the SI unit. Instead, you could put a human-level temperature at a round number like 1000 new degrees so everyone always has the leading 1 in there for everyday values.
  - boondaburrah 10y ago
    Yeah, but inches are a unit of length and pint is a unit of volume. Therefore a pint is more relevant here. Yeah technically a cubic inch/foot is volume, but it's not the purpose-built one. To be honest, the volume system in US customary is the only one that makes sense. Everything's power-of-two friendly. If we could revise the others to mesh with that idea then we could have one power-of-10 system (metric) and then a power-of-two system.
    - astrodust 10y ago
      That's why there's acre-feet! Because gallons aren't good enough.
protomyth 10y ago
If we are talking about Mars, then the colony might not like the Earth-centric origin[1] of the definition of meter, but be ok with human centric foot. 1). The original definition of meter was based on the size of the Earth.

posterboy 10y ago

I thought Kelvin would be the appropriate unit for temperature differences, deg. Celsius be only used for absolute values.

freeone3000 10y ago

It takes one BTU to heat one pound of water, one pint, one degree Fahrenheit. The units may be arbitrary, but they still line up.

david-given 10y ago
Is that a US or a UK pint?
astrodust 10y ago
Yeah, but a pound of water is not a cubic foot. A pint has nothing to do with inches.
- ars 10y ago
  That has nothing to do with temperature. You can keep metric and use Fahrenheit with very little change. And you got your units wrong anyway: "To heat one cubic centimetre of water up 1°C takes 1 Joule" - you mean 1 calorie, not 1 Joule. Change Celsius to Fahrenheit and only calorie changes, and since it's anyway not part of SI it makes little difference. Joule is the main energy unit, and it's not tied to Celsius at all. I totally get the arguments for metric - except for temperature. For temperature Fahrenheit is the better scale. Look here: https://en.wikipedia.org/wiki/International_System_of_Units#/media/File:SI_base_unit.svg https://en.wikipedia.org/wiki/International_System_of_Units#... And notice how Kelvin stands alone - it's not tied to any other unit. It can be replaced with almost no impact.
  - averagewall 10y ago
    A difference in temperature has the same numerical value in both degrees C and K. Often differences in temperature are all we're interested in so C is often interchangeable with K. If you use Fahrenheit, then you lose that easy relationship unless you also use Rankine for absolute temperature. But nobody, not even Americans, has even heard of Rankine so it would be a far bigger challenge to get anyone to use that than just Fahrenheit alone. Perhaps an even more elegant unit for temperature would be thermal energy per degree of freedom per particle, which would be joules in SI. I'm not sure if that's really correct tho.
    - ars 10y ago
      > A difference in temperature has the same numerical value in both degrees C and K. I know, I used them basically interchangeably in my post. > unless you also use Rankine If people used Fahrenheit more often they would use Rankine more often as well (and yes, I was aware of it before this discussion). > which would be joules in SI Joules is a unit of energy, not temperature. You need to multiply by entropy to get temperature. It would be one thing if the unit for temperature was based on the SI units, fine. But it's not - it's completely arbitrary, and since that is the case you might as well use the more usable Fahrenheit. If I were doing it I would redefine it such that 1 joule of energy applied to 1 gram of water = 1 new-degree. (Right now it's 4.2 joules.) That would make the temperature scale less coarse, which is good. Then make absolute zero -1000 new-degrees.
      - averagewall 10y ago
        Isn't temperature an energy scaled by the Boltzmann constant? That means it's proportional to the energy of something. Why not just use that energy directly instead of converting it to another unit? That's what I means about using Joules for temperature - divide kelvins by Boltzmann's constant Why on earth would you make absolute zero anything other than 0? That's the major problem of Fahrenheit and the reason Celsius is not the SI unit. Instead, you could put a human-level temperature at a round number like 1000 new degrees so everyone always has the leading 1 in there for everyday values.
- boondaburrah 10y ago
  Yeah, but inches are a unit of length and pint is a unit of volume. Therefore a pint is more relevant here. Yeah technically a cubic inch/foot is volume, but it's not the purpose-built one. To be honest, the volume system in US customary is the only one that makes sense. Everything's power-of-two friendly. If we could revise the others to mesh with that idea then we could have one power-of-10 system (metric) and then a power-of-two system.
  - astrodust 10y ago
    That's why there's acre-feet! Because gallons aren't good enough.

protomyth 10y ago

If we are talking about Mars, then the colony might not like the Earth-centric origin[1] of the definition of meter, but be ok with human centric foot. 1). The original definition of meter was based on the size of the Earth.