4 ms·

interestingly, no. Temperature can become infinitely high, and you can still add heat, at which point it becomes infinitely low. You can carry on adding heat, a

interestingly, no. Temperature can become infinitely high, and you can still add heat, at which point it becomes infinitely low. You can carry on adding heat, and the temperature will get back to absolute 0. https://chemistry.stackexchange.com/questions/36885/how-is-negative-temperature-hotter-than-infinite-temperature https://chemistry.stackexchange.com/questions/36885/how-is-n...

whatshisface 5y ago
You can't heat something to negative temperature, although negative temperature things will transfer energy to positive temperature things. Negative temperature can be achieved through lining up many small magnets against a larger magnetic field. Disordering the magnets will reduce the potential energy, running opposite to the usual trend where increasing disorder involves the occupation of higher-energy states.
olliej 5y ago
How does it become infinitely high? Temperature is a measure of average particle speed, and that’s limited to the speed of light (I’m not a physicist so I’m willing to be corrected, but this doesn’t jibe with my low level compulsory physics courses from uni :) )
- crdrost 5y ago
  Temperature has to do with how the entropy changes with the addition of energy. It helps to use the “coldness” or “thermodynamic beta” scale, β = ΔS/ΔΕ is the coldness of a system, the thermodynamic temperature is defined as 1/(k β) where k is a conversion factor, the Boltzmann constant, to convert between units of energy and kelvins. For most normal systems, entropy increases with an addition of energy, and they have a positive coldness. Confusingly, the lower the entropy change, the less cold or hotter we would regard it: if you bring two systems into contact, they share energy to maximize their total entropy, so something which has low coldness = low entropy change will donate a lot of energy to something with a higher coldness = higher entropy change, the smaller negative will be balanced out by a larger positive. You can extrapolate this to an infinite temperature, this would be an object with β = 0 or zero coldness, it can take or lose energy without changing its entropy at all. An example is an assembly of electron spins in a magnetic field, when 50% of them are aligned with and 50% are aligned against the magnetic field: this is the most entropic that the spin system could possibly be, so there is no way to increase it and to first order changes in energy do not decrease it. It has zero coldness or infinite temperature. Add a little bit of energy and it is in the state where it actively wants to lose energy, putting more energy into the system requires aligning more of the spins along the magnetic field. This is a negative coldness, which is also regarded as a negative temperature by this T =1/(k β) formula.
q-big 5y ago
> Temperature can become infinitely high, and you can still add heat, at which point it becomes infinitely low. You can carry on adding heat, and the temperature will get back to absolute 0. Perhaps the correct measure is not temperature, but inverse temperature (i.e. 1/T)?

whatshisface 5y ago

You can't heat something to negative temperature, although negative temperature things will transfer energy to positive temperature things. Negative temperature can be achieved through lining up many small magnets against a larger magnetic field. Disordering the magnets will reduce the potential energy, running opposite to the usual trend where increasing disorder involves the occupation of higher-energy states.

olliej 5y ago

How does it become infinitely high? Temperature is a measure of average particle speed, and that’s limited to the speed of light (I’m not a physicist so I’m willing to be corrected, but this doesn’t jibe with my low level compulsory physics courses from uni :) )

crdrost 5y ago
Temperature has to do with how the entropy changes with the addition of energy. It helps to use the “coldness” or “thermodynamic beta” scale, β = ΔS/ΔΕ is the coldness of a system, the thermodynamic temperature is defined as 1/(k β) where k is a conversion factor, the Boltzmann constant, to convert between units of energy and kelvins. For most normal systems, entropy increases with an addition of energy, and they have a positive coldness. Confusingly, the lower the entropy change, the less cold or hotter we would regard it: if you bring two systems into contact, they share energy to maximize their total entropy, so something which has low coldness = low entropy change will donate a lot of energy to something with a higher coldness = higher entropy change, the smaller negative will be balanced out by a larger positive. You can extrapolate this to an infinite temperature, this would be an object with β = 0 or zero coldness, it can take or lose energy without changing its entropy at all. An example is an assembly of electron spins in a magnetic field, when 50% of them are aligned with and 50% are aligned against the magnetic field: this is the most entropic that the spin system could possibly be, so there is no way to increase it and to first order changes in energy do not decrease it. It has zero coldness or infinite temperature. Add a little bit of energy and it is in the state where it actively wants to lose energy, putting more energy into the system requires aligning more of the spins along the magnetic field. This is a negative coldness, which is also regarded as a negative temperature by this T =1/(k β) formula.

q-big 5y ago

> Temperature can become infinitely high, and you can still add heat, at which point it becomes infinitely low. You can carry on adding heat, and the temperature will get back to absolute 0. Perhaps the correct measure is not temperature, but inverse temperature (i.e. 1/T)?