3 ms·

See also: https://en.wikipedia.org/wiki/Negative_temperature https://en.wikipedia.org/wiki/Negative_temperature

by OscarCunningham 8y ago

sampo 8y ago
So +0K is the lowest low, and -0K is the highest high.
- OscarCunningham 8y ago
  Right. In many contexts it makes more sense to use 1/T. Then there's no discontinuity and as things get hotter you decrease smoothly from positive, through 0, to negative.
  - dTal 8y ago
    1/0 seems like a pretty major discontinuity.
    - chowells 8y ago
      There's no discontinuity at 0. It's a limit point that is unreachable, as far as we know. That's why 1/T is a better measure. It makes it obvious that +0k is the unreachable limit of "adding a quantum of energy results in an infinite increase in entropy". (-0k is the unreachable limit of "adding a quantum of energy results in an infinite decrease in entropy".)
  - evincarofautumn 8y ago
    I remember when I first learned about absolute zero, ages ago, and thought “if it’s unreachable, it must be like an asymptote…but that would mean we’re measuring temperature ‘upside-down’…” Much later, I learned about that very thing (1/T, “thermodynamic beta”) while wikiwalking after hearing about the concept of negative temperature. Then I fell into a rabbit-hole wondering if we also measure speed upside-down in that way, since you can’t accelerate to light-speed. And indeed, when you’re talking about relativistic effects, units of time per distance can be more illustrative sometimes than our intuition of distance per time.
    - wnoise 8y ago
      For speed we don't measure it "upside down", no. But there is another transformation: "rapidity", which does add linearly (at least for one spatial dimension) and goes to infinity when velocity goes to c. https://en.wikipedia.org/wiki/Rapidity https://en.wikipedia.org/wiki/Rapidity
      - evincarofautumn 8y ago
        Well no, I just meant that sometimes working in inverse units makes things easier to understand than the “intuitive” units you use in daily life. “Time per distance” helped me personally get a better intuitive sense of time dilation and length contraction. I hadn’t heard of rapidity before, but it’s really interesting, and makes sense after some musing—thanks!
- antidesitter 8y ago
  This is why it’s more natural to think in terms of thermodynamic beta (inverse temperature).

See also: https://en.wikipedia.org/wiki/Negative_temperature https://en.wikipedia.org/wiki/Negative_temperature

sampo 8y ago

So +0K is the lowest low, and -0K is the highest high.

OscarCunningham 8y ago
Right. In many contexts it makes more sense to use 1/T. Then there's no discontinuity and as things get hotter you decrease smoothly from positive, through 0, to negative.
- dTal 8y ago
  1/0 seems like a pretty major discontinuity.
  - chowells 8y ago
    There's no discontinuity at 0. It's a limit point that is unreachable, as far as we know. That's why 1/T is a better measure. It makes it obvious that +0k is the unreachable limit of "adding a quantum of energy results in an infinite increase in entropy". (-0k is the unreachable limit of "adding a quantum of energy results in an infinite decrease in entropy".)
- evincarofautumn 8y ago
  I remember when I first learned about absolute zero, ages ago, and thought “if it’s unreachable, it must be like an asymptote…but that would mean we’re measuring temperature ‘upside-down’…” Much later, I learned about that very thing (1/T, “thermodynamic beta”) while wikiwalking after hearing about the concept of negative temperature. Then I fell into a rabbit-hole wondering if we also measure speed upside-down in that way, since you can’t accelerate to light-speed. And indeed, when you’re talking about relativistic effects, units of time per distance can be more illustrative sometimes than our intuition of distance per time.
  - wnoise 8y ago
    For speed we don't measure it "upside down", no. But there is another transformation: "rapidity", which does add linearly (at least for one spatial dimension) and goes to infinity when velocity goes to c. https://en.wikipedia.org/wiki/Rapidity https://en.wikipedia.org/wiki/Rapidity
    - evincarofautumn 8y ago
      Well no, I just meant that sometimes working in inverse units makes things easier to understand than the “intuitive” units you use in daily life. “Time per distance” helped me personally get a better intuitive sense of time dilation and length contraction. I hadn’t heard of rapidity before, but it’s really interesting, and makes sense after some musing—thanks!
antidesitter 8y ago
This is why it’s more natural to think in terms of thermodynamic beta (inverse temperature).