Timeline for Why does it take so long for a gas to reach a thermal equilibrium?
Current License: CC BY-SA 4.0
9 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| May 5, 2021 at 13:01 | comment | added | Alex Robinson | Would there not be a difference between the speed of the molecules themselves compared to the transfer of energy? would that not make the process happen faster | |
| May 5, 2021 at 1:55 | comment | added | NoLongerBreathedIn | @Acccumulation makes a point, but the energy actually moves according to the heat equation, and therefore proportional to the gradient of temperature; the end result is that the energy spreads proportional to sqrt(t). | |
| May 4, 2021 at 20:18 | comment | added | leftaroundabout | @Acccumulation well, they do hold in a collisionless-ideal gas that you somehow magicked to have Maxwell-Boltzmann distribution all along! But in reality, too-thin gases indeed don't have this. Space plasmas tend to follow a kappa distribution rather than Maxwell-Boltzmann (but they're anyway much more complicated than ideal gases, because of long-scale MHD effects). — Pragmatically speaking, it makes more sense to define an ideal gas as one where the mean free path is much longer than the mean particle distance, but still much smaller than the total system. | |
| May 4, 2021 at 17:43 | comment | added | Acccumulation | @leftaroundabout So the ideal gas laws don't apply to ideal gasses? | |
| May 4, 2021 at 17:43 | comment | added | Acccumulation | But when they hit another molecule, they transfer some of their energy. It's how fast energy is moving, not individual molecules, that matters. | |
| May 4, 2021 at 9:01 | comment | added | leftaroundabout | @sebzim4500 that's a bit tricky to answer, because in gases of such low density the very concept of temperature becomes problematic. You can't really measure it in a thermodynamic way at all anymore, but instead need to directly measure the velocities of individual particles (can be done with Doppler spectroscopy). In outer space, the thin gases actually tend to be so hot (!) that the particles are ionised (plasma), which again prevents quick long-scale thermalisation because the particles are forced on gyration paths. | |
| May 3, 2021 at 17:35 | comment | added | sebzim4500 | Ah I see. I was imagining the air to be 'almost ideal', i.e. particles bouncing around in the container only occasionally hitting each other. Does that mean that a very low density gas behaves the way I described, where it hits thermal equilibrium almost instantly? | |
| May 3, 2021 at 17:34 | vote | accept | sebzim4500 | ||
| May 3, 2021 at 17:01 | history | answered | mike stone | CC BY-SA 4.0 |