Posted: Jan 06, 2019 6:00 pm
by Cito di Pense
Macdoc wrote:
Hot water does not convect?


Yes but pressure doesn't change significantly the way a gas does and it is entirely temperature dependent - very hard to compress further unlike a gas or a plasma.


Well, actually, pressure does change, so you probably meant to type 'volume' instead of 'pressure'. Maybe you've experienced clearing your ears when SCUBA diving or even just bobbing around in a swimming pool. Liquids are mainly incompressible, which means that their volume does not change much with pressure or temperature, but compressibilities and thermal expansivities are not negligible for many specified sets of working conditions.

My reading is that the compressibility of plasma is to first order related to the Mach number of the flow. At M < .3, the flow may be considered incompressible. FWIW, densities in stellar interiors are much higher than those of normal liquids. My further reading is that stellar interiors are in hydrostatic equilibrium when not transitioning off the main sequence or undergoing some other cataclysmic event at the end of a stellar lifetime.