Vaccum

[swansont]

Note: antimatter discussion moved here

[Norman Albers]

Can't we say 'vacuum' means the evacuated state of whatever residual mass densities, atoms or plasma ions? This, relevant to whatever we are interested in measuring. Also present here is whatever radiation density.

 

Definitions of temperature involve equilibrium energy distributions. The blackbody radiation density, or temperature ambience, is presumably that of the walls of an experiment regime.