Few weeks ago a respected magazine brought some excitement with a story on missing bond between Thermodynamics and Relativity. My question is what satisfies the definition of relativistic gas and how would that differ from single star systems with shifted spectra? Take for example spinning galaxies that have different shifts in edges approaching or moving away from us. However we often hear the areas closer to the center to have whirls of gas - where does it count in? Today in New Scientist there is a brief and mostly unrelated passage that says that cosmic rays are affected by the photons of CMB. http://space.newscientist.com/article/dn12818 I guess that section is about collisions with CMB photons that seem to average the possible cosmic rays somehow. Comments?