On 8/1/17 1:59 AM, jacobnavia wrote:

Question:

Suppose a gargantuan cloud of hydrogen gas (40-50 Giga ly across) at 2.7
degrees K.

And a planet with some astronomers in it somewhere. Wouldn't the
background emission of all that gas mimick the CMB?

The kinetic theory of gases indicates such a 2.7K gas
would have a translational velocity(v) sqrt(kT/m) of ~.2 km/sec.
It is unclear how such a m*v^2 kinetic energy
would be converted into photons observable by astronomers therein.
(k*2.7K equivalent Rydberg energy states are on the order of n~10^5)