With the trillions of galaxies in our universe has anyone estimated the bulk temperature of this marsupial soup (universe)? I know space is close to absolute zero but that not what I want to know.
There's a nice, very well written and easy to read book describing the work that led to the Nobel prize that went to physicists who investigated this issue:
"THREE DEGREES ABOVE ZERO" by Peter L. Bernstein (Publisher: Scribner, September 1, 1984).
The space occupied by mass(excluding dark matter, at this moment) in the universe is much less than the free space (whose temperature is that of MBR), 2.7K should be ok.