From Oriole Parker-Rhodes
How can 20,000 K be called relatively cool
(21 April, p 38)?
Background radiation is only 3 K, isn’t it? What temperature is the rest of space?
Stephen Battersby writes: As well as the 3 K background radiation,
intergalactic space is filled with a tenuous gas at millions of kelvin. Atoms in
a gas have to collide to emit radiation, and these widely separated atoms rarely
do, so they can’t cool down.
Llangoed, Anglesey
