Temperature of space - pioneer 10

[kurious]

What is the magnitude of the temperature of space at 20 - 70 AU from
the sun?
And how much would a piece of copper, aluminium or iron contract by at
this temperature?Assuming the pioneer 10 space probe is made from these metals!

 

[Integral]

Empty space does not have a temperature. The spacecraft has temperature. This temperature is determined by the amount of thermal energy lost to deep space compared to the amount of heat energy generated by the craft. I would think that the designers of spacecraft are able to compensate for the variation in spacecraft temperature in low Earth orbit to its temperature in deep space.

 

[Nereid]

The thin plasma of interstellar space has a temperature, but it would take a very, very long time for an object as massive (relative to the plasma) as a space probe to come into equilibrium with the plasma. And as Integral said, the probe is not inert; it has its own sources of internal heat.

More important for solid objects is radiative heating - interstellar dust (for example) will reach an equilibrium temperature when the total energy it absorbs from the UV, light, IR, etc that falls on it balances the thermal energy (EM) it emits.

Out beyond the orbit of Neptune, there are many small bodies ... Pluto, Varuna, ... the recently discovered Sedna, and many considerably smaller. These bodies (too small to be called planets) likely have surface temperatures that are close to thermal equilibrium with the incident radiation, and with the primary source of heat being the distant Sun. IIRC, this is ~30K.

 

[kurious]

The temperature of the microwave background is 2.7 K .
If I reduce the volume of the universe to 10^-35 metres radius -around the time of
the big bang, does the microwave background give the value of 10^32 K proposed by weinberg and others, or are there other contributions to consider?

 

[MiGUi]

If you reduce the scale of the universe to such low volume, then the physics can not tell you valid results because you are talking about singularity conditions...

MiGUi

 

[Nereid]

It might be interesting to look at temperature vs time in various models of the universe. A nice, robust definition of 'temperature' would be useful. Getting back to times just after the first Planck time would surely involve some consideration of all the relevant phase changes, and I suspect that would bring in the adequacy of our extrapolations to energies far beyond those accessible with today's Earth-bound colliders.