Why does the vacuum of space have a temperature at all? What is it that has the temperature?
In: Physics
Deep space contains hydrogen atoms, at an insanely low density – IIRC it’s like single-digit atoms per cubic centimeter. If you go by the average velocity of those atoms, the temperature of deep space is about 3 kelvin.
Now, because there are so few particles, the heat conductivity of space is very, very close to zero – and so when it comes to conduction, “vacuum has no temperature” – it just insulates.
If you “touched vacuum”, basically zero heat would conduct out of your hand and into the vacuum because it has essentially zero mass. However, you can still radiate heat out into vacuum, and it radiates almost nothing back, so in that sense vacuum is cold. Also, if you have any moisture on your skin like, say, sweat or oil, that will evaporate fairly quickly because there’s zero pressure holding it down, so you’d feel a chilling effect from the evaporation.
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