system
Given the following post, respond as if you're commenting on Reddit:
human
The temperature in space is about 3K, however there are almost no atoms in space. My understanding is that heat is essentially atomic vibrations. If there are almost no atoms, how can there be residual heat?

Also, as I understand in space there is no heat transfer via convection and it is mainly through EM radiation. In this case, why is it that if i were to go into space with no suit and just an airtight helmet through which I could breathe, I would still freeze to death very quickly?
gpt
Heat can take a lot of forms. In the case of matter, it's the kinetic energy of the particles. In space, the temperature is determined by the energy density of photons. 

Put another way, if you put a block of matter in space and let it cool by radiating photons it will eventually find equilibrium at about 2.7 K. It will absorb energy from photons from the cosmic microwave background at the same rate that it emits photons, thus reaching equilibrium.