Hi all, I've recently been reading about the Unruh effect, and there are a few things that I'm not very clear on: 1) An accelerating observer will see a vacuum filled with particles in thermal equilibrium (a warm gas) where an inertial observer would see zone. I'd originally read that the accelerated observer would see thermal (black-body) radiation only, which I had understood as EM radiation with a specific spectrum. However, more recently I read another source which said that the vacuum see by the accelerated observer would also contain a 'soup' of charged elementary particles, e.g., leptons etc. So would the accelerated observer see / interact with other 'real' particles? Or are we talking about virtual particles (since these are vacuum states). 2) If I have, let's say, a Proton, accelerating, would it's interaction with the vacuum mean interaction with other, e.g., electrons in the vacuum? Again, I'm probably getting confused here. Don't phenomena like pair production require specific energies... i.e. I would expect the proton to interact only with EM photons until it's energy (from the acceleration) was large enough to produce an e.g., electron-positron pair. That is, this should be a quantized effect. 3) The formula for the temperature observed by the accelerating proton is straightforward, but how does this translate into an expected density of photons, leptons etc. that the proton would actually interact with? Hoping someone can shed some light on the above (no pun intended).