There's no such thing as an anti-photon. In the case you are describing - pair production - both of the particles are virtual particles. They can be an electron and a positron (anti-electron), a quark and its anti-quark, etc - any particle/antiparticle pair. However a photon is its own anti-particle. (See http://en.wikipedia.org/wiki/Antiparticle ) And your explanation of the uncertainly principle is wrong. The time-energy formulation says (uncertainty in time) * (uncertainty in energy) = hbar, so the time limit for the life of the virtual particles is Planck's constant / energy (or Planck's constant divided by mass, since mass and energy are proportional and we measure the mass of these particles in units of electron-volts anyhow). Note that if it's mass * hbar, as you have above, then the higher the mass is, the longer the particles can stick around! That's exactly backwards. It's the tiny little particles that are flickering in and out of existence, not huge massive objects! If it were mass*hbar, you'd have virtual planets, stars and galaxies - the larger the object the more likely it would be to suddenly appear out of nowhere! This is an amusing thought but doesn't accurately describe the reality that we find ourselves living in.