I understand that vacuum fluctuations can spring into and out of existence within a sufficiently short period of time, under the uncertainty constraint. However, I am currently a little confused over how this constraint is applied. 1) Does one use del E.del t = h bar (the commutation relationship) or h bar /2 (the uncertainty relationship)? 2) Does the temporal duration of this vacuum fluctuation thus extend from - del t to + del t ? 3) Consequently, to the extent that it is potentially meaningful, does this mean that the maximum spatial extension of the vacuum fluctuation is 2c del t? 4) Therefore, if this vacuum fluctuation comprises a virtual particle - antiparticle pair, does this mean they can be treated as having a typical separation of c del t? 5) Finally, would del E in the above formula be the massenergy of either particle if real, or the massenergy of the pair if real? Any advice on this would be appreciated, as these various factor of two possible differences in interpretation could become vitally important in determining what types of particles and antiparticles could potentially be released by a given strength of tidal gravitational field.