It's a well-known but normally ignored paradox that the senses do not confront the phenomena they apparently receive at the time these inputs ‘actually’ occur. For most practical purposes of course, given the speeds of light and sound, the gap between occurrence and perception is so short as to be invisible. But consider for instance the case of lightning and thunder, where the disparity is patent. As it may be, even more strikingly, if one were shot at a sufficient distance. In that case the victim would first perceive the muzzle-flash, then the impact of a supersonic bullet, and finally (ceteris paribus) hear the shot. Not that most people in such circumstances would be likely to reflect on these matters, but there it is. The scholar can afford an apparently callous displacement.

In other cases however the disparity is so enormous that we habitually suppress it by certain kinds of counterfactual conventions, in order to be able to talk sensibly or retain our sanity. We speak of ‘visible’ celestial objects thousands of light-years away as if we thought we were seeing them as they are; yet if we are contemplating something 10,000 light-years away, this is a measure not just of distance but of real time; any photon reaching us from this object has taken 10,000 years to get here, so we are in fact seeing something that ‘happened’ 10,000 years ago, literally looking into the past.