I think I understand much of SR and some GR, but I'm always stuck when this thought comes to mind.It looks like a stupid proposition and never appears in discussions, but want it cleared up. Consider two objects separated by some distance comparable to the speed of light. Thus each observer would actually be observing the activities of the other one's past.If they are apart by c metres, then each one would observe the activity of the other a second earlier of what's happening now in the latter's vicinity. When we lorentz transform time from that measured in one frame to another, we don't consider this difference in times. For example, the transformation for bodies separated by distance y should be t(prime)=gamma* (t-vx/c^2 + y/c) where x is the distance to the point as measured in the stationary observer's frame, y is the dstance between the point and the moving observer. The factor y/c is a corrective one(or so I think) added by myself to correct for difference in times due to separation.