Imagine a very long row of clocks fastened to cameras. Each camera/clock unit faces a similarly equipped rocket. We now have two very long parallel lines of stationary clocks which can all be synchronized. When the clocks reach 01:00:00 the cameras start recording and the rockets accelerate rapidly for 1 second along the line of the stationary clocks. We now have a situation akin to clocks on a train moving alongside clocks on a platform.

Special relativity predicts that the two sets of clocks will no longer be synchronized and the time differences will increase along the lines of clocks. So if the lines are sufficiently long the leading clock will be delayed to before 01:00:00. Such a time cannot be filmed before the start of the experiment. If one says the leading clock does not jump back to before 01:00:00 then all the other moving clocks will need to show correspondingly later times. The moving clocks will, on average, move into the future compared with the stationary clocks. This does not seem to be predicted. We also have the problem of knowing how the leading clock, assuming it knows it faces a logical problem, is able to tell all the other clocks to adjust their times into the future.

In reality I think clocks that are considered to be moving would not variously leap backwards and forwards in time. I believe this to be the case because identical clocks under identical conditions must behave identically. If there is a plausible physical mechanism by which identical clocks can jump to different times, despite undergoing identical accelerations, please will someone explain it. (SR’s assumptions, and the cognate assumptions of Minkowski space, do not constitute a physical mechanism.)

An assumption underlying SR’s predictions is that objects are fundamentally changed by observation. Distant observers having different speeds relative to clocks, or to the Earth, are able to produce differing clock times and rates and different physical sizes of the Earth. But there is no logical or experimental reason to think this is the case. Clocks slow down as a result of acceleration but this involves a change in kinetic energy; observations do not. Again, if there is a plausible physical mechanism by which an observer can compress the Earth, please will someone explain it. I can find no experimental support for non-simultaneity (or symmetrical time dilation or distance contraction).

P.S. By symmetrical time dilation I mean SR's predicted dilation effects are necessarily always equal. The slowing effect just depends on relative speed and this must be the same for both observers. For me, the speed must arise from accelerations involving a change in kinetic energy. It does not depend on the speed between the observers per se. So whilst observers may be accelerated to equal speeds, this is not the case in general.