What caused us to have relative time

[PAllen]

All inputs are not symmetrical in the SR version of the twin paradox, which is why it is at least logically possible that conclusion be non-symmetric.

The asymmetry is physically apparent in the fact that the twins experience different acceleration.

It will also show up quite clearly if you just try working the problem in a frame in which the traveling twin is at rest during either the outbound or the inbound leg of the trip (Try it! Don't just take my word for it).

I think sugdub doesn't dispute the twins scenario (because there is asymmetry). What he/she claims is that the symmetric time dilation is not 'real' or 'actual' precisely because it is symmetric.

 

[Dale]

You are welcome. Concerning clocks “actually" running slow I precisely mean what physicists indicate in the context of the “twins” thought experiment: the “moving twin”, when coming back, will be younger than the other one, because his/her clock ran slower all along the trip.

Then nature disagrees with you. Clocks do "actually" run slow according to your definition. This experiment has been done many times in many different ways, and the results agree with SR's predictions.

My statement is that SR cannot, from a pure logical standpoint, justify that the “moving clock” ran slower: all inputs being fully symmetrical, the conclusion cannot be non-symmetrical.

Your statement is irrelevant for two reasons.

First, it is irrelevant because the assertion that you are attributing to SR is not an assertion that SR makes for inertial clocks. I detailed the assertion that SR actually makes above, and that one is fully symmetrical for inertial clocks. Your objection is therefore simply a strawman fallacy.

Second, it is irrelevant because your definition of "actually" involves an asymmetric situation. So an argument from symmetry simply doesn't apply to whether or not clocks "actually" slow down.

 

[Dale]

I think sugdub doesn't dispute the twins scenario (because there is asymmetry). What he/she claims is that the symmetric time dilation is not 'real' or 'actual' precisely because it is symmetric.

That isn't what Sugdub mentioned as the definition of "actually".