Temporal Thought Experiments III

A 2-Part Comic Strip

Part 1

Panel 1: At 2:00 pm on 1 June 2030, character A witnesses the assassination of the President.

Panel 2: A constructs a time machine in a laboratory.

Panel 3: A departs/disappears in his time machine.

Panel 4: The laboratory and indeed the universe continue to exist.

Part 2

Panel 1: At 2:00 pm on 1 June 2030, A witnesses an older version of himself preventing the assassination.

Panel 2: The President thanks the older A.

Panel 3: The older A converses with the younger A who will not construct a time machine or travel through time to save the President.

Panel 4: Both As continue to exist in what they agree is timeline 2.

In that scenario:

A's construction of a time machine succeeds the assassination of the President in timeline 1;

the President thanking A succeeds A's prevention of the assassination in timeline 2;

timeline 2 succeeds timeline 1 in a second temporal dimension.

An alternative scenario (scenario 2): the events of timeline 1 did not happen but are merely "remembered" by the older A who appeared/arrived from nowhere and nowhen to save the President.

My assessment:

scenario 2 is counterintuitive and contravenes conservation of energy;

however, both scenarios are logically possible;

however (again), any narrative that alternates between scenarios 1 and 2 is logically incoherent.

It makes no sense for a time traveller to say, "I exist now but, because of something that happened at an earlier time, I might not exist now." If he is talking about it, he does exist now.