Ok, I took some time to try to process the changes in time that you all took the time to write about. I hope we are all in the same space-time!
One thing I am not reading here, is the cascade/multiple effect of a travel and action in time. Let's use our favorite time travel animals, Gracie and George as examples:
Kirk and crew travel in time from Universe A to a point in the past where there are whales. We cannot say for sure whether They travelled back Universe A, nor can we say they returned to Universe A. But if they did, Universe A would not necessarily be a welcoming place for whales. The ecosystem was without the whales, and the food they ate, animals they coexisted with, balance of relationship with and interaction of the creatures and plants and chemistries would likely be different. If they returned to a parallel/invisible/duplicate but not identical -down to the quantum level - Universe B, there would likely be similar changes that the whales would find challenging or impossible to cope with. Plus, if they did not return to Universe A, where the whales originally existed, albeit in Universe A's "past", then the Earth of Universe A is destroyed by the WhaleProbe. And then, the Paradox kicks in. How could they have left Universe A if it was destroyed (because they did not return to
that Universe with the whales) and how could they return to a different Universe in the same circumstance -that of needing whales - if they never existed at the beginning of the whole causality because they never brought Gracie and George back to the Universe they left from?
And now, copious quantities of Michelob and pizza are called for...in all Universes!
