What Have You Got Now?

Speaking of time-travel science fiction, which I haven't yet but will soon (SWIDT?)...

I watched the second episode of Legends of Tomorrow last night. Slight spoiler ahead. (Sorry, this is not exactly bookish, but relates to storytelling, at least.)

Old dude from the present goes back and meets his younger self in the 1970s. Younger self has startling new experiences as a consequence. Yet, older self doesn't have those memories. What have you got now?

Marty likewise didn't remember his life with his cool parents, in Back to the Future, as was well pointed out in the Everything Wrong With BTTF video.

Time alteration is tricky stuff, and most writers don't seem up to it. There was some show, I can't recall what now, that the person ended up with two sets of memories. That, at least, addresses the paradox.

/rant

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