Thanks Hive account@mikedibaggio ! I might or might not take this hook any further, as it was just a mechanism to explain why Merwin is losing his job. So feel free to use the idea or expand on it.

Yeah, the philosophical and causality hoops. But this story is about traveling through the multiverse, so I think I can just sidestep causality problems by positing that past and future don't exist as such, but only as a subset of an infinity of parallel nows.