Ah, yes, he was a theoretical physicist who expanded on Hugh Everett's original interpretation of how universal wavefunction operates. The basis to the idea is that every possible choice that could have been made in history allows for the creation of an alternate universe, one where the choice was made differently.

[There's no judgement in the fact Sam doesn't know this already, Max is aware that not everyone researches these sorts of things just for the sake of research.]

For example, perhaps there's a world where America never joined the second world war, and it was lost as a result.