Why You Can’t be Everywhere at Once.
If electrons have no mass (and sometimes they don’t, as in Graphene), then they could theoretically travel at the speed of light. Of course, at the speed of light, time has no meaning – it stops. When time stops, an electron could be everywhere at once; reference Feynman’s One Electron theory.
A single electron could, in the absence of time, exist in every energy state in every atom of every molecule of everything in the Universe. The theory is, um, startling.
The big “But” is the fact that electrons do not travel anywhere close to the speed of light (although the field does). And electrons have a measurable mass compared to a Proton. Theoretically.
Except Graphene’s electrons are traveling at c. So time has stopped for Graphene. So, if we are ever going to build a time machine, it will have to be made, probably, from pure Graphene.
But you still can’t be everywhere at once, because you would have to be made of Graphene, and we haven’t figured out how to do that.