Some physicists are drawn instead to the Many Worlds interpretation of quantum mechanics, in which observers in some universes see the electron go through the l

Some physicists are drawn instead to the Many Worlds interpretation of quantum mechanics, in which observers in some universes see the electron go through the left slit, while those in other universes see it go through the right slit This phrasing is so unfortunate - a much better understanding of MWI comes from looking at its original name, the "theory of the universal wave function": there is only one universe, it just happens to be described by a single wave function that describes the superposition of many different possible states that the universe could be in. The nice aspect of this theory is that it is mostly identical to the Copenhagen interpretation, but resolves the problem of wave function collapse in a perfectly clean way: there is no collapse, it's just that the act of observation causes the observer to become entangled with whatever it is that they're observing. If you really want to talk about multiple universes, you should at least clarify that it is the act of observation that causes the split between universes. So it's not like there are multiple pre-existing universes, and in some of them the electron goes left while in others it goes right. Rather, you as the observer start it one pre-existing universe, and by the observation the universe splits into a "left version" and a "right version". It's a subtle but important difference.