Physics is complicated, and quantum theory is especially complicated. Many of the concepts belonging to the world of quantum mechanics won’t be easily (or ever) grasped by untrained minds, but the Many-Worlds theory isn’t that hard to understand – at least on the surface.
It’s the idea that the reality and timeline we’re living in is just one of an infinite number, all existing alongside one another.
It’s difficult to test, though, so scientists get into pretty heated discussions about whether it could be true, what it means, and whether or not it could ever be proven.
Let’s go to the beginning: before the 1950s we had the Copenhagen interpretation, which said that at the quantum (very, very small) level, matter exists in all possible states at once (particle, wave, etc), as a wave function. It also says that once you observe the quantum wave function, it chooses which state it will be in (kind of like Schrödinger’s cat).
This is connected to Heisenberg’s Uncertainty Principle, which says that because we affect the wave function’s behavior through observation, we can never ben sure where it is or what it is doing when we’re not observing it.
In the 1950s, a Princeton student named Hugh Everett III was studying quantum mechanics with those principles in mind, when he wondered what if, when the object “chooses” whether to be a particle instead of a wave, there was a split in the universe that created another timeline where the object chose to be the opposite?
His theory would mean that for everything that happens – every action you decide to take or not to take – there are timelines (or worlds) where something else happened, i.e. an infinity of timelines.
Though Hollywood has taken the principles of this theory and run with them (looking at you, Fringe, but you’re not alone), not all physicists subscribe to the theory (though the majority do subscribe to the Copenhagen interpretation).
But a growing number are admitting it could be the case.
One of those scientists is Sean Carroll, who does his best to explain objections to Everett’s interpretation.
“In classical mechanics, it’s quite a bit of work to accommodate extra universes, and you better have a good reason to justify putting in that work. That is not what happens in quantum mechanics. The capacity for describing multiple universes is automatically there. We don’t have to add anything.”
Accepting the possibility of the many-worlds interpretation means questioning the nature of reality – that there are infinite versions of you living infinite alternate decisions out there. One who didn’t break up with that guy in college, who decided to major in something different, who decided to have eggs for breakfast this morning instead of cereal, .
It’s mind-boggling to think about, and, as with almost everything in the world of theoretical physics and things that seem like science fiction, it’s almost impossible to truly wrap your mind around.
But takeaway this: even if there are infinite yous, you’re still unique – you’re the only person who has made all of the decisions exactly the way you have.
Up until this point, at least.