No.
“Multiple universes” is just one theoretical interpretation of what the experiment shows us. But there are other theories that could also explain it.
One of the problems with the multiple universes theory is that so far, we can’t come up with another experiment that would definitely prove if this explanation was true.
We really don’t know “why” most of quantum theory works. We just know that it does. Absolutely, amazingly, incredibly reliably.
Latest Answers