I just wanted to link to Sean Carroll’s post defending the many-worlds interpretation of quantum mechanics. Sean has a habit of getting this sort of thing right.
He explains that the multiple worlds are not an add-on to the theory but instead are simply what happens naturally when you take the equations of the theory at face value. The standard (“Copenhagen”) interpretation is the one that needs to postulate an ad hoc extra rule. We should simply rename things:
- The “many-worlds interpretation of quantum mechanics” should henceforth be known as “quantum mechanics.”
- The Copenhagen interpretation should henceforth be known as “the disappearing-worlds interpretation of quantum mechanics.”