Sean Carroll has been touting his new book in the media and on his podcast (and if you’re not familiar, you should be), and interviewing people related to the subject recently to try to explain the intricacies of Quantum Mechanics, such as the great Leonard Susskind (which is a wonderful podcast you should listen to). And because it is Sean Caroll backing the many worlds theory, it’s not being thrown under the bus so easily this time - because he’s taking the actual physics seriously enough to accept the consequences of what it means and not just ignoring the parts we may find “uncomfortable”.
Do I accept the many worlds conclusion? Well, after listening to his explanations in depth on his podcast for several hours over the summer, yes I do. It sounds incredible, but so did Relativity when it was first proposed - and the same can be said for many other scientific theories which have been since accepted, such as the age of the universe, the big bang, evolution, atomic theory, plate-tectonics, and so much more. They all sounded ludicrous at the time and were rejected out of hand because they sounded ludicrous, but they were exactly what the science said was happening. So if Quantum Mechanics says that the many worlds theory is what happens, and we know that Quantum Mechanics works (because we use it all the time and it actually works), then that’s what happens. It may sound incredible, odd, and bizarre, but so much which science has taught us is just that: that we live in a universe which is incredible, odd, and bizarre.