There is only one Sean Carroll at Caltech in the world we know. But he could exist in of a multitude of worlds incrementally different from this one. (Credit: Bill Youngblood/Corey S. Powell)

Let’s begin at the beginning. What is the Many
Worlds Interpretation?

It begins with quantum mechanics, which is our
best theory of elementary particles and the microscopic world. There’s this
thing in quantum mechanics that says, before you look at an object it’s not in
any definite location. It’s