Many Worlds

Yesterday's post discussed the multiverse and how contemporary scientists seem to be drawn toward theories for which there's very little evidence, which seems like a very unscientific thing to do.

Today I want to reflect a bit on a theory that's often confused with the multiverse and sometimes goes by the same name but is actually different. This is the Many Worlds hypothesis.

In a column for the Wall Street Journal science writer John Horgan reviews a book by physicist Sean Carroll titled Something Deeply Hidden in which Carroll argues that the simplest version of quantum mechanics entails the idea that every time a quantum particle such as an electron is jostled or observed the universe splits.

A consequence of this is that there exists an infinite number of worlds in which an infinity of different versions of you exist simultaneously with your existence in this world.

Here's Horgan:

The universe supposedly splits, or branches, whenever one quantum particle jostles against another, making their wave functions collapse. This process, called “decoherence,” happens all the time, everywhere. It is happening to you right now. And now. And now. Yes, zillions of your doppelgängers are out there at this very moment, most likely having more fun than you.

The number of universes created since the big bang, Mr. Carroll estimates, is 2 to the power of 10^112 . Like I said, an infinitude.

If Carroll weren't so smart and such a good writer a lot of people might think he has taken leave of his senses.

After all, if his interpretation of quantum mechanics leads to the conclusion that there are an infinity of worlds and an infinity of different iterations of you and me then the appropriate conclusion to draw, it would seem, is that there's probably something wrong with his interpretation of quantum mechanics, even if we can't put our finger on what it is.

Horgan goes on:

I am not a multiverse denier .... [b]ut I’m less entertained by multiverse theories than I once was, for a couple of reasons. First, science is in a slump, for reasons both internal and external. Science is ill-served when prominent thinkers tout ideas that can never be tested and hence are, sorry, unscientific.

Moreover, at a time when our world, the real world, faces serious problems, dwelling on multiverses strikes me as escapism—akin to billionaires fantasizing about colonizing Mars. Shouldn’t scientists do something more productive with their time?

Some questions suggest themselves here. Carroll may be right or wrong, but whichever he is, what difference does it make to how anyone lives their lives or to how we view the world? And if it makes no difference what is its value? What's the point?

Carroll might reply that knowledge is an end in itself, and perhaps he'd be right, but a theory is knowledge only if we can establish its truth, and that's something which is very difficult to imagine anyone doing.