Ruminations on multiverses; they are not real (Introduction)

by David Turell , Wednesday, January 24, 2018, 00:26 (2495 days ago) @ David Turell

They are probably figments of the imagination of scientists who do not want to give up a source of speculative papers and grant money:

https://www.npr.org/sections/13.7/2018/01/22/579666359/scientific-theory-and-the-multiv...

"Today, the idea that we live in a multiverse has become popular in the foundations of physics. The multiverse collects all universes in which the constants of nature — Newton's constant and about two dozen more — can take on any value. Each combination of constants is realized in infinitely many universes.

"And not only the constants can change from one universe to another, the locations of particles relative to each other can also be different. Since there are infinitely many universes in which to arrange the particles, some of these universes will be very similar to our own, just that eventually some initially tiny deviation will lead to an alternative history. Thus, somewhere in the multiverse our lives play out in any which way you can imagine.

"But before you pack your bags and search for a universe more to your liking, let me add there's no way to cross over into another universe or even interact with one. This only works in science fiction. Indeed, to my taste, the multiverse itself is already too close to fiction.
Many theoretical physicists have argued the conclusion that we live in a multiverse is based on sound scientific reasoning. But that isn't so — and I will tell you why.

***

"If Ockham could see what physicists are doing here, he'd pray for God to bring reason back to Earth. You should remove unnecessary assumptions, alright. But certainly you shouldn't remove assumptions that you need to describe observations. If you do, you'll just get a useless theory, equations from which you can't calculate anything.

"These useless theories which lack assumptions necessary to describe observations are what we now call a multiverse. And they're about as useful as Ockham's prayers.

"Since you cannot calculate anything in the multiverse, the assumptions which physicists removed must then be replaced with something else. That "something else" is a probability distribution on the multiverse, which tells you not what we do observe, but what we are likely to observe. But it is simpler to assume a constant than an infinite number of universes with a probability distribution over them. Therefore, Ockham's razor should shave off the multiverse. It's superfluous. Unfortunately, this argument carries little weight among many of today's theoretical physicists who value the multiverse because it excuses boundless speculation.

***

"Let me also add that these examples of "predictive" multiverses are ad hoc constructs invented for the very reason of convincing skeptics that some types of multiverses can have observable consequences. Don't fall for it. Just because a theory is falsifiable doesn't mean it's scientific. For a theory to be scientific its predictions must also have a reasonable chance to accurately describe reality. Construing up one of an infinite number of multiverse variants has no reasonable chance.

***

"Why then has the idea become popular? A cynic may argue it's because the multiverse offers infinitely many new opportunities for paper writing. But I don't want to feign hypotheses.
Let me thus stick to the facts: To our best knowledge, assuming the existence of any universe besides our own is unnecessary to explain anything we have ever observed. In the best case, then, the multiverse is an interpretation.

"You can believe that the seeming arbitrariness of the constants of nature is due to an infinite number of other universes. You can believe that, but you don't have to. Science cannot confirm that the other universes exist, but it also cannot rule them out. Just like science cannot rule out the gods and angels."

Comment: Sabine Hossenfelder at her best. Like string theory theory not likely to be of any help in understanding the universe.