As a case in point, philosophers nearly all have wrong ideas about quantum mechanics, and here is one learning crackpot ideas from a fringe publicity-seeking physicist.

Physicist Sean M. Carroll was on a philosophy show, the rationally speaking podcast, defending parallel universes:

Julia Galef: You mentioned the concept of simplicity. I've encountered a lot ofNo, Carroll misunderstands math and physics.

confusion -- also experienced a lot of confusion – over, how do you decide which theory is simpler than another theory?

For example, I've heard critiques of the Many Worlds, or Everett, interpretation of quantum mechanics, to the effect that, "Look, if you're going posit this infinite or uncountably large number of worlds in order to explain this data we're getting, then that's an incredibly extravagant, or incredibly complex, theory. And we should really go for a simpler one, in which there is only one world MM the world that we can see, basically."

Sean Carroll: I would say there are various reasonable critiques of the Many Worlds program; that is not one of them.

Julia Galef: Right. That's what I thought you'd say. [00:14:00]

Sean Carroll: Yeah. To put it as bluntly as possible, that's just wrong. That's just a mistake. It's just a misunderstanding.

Because, again, we're not positing many, many worlds. We are taking the formalism of quantum mechanics that is always there. The Hilbert space, that we call it, which is where the wave function lives, it’s the mathematical structure that a particular quantum state is an element of. The Hilbert space is just as big for someone doing a different interpretation as for someone doing Many Worlds. It doesn't get any bigger. Hilbert space is big. It includes a lot of possibilities. All we're saying is, Hilbert space is all there is, then you stop after you have that. There’s not other structures or other rules or other interpretative dances that you're allowed to do.

To say that positing a lot of worlds is extravagant is to get it exactly backwards. We're positing the minimal mathematical structure needed to make sense of quantum mechanics. Everyone posits Hilbert space. We're just admitting that it's real rather than denying that.

Probability is a mathematical device for estimating the likelihood of an event occurring. Carroll says that quantum mechanics is all about probability, but he rejects the way everyone else understands probability. To him, all events occur with certainty, but maybe in other universes.

Physics is about observables. But Carroll insists on attributing reality to all these extra universes that no one can ever observe.

I have posted more detailed arguments on what is wrong with many-worlds. I just want to note here that the blind is leading the blind.

The conversation gets goofier when they discuss morality.

Julia Galef: Right. There was this case -- I don't remember who this was -- one Everettian who I know, she was crossing the street and I guess she wasn't looking where she was going, and the car slammed on its brakes to avoid hitting her.This is crazy talk. No, that Everettian did not lose copies of herself in alternate universes. The block universe version of time is another stupid idea, and has little to do with the situation.

She was really shaken by this -- which that made sense to me, It makes sense to be shaken if you're almost hit by a car -- but she then explains that the reason she felt so shaken was that she had "lost a lot of measure." In other words, there were a lot of almost identical copies of her who had gotten hit by the car, since it was kind of a toss up whether the car would have hit her or not. Over the set of all copies of her --

Sean Carroll: I'm not sure that attitude can be consistently maintained if you also believe in a block universe version of time, where eventually we're all dead.

Julia Galef: I'll past that on! I don't know if that will cheer her up or not.

You have a bee in your bonnet about "philosophers".

ReplyDelete1. Have you forgotten Ayn Rand? Everyone's a philosopher.

2. You say philosophers misconstrue QC. Then you show us one of them, Carroll, but introduce him as a physicist rather than s philosopher.

Seems to me that a better intro would run like "Here is a physicist who fails to grasp the philosophical ramifications of QC." Unless your position is that all philosophy is either established physics or worthless, in which case you abandon Rand.

You have a bee in your bonnet about "philosophers".

ReplyDelete1. Have you forgotten Ayn Rand? Everyone's a philosopher.

2. You say philosophers misconstrue QC. Then you show us one of them, Carroll, but introduce him as a physicist rather than s philosopher.

Seems to me that a better intro would run like "Here is a physicist who fails to grasp the philosophical ramifications of QC." Unless your position is that all philosophy is either established physics or worthless, in which case you abandon Rand.