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Imagine you go back in time with a couple measuring cups. And you give it to some premathematical cave men. And you give them time to play with the cups. And suppose that, as a result, the cave men have learned the mathematical laws of addition before they know how to count.

What incredible stories do you think they would come up with about why 2+3=5 and 3+2=5 but 2+5=7?

The mathematical laws of quantum mechanics were discovered (informed by the mathematical laws of classical mechanics, which dictate things like energy conservation) without an underlying physical model. That is to say, we know how to do the math, and we know how to use the math to make predictions, but we’re not exactly sure what the math is describing.

Today, on the Ti-Phy, we’re going to talk about the schools of philosophy for interpreting quantum mechanics. It’s pretty great.

Our guest is an author named Christopher Reynaga. The author of my favourite story ever “I only am escaped alone to tell thee” where Captain Ahab is obsessed with hunting Cthulhu. It has a line in it that is so marrow-chillingly good: “*He is the Christ come to try and deliver us all, and there’s not enough blood in him to save us” ha. *

* *If perhaps you would like to listen to a pocast version, it has been masterfully read by Graeme Dunlop on the DrabbleCast.

Physicists: Tia Miceli, Ken Clark

Intro Music: Ted Leo and the Pharmacists

Exit Music: John Vanderslice

Transcript: Ep_49_Parallel_Philosophies

I really enjoy these podcasts! The format is great, and I love the idea of explaining all these crazy physics concepts in the manner that you and your Titanium Physicists do.

Regarding this particular topic: the problem of energy conservation in the many-worlds interpretation (MWI) is not actually a big issue. The typical assumption is that the entire universe really is a giant wavefunction, and there is some Hamiltonian that evolves this wavefunction. The evolution of this universal wavefunction is guaranteed to satisfy energy conservation on each of the branches since the Hamiltonian of the universe will act linearly on the various components of the wavefunction. Of course, if the Hamiltonian is some crazy thing, then all bets are off, but the problem in that case is the evolution law of the universe, not the fact that the wavefunction has multiple terms that appear as basically decoupled worlds

There are a number of much more serious problems at the heart of MWI. One has to do with how the Born probabilities emerge from the interpretation. Some claim that this has been settled, but I think there are many people who think about these issues who fail to be convinced. The basic problem boils down to two things: First, what is the meaning of probability in this interpretation? Afterall, anything that can happen does happen, so the probability of any possible outcome is basically 1 (at least if you are naive about it). Second, even if you have a sensible answer to the first question, why are the probabilities that emerge the Born probabilities rather than some kind of logic whereby, anytime a branching occurs, you just apply an equal weighting of probability to each branch? The arguments to get around this are quite tortured, and I have not been particularly impressed by them so far.

Note: I’m not saying the arguments that solve the above problems are wrong. But I am pretty convinced that they undermine the main reason for believing in MWI, which is that it is the simplest of the possible interpretations since it “just follows from the math” of quantum mechanics. That is a typical selling point of the interpretation, but then, on encountering problems like the one I mention above, you have to start layering on new axioms on top of the standard quantum ones. It makes me wonder why proponents can’t just assume the Born probabilities from the outset—that would at least be simpler and more direct.

There are other major problems, but this is probably enough for one comment.

Thanks so much for the podcasts! I found S…SO back in February and just this week finished catching up on every episode of every BMN podcast and couldn’t be happier. Despite my background in geology, I think TiPhi is my favorite. I just love the depth and clarity with which you present information at a much higher level than other shows. In fact, TiPhi is the only one I listen to at 1x speed as opposed to 1.5x, just because I don’t want to miss a thing.

Regarding this recent episode, you talk about the Copenhagen supporters reconciling spooky action at a distance by rewriting “nothing travels faster than the speed of light” to “no information travels faster than the speed of light.” I’m curious if there’s any conceivable way for an observer to know when a wave function has been collapsed. My gut says no, because the act of observing the particle sufficiently to detect when its wave function collapses would probably itself collapse the wave function. If I’m wrong and you could know when a wave function collapses, then you could transmit information via spooky action at a distance by having a bunch of “lunchboxes full of apples” and communicate either via morse code (frequency pattern of one person opening lunchboxes) or by some code (e.g. one if by land, two if by sea). Just a fun thought I had that probably ultimately falls short.

Thanks again for the hours (and hours and hours) of entertainment and knowledge!

Great show. Tied my mind grapes in a knot and I love it!

I’m sure you know this, but Hugh Everett (the creator of the “Many Worlds Theory”) is the father of Mark Everett, lead singer of “The Eels.”

I’ve always felt most comfortable with the DeBroglio-Bohm Theory, but that may be because it’s so much more intuitive than many of the other interpretations, in a classical sense (I mean, I don’t know for sure. This field isn’t infer people who like their explanations to be easy and black and white)

I would like to hear a discussion on that. Or is it not taken seriously enough by particle physicists?