Yudkowsky on Physics

An interlocutor recently spoke disdainfully of Eliezer Yudkowsky's writings about Quantum Physics.

The relevant excerpt is:

like the infamous quantum mechanics sequence, that seemed to fail to change anyone's mind with relevant domain knowledge

And I replied:

It's funny that you should mention the quantum mechanics sequence. That was actually my introduction to his thinking.

I did a degree in pure and applied maths, and although I was definitely on the "pure" side, QM was one of the things I'd gone to university to understand, so I took a couple of courses on it.

There's no question that I could do the maths, and I could solve all the examples and exam questions, and my teachers seemed very pleased with how well I took to it.

But it made absolutely no sense to me as a theory of how the universe worked. I don't mean that it was counter-intuitive. Lots of things in probability and physics are counter-intuitive. I just mean that I really didn't understand how to set up the problems, or what it meant to live in a universe which ran on QM. 

Whenever someone took a physical problem and represented it as a piece of quantum mechanical maths, the set-up for the problem just seemed completely ad-hoc. And any attempt to think about how such a universe might support living beings was hopeless. It really seemed to me that observers, and conscious observers at that, were part of the fundamental physics. And that they had to act from outside the physics.

My teachers were very much of the 'shut up and calculate' school. We know it doesn't really make sense, they said, but people have been beating their brains out about this for something like seventy years and no-one's really come up with a way of looking at it that makes intuitive sense. But on the other hand, the calculations do give us a way of predicting the results of lots of otherwise incomprehensible experiments. Your best bet is to push on with doing the calculations and maybe by the time you get to Quantum Field Theory it will have started to feel more normal.

I wouldn't accept that. But I hadn't got anything better, so I eventually just gave up on the subject.

I stayed curious though, and in fact later on I had several conversations with people doing actual PhDs in QM, where it became obvious that they just didn't get it. They had really fundamental misunderstandings of what was happening in simple set-ups like the double-slit experiment.

Which didn't stop them making worthwhile contributions, of course. Euler didn't get a lot of the stuff he worked on, he makes some quite silly errors with complex numbers at times, because he didn't understand what they were. But his intuition and technical skill allowed him to get results that ended up being actually proved very much later. This is quite normal in mathematics, and is probably the real difference between pure and applied maths.

One day someone told me that they'd read an explanation of QM that seemed sane, and that I should take a look at it. They linked to EY's essay on Less Wrong.

And finally I got it. I don't claim to understand how the quantum universe works, or what consciousness is, or anything like that, any more that I would claim that about a classical universe.

But it doesn't seem mystical anymore. I can at least understand the model itself, if not how it relates to physical reality.

The mathematical model that looks like a wave equation represents a 'magic reality fluid' that sloshes around over the space of all the possible configurations of the universe.

There's no collapse, no mysterious observer effects, no physical systems behaving differently depending on who's measuring what and when they're looking at the measurements.

It's all just nice and sane and deterministic and predictable and follows laws.

And I absolutely didn't get that until I read EY's quantum sequence, which is really no more than a particularly well-written explanation of the many-worlds point of view written by an autodidact who'd managed to puzzle out for himself something that I'd been well and professionally taught by renowned experts at a famous university.

A little later I decided to have a go at Umesh Vazirani's Quantum Computation course on Coursera, and it made perfect sense. I could just do it. There wasn't anything funny or baffling going on. I don't think that would have been true if I hadn't read EY's QM essays.

So I don't know if you'd count that as 'changing the mind of someone with relevant domain knowledge', but it certainly seemed important to me.

And I decided that I liked this man and his thinking and his style of writing, and that's why I read the rest of The Sequences.