355 | Solo: Looking Quantum Mechanics in the Eyeball
episode
Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
1h 44m
2 speakers
8 chapters
transcribed 2 months ago
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Transcript generated automatically by AI and may contain errors.
What are the main obstacles to understanding quantum mechanics?
Hello, everyone, and welcome to the Mindscape Podcast. I'm your host, Sean Carroll. You might remember about a year ago, we had a podcast episode with Niesh Afshordi and Phil Halper. Now, Niesh is a well-known, respectable working cosmologist at Perimeter Institute, and Phil is a science communicator who makes YouTube videos trying to explain ideas in physics and so forth. And he's a And the two of them, the reason we had them on the podcast is because they had a book out, Battle of the Big Bang, which was in part based on surveys they did rather than trying to push their own view of what happened at the Big Bang. They surveyed all sorts of scientists, all sorts of physicists, and came up with a sort of way of thinking about all the possible methods that people have proposed to understand what happened at the Big Bang.
Now, more recently, in the last few weeks, I guess, Phil and Niesh have come out with another survey result. They were asked by the American Physical Society, and they teamed up with some other people to survey physicists on a whole bunch of questions that can be considered not yet settled. Let's put them that way. You know, you want to say controversial or whatever, but science always has controversies. It's not like some flaw in the system. Everything we understand is put in the bucket of things we understand, and everything we don't, which is what is interesting and we talk about, is somehow controversial. So they were asking physicists about all these big questions, like what is making the universe accelerate?
What happened at the Big Bang? Of course, they're going to ask them about interpretations of quantum mechanics, right? That's one of the most famous unsolved issues in quantum mechanics. And if you've hung around these sorts of surveys long enough, this is certainly not the first one of its kind, you'll not be surprised to hear that among physicists, the Copenhagen interpretation gets more votes than any other interpretation. It doesn't get the most votes. It's about a third of the people surveyed, but all the others are split. I think in second place was Many Worlds, but there's a whole bunch of support for other possibilities. Now, if you read in the survey, what do you mean by the Copenhagen interpretation?
They define it as an object's behavior is described by a multi-state wave function which collapses to one state when an object is measured. I kind of don't agree with that way of stating what Copenhagen says. I do think, however, it's fine for the survey in the sense that most of the physicists who said yes to that particular option for the interpretations of quantum mechanics probably had something like that in mind. The problem with that, of course, is that it's hilariously ill-defined. It's not a good scientific theory. It's not even a scientific theory. Not because it's wrong. There are plenty of scientific theories that are wrong but are still scientific theories. It's just not defined. Right there in the definition, in the attempt the definition, you say that the state collapses to one state when an object is measured.
You don't say what it means for an object to be measured, and no one in the Copenhagen world has ever said that. Some of them have tried to say things like decoherence, etc., etc., but that doesn't tell you when this wave function is supposed to collapse. Now, the reason I bring this up is because There are people who are serious about the foundations of quantum mechanics and still lean in the direction of something like the Copenhagen Interpretation. So it's possible to take it seriously and really think it through. I just don't think that most physicists have. If you do, you end up going down the road of people like Niels Bohr and Werner Heisenberg and John Wheeler who deny the reality. of the wave function and go so far as to say that they deny reality entirely until you have a measurement outcome that is a very very philosophically radical view to take and i suspect that most of the people in the physics survey who said that their copenhagenists don't actually have that view themselves but mostly because they haven't thought about it very carefully
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Chapters
8 chapters
1
What are the main obstacles to understanding quantum mechanics?
0:00–10:30
2
How do physicists interpret the Copenhagen interpretation?
10:30–36:13
3
What is the Everettian version of quantum mechanics?
36:13–47:12
4
How does the wave function relate to reality?
47:12–53:54
5
What challenges does Everettian quantum mechanics face?
53:54–1:00:18
6
How can we define subsystems in Hilbert space?
1:00:18–1:05:50
7
What role does locality play in quantum mechanics?
1:05:50–1:20:24
8
How do we carve Hilbert space at its joints?
1:20:24–1:44:00
Speakers
2 identifiedMore from Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas
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364 | Stuart Firestein on How Science Relies on Ignorance and Failure
363 | Chandra Sripada on How LLMs and Humans are Cognitive Cousins
Mindscape Ask Me Anything, Sean Carroll | August 2026