Sixty Symbols on Quantum Mechanics

I’m currently working hard to finish a paper on the Everett (Many-Worlds) approach to quantum mechanics, collaborating with Charles (“Chip”) Sebens from the University of Michigan. It’s an area that lies at the intersection of “foundations of quantum mechanics” and “philosophy of physics,” and neither of those is really my expertise — but I’m trying to learn! More when the paper comes out, hopefully quite soon.

Meanwhile, I end up posting a lot of videos rather than really blogging, until the larger crush of work is lifted a bit. While I was in Nottingham I had the pleasure of sitting down to record for their series of Sixty Symbols videos, which is a terrific series that I’m happy to recommend. Here’s me chatting about the different approaches to quantum mechanics.

Forthcoming: me chatting about the Higgs boson, and me chatting about the arrow of time. My time in England involved a lot of chatting, it’s true.

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38 Responses to Sixty Symbols on Quantum Mechanics

  1. Nathan says:

    Hi Sean, sorry if this is the wrong place to bring this up, but the rss feed for this blog doesn’t seem to be loading any stories.

  2. Craig McGillivary says:

    How does the many worlds interpretation handle situations where it isn’t a 50-50 chance. If some observation has a 25% chance do you then get 4 worlds with one of them coming out one way and three coming out the other? What happens if the probability isn’t a rational number?

  3. Gizelle Janine says:

    Craig: In QM, even small probablities have the chance of happening. When talking about how those probablities are distributed, I can’t say. Overall I’d say that’s the closest I can get to explaining that. Wikipedia usually helps. David Albert’s textbook Time and Chance is a good place to start too. Or is it QM and Experence? 🙂

    Sean: I as well experience problems with the RSS feed, for some odd reason it doesn’t update.

  4. David says:

    Carroll I’m eagerly awaiting answers to the issues raised by M. Porter. If someone like yourself feel entitled to mock anti-MWI’ers then you better have an award winning paper which resolves the issues raised by M.Porter aswell as the rest of the preferred basis problem and the Born Rule. And do not simply refer to work by Wallace et al.
    The last time your brought up the decision-theoretic approach to the probability problem you were utterly unable to defend it against criticism by Huw Price and others who has written several papers on the issue…

    You also defended the multiverse interpretation by Susskind and Bousso last year, which is ridiculously different from the “Oxfordian mwi” so it is becoming increasingly obvious that your affection for the everettian interpretation has nothing to do with science or rationality, but is rather the result of your personal fascination with some vague scifi multiverse, but please prove me wrong by solving these problems once and for all.

  5. unifphys says:

    Sean, you said, “If there were no environment then universes would not split.”

    But if the universe as a whole is described by its own wave function, then what is the environment for the universe as a whole that it needs to interact with in order for it to split?

  6. Sean Carroll says:

    You can interpret that as “if it were not possible, for any particular system of interest, to divide the wave function of the universe into that system and an environment.”

  7. David says:

    So… Dodging the actual open problems?

  8. what would Witten do? says:

    Sean, MWI is favored by cosmologists.

    I’m not a cosmologist. It must be admitted, for example, that MWI is wildly–even maximally–unparsimonious.

    I don’t see what’s wrong with just admitting some properties are of the combined system+apparatus. The whole is strictly greater than the sum of the parts. Relational ‘neo-realism’ solves everybody’s problems.

  9. Rhiny D says:

    Dear Sean, Great video’s! I’ve only learned recently of you’re contributions to and opinions on science. My background is not very math heavy, but I do have a Msc. In my never ending quest to try and understand the world, it was one of your video’s (or rather a video with you in it) on QM that made me understand part of QM, that I didn’t before. Of course lot’s of question arose in my mind of which I’ll only ask one. But more importantly, I wanted to thank you for explaining such difficult subjects in an understandable way. Many thanks indeed.

    My question is related to your “no-one ever tells you, but it’s fields” answer. If you have two particles that bump into each other, how would that course of events be (visually) represented in fields?

  10. Eric says:

    Thank you! Excellent video. I will be passing this video on to the kids. It does an excellent job presenting the material. I think they will get more of this than a years worth of high school physics.

  11. Eric says:

    Edit didn’t work. Maybe your site is too popular today.

    I got more out of this than a years worth of high school physics, and it was a good physics class…

  12. zbynek says:

    Hi – sorry I’m quite late at your website and conversation has probably moved on but is it not possible that instead of an infinite amount of cars/universes which split into all the different possibilities you could have only one universe but multiple dimensions of time as in the “back to the future” film series and each of these separate timelines following a different quantum outcome, the splitting then not due to interactions or observations of particles or waves but as in the “normal” progression of time (units) that we perceive along the future (t)-axis also continuous progression (possibly as you describe in GRW) along alternative future (x,y,z…) axes that we cannot perceive, unless possibly at small scales as in the double slit experiment? – it would seem that way you avoid the conundrum of all those infinite superimposed cars as well as having to define what exactley causes the splitting and collapsing