Brian Cox up the Exclusion Principle

I know a few students of Quantum Mechanics read this blog so here’s a little challenge. View the following video segment featuring Sir Brian of Cox and see if you can spot the deliberate (?) mistake contained therein on the subject of the Pauli Exclusion Principle.

When you’ve made up your mind, you can take a peek at the objection that’s been exercising armchair physicists around the twittersphere, and also a more technical argument supporting Prof. Cox’s interpretation from a university in the Midlands.

UPDATE: 23/2/2012 Meanwhile, over the pond, Sean Carroll is on the case.

21 Responses to “Brian Cox up the Exclusion Principle”

  1. Well, as far as I know, PEP Only applies to a single system.

    In that if you have two discrete systems you could have two electrons in the same state one in each however you couldn’t have two in the same state in the same system.

    However, if you were to assume the universe was just one big box full of atoms you could say that. (Its not, but neither does a nuclei have a continuous number of nucleons 😉 )

    • Yeh. There’s the universe. Which other system were you talking about? 🙂

      Of course, it’s all “imperceptible” and therefore not of much interest to me as an experimentalist. But it seems to me a correct interpretation of QM as it stands.

    • You’re a real physicist when you can differentiate with respect to a discrete variable. And also odd numbers are generally very close to even numbers.

    • Anton Garrett Says:

      I heard of someone who got the correct answer for an integral by differentiating with respect to pi!

      • telescoper Says:

        “Cancelling the d’s” is of course an excellent method for solving differential equations..

  2. The bone I’d pick is just that “quantum state” is not the same as “energy state”, whereas they seem to me conflated in the video, but otherwise isn’t this just the non-locaity of quantum mechanics we all know and love?

    • I think so, yes. Non locality, identical particles, one big system, there you have it. (Quantum state is not the same as energy state, that’s true of course, but at most a minor mis-speak or simplification, & not repeated in the WSJ.)

  3. Ralph Hartley Says:

    The energy levels of every electron in the universe might change “instantly”, but you can’t measure energy instantly, so the universe never gets caught violating causality. Time and energy are just like position and momentum, you can’t measure both exactly. To detect the change in a distant electron, you have to measure its energy extremely accurately, but that means each measurement takes a very long time, and you can’t tell when it changed.

  4. Anton Garrett Says:

    He’s part right, part wrong. I recall a paper showing that the Pauli principle can never be used to communicate between distant fermions. However, Bell experiments show that the universe IS monist at the next ontological level – the so-called hidden variables (even though we see their *effects* when two identically prepared silver atoms go different ways in a Stern-Gerlach apparatus; deny their existence only if you are willing to give up all hope of a theory stating which way the next atom will go – ie of doing what physicists should do).

    I do not intend to level any personal criticism at Brian Cox, but I do regret that the media nowadays choose somebody with his screen persona.

    • So what part of what he said was wrong then? Quantum mechanics as it stands must have non-locality. Hidden variables are necessary if you wish to do away with the non-locality, but non one has found a description with hidden variables yet and I see no compelling reason that they must exist.

      • telescoper Says:

        Hidden variables don’t get you away from the non-locality. Local hidden variable theories definitely don’t work…

      • Entirely the opposite, Sesh. Either you have non-local hidden variables, or you have locality but sacrifice the reality of definite classical states. But the confirmed predictions of quantum mechanics are incompatible with local hidden variables.

      • Cross posted. And Peter beat me to it.

      • Ah, yes, thanks for pointing that out. I suppose I was confused by Anton’s post claiming something Brian Cox said was wrong. Actually I’m still not sure what he was referring to.

      • Anton Garrett Says:

        Yes, I might have been clearer. If you don’t believe in hidden variables then you will say nothing changes anywhere else in the universe when Cox does his thing. And (disappointingly) many physicists take that view.

  5. Pauli quotes: “I know a great deal. I know too much.
    I am a quantum ancient.”

    Pauli had a long association with Carl Jung, and their
    letters were published under title – “atom and archetype” –
    Their conclusions about reality relates to the idea that
    number is the most primal archetype of order in the
    human mind, i.e., pre-existent to consciousness.

    In that vein I share this experience, which was verified
    by senior researchers at Princeton University, as a prime
    example of an “acausal connection.”

    The Big Dream: “I’m in a classroom, where a teacher,
    (a woman) is talking about astronomy. The scene changes
    to a field where two bears are romping and a duck is flying
    overhead.” End….

    This dream is telling us that a star in Ursa Minor, (little dipper)
    has gone supernova. The star is Kochab, an orange giant, some
    126 light-years distant. There is the possibility that the light-energy
    of Kochab as a supernova will appear this year….

    The acausal connection is this: Correctly interpreted with the
    dream symbols converted to number value, it appears as:, which relates to the winning numbers drawn
    in the NY Lottery game, some 12 hours later.

    As Pauli said: “our primary mathematical intuitions can be
    arranged before we become conscious of them.”

    Jung added: “man has need of the word, but in essence,
    number is sacred.”

    These messages have appeared a few times over the years,
    with the first one telling me who is sending them.
    1.7.8….11:31….28.39 Not at all difficult in figuring this out!

    “such is the nature of reality, that anyone can experience that
    which is least understood.” TDL

  6. stringph Says:

    And I thought Brian was an experimental physicist .. i.e. unconcerned with effects which are, either in principle or in practice, completely unmeasurable. It’s the luminiferous ether all over again…

    If you want to tell me that everything in the universe is connected but the connection has no measurable consequence in an overwhelming majority of cases, go ahead, but don’t pretend it’s a statement about physical reality and don’t claim it as a contribution to public understanding of science.

  7. […] a read. My colleagues at Nottingham have also discussed the controversy, and Telescoper asked if Brian had Cox-ed up the explanation of the exclusion […]

  8. […] a read. My colleagues at Nottingham have also discussed the controversy, and Telescoper asked if Brian had Cox-ed up the explanation of the exclusion […]

  9. […] a read. My colleagues at Nottingham have also discussed the controversy, and Telescoper asked if Brian had Cox-ed up the explanation of the exclusion […]

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