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No 2 electrons can have the same energy state

  1. Dec 22, 2011 #1
    i was watching the Brian Cox 'night with the stars'. He said that no 2 electrons can have the same energy state. Is this correct? i thought they couldn't have the same quantum numbers but can even share the same orbital (thus same energy). I also thought this applied to the same atom only, but he stated it applies to the universe and every time an electron in an atom jumps to a new energy state, actually he just said has more energy, then every electron in the universe has to adjust its energy state, instantly. Can someone put some detail on this as i havent come across this before. The only understanding i have of particles seemingly being able to communicate instantly no matter how far apart they are is in entanglement, but he didnt seem to be suggesting this was the mechanism.
  2. jcsd
  3. Dec 22, 2011 #2


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    No two electrons can occupy the same state, although they are perfectly happy to occupy different states with the same energy.
    I hope he didn't say that, because it's nonsense. In most cases, electron states are localized to a single atom [usually!] and if an electron in atom A becomes excited it has no effect at all on atom B. Certainly not to the atoms on Alpha Centauri.
  4. Dec 22, 2011 #3
    yes he stated every other electron across the universe has to switch its state to ensure no 2 electrons have the same energy state.
  5. Dec 22, 2011 #4


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    That statement is wrong. First, the correct statement is "The (non-relativistic) many-body wave function of interacting electrons must be anti-symmetric." Only with a bunch of approximations (namely, a mean-field model of electronic interactions) this turns into "In a Slater determinant, no two electrons can occupy the same spin-orbital" (from which that "no same states"-statement originates). And *even then*, two electrons can still happily occupy different spin-orbitals with the same energy, as long as they differ in some other quantum number (e.g., spin, spatial symmetry, etc).

    This is not merely a technicality. The "states" (one-particle states, also called "orbitals") this guy is speaking about simply don't exist. They are properties of approximations.
  6. Dec 22, 2011 #5
    Professor Cox had a gratuitous laugh at new-age mysticism. Then, later, he introduced what looked like instantaneous action at a distance without any explanation. Downright spooky. Could the universe somehow be represented by a single huge time-independent wave function? Was Prof. Cox talking about the holographic principle? Should he have mentioned entanglement (as has been suggested above)?
    Prof. Cox did not explain it at all and I think it should therefore have been left out.
  7. Dec 23, 2011 #6
    See also this thread: https://www.physicsforums.com/showthread.php?t=561511 and reply from the man himself (becox).
  8. Dec 23, 2011 #7
    tx didnt see that one.
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