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Observer Big Bang? How come electrons have a wave nowadays?

  1. May 26, 2015 #1
    Hi. From what I've read about the "observer effect" in the two slit experiment, the electron's wave function collapses due to photons altering its momentum. Now, in the beginning of the universe photons couldn't escape the original Big Bang fog until it cleared out, so these should have interacted with "all" electrons in the early universe. Then how come electrons, or any other particle, behave as wave nowadays? Is there some mechanism in which electrons "expand" their wave again?
     
  2. jcsd
  3. May 26, 2015 #2

    atyy

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    Roughly, we don't observe the positions of the electrons very precisely, so they don't "fully collapse".

    More generally, the wave function of an object is not necessarily real, and it is just a tool to calculate the probabilities of what we observe. So whether the wave function has collapsed or not is subjective.
     
  4. May 26, 2015 #3
    Ok, but maybe it collapsed more and more with each strike? With all photons and electrons in such narrow volume of the early universe there should have been a lot of collisions, and the wave feature shouldn't be perceptible nowadays. I can only think the original wave initially had a very large amplitude, but then the universe was very compact at the same time. Maybe the wave was larger than the universe, pushing it outward and causing the inflation?

    But the wave function and its collapse is demonstrated in the screen of the experiment. So the wave is ideal when the electron moves without measurement, and becomes real when measured by the "observer" or the screen. Isn't it?
     
  5. May 26, 2015 #4

    bhobba

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    No.

    Here is a correct analysis of the double slit experiment:
    http://arxiv.org/ftp/quant-ph/papers/0703/0703126.pdf

    This wave particle duality stuff is a myth:
    http://arxiv.org/pdf/quant-ph/0609163.pdf

    Now the myths you have from reading popularisations has been at least challenged, here is its true essence:
    http://www.scottaaronson.com/democritus/lec9.html

    It will take a while to sink in - don't be too worried if it feels funny at first in thinking about QM this way - but once you do issues like yours are seen as non issues.

    Thanks
    Bill
     
    Last edited: May 26, 2015
  6. May 26, 2015 #5
    Thanks, I'll check that!
     
  7. May 27, 2015 #6

    atyy

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    The other electrons are not what collapses the wave function. It is you and your apparatus that collapses the wave function.

    In the double slit, you make a very accurate measurement of the electron's position. You don't do that when you observe the electrons in the sun or other stars.
     
  8. May 27, 2015 #7
    I think the original question is partly based on the idea that when a wave "collapses", it always becomes a "point" or "small lump". This is not always the case -- one wave, on observation, can collapse into another kind of wave and continue to evolve as a wave (e.g. a polarizer collapses the incident light into a wave that is now aligned with the polarizer, and it's still a wave after collapse). The extent of the waviness would remain the same even after many repetitions of this process. Perhaps the only situation where the quantum wave is permanently trapped within a negligible volume, is when it is slurped up by a black hole.

    Of course, there is also another assumption in the original question, i.e. that interaction between two or more particles will surely lead to collapse. This assumption has been dealt with in other replies.
     
    Last edited: May 27, 2015
  9. May 28, 2015 #8

    bhobba

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    One key point here is collapse is only part of some interpretations, not all. We have a number that do not have it, and its certainly not part of the formalism.

    Thanks
    Bill
     
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