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B Understanding the probability cloud?

  1. Aug 13, 2017 #1
    I understand that the concept of a atom resembling a solar system is disregarded as being untrue because this is based on the Bohr model which doesn't represent how an electron would actually appear in its probability cloud. However, would it be possible that if there were an observer on the electron that From it's observable plane it might orbit on a given plane from its perspective given how bizzare things get at the quantum level?

    From a regular Joe with just a tenuous grasp on the mere basics.
  2. jcsd
  3. Aug 13, 2017 #2


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    Staff: Mentor

    Not possible.

    You threw those words "actually appear" and "perspective" out there, but you need to think a bit more about what they might mean in this context. Macroscopic things have an actual appearance: light reflected from the object forms and image on the retinas of our eyes, a piece of photographic film, the array of photosensors inside a digital camera, whatever we're using to form the image, we look at the image, and we say that that's how the object "appears". But we can't reflect light off of an electron; all we can do is send a photon in the general vicinty of the atom, and every once in a while it comes out a different angle than we went in. Nor can we attach a piece of photographic film or an array of photosensors to the electron to come up with the "perspective" of an observer on the electron.

    So we don't have any sensible notion of "appearance" or "perspective". However, that doesn't mean that things are bizarre at the quantum level, it means that they're different. Let go of the idea that very small things are like the macroscopic objects that surround us, except smaller and harder to study, and then you can start understanding the different but not bizarre rules that govern their behavior.
  4. Aug 13, 2017 #3
    Thanks for the reply Nugatory. I didn't mean to say that we would be the observer of the electron with some instrument. Let's say that an atom does behave like a mini solar system, and on an electron there was an observer. Would he observe the electron as orbiting on a set axis within his observable plane or would he see his "planet" appearing randomly in its probability cloud.
  5. Aug 13, 2017 #4

    We employ frame transformations all the time in particle physics. So we can imagine putting an "observer" on an electron -- or even the electron as the observer of its surroundings. It doesn't matter what frame of reference we use to solve Schrodinger's equation. So the problem I see with the OP's suggestion is not imagining an observer on the electron, but addressing the more interesting question of what an electron, a nucleus, or an atom are and what "orbiting" means in QM. Those are the questions our "regular Joe" needs to look into and he can't do that without studying QM.
  6. Aug 14, 2017 #5


    Staff: Mentor

    QM is a theory about observations that appear here in the macro world. Whats going on in between the theory is silent about. Since ts not part off the macro world what you suggest the theory says nothing.

    This 'cloud' is simply visualization of the calculation of those probabilities from whats called the wave-function. It's part of interpretations what the wave-function means. You can look them up if interested, but personally I wouldn't worry until you have studied some properer QM from a good text.

    Two start with for beginners I like Susskind's books:

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