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Newbie question about quantum physics

  1. Jun 17, 2015 #1
    So... My question is quite simple. If i took an electron from an atom and put it in th palm of my hand (the electron has absolutely no kinetic or potential energy in this case, its resting), before i close my hand it will be there, but when i close my hand it might not. Am i right?
  2. jcsd
  3. Jun 17, 2015 #2
    It depends on the environment that the electron is in. A chaotic environment like your hand in open air would not necessarily assume the electron is in your hand. You should look up the Heisenberg uncertainty principle, for it is fundamental to quantum mechanics. Quantum mechanics forces us to think of an electron as a cloud of probability, with no single point being the only point that it must be. It COULD be anywhere, but there might be a higher probability being in your hand for some reason (my knowledge ends at this reasoning).
  4. Jun 17, 2015 #3


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    It's not really meaningful to say that the electron has no kinetic or potential energy, but I'll assume that by "no kinetic energy" you mean that the electron isn't moving relative to you, and by "no potential energy" you mean that there's no nearby source of electrical fields strong enough to noticeably affect the behavior of a charged object in your hand.

    And with that said... no, it is not right. I'd guess that you've heard something about how quantum mechanics says that "things are only there if they're observed" or some such, and you're trying to prevent observation by closing your fist? That's not what quantum mechanics says, and if you search this forum for "conscious observer" you'll find a number of threads discussing what it does say.
  5. Jun 17, 2015 #4
    The "hand" is a representation of a perfect environment, i didnt mean it literally.
  6. Jun 17, 2015 #5
    Yes i am starting to study chemistry but i am interested in physics, therefore my understanding of qm is low. So... My question is not literal. If an electron was standing in one place, in space, without any movement relative to anything, will it stay there after it is observed for the second time (considering that the temperature is absolute zero)
  7. Jun 17, 2015 #6
    That is a big "IF"

    QM is just not that way.
  8. Jun 17, 2015 #7
    Yeah i know... I just wondered what it would look like if it was in that state.
  9. Jun 17, 2015 #8
    The thing is all our observations so far are limited to the state we are in and it is impossible for us right now to observe it in an absolute perfect enviroment therefore everything can be put in question. I mean, yes it works, but is it really the way it is? Would it behave the same way in a galaxy and in empty space whereby it wouldnt be affected by conditions that affect us?

    Edit: conditions: speed is one we cant affect on and we know of. But we dont know everything untill we realize how does the universe behave (i mean, cmon, we dont even know how do galaxies hold together and not get ripped appart due to unsufficient force to hold it together). So our observations are quite subjective.

    Edit 2: even speed can have a big influence considering that we are working with something that is extremely small and easly affected. We observe the enviroment we live in, not the world around us. Therefore search for reality is kind of pointless unless we find out does the envoroment have influence on observations.
    Last edited: Jun 17, 2015
  10. Jun 17, 2015 #9
    I'd love to hear opinions on the post above
  11. Jun 17, 2015 #10


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    It's rambling nonsense. Learn some physics properly.
  12. Jun 17, 2015 #11
    Maybe i do not know physics well, but niether you can say that you know everything about the conditions that play part in our existance? Im just kind of more the Einstein type, even though i accept the qm as it is.
  13. Jun 17, 2015 #12
    there is no such state, that's the point.
  14. Jun 17, 2015 #13
    What do you mean by that? I ment it in a way if an electron would find itself inside blank space outside of a galaxy where it isnt affected by gravity or any other force in any manner. Its hypothetical, yes. But it exist, just not achievable by technology we have today. I was wondering would the physics be the same at that state.
  15. Jun 17, 2015 #14

    There is no state where the position of the electron is well determined and the velocity (or momentum) is zero (aka, the momentum is well determined too). That state is just not possible in QM, there is no way of realizing it in laboratory or in the nature.
  16. Jun 17, 2015 #15


    Staff: Mentor

    That's not possible because of the Heisenberg's uncertainty principle it cant handle a well defined momentum (standing means zero momentum) and position (in one place means it has a definite position) at the same time. BTW that's why absolute zero is impossible.

    If you are just starting out I would suggest the following rather that the semi historical approach of most books:

    The usual approach IMHO in many cases leads to confusion.

  17. Jun 17, 2015 #16
    An excellent answer i must say. I thought absolute zero was possible in the scenario, but considering the laws its logical that it isnt, and if it was, my question would make sense. I was thinking on learning QM but currently im busy with german and my studies in pharmacy, but when i find time, i will buy some books to start with!
  18. Jun 17, 2015 #17
    One more thing. When the particle is defying the absolute 0 by its movement, from where does the energy comes from? What is keeping it moving if no artificial interfeering is involved? This is probably a quite easy question but since i have little knowledge in QM... :D
  19. Jun 17, 2015 #18


    Staff: Mentor

    You are falling into a trap of ascribing properties to an unobserved quantum system - you cant do that.

    But as far as movement goes cognate of Newtons first law.

  20. Jun 17, 2015 #19
    Ok. Qm is really confusing. I'll start off from the basics but what really interests me now is what happens when we do not observe it. Thanks for the answers.
  21. Jun 18, 2015 #20


    Staff: Mentor

    That parth leads nowhere. The theory is silent on what happening when not observed.

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