Notices
Results 1 to 29 of 29

Thread: Uncertainty Principle, Schrodinger's cat & the Electrons

  1. #1 Uncertainty Principle, Schrodinger's cat & the Electrons 
    Forum Freshman
    Join Date
    Aug 2010
    Posts
    31
    I've read from a lot of sources regarding Heisenberg Uncertainty Principle. I believe it is somewhat related to Schrodinger's cat.(why is that the assumption is that the cat is both 'alive AND dead', and not 'alive OR dead'?) But I do not understand the 2 theories.
    Could someone explain these to me as well as how electron location cannot be pinpoint. (does this also mean a single electron can be in more than one place at one time?) Why is it that the observation or measurement itself affects an outcome, so that the outcome as such does not exist unless the measurement is made?

    I would really appreciate an answer to these matter. Thank you very much.


    Reply With Quote  
     

  2.  
     

  3. #2  
    Suspended
    Join Date
    Aug 2010
    Posts
    179
    Schroedinger's Cat was a thought experiment which stated that until we observe the cat in the box (either being dead or alive) we do not actually know that its dead or alive. (The Box, in the thought experiment, was previously pumped with toxic gas).

    Hiesenburg's uncertainty principle stated that certain physical properties, like position and momentum or energy and time, cannot simultaneously be known to arbitrary precision. If we know one, we have affected the system and we can not measure the other without the previous measurement now not being true.

    I.e. photons interact wih electrons, so when measuring the position of the electron we change its momentum and hence simaltaneous measurement becomes invalid.


    Reply With Quote  
     

  4. #3  
    Forum Freshman
    Join Date
    Aug 2010
    Posts
    31
    I've read similar explanation to yours but i still dont get it.

    Besides why is it dead AND alive, and not dead OR alive?
    Reply With Quote  
     

  5. #4  
    Moderator Moderator Janus's Avatar
    Join Date
    Jun 2007
    Posts
    2,242
    Quote Originally Posted by mrsmile
    I've read similar explanation to yours but i still dont get it.

    Besides why is it dead AND alive, and not dead OR alive?
    In QM the state of a given particle can be "undetermined" until is is measured or observed. Now this goes deeper than just that "we can't know what it is until we measure it", but actually means that it is actually in neither state until an measurement is made. For instance, a particle has two possible spins, up or down, but until the actual spin is measured, it is has neither spin. It doesn't "decide" which spin value it has until it is measured.

    Schroedinger's Cat was an attempt to expand this concept from the quantum scale to the macroscopic scale. A single particle of a radioactive isotope with a given half-life is set to trigger the escape of a toxic gas in a box containing a cat.

    After the half life of the particle has expired, there is a fifty-fifty chance that the particle has decayed. However, until the particle's state is actually measured, it is just that, only a probability; it is in a state of neither decayed nor not decayed.

    The argument goes, that since the release of the gas and the death of the cat rely on whether or not the particle has decayed, until an actual measurement of the particle's state is made, the fate of the cat is in that same state of in-determinism, neither dead or alive (or some would say in a state of being both at the same time).

    So until someone looks into the box, the cat is neither alive or dead, and only upon the opening of the box, will "decide" which state it is in.

    The main flaw with the experiment is in the idea of what constitutes a "measurement" of the particle's state. Do you actually need an intelligent observer to look into the box before the fate of the cat is resolved? Wouldn't the cat itself count as an observer? What about the device that triggers the release of the gas? In which case, the "decision" as to the fate of the cat could be made before the box is opened.
    "Men are apt to mistake the strength of their feelings for the strength of their argument.
    The heated mind resents the chill touch & relentless scrutiny of logic"-W.E. Gladstone


    Edit/Delete Message
    Reply With Quote  
     

  6. #5  
    Forum Freshman
    Join Date
    Feb 2010
    Posts
    84
    The main flaw with the experiment is in the idea of what constitutes a "measurement" of the particle's state. Do you actually need an intelligent observer to look into the box before the fate of the cat is resolved? Wouldn't the cat itself count as an observer? What about the device that triggers the release of the gas? In which case, the "decision" as to the fate of the cat could be made before the box is opened.
    The issue for me is when does the wave-function collapse into a classical state -- when does that atom actually decay and emit radiation? That is the moment an "observation" is (or can be) made. This pushes the issue back into the micro world and relieves us of needing an Intelligent Observer. But it's possibly an infinite regress and not a real answer to the paradox.
    Reply With Quote  
     

  7. #6  
    Forum Freshman
    Join Date
    Aug 2010
    Posts
    31
    How do the physicist (Schrodinger) know that a particle is not in either state when it is not being observed?
    Reply With Quote  
     

  8. #7  
    Forum Isotope
    Join Date
    Feb 2009
    Location
    Transient
    Posts
    2,914
    It's a philosophical argument, not one from a scientific mindset. The concept is that events don't happen until something observes it as happening/happened. It's not a great way to look at physics unless you plan on misinterpreting it all. The cat is one or the other, not both and not neither. You just don't know yet which it is, and have to find out which it is to be certain. However, the detector already observed the decay, if it happened, and killed the cat, if the atom decayed. The observation was already made long before you open the box, through misinterpretation the whole thought experiment has turned into just another excuse to attempt to make humans out to be more special than they are.
    Wise men speak because they have something to say; Fools, because they have to say something.
    -Plato

    Reply With Quote  
     

  9. #8  
    Forum Freshman
    Join Date
    Aug 2010
    Posts
    31
    But why use a philosophical method of thinking in quantum physics (which is in the field of science)?
    and how did that kind of argument that something is what it is not until it is observed arise?
    and isnt dead and alive seem flawed, isnt the assumption that the cat could be alive OR dead more accurate?
    Reply With Quote  
     

  10. #9 its more then that 
    Suspended
    Join Date
    Aug 2009
    Location
    Israel
    Posts
    272
    Quote Originally Posted by mrsmile
    But why use a philosophical method of thinking in quantum physics (which is in the field of science)?
    and how did that kind of argument that something is what it is not until it is observed arise?
    and isnt dead and alive seem flawed, isnt the assumption that the cat could be alive OR dead more accurate?
    well its more , there movement back and forth many times in the time dimention , so the two option are corect and afect by eachater in the future . thanks
    Reply With Quote  
     

  11. #10  
    Forum Isotope
    Join Date
    Feb 2009
    Location
    Transient
    Posts
    2,914
    Quote Originally Posted by mrsmile
    But why use a philosophical method of thinking in quantum physics (which is in the field of science)?
    and how did that kind of argument that something is what it is not until it is observed arise?
    and isnt dead and alive seem flawed, isnt the assumption that the cat could be alive OR dead more accurate?
    The intended method wasn't philosophical. The interpreted method is. All of your concerns are regarding the concerned method. The point of the thought experiment was to show that uncertainty exists until there is some measurement made, given various circumstances. To show that we can only truly deal in probabilities, and not certainties, based on the given model. That's the point. No absolutes.

    And also, don't pay any attention to Water Nosfim. He's full of BS
    Wise men speak because they have something to say; Fools, because they have to say something.
    -Plato

    Reply With Quote  
     

  12. #11  
    Forum Freshman
    Join Date
    Aug 2010
    Posts
    31
    deleted......
    Reply With Quote  
     

  13. #12  
    Forum Freshman
    Join Date
    Aug 2010
    Posts
    31
    So is this whole thing a postulation and a way to interpret things or has it been proven?

    If we see from probability point of view, isnt it suppose to be dead OR alive, given at AN INSTANTENOUS POINT OF TIME.
    Reply With Quote  
     

  14. #13  
    Suspended
    Join Date
    Aug 2010
    Posts
    179
    The Copenhagen interpretation of quantum mechanics implies that after a while, the cat is simultaneously alive AND dead. Because we dont know if it is alive OR dead.

    Yet, when we look in the box, we see the cat either alive or dead, not both alive and dead
    Reply With Quote  
     

  15. #14  
    Forum Radioactive Isotope MagiMaster's Avatar
    Join Date
    Jul 2006
    Posts
    3,440
    No, the cat is only ever both if we use a very anthropocentric definition of observer. Really, unless you can completely isolate the box from all forms of energy transfer from outside (which would be basically impossible) it's state will collapse to either alive or dead before you open the box. You can understand why this would be by considering that there'd be many ways to determine whether the cat's alive or not without opening the box (sound, air movement, temperature readings, etc.).
    Reply With Quote  
     

  16. #15  
    Time Lord
    Join Date
    Mar 2007
    Posts
    8,035
    Quote Originally Posted by MagiMaster
    No, the cat is only ever both if we use a very anthropocentric definition of observer. Really, unless you can completely isolate the box from all forms of energy transfer from outside (which would be basically impossible) it's state will collapse to either alive or dead before you open the box. You can understand why this would be by considering that there'd be many ways to determine whether the cat's alive or not without opening the box (sound, air movement, temperature readings, etc.).
    It depends how you look at it. Einstein claiming that velocity and time are all relative to the observer isn't a whole lot different from this. The cat's alive/dead state is also just like that: relative to the observer. Relative to another observer, say one located inside the box, the cat has a definite state.
    Reply With Quote  
     

  17. #16  
    Forum Isotope
    Join Date
    Feb 2009
    Location
    Transient
    Posts
    2,914
    Quote Originally Posted by kojax
    Quote Originally Posted by MagiMaster
    No, the cat is only ever both if we use a very anthropocentric definition of observer. Really, unless you can completely isolate the box from all forms of energy transfer from outside (which would be basically impossible) it's state will collapse to either alive or dead before you open the box. You can understand why this would be by considering that there'd be many ways to determine whether the cat's alive or not without opening the box (sound, air movement, temperature readings, etc.).
    It depends how you look at it. Einstein claiming that velocity and time are all relative to the observer isn't a whole lot different from this. The cat's alive/dead state is also just like that: relative to the observer. Relative to another observer, say one located inside the box, the cat has a definite state.
    Yes, but that goes around the workings of the question.
    Wise men speak because they have something to say; Fools, because they have to say something.
    -Plato

    Reply With Quote  
     

  18. #17  
    Forum Freshman
    Join Date
    Jun 2006
    Posts
    94
    My 5 cents worth;
    The uncertainty is lack of knowledge about the state of a system. If a clock
    inside the box was set to stop when the decay was detected, or the gas was
    released, etc., it would prove that the cat had been dead (a certainty) but
    the observer did not know because he hadn't looked.
    The radioactive element either decays or it doesn't. This is not uncertainty
    but unpredictability. Obviously if you can't predict when an event occurs,
    then you must keep checking. If you use a device to detect the event, the
    observer still needs to check the device to become aware of the event. The
    awareness of the event only has meaning to the human observer.

    A simple example of superpostion of states, which is what the cat scenario is
    attempting to demonstrate, is a coin flipped into the air. It would be heads
    and tails while moving, but at rest would be heads or tails (excluding on
    edge). Even though the coin oscillates between h and t, its average state is
    a 50% mixture for each cycle. There is nothing in the behaviour of the cat
    (an alive or dead cycle), or the the radioactive element, that corresponds to
    the coin behaviour.
    Reply With Quote  
     

  19. #18  
    Forum Freshman
    Join Date
    Aug 2010
    Posts
    94
    The Schrodingen wave of a white Schrodingen cat, that is in the left side of a box and also in the right side of a box, mangles a schrodingen wave of a photon.

    So what happens to the photon? About the same as if there where 2 white (reflecting) cats.
    Those 2 cats shoud be white, but semi-transparent.
    Reply With Quote  
     

  20. #19  
    Forum Freshman
    Join Date
    Aug 2010
    Location
    United Kingdom
    Posts
    15
    Schrodinger published the article regarding the Schrodinger's Cat hypothesis as a attack on the Copenhagen Interpretation where the Uncertainty Principle consisted of the basis of the interpreation along with Shrodinger's own Wave Equation. He was highly critical of the interpretation, in particular the Uncertainty Principle, and therefore devised the cat analogy to prove the ridiculousness of the interpretation. Despite failing to lure the scientific community from Heisenberg's Uncertainty Principle, the cat analogy rather sparked another branch of physics and possibly led to the Many Worlds Interpretation.
    Reply With Quote  
     

  21. #20  
    Time Lord
    Join Date
    Mar 2007
    Posts
    8,035
    Quote Originally Posted by Arcane_Mathematician
    Quote Originally Posted by kojax
    Quote Originally Posted by MagiMaster
    No, the cat is only ever both if we use a very anthropocentric definition of observer. Really, unless you can completely isolate the box from all forms of energy transfer from outside (which would be basically impossible) it's state will collapse to either alive or dead before you open the box. You can understand why this would be by considering that there'd be many ways to determine whether the cat's alive or not without opening the box (sound, air movement, temperature readings, etc.).
    It depends how you look at it. Einstein claiming that velocity and time are all relative to the observer isn't a whole lot different from this. The cat's alive/dead state is also just like that: relative to the observer. Relative to another observer, say one located inside the box, the cat has a definite state.
    Yes, but that goes around the workings of the question.
    That's why it is important to ask the right questions. Otherwise whatever answer you get will be meaningless.

    In a sense, Schrodinger's cat is arguing that the observer determines the past at the moment of observation. The only reason it would seem ridiculous to anyone is if they reject reverse-time causality.
    Reply With Quote  
     

  22. #21  
    Forum Professor
    Join Date
    Nov 2009
    Location
    Northumbria UK
    Posts
    1,043
    Today I found a disposable camera that I last used in 2004, without having the film developed. The use by or develop by date printed on the camera is 01/2006. I am going to take it into town today or tomorrow to try and have the film developed. There is an uncertainty here about whether the film will develop or not. My question, is there any serious Physics at play here, or is a Schrodinger`s cat leaping about ? This is a serious question, I suppose I could have phrased it better, but do not know how.
    .
    Reply With Quote  
     

  23. #22 well 
    Suspended
    Join Date
    Aug 2009
    Location
    Israel
    Posts
    272
    Quote Originally Posted by Dave Wilson
    Today I found a disposable camera that I last used in 2004, without having the film developed. The use by or develop by date printed on the camera is 01/2006. I am going to take it into town today or tomorrow to try and have the film developed. There is an uncertainty here about whether the film will develop or not. My question, is there any serious Physics at play here, or is a Schrodinger`s cat leaping about ? This is a serious question, I suppose I could have phrased it better, but do not know how.
    well if you know the future , the uncertainty get small , and it afect Schrodinger`s cat
    . thanks
    Reply With Quote  
     

  24. #23 Re: well 
    Suspended
    Join Date
    Aug 2009
    Location
    Israel
    Posts
    272
    Quote Originally Posted by Water Nosfim
    Quote Originally Posted by Dave Wilson
    Today I found a disposable camera that I last used in 2004, without having the film developed. The use by or develop by date printed on the camera is 01/2006. I am going to take it into town today or tomorrow to try and have the film developed. There is an uncertainty here about whether the film will develop or not. My question, is there any serious Physics at play here, or is a Schrodinger`s cat leaping about ? This is a serious question, I suppose I could have phrased it better, but do not know how.
    well if you know the future , the uncertainty get small , and it afect Schrodinger`s cat
    . thanks
    the future come from many dircation and when you see one you stabiliz on one
    Reply With Quote  
     

  25. #24  
    Forum Radioactive Isotope MagiMaster's Avatar
    Join Date
    Jul 2006
    Posts
    3,440
    Quote Originally Posted by Dave Wilson
    Today I found a disposable camera that I last used in 2004, without having the film developed. The use by or develop by date printed on the camera is 01/2006. I am going to take it into town today or tomorrow to try and have the film developed. There is an uncertainty here about whether the film will develop or not. My question, is there any serious Physics at play here, or is a Schrodinger`s cat leaping about ? This is a serious question, I suppose I could have phrased it better, but do not know how.
    Physics are at play here, but I don't think quantum uncertainty has anything to do with it more than anything else. I think this would fall under chemistry.
    Reply With Quote  
     

  26. #25  
    Forum Professor
    Join Date
    Nov 2009
    Location
    Northumbria UK
    Posts
    1,043
    Water Nosfim and MagiMaster, thank you for your replies.
    .
    Reply With Quote  
     

  27. #26  
    . DrRocket's Avatar
    Join Date
    Aug 2008
    Posts
    5,486
    Quote Originally Posted by MagiMaster
    Quote Originally Posted by Dave Wilson
    Today I found a disposable camera that I last used in 2004, without having the film developed. The use by or develop by date printed on the camera is 01/2006. I am going to take it into town today or tomorrow to try and have the film developed. There is an uncertainty here about whether the film will develop or not. My question, is there any serious Physics at play here, or is a Schrodinger`s cat leaping about ? This is a serious question, I suppose I could have phrased it better, but do not know how.
    Physics are at play here, but I don't think quantum uncertainty has anything to do with it more than anything else. I think this would fall under chemistry.
    Chemistry -- a branch of applied quantum electrodynamics.
    Reply With Quote  
     

  28. #27  
    Forum Professor
    Join Date
    Nov 2009
    Location
    Northumbria UK
    Posts
    1,043
    Dr Rocket,
    It has all become very clear now, I will report back to you on Monday with regard to the developed film. :?
    .
    Reply With Quote  
     

  29. #28  
    Forum Ph.D.
    Join Date
    Dec 2006
    Posts
    963
    Quote Originally Posted by jartsa
    The Schrodingen wave of a white Schrodingen cat, that is in the left side of a box and also in the right side of a box, mangles a schrodingen wave of a photon.

    So what happens to the photon? About the same as if there where 2 white (reflecting) cats.
    Those 2 cats shoud be white, but semi-transparent.
    Could you use simpler language in your posts?
    This would help less gifted individuals to grasp the subtlety of your thinking.
    Reply With Quote  
     

  30. #29  
    Forum Freshman
    Join Date
    Aug 2010
    Posts
    94
    Quote Originally Posted by Halliday
    Quote Originally Posted by jartsa
    The Schrodingen wave of a white Schrodingen cat, that is in the left side of a box and also in the right side of a box, mangles a schrodingen wave of a photon.

    So what happens to the photon? About the same as if there where 2 white (reflecting) cats.
    Those 2 cats shoud be white, but semi-transparent.
    Could you use simpler language in your posts?
    This would help less gifted individuals to grasp the subtlety of your thinking.

    No I could not.


    Is it possible to the un-gifted person to not to understand, instead of misunderstanding?
    Reply With Quote  
     

Bookmarks
Bookmarks
Posting Permissions
  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •