4 ms·

Are people really that confused about the difference between fundamental natural uncertainty, and the measurement problem?

antonvs 9y ago
Are you referring to the first paragraph of the article, or something else? The first paragraph describes the observer effect, not the measurement problem or the uncertainty principle. The observer effect is indeed often confused with the uncertainty principle.
- wadkar 9y ago
  I thought the act of observation was what caused the uncertainty. But it appears to me that you’re saying that may not be the case. Could you please enlighten me? What causes the uncertainty if not the act of measurement (observation?) Do the two terms, observation and measurement have different meaning? Could you please explain me the difference? Thanks much!
  - QAPereo 9y ago
    A really good way to get an intuitive grasp is to spend some time getting a handle on quantum tunneling.
    - wadkar 9y ago
      I do happen to know quantum tunneling a bit. I had the fortune to use a electronic tunnel microscope to observe the surface of gold (Ag) surface. But I can’t seem to “intuitively grasp” it
      - QAPereo 9y ago
        The electron’s wavefunction isn’t localized like the classical “billiard ball” and has a nonzero chance of being on the other side of a barrier. The truth is that it has a nonzero chance of being on the other side of the galaxy, albeit a much lower chance than tunneling across a microscopic barrier. In macroscopic terms, the only way you could pin the thing down is by stopping it cold (in microscopic terms, you’d detect it by interacting with it, a la a photon detector). This isn’t just a matter of equipment you use to detect the electron, or photon, or anything with an apparent de Broglie wavelength. It really is a matter of the electron existing with some level of uncertainty regarding correlated variables like position and momentum. Mind you At high energy’s macroscopic objects will display characteristic wavelength, and be obviously subject to the same uncertainty. It’s just that in our universe, in our lives, we live at very large scales and low energies compared to an electron.
  - marcosdumay 9y ago
    Fundamental uncertainty is indeed caused by different observations "interfering with each other. And that interference is only inevitable because of the observer effect. It's kind of meaningless to claim that observation is the cause of the uncertainty, but I do think you are on the right path. Still, even being related, the observer effect and the fundamental uncertainty are different concepts. For example, observations may not interfere at all, but they would still change your system.
    - wadkar 9y ago
      Err, I must confess this is confusing to me. On one hand the GP stated that observation and the “inference” or the uncertainty are two different phenomena. But you seem to suggest otherwise. Did I get something wrong here?
      - marcosdumay 9y ago
        They are different, but related. Observation effect is: when you observe a characteristic of an object, you change that object on a way that what you observed (that was one of some possibilities) is now the only possibility. Uncertainty is: there are some characteristics that when you observe one of them, you change the others invalidating any previous measurement.
        QAPereo 9y ago
        Uncertainty doesn’t require observation, you may be thinking of perturbation?
    - akvadrako 9y ago
      Fundamental uncertainty has nothing to do with observations - it's inherit in the physical/mathematical representation of a state as explained by the comment above yours.
      - marcosdumay 9y ago
        Hum... Uncertainty is not about states, it is about observables. It is a characteristic of the Universe that you can't measure momentum and position with perfect accuracy, it does not matter what state the stuff you are measuring is in. And it happens because observing momentum messes with the objects position, and the other way around.
  - hackinthebochs 9y ago
    The physics is really a distraction when it comes to understanding the origin of the uncertainty principle. The uncertainty principle in physics is really due to the mathematics of whats called conjugate variables. Consider a particle moving through space. You observe the point particle at some instantaneous time. Since you've only observed one instance in time, the frequency content of the path the particle carves out could be anything. That is to say, the observed position is consistent with all possible frequencies so you can't rule anything out yet. As you expand the time window of your observation, the set of possible corresponding frequencies shrinks. The longer you observe, the more you can hone in on the frequency of the particle. It's like how astronomers have to observe an asteroid over a long period of time to be certain of its trajectory. But what if you asked where exactly the frequency f of the particle occurred? At what point was the frequency exactly f? The problem is you needed to observe the particle over a period of time to confidently determine the frequency f, and so you no longer can give a precise location of where f occurred. Frequency and position are conjugate variables: as you learn one more precisely, you necessarily lose precision in your knowledge of the other one.
    - emerged 9y ago
      This was by far the most concise and easily understood description of the uncertainty principle I've heard.
wadkar 9y ago
Could you please explain what you mean by “fundamental natural uncertainty”? Why is it (i.e. uncertainty) fundamental? What makes it natural? Can we not observe it in an artificial (i.e. not natural) setting? Thanks!
- QAPereo 9y ago
  I mean that the uncertainty in complementary variables such as position and momentum exists with or without the act of observation, or measurement. We can certainly observe it in an artificial setting, but it’s also the reason that the sun “burns” nuclear fuel the way it does.
  - wadkar 9y ago
    Wow, that sounds very profound - whether we observe (measure?) or not the uncertainty will be there. I must admit I couldn’t understand the connection with the sun burning up the fuel. Perhaps you could elaborate on it a bit more?
    - QAPereo 9y ago
      Happily! The sun lacks the necessary mass to burn using the nuclear reaction it uses (CNO), and quantum tunneling is the answer to how it burns. For a brief discussion on the reasons why: https://www.physicsforums.com/threads/quantum-tunneling-in-the-sun.703818/ https://www.physicsforums.com/threads/quantum-tunneling-in-t... For more depth: http://earthweb.ess.washington.edu/ess-102/FALL12/Lecture14_NuclearFusion.pdf http://earthweb.ess.washington.edu/ess-102/FALL12/Lecture14_... For the technical end of it: http://www.astro.princeton.edu/~gk/A403/fusion.pdf http://www.astro.princeton.edu/~gk/A403/fusion.pdf
  - dboreham 9y ago
    Also the reason various semiconductor devices work (and sometimes don’t work).
carterehsmith 9y ago
I must admit that I am one of those confused people. And this (from Wikipedia) is not helping: "Heisenberg utilized such an observer effect at the quantum level (see below) as a physical "explanation" of quantum uncertainty. It has since become clearer, however, that the uncertainty principle is inherent in the properties of all wave-like systems,[8] and that it arises in quantum mechanics simply due to the matter wave nature of all quantum objects." So... yeah, lay people (ie me) get really confused. Heisenberg said, that that was because of this, but then, it became "clearer" that it was not because of this, but because of that. So yeah if it was because of "that", how about we remove that Heisenberg interpretation from Wikipedia (except as a historical footnote) because it is not considered appropriate or clear enough anymore.
- QAPereo 9y ago
  To be fair, you have it exactly right. He had hypothesis which turned out to be incorrect, or at the very least not the whole story, and the story is weird and hard to believe. The truth is it’s taken a long time and a lot of testing Tom produce the current admittedly imperfect understanding of quantum mechanics. It is the wave-like nature (part of a dual nature) of everything (although for atoms and larger things they need to be very energetic to display that wavelength) which leads to the weird behavior our species has spent the last century coming to grips with.

antonvs 9y ago

Are you referring to the first paragraph of the article, or something else? The first paragraph describes the observer effect, not the measurement problem or the uncertainty principle. The observer effect is indeed often confused with the uncertainty principle.

wadkar 9y ago
I thought the act of observation was what caused the uncertainty. But it appears to me that you’re saying that may not be the case. Could you please enlighten me? What causes the uncertainty if not the act of measurement (observation?) Do the two terms, observation and measurement have different meaning? Could you please explain me the difference? Thanks much!
- QAPereo 9y ago
  A really good way to get an intuitive grasp is to spend some time getting a handle on quantum tunneling.
  - wadkar 9y ago
    I do happen to know quantum tunneling a bit. I had the fortune to use a electronic tunnel microscope to observe the surface of gold (Ag) surface. But I can’t seem to “intuitively grasp” it
    - QAPereo 9y ago
      The electron’s wavefunction isn’t localized like the classical “billiard ball” and has a nonzero chance of being on the other side of a barrier. The truth is that it has a nonzero chance of being on the other side of the galaxy, albeit a much lower chance than tunneling across a microscopic barrier. In macroscopic terms, the only way you could pin the thing down is by stopping it cold (in microscopic terms, you’d detect it by interacting with it, a la a photon detector). This isn’t just a matter of equipment you use to detect the electron, or photon, or anything with an apparent de Broglie wavelength. It really is a matter of the electron existing with some level of uncertainty regarding correlated variables like position and momentum. Mind you At high energy’s macroscopic objects will display characteristic wavelength, and be obviously subject to the same uncertainty. It’s just that in our universe, in our lives, we live at very large scales and low energies compared to an electron.
- marcosdumay 9y ago
  Fundamental uncertainty is indeed caused by different observations "interfering with each other. And that interference is only inevitable because of the observer effect. It's kind of meaningless to claim that observation is the cause of the uncertainty, but I do think you are on the right path. Still, even being related, the observer effect and the fundamental uncertainty are different concepts. For example, observations may not interfere at all, but they would still change your system.
  - wadkar 9y ago
    Err, I must confess this is confusing to me. On one hand the GP stated that observation and the “inference” or the uncertainty are two different phenomena. But you seem to suggest otherwise. Did I get something wrong here?
    - marcosdumay 9y ago
      They are different, but related. Observation effect is: when you observe a characteristic of an object, you change that object on a way that what you observed (that was one of some possibilities) is now the only possibility. Uncertainty is: there are some characteristics that when you observe one of them, you change the others invalidating any previous measurement.
      - QAPereo 9y ago
        Uncertainty doesn’t require observation, you may be thinking of perturbation?
  - akvadrako 9y ago
    Fundamental uncertainty has nothing to do with observations - it's inherit in the physical/mathematical representation of a state as explained by the comment above yours.
    - marcosdumay 9y ago
      Hum... Uncertainty is not about states, it is about observables. It is a characteristic of the Universe that you can't measure momentum and position with perfect accuracy, it does not matter what state the stuff you are measuring is in. And it happens because observing momentum messes with the objects position, and the other way around.
- hackinthebochs 9y ago
  The physics is really a distraction when it comes to understanding the origin of the uncertainty principle. The uncertainty principle in physics is really due to the mathematics of whats called conjugate variables. Consider a particle moving through space. You observe the point particle at some instantaneous time. Since you've only observed one instance in time, the frequency content of the path the particle carves out could be anything. That is to say, the observed position is consistent with all possible frequencies so you can't rule anything out yet. As you expand the time window of your observation, the set of possible corresponding frequencies shrinks. The longer you observe, the more you can hone in on the frequency of the particle. It's like how astronomers have to observe an asteroid over a long period of time to be certain of its trajectory. But what if you asked where exactly the frequency f of the particle occurred? At what point was the frequency exactly f? The problem is you needed to observe the particle over a period of time to confidently determine the frequency f, and so you no longer can give a precise location of where f occurred. Frequency and position are conjugate variables: as you learn one more precisely, you necessarily lose precision in your knowledge of the other one.
  - emerged 9y ago
    This was by far the most concise and easily understood description of the uncertainty principle I've heard.

wadkar 9y ago

Could you please explain what you mean by “fundamental natural uncertainty”? Why is it (i.e. uncertainty) fundamental? What makes it natural? Can we not observe it in an artificial (i.e. not natural) setting? Thanks!

QAPereo 9y ago
I mean that the uncertainty in complementary variables such as position and momentum exists with or without the act of observation, or measurement. We can certainly observe it in an artificial setting, but it’s also the reason that the sun “burns” nuclear fuel the way it does.
- wadkar 9y ago
  Wow, that sounds very profound - whether we observe (measure?) or not the uncertainty will be there. I must admit I couldn’t understand the connection with the sun burning up the fuel. Perhaps you could elaborate on it a bit more?
  - QAPereo 9y ago
    Happily! The sun lacks the necessary mass to burn using the nuclear reaction it uses (CNO), and quantum tunneling is the answer to how it burns. For a brief discussion on the reasons why: https://www.physicsforums.com/threads/quantum-tunneling-in-the-sun.703818/ https://www.physicsforums.com/threads/quantum-tunneling-in-t... For more depth: http://earthweb.ess.washington.edu/ess-102/FALL12/Lecture14_NuclearFusion.pdf http://earthweb.ess.washington.edu/ess-102/FALL12/Lecture14_... For the technical end of it: http://www.astro.princeton.edu/~gk/A403/fusion.pdf http://www.astro.princeton.edu/~gk/A403/fusion.pdf
- dboreham 9y ago
  Also the reason various semiconductor devices work (and sometimes don’t work).

carterehsmith 9y ago

I must admit that I am one of those confused people. And this (from Wikipedia) is not helping: "Heisenberg utilized such an observer effect at the quantum level (see below) as a physical "explanation" of quantum uncertainty. It has since become clearer, however, that the uncertainty principle is inherent in the properties of all wave-like systems,[8] and that it arises in quantum mechanics simply due to the matter wave nature of all quantum objects." So... yeah, lay people (ie me) get really confused. Heisenberg said, that that was because of this, but then, it became "clearer" that it was not because of this, but because of that. So yeah if it was because of "that", how about we remove that Heisenberg interpretation from Wikipedia (except as a historical footnote) because it is not considered appropriate or clear enough anymore.

QAPereo 9y ago
To be fair, you have it exactly right. He had hypothesis which turned out to be incorrect, or at the very least not the whole story, and the story is weird and hard to believe. The truth is it’s taken a long time and a lot of testing Tom produce the current admittedly imperfect understanding of quantum mechanics. It is the wave-like nature (part of a dual nature) of everything (although for atoms and larger things they need to be very energetic to display that wavelength) which leads to the weird behavior our species has spent the last century coming to grips with.