Heisenberg's Uncertainty Principle
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Well this is a section of the forum named "Education" and this wasn't pre-prepared pop science spoon feeding. These discussions amongst experts are informal and often shed light on how different people perceive differences, they also typically give insights into the history and view held at the time, all of this is an important aspect of science education.
I enjoyed Fay Dowker's explanation (at 6:32) of Heisenberg taking empirical data and using that to define a precise way to predict probabilities and energies. Where he realized that the position of the electron can be represented by a matrix which gives rise to an analog of the old Newtonian laws of motion, I'd never heard it explained this way before and it was interesting to hear of the history of these ideas.
Bragg does a superb job too of asking layman questions, often pushing the guests to explain things in different ways to an audience of intelligent listeners but who are nevertheless not experts in the subject.
OK, that answers my question. Sometimes there are links with no explanations.
Apologies, I can see how that looked now, just a URL, hardly helpful!
Hi,
I do not have time to watch/listen to all that so not sure what their point is.
I have read though that the HU Principle is not what it used to be. It used to be a universal, immutable law, but we have to look at the time frame wherein it was designed. It was designed at an early stage of quantum physics, and things have progressed since then.
Since quantum physics is more basic and general then physics could have been at that time, there could have been properties that were not known then, and apparently there were. Quantum physics experiments can be set up to be exactly the same in every way, and that means statistical results could be extracted. The idea here is that the more experiments you do, the more precise the measurements get, and that's the basis of statistical measurements. This means that if you do the experiment enough times, you can get results that are very precise, and the means you can measure everything about a particle.
I read about this some time ago and don't remember much about it, but I'm sure you can look it up on the web for more details.
No, you can get precise statistical information about a large collection of particles. This has nothing to do with the uncertainty principle.
Maybe you are thinking of the 2012 Nobel Prize awarded to David Wineland and Serge Haroche for their work in using photon traps to make non-destructive measurements of the trapped photons using large atoms.
The technique allows for non-destructive interaction and measurement, something usually not possible because measurement causes decoherence—”wave function collapse”. This is more relevant to Schrödinger than Heisenberg—though it is very important and something that previously seemed impossible.
To the extent it is decoherence that prevents the measurement of both position and momentum (for example) this work may be relevant, but so far as I know, no one has found a way to circumvent Heisenberg’s principle.
This is much more complex than would be elucidated by any intuitive or cursory examination.
It has nothing to do with the uncertainty principle to YOU (sorry to seem so abrupt with this).
This is on the quantum level.
Keep in mind he was back around the late 1920's, a lot has changed since then.
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Hi,
I don't think that is it. The experiments I was talking about have to perform the experiment over and over again.
I'll see if I can find a link but I can't promise anything
Here's a quick quote I found, but I'm not sure if this is what I was talking about though...
QUOTE:
(Phys.org)—If an object traveling through spacetime can loop back in time in a certain way, then its trajectory can allow a pair of its components to be measured with perfect accuracy, violating Heisenberg's uncertainty principle. Feb 19, 2013
END QUOTE.
That's different I'm pretty sure, but maybe interesting too. I haven't checked it out yet though.
I also found this in another article from 2003:
" The new uncertainty relation between measurement error and disturbance is no more just conjecture, but physical law. "
That refers to the imprecise Heisenberg's principle and replaces it with another more clear and accurate mathematical statement (note the work "new").
Unfortunately, that's not the original article I read either which I think I can sort of explain a little. It read like it came from the fact that one of the laws of physics that says that there is no difference between one electron (or some other particles) and another. There is no distinct identity. Taking that to the extreme, an experiment was performed where, basically, they could create the EXACT same experiment as many times as they liked, and it was exact in every possible detail. What they did basically was then measure the two quantities, but only one in each of two experiments (actually more than that), and because the experiments were quantum exact, they could measure both quantities perfectly.
It's sort of like hitting a pool ball into a corner pocket, and measuring the speed, then shoot another one with the same weight and same force into the same pocket and measure the position as it rolls (or maybe the spin). That's of course not the same thing but just an illustration because with objects like these there is bound to be uncontrollable fluctuations, but with particles that have no identity the path and everything about the particles could be made to be exactly the same.
Note when we talk about this stuff we also have to talk about the date.
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I stand by what I said. If you don’t understand it, that is not my problem.
Of course even if you do that you aren’t measuring the two with equal precision at the same time. Which is what Heisenberg says. You are measuring each at different times, and not avoiding the decoherence, just measuring a time-differing twin.
Hi,
I do not think that matters at all, and there still might even be workaround to that.
The reason I do not think it matters is because the reference to 'time' is implicit, which would be because a normal measurement would have to come at the same time, that is, at the same instant, and what you are implying is you would want to see the measurements done at the same instant. That in the normal sense would mean we would need two measuring instruments that are both turned 'on' and ready to go so when that instant came, you would get both measurements at the exact same instant. That's because it would be classically necessary to do that. If a pitcher threw a baseball and we wanted to measure its speed and spin, it would never even dawn on anyone to think of anything but that one measurement instant because there was no such thing yet as throwing it twice to get the two measurements separately, and it would be obvious that we'd have to do it at the same instant because if we delayed the measurement of the spin the ball would have spun a little before that measurement because it would have been done at a different instant.
But just because we do not get them at the same instant with a new experiment does not mean that we did not measure them properly. The key to this experiment is whether or not we would get the same results either way: measuring both properties at the same instant, or measuring them at two different instants yet getting the same exact (in every way) measurements that we would have gotten had we been able to do them both at the same instant.
In other words, if we measured 1 meter per microsecond and a spin of 100 rads per second using the new experiment but could not do that with the old experiment, then if it was possible to do it that way with the old experiment, we would have measured the same thing.
There may be two workarounds even for that problem with having to do it at the same instant though, although I do not think it would be necessary.
The first is, if you could do two experiments one after the other that produce the correct results, then why not do two measurements at the same 'timae' (instant) and then the results would be extracted at the same instant.
The other possibility is possibly going back in time to do the second measurement, which would in theory be the same exact instant.
There are other problems that come up also though. Heisenberg's Uncertainty attempts to explain a problem with measurement based on the perturbation of a fundamental particle. In order to perturb the particle, it has to interact with another particle, and therefore to measure the particle you have to disturb it, and the more you disturb it the better measurement you get of that one parameter. That's no longer true so another formulation had to be made, which isn't really the HU principle anymore, although I see it still being called that in some articles.
There may be nothing wrong with saying it is right anyway though because it is true in so many circumstances. I think it is just a matter of going one more level deeper in theory. It's like we were at level 0 before it was formulated, then went to level 1 when he first formulated it, then later went to level 2 after it was reformulated, then to level 3 when it was reformulated again. Notice I used the word "it" several times when really 'it' was a different thing each time. That's probably because we get stuck with using the same name when the first person to discover something new at the time broke ground for the first time.
I'm not sure what else I can say about this though I am not in a position to go through all the math on this. I can only report what I have read over time.
It's interesting to talk about, but as you said it's hard to prove anything with a casual discussion.
Hi,
Well thank you, but with all due respect, and I say that sincerely, I could say the same thing to you.
This happens because we are doing what Ya'akov suggested: talking casually about a very deep topic.
Some of us are, others are not.
Naw, just what I have for a sense of humor, it does seem from here that things are heating up. But other than that I was just joking. I am following this thread closely because it is of the kind of thing I like to learn. Unfortunately for me I cannot process much of what I read.
