# Uncertain about Heisenberg's Principle **URL:** \ **Category:** Factual Questions\ **Created:** [November 1, 2017, 1:41am UTC](https://boards.straightdope.com/t/uncertain-about-heisenbergs-principle/800354 "2017-11-01T01:41:05Z")\ **Posts on this page:** 16\ **Page:** 2
**Author:** ![CurtC](https://avatars.discourse-cdn.com/v4/letter/c/ce73a5/32.png) [@CurtC](https://boards.straightdope.com/u/CurtC)\ **Post date:** [November 2, 2017, 2:19pm UTC](https://boards.straightdope.com/t/uncertain-about-heisenbergs-principle/800354/21 "2017-11-02T14:19:20Z")
> [@DSYoungEsq](#): > > Oh, please, that’s like saying that, if no one sees it, the tree doesn’t fall. I’m not sure if this was just for humor, but someone please correct me if I’m wrong. The different views are: Person A: Because of fundamental measurement uncertainties, we can never measure the momentum and the position of a particle together with arbitrary precision. Person B: It’s more than that - the uncertainty is a feature of the physics. Nature itself doesn’t know these properties beyond that precision. Me: Those two ideas are actually the same thing. If there’s no way for us to observe, even in principle, with arbitrary precision, then how is that different from saying that those quanties don’t actually exist? ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [November 2, 2017, 2:32pm UTC](https://boards.straightdope.com/t/uncertain-about-heisenbergs-principle/800354/22 "2017-11-02T14:32:52Z")
It may seem like a distinction without a difference, but believe it or not, it actually is possible to tell, using things like Bell’s Inequality. And the experiments on that do in fact show that the quantities really don’t exist, rather than existing and just being unobservable. ---
**Author:** ![Pantastic](https://avatars.discourse-cdn.com/v4/letter/p/3bc359/32.png) [@Pantastic](https://boards.straightdope.com/u/Pantastic)\ **Post date:** [November 2, 2017, 4:12pm UTC](https://boards.straightdope.com/t/uncertain-about-heisenbergs-principle/800354/23 "2017-11-02T16:12:27Z")
> [@CurtC](#): > > Me: Those two ideas are actually the same thing. If there’s no way for us to observe, even in principle, with arbitrary precision, then how is that different from saying that those quanties don’t actually exist? Position A says that there are hidden variables, it’s just practically impossible to observe both the position and momentum, position B says that there aren’t hidden variables, you don’t actually have an exact position and momentum. It’s different because in case A these things exist and so affect how the world word, but we just can’t measure both, while in B they don’t actually exist and the world works without them existing. If you want a more detailed explanation, you’ll want to read on Bell’s theorem: [Bell's theorem - Wikipedia](https://en.wikipedia.org/wiki/Bell%27s_theorem) All of the experiments that have been done are with person B and not person A: > **[Bell test](https://en.wikipedia.org/wiki/Bell_test_experiments)** > > A Bell test, also known as Bell inequality test or Bell experiment, is a real-world physics experiment designed to test the theory of quantum mechanics in relation to Albert Einstein's concept of local realism. Named for John Stewart Bell, the experiments test whether or not the real world satisfies local realism, which requires the presence of some additional local variables (called "hidden" because they are not a feature of quantum theory) to explain the behavior of particles like photons and e... ---
**Author:** ![allotrope](https://avatars.discourse-cdn.com/v4/letter/a/edb3f5/32.png) [@allotrope](https://boards.straightdope.com/u/allotrope)\ **Post date:** [November 8, 2017, 9:34pm UTC](https://boards.straightdope.com/t/uncertain-about-heisenbergs-principle/800354/24 "2017-11-08T21:34:35Z")
Would quantum tunneling be an example of the uncertainty principle in action? A particle disappears from one side of an energy barrier and reappears on the other side without having traversed the distance in between. Isn’t that possible because the particle’s position only exists in a stochastic sense. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [November 8, 2017, 10:24pm UTC](https://boards.straightdope.com/t/uncertain-about-heisenbergs-principle/800354/25 "2017-11-08T22:24:34Z")
It’s vaguely related, I suppose, in that both are consequences of particles being waves. But it’s not as simple as you describe: For instance, the difficulty of tunneling depends on just how high the energy barrier is between the two states, which wouldn’t be the case if it were purely a result of the uncertainty in position. ---
**Author:** ![Trinopus](https://avatars.discourse-cdn.com/v4/letter/t/2bfe46/32.png) [@Trinopus](https://boards.straightdope.com/u/Trinopus)\ **Post date:** [November 8, 2017, 11:20pm UTC](https://boards.straightdope.com/t/uncertain-about-heisenbergs-principle/800354/26 "2017-11-08T23:20:43Z")
> [@Chronos](#): > > . . . For instance, the difficulty of tunneling depends on just how high the energy barrier is between the two states . . . Just double-checking, is this correct? Back in my old college physics class, we did tunneling math, and it only depended on the distance, i.e., how wide the barrier was. We never made any calculations based on the height of the barrier, or the depth of the “potential well.” Were we, maybe, just using a simplified model? ---
**Author:** ![Leo\_Bloom](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leo_bloom/32/10377_2.png) [@Leo\_Bloom](https://boards.straightdope.com/u/Leo_Bloom)\ **Post date:** [November 9, 2017, 4:59pm UTC](https://boards.straightdope.com/t/uncertain-about-heisenbergs-principle/800354/27 "2017-11-09T16:59:20Z")
> [@Senegoid](#): > > … > … HUP states that such a particle really truly doesn’t have both a precise position and a precise location all at once. This comment (and it surrounding context), is, thanks to the eternal vigilance of the physicists in SD, probably on a cut-and-paste by now. An interesting question is _why_ most people, when they want to bust their brains, always prefer The Weak Heisenberg Corollary–as I am terming it now, awaiting better suggestions–of the measurement of “things.” Even in the continuing words of the **Senegoid** cite right here is where the bile begins to rise in the throat of normal humans [heh], so to speak: > [@](#): > > The more precisely you measure one, the less precisely the other measure even exists at all. . Well, you, **Senegoid** , just said that something about that “one”–or even using a demonstrative “that,” so something “is”; but you just said “it is not” (has no existence in space and time; we haven’t mentioned statistics/Einsteinein games). And even more: But at the same time the sentence continues and you _are_ talking about “measurement”–and even in good old-fashioned ways of one measurement being better than the other–“hey, just like what I (the Weak Heisenberg Corollary-er) just said!” “It [meaning somehow is an “is”/exists] is not [non-exists]” is a paradox, which has been examined by logicians and language philosophers and since the Greeks as a phenomenon of these things sentences and (other) symbolics. But never physicists. Physicists, like Bill Clinton, have redefined what “is” is; or, better put, have found that our whole kablooey has “is”'s that are chancy, but no less real. And and yes, they are perfectly happy recipients of demonstrative adjectives and to “be in” the company of the usual “is”'s ---
**Author:** ![Leo\_Bloom](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leo_bloom/32/10377_2.png) [@Leo\_Bloom](https://boards.straightdope.com/u/Leo_Bloom)\ **Post date:** [November 9, 2017, 5:06pm UTC](https://boards.straightdope.com/t/uncertain-about-heisenbergs-principle/800354/28 "2017-11-09T17:06:46Z")
> [@Blue\_Blistering\_Barnacle](#): > > Well, through the roof of a mouse’s dollhouse. This is either very funny or very mean. Does the mouse keep a cat? ---
**Author:** ![Leo\_Bloom](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leo_bloom/32/10377_2.png) [@Leo\_Bloom](https://boards.straightdope.com/u/Leo_Bloom)\ **Post date:** [November 9, 2017, 5:12pm UTC](https://boards.straightdope.com/t/uncertain-about-heisenbergs-principle/800354/29 "2017-11-09T17:12:09Z")
> [@DSYoungEsq](#): > > Oh, please, that’s like saying that, if no one sees it, the tree doesn’t fall. I would submit, in another context beloved in this forum, that no one sees the last digit in one realm of of numeric representation, yet accepts that “the tree” 1/3 _does_ exist _just as firmly_ in its realm, despite the unfortunate presence of the unseeable 0.333333… ETA: For the record, it’s hear. ---
**Author:** ![Senegoid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/senegoid/32/6606_2.png) [@Senegoid](https://boards.straightdope.com/u/Senegoid)\ **Post date:** [November 9, 2017, 5:52pm UTC](https://boards.straightdope.com/t/uncertain-about-heisenbergs-principle/800354/30 "2017-11-09T17:52:12Z")
You just gotta accept and understand the fundamental nature of Quantum Anything, which as I stated, is: > [@Senegoid](#): > > Yeah, that’s weird. Quantum physics is weird. Get used to it. ETA: **kunilou** himself, by the very thread title of the OP, shows that he gets it. ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [November 9, 2017, 9:55pm UTC](https://boards.straightdope.com/t/uncertain-about-heisenbergs-principle/800354/31 "2017-11-09T21:55:18Z")
> [@Senegoid](#): > > Quantum physics is weird. Get used to it. Yup. Even when we get really clever and think we can find a way around the Uncertainty Principle mother nature already has her bases covered. Imagine if you cooled a particle to very nearly absolute zero. We could know the position and velocity of the particle with great precision (you can never actually reach absolute zero but we can get very, very close). The lower the temperature the less velocity the particle has by definition and if it is not moving its position is known with precision as well. Turns out when they tried this something called a [Bose-Einstein Condensate](https://www.livescience.com/54667-bose-einstein-condensate.html) formed. Basically the particle sort of smeared itself out. Since its velocity was low it needed another way to stay within the HUP so it got…fuzzy for lack of a better word so we could not say where in the fuzziness it was consistent with the HUP. ---
**Author:** ![Leo\_Bloom](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leo_bloom/32/10377_2.png) [@Leo\_Bloom](https://boards.straightdope.com/u/Leo_Bloom)\ **Post date:** [November 9, 2017, 10:07pm UTC](https://boards.straightdope.com/t/uncertain-about-heisenbergs-principle/800354/32 "2017-11-09T22:07:38Z")
> [@Whack-a-Mole](#): > > Yup. > … Username/thread topic alert…sort of. 🙂 ---
**Author:** ![g8rguy](https://avatars.discourse-cdn.com/v4/letter/g/7cd45c/32.png) [@g8rguy](https://boards.straightdope.com/u/g8rguy)\ **Post date:** [November 10, 2017, 3:26am UTC](https://boards.straightdope.com/t/uncertain-about-heisenbergs-principle/800354/33 "2017-11-10T03:26:31Z")
I don’t mean to be too pedantic, **Whack** , but I don’t think that’s quite right. Which is not to say that’s not on the right track. A BEC just means that the vast majority of the particles in a system occupy the same state (see [wikipedia](https://en.wikipedia.org/wiki/Bose%E2%80%93Einstein_condensate), for example: “Under such conditions, a large fraction of bosons occupy the lowest quantum state”). It’s not terribly meaningful to speak of a BEC with a single particle. But even if you have only a single particle (and hence no BEC), you can’t simultaneously determine position and momentum with arbitrary precision. This may be easiest to understand in terms of [zero-point motion](https://en.wikipedia.org/wiki/Zero-point_energy#The_uncertainty_principle) (which is, of course, a consequence of the uncertainty principle). The point I’m getting at is that while not every very cold thing is a BEC, every very cold thing does have zero-point motion. So it’s probably better to use zero-point motion to explain how one can’t just freeze something down to near absolute zero and thereby observe well-defined positions and momenta. ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [November 10, 2017, 3:37am UTC](https://boards.straightdope.com/t/uncertain-about-heisenbergs-principle/800354/34 "2017-11-10T03:37:27Z")
> [@g8rguy](#): > > I don’t mean to be too pedantic, **Whack** , but I don’t think that’s quite right. Which is not to say that’s not on the right track. > > A BEC just means that the vast majority of the particles in a system occupy the same state (see [wikipedia](https://en.wikipedia.org/wiki/Bose%E2%80%93Einstein_condensate), for example: “Under such conditions, a large fraction of bosons occupy the lowest quantum state”). It’s not terribly meaningful to speak of a BEC with a single particle. But even if you have only a single particle (and hence no BEC), you can’t simultaneously determine position and momentum with arbitrary precision. This may be easiest to understand in terms of [zero-point motion](https://en.wikipedia.org/wiki/Zero-point_energy#The_uncertainty_principle) (which is, of course, a consequence of the uncertainty principle). > > The point I’m getting at is that while not every very cold thing is a BEC, every very cold thing does have zero-point motion. So it’s probably better to use zero-point motion to explain how one can’t just freeze something down to near absolute zero and thereby observe well-defined positions and momenta. Thanks…I’ll have to read up on it more it seems. Interesting stuff. ---
**Author:** ![Trinopus](https://avatars.discourse-cdn.com/v4/letter/t/2bfe46/32.png) [@Trinopus](https://boards.straightdope.com/u/Trinopus)\ **Post date:** [November 10, 2017, 5:25pm UTC](https://boards.straightdope.com/t/uncertain-about-heisenbergs-principle/800354/35 "2017-11-10T17:25:20Z")
> [@g8rguy](#): > > . . . The point I’m getting at is that while not every very cold thing is a BEC, every very cold thing does have zero-point motion. So it’s probably better to use zero-point motion to explain how one can’t just freeze something down to near absolute zero and thereby observe well-defined positions and momenta. Back in my college days, I was taught this was why helium stayed liquid, even at temperatures where it “ought” to freeze solid. If it were solid, its momentum would be too-well defined. True…or dumb stuff my old prof mistaught me? (Or I mislearned.) ---
**Author:** ![ftg](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ftg/32/2801_2.png) [@ftg](https://boards.straightdope.com/u/ftg)\ **Post date:** [November 10, 2017, 10:02pm UTC](https://boards.straightdope.com/t/uncertain-about-heisenbergs-principle/800354/36 "2017-11-10T22:02:36Z")
> [@Trinopus](#): > > Back in my college days, I was taught this was why helium stayed liquid, even at temperatures where it “ought” to freeze solid. If it were solid, its momentum would be too-well defined. > > True…or dumb stuff my old prof mistaught me? (Or I mislearned.) You likely misremember. Nothing special about He turning solid (other than being very, very difficult due to being a tiny noble gas). Absolute zero and the Uncertainty Principle do apply. As long as you take an old fashioned view of absolute zero. But at all recent thinking gets into quantum background stuff and all which moots all that. [Previous page](https://boards.straightdope.com/t/uncertain-about-heisenbergs-principle/800354.md?page=1)