Zeroing in on Zero-Point Motion Inside a Crystal

(physics.aps.org)

44 points | by lc0_stein 3 days ago ago

15 comments

  • taneq 3 days ago ago

    > However, the Heisenberg uncertainty principle dictates that the motion can’t go exactly to zero—there will always be fluctuations.

    Is that what it dictates? I thought it was about observation (in the sense of interactions with other particles, noting to do with consciousness) inescapably and unpredictably altering the observed property.

    • jagged-chisel 3 days ago ago

      No it does not dictate such. And you’re describing “the observer effect.”

      Heisenberg says the more accurately you measure one property, the less accurately you can measure a second [related] property. The usual property pair used in explaining the principle are position and momentum.

      • irjustin 3 days ago ago

        > Heisenberg says the more accurately you measure one property, the less accurately you can measure a second [related] property.

        mmm you've redescribed what the parent post was saying.

        Heisenberg's principal is about the _knowability_ and not the measurement. So it's fundamental regardless of whether you measure it or not.

        This is why it's impossible to cool something to absolute zero. Because fundamentally, it's position is becoming knowable, so it gains momentum, regardless if it's being measured or not.

        • jagged-chisel 6 hours ago ago

          I didn’t. As I said, taneq mentions the observer effect. This is not the same as the Heisenberg Uncertainty Principle.

        • Khaine 2 days ago ago

          Doesn't measurement == knowability ?

          like you don't truly know something until you measure it?

          • irjustin 2 days ago ago

            Knowability directly means "ability to know" meaning whether you are even able to know it at all i.e. you can/can't ever know it.

            The Heisenberg uncertainty means you can't know it (i.e. it's not a value/property exists to extract), regardless if you try to measure it.

            • Khaine 14 hours ago ago

              I took knowability to be, how well you know the properties of a particle? For example, if you could perfectly knew the position of a particle, then you would have no knowledge of its momentum.

              I thought Hisenberg meant the more you knew about one property (i.e. the smaller the bound on the position of a particle) the less you knew about the other property.

              I'm not an expert on this, so more than happy to be corrected.

              • jagged-chisel 6 hours ago ago

                irjustin is either redefining words to suit their purpose, or isn’t articulating their point well.

                To even “know” position, one must measure it. Because electrons are always in motion, if you want to know their speed perfectly, you won’t know their position precisely. You’ll have a probability of where the electron should be, but no definite position.

                That’s all Heisenberg has to say. It doesn’t talk about your observations changing the thing you observed, it doesn’t “cause” anything to happen, it is not dependent on the consciousness of the observer and doesn’t make effects itself.

        • jagged-chisel 2 days ago ago

          There is no cause and effect in Heisenberg, nor due to it.

    • Joel_Mckay 2 days ago ago

      "What ACTUALLY Happens at the Planck Length?" (Physics Explained)

      https://www.youtube.com/watch?v=f3jhbui5Cqs

      The math sifts out in some hilarious ways. =3

    • drdeca 3 days ago ago

      The Heisenberg uncertainty principle says that in no state is the product of the standard deviations of what would be measured if you measured position, and what would be measured if you measured momentum, less than hbar or hbar/2 or something like that (I forget the exact constant. It is on the order of hbar.).

      As such, if the position uncertainty isn't infinite, the momentum uncertainty is nonzero.

    • irjustin 3 days ago ago

      Common misconception, probably because it's the one that gets repeated the most/easiest to understand. It's more fundamental than measurement, observation.

      PBS Spacetime has something on it[0].

      [0] https://www.youtube.com/watch?v=izqaWyZsEtY

    • undefined 3 days ago ago
      [deleted]
  • rokkamokka 3 days ago ago

    Star gate zero point modules incoming?

    • tucnak 2 days ago ago

      There is a whole subcommunity of highly respected physics quacks like that one guy from Lockheed obsessed with propellantless propulsion. They are very much into zero-point stuff and how they do it is semi litho.