Zeroing in on Zero-Point Motion Inside a Crystal | Hacker News Reader

Zeroing in on Zero-Point Motion Inside a Crystal

physics.aps.org

45 pointslc0_stein16 comments

> 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.

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.

> 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.

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

Doesn't measurement == knowability ?

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

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.

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.

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.

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

https://www.merriam-webster.com/dictionary/knowability

Man you're frustrating. I'm literally using the definition. Just because you don't know what it means...

> I took knowability to be, how well you know the properties of a particle?

No, I'm using the literal definition: https://www.merriam-webster.com/dictionary/knowability

> 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.

Yes, this is it, but remove "you knew"... just - property. The more one property is defined, the less the other property is.

The key I'm trying to get across is it doesn't matter what you, the observer know/don't know (i.e. measure). As temp ->abs_zero, momentum becomes more-undefined/fuzzier. Nothing to do with you measuring.

The "other" property is fundamentally undefined (i.e. not knowable, i.e. able to be known).

Maybe we're getting hung up on our shared understanding of "knowable" and I shouldn't have used it, but it is, technically, the correct usage.

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

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.

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

"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

Star gate zero point modules incoming?

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.

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