HUP Greeting: Meaning & Opinions

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Discussion Overview

The discussion revolves around the Heisenberg Uncertainty Principle (HUP), exploring its implications on measurement and the nature of particles in quantum mechanics. Participants express varying interpretations of the principle, its foundational assumptions, and its consequences in both theoretical and practical contexts.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants suggest that the HUP implies it is impossible to measure a particle's position and momentum with absolute certainty.
  • Others argue that while measurements cannot be exact, it does not necessarily mean that particles lack defined properties at all times.
  • A participant questions whether the HUP applies only during measurement, proposing two interpretations: total uncertainty or a form of certainty despite measurement limitations.
  • There is a discussion about the implications of wave function collapse during measurements and how this affects the certainty of position and momentum.
  • Some participants mention the role of statistical interpretations in quantum mechanics, such as the Born interpretation, which focuses on probabilities rather than certainties.
  • One participant raises the idea of describing a particle's properties as functions of time based on known initial or final states, while another counters that initial states cannot be known accurately.
  • The relationship between the HUP and the de Broglie hypothesis is mentioned, with a suggestion that understanding one can lead to insights about the other.
  • A participant references the pilot wave theory, suggesting that it posits hidden variables that could imply a form of certainty despite measurement limitations.

Areas of Agreement / Disagreement

Participants express multiple competing views regarding the implications of the HUP, particularly concerning the nature of particles and the certainty of their properties. The discussion remains unresolved, with no consensus on the interpretations of the principle or its foundational implications.

Contextual Notes

Participants acknowledge limitations in their understanding of quantum mechanics concepts such as commutators, eigenstates, and the mathematical framework underlying the HUP. There is also a recognition of the dependence on definitions and interpretations in discussing the implications of the principle.

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Greeting to everyone. This is my first time here (A bit nervous)

According to many sources, many books, "Heisenberg uncertainty principle" tells us that it is impossible to measure anything exactly. I agree as the proving equation does not apply any measuring instrument at all which means that even the best measuring instrument will never gives us exactly measuring.

Now comes to the problem. Does the HUP only applied when there is measuring ?
I have two opinion about this:
1. We can not measure anything exactly which means nothing is certain at all.
2. Although we can not measure/predict anything exactly, everything is certain.

Thank you very much.
 
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I was JUST thinking about asking this myself. I believe the mainstream view is that no particle has a 100% definite position and momentum at any point in time, but I really don't know why that is believed to be the case.
 
Thank you very much for fast reply

"no particle has a 100% definite position and momentum at any point in time"
I'm not sure about this (need some more explanation)

All I've read, HUP only told me that we can't measure two values exactly at the same time. So if we don't measure momentum, we can know the exact position. Or if we don't measure position, we can know the exact momentum of the particle. So there might be exact position OR momentum for the particle depends on how we measure.

Is my understanding wrong ?
 
Drakkith said:
I was JUST thinking about asking this myself. I believe the mainstream view is that no particle has a 100% definite position and momentum at any point in time, but I really don't know why that is believed to be the case.

I don't know if this is the very reason why (i.e. the deeper physical meaning) but it comes in part from the incompatibility/ non - vanishing commutator of the momentum and position operators. If you make a position measurement then the system will collapse to a certain position eigenstate but there will still be multiple eigenvalues possible for the momentum operator. If you then immediately try to make a momentum measurement while the system is in that state it will collapse to a certain momentum eigenstate but now you have multiple eigenvalues possible for the position operator.
 
If you measure the position of a particle, the wave function collapses into a spike. It's then possible to measure to the momentum of the particle, however, it will collapse again into a defined wavelength but the position you first measured won't be the same!

There is, however, a way to make it so when you measure the momentum you won't disturb the particle but I can't remember it off the top of my head
 
romsofia said:
If you measure the position of a particle, the wave function collapses into a spike. It's then possible to measure to the momentum of the particle, however, it will collapse again into a defined wavelength but the position you first measured won't be the same!

This might be the answer. I forgot to think about wave function. Thank
 
I'm not asking for some deeper understanding, I'm asking why we accept that particles simply don't have a defined position and momentum. I've read a little bit on QM, but I have no idea how to even do most of the math to figure this stuff out, which is probably why I don't really understand most of it. For example, I have no idea what a commutator is. Nor what eigenstates and eigenvalues are. Heck, I don't even know how to do a function.
 
Drakkith said:
I'm not asking for some deeper understanding, I'm asking why we accept that particles simply don't have a defined position and momentum. I've read a little bit on QM, but I have no idea how to even do most of the math to figure this stuff out, which is probably why I don't really understand most of it. For example, I have no idea what a commutator is. Nor what eigenstates and eigenvalues are. Heck, I don't even know how to do a function.

That comes from when you make the change from a particle, to a wave function, and when you do that you start to use a thing called Born statistical interpretation! It pretty much says what's the probability of finding the particle between two points at a certain time given the wave function. Really all you can do with QM is find POSSIBLE results, since QM just gives us statistical information.
 
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romsofia said:
That comes from when you make the change from a particle, to a wave function, and when you do that you start to use a thing called Born statistical interpretation! It pretty much says what's the probability of finding the particle between two points at a certain time given the wave function. Really all you can do with QM is find POSSIBLE results, since QM just gives us statistical information.

Alright. Now, I understand that the measurement of a particle can't determine position and momentum 100% accurately, but why the leap from there to the belief that a particle simply doesn't ever have it ?
 
  • #10
Drakkith said:
Alright. Now, I understand that the measurement of a particle can't determine position and momentum 100% accurately, but why the leap from there to the belief that a particle simply doesn't ever have it ?

I don't have the time at this very moment to answer that (going to sleep). However, tomorrow I will have an answer to post (assuming no one else answers it)! Pretty much saying, good question :P and I have to think about it in the morning.
 
  • #11
Even though measurement can't be made directly, wouldn't it be possible to describe the position, velocity, acceleration, momentum, ..., of a particle as functions with respect to time, based on a known (possibly calculated) initial state and/or final state and the characteristics of the environment?
 
  • #12
rcgldr said:
Even though measurement can't be made directly, wouldn't it be possible to describe the position, velocity, acceleration, momentum, ..., of a particle as functions with respect to time, based on a known (possibly calculated) initial state and/or final state and the characteristics of the environment?

I don't think so, as we cannot know those initial states. It's all about probabilities.
 
  • #13
Drakkith said:
I don't think so, as we cannot know those initial states. It's all about probabilities.
I was also thinking along the line of a final state, such as an electron's collision being detected after going through some type of accelerator. Assuming the accelerator was programmed so there was only a tiny window of opurtunity for anyone of a number of electrons initially injected into the accelerator that would end up being accelerated and colliding with some target, and based on the time of impact, could math be used to describe the electrons path as it went through the accelerator?
 
  • #14
hup is consequence of de broglie hypothesis...so first one need to understan de broglie n if you do u can derive it quite simply
 
  • #15
darkxponent said:
hup is consequence of de broglie hypothesis...so first one need to understan de broglie n if you do u can derive it quite simply

Care to enlighten us?
 
  • #16
darkxponent said:
hup is consequence of de broglie hypothesis...so first one need to understan de broglie n if you do u can derive it quite simply

About Pilot Wave ?

I found this on wikipedia. http://en.wikipedia.org/wiki/Pilot_wave#Principles

The position and momentum of every particle are considered hidden variables; they are defined at all times, but not known by the observer; the initial conditions of the particles are not known accurately, so that from the point of view of the observer, there are uncertainties in the particles' states which conform to Heisenberg's Uncertainty Principle.

So is my second hypothesis right ?
"Although we can not measure/predict anything exactly, everything is certain."

Still not sure about this correctness from wikipedia.

Thank in advance for many replies.
 
  • #17
I don't think the pilot wave is viewed as the most accurate model though.
 
  • #18
It's a Fourier transform thing. The same thing happens with classical waves, eg. sound. Here is a good example:
http://scienceblogs.com/builtonfacts/2010/03/hearing_the_uncertainty_princi.php
https://www.physicsforums.com/showthread.php?t=383906

RE: pilot wave. It uses the same math so it is as accurate as any other interpretation.
 
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  • #19
Drakkith said:
Care to enlighten us?

its not that easy to enlighten anyone on a website...u search the net or textbooks u will find it...
U can easily understand through the names
see de brogle HYPOTHESIS it is hypothesis

and HUP is not hypothesis it is derived using de brogle hypo only
 
  • #20
darkxponent said:
its not that easy to enlighten anyone on a website...u search the net or textbooks u will find it...
U can easily understand through the names
see de brogle HYPOTHESIS it is hypothesis

and HUP is not hypothesis it is derived using de brogle hypo only

Got it. I'll have to do some reading.
 
  • #21
Delta Kilo said:
It's a Fourier transform thing. The same thing happens with classical waves, eg. sound. Here is a good example:
http://scienceblogs.com/builtonfacts/2010/03/hearing_the_uncertainty_princi.php
https://www.physicsforums.com/showthread.php?t=383906

RE: pilot wave. It uses the same math so it is as accurate as any other interpretation.

Oh, wow! That makes so much sense lol.Thanks for the links!
 
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