Atom's Place and Speed: A Curious Question

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Discussion Overview

The discussion centers around the implications of the Heisenberg Uncertainty Principle (HUP) on the position and momentum of atoms, exploring whether these properties exist simultaneously and how they relate to our understanding of quantum mechanics. The conversation includes interpretations of the HUP, experimental evidence, and the nature of reality as influenced by observations.

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Exploratory

Main Points Raised

  • Some participants propose that the HUP indicates limits to our knowledge of a particle's position and momentum, suggesting that these properties may not exist simultaneously in a definitive sense.
  • Others argue that the HUP is a complete representation of quantum reality, implying that our observations shape the nature of what we can know about particles.
  • A participant mentions the "Bell experiment" as evidence against the hidden variables interpretation, which posits that particles have definite properties that we cannot measure.
  • Another participant challenges the notion that the HUP applies universally, suggesting that one can measure both position and momentum accurately under certain conditions, such as using a bubble chamber.
  • There is a reference to Heisenberg's assertion that the HUP pertains to our predictive capabilities rather than the actual state of particles in the past.

Areas of Agreement / Disagreement

Participants express differing views on the implications of the HUP, with no consensus reached on whether atoms possess specific positions and speeds at any moment or if these properties are fundamentally uncertain.

Contextual Notes

The discussion includes varying interpretations of quantum mechanics and the HUP, highlighting the complexity and ongoing debates in the field. Some claims depend on specific experimental setups or philosophical interpretations that are not universally accepted.

Who May Find This Useful

This discussion may be of interest to students and enthusiasts of quantum physics, particularly those exploring foundational concepts and interpretations of quantum mechanics.

Wilsh
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Just because one cannot know both where an atom is and how fast it is moving, does that mean that it doesn’t have a specific place and speed at any moment?
 
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Welcome to PhysicForums, Wilsh!

That is a great question, and one that is the subject of ongoing debate. Many physicists interpret the HUP to say that there are experimental bounds to our knowledge of a fundamental particle (such as an electron).

There are others who say that the HUP is a "complete" representation of the quantum world, and that reality is shaped by the nature of observations we make upon it.

Ultimately, it is a matter of your interpretation. However, there are trade-offs. If you assert that there is an exact simultaneous position and momentum for a particle, you must be prepared to accept non-locality of cause and effect.
 
The "Bell experiment" claims to show that the "hidden variables" interpretation (that, for example, an electron really has a specific position and momentum, we just can't measure all of the variables) cannot be true.

(Oh, and while the map is not the territory, the map is a territory!)
 
Welcome to PhysicForums, Wilsh!

Wilsh said:
Just because one cannot know both where an atom is and how fast it is moving

Who told you that? Just inject it into the bubble chamber and you will see it trajectory and could measure where an atom was and how fast it was moving.
I am sure that after second thought DrChinese agree with me that this will prepare you to accept locality of cause and effect.

Welcome again to PF.

My best wishes, Wilsh!

Dany.
 
Last edited:
HallsofIvy said:
(Oh, and while the map is not the territory, the map is a territory!)

:biggrin: I like it!
 
Wilsh said:
Just because one cannot know both where an atom is and how fast it is moving, does that mean that it doesn’t have a specific place and speed at any moment?

As Heisenberg himself pointed out, HUP does not apply to the past, it is only about our capacity to make predictions.

Put a point source very far away from a screen and let it emit particles for a very short period of time. Once you detect a particle at the screen you can calculate both its position and momentum with unlimited accuracy.
 
Thanks a lot guys. I'm trying to learn some things about quantum physics so I'll probably be asking more questions. Oh and some forewarning. Sorry for my ignorance I'm only a senior in high school. But I'm stoked that you guys are so helpful.
 

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