Classical paths and bubble chambers

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Discussion Overview

The discussion centers around the nature of particle paths in bubble chambers, particularly in relation to classical and non-classical behavior of particles like electrons. Participants explore the implications of quantum mechanics, uncertainty, and measurement limitations in the context of bubble chambers, which are used to visualize particle interactions.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants question what is being measured in a bubble chamber if electrons do not follow classical paths, suggesting that the uncertainty might be negligible in this context.
  • Others note that bubble chambers measure the tracks of charged particles, which indicate direction but do not directly provide kinetic energy or velocity without specific experimental setups.
  • One participant mentions that the dynamics in a bubble chamber are of sufficient scale for classical mechanics to apply, implying a potential reconciliation between classical and quantum descriptions.
  • There is a discussion about the interactions of charged particles in a bubble chamber, highlighting that they are considered "free" and not subject to the same boundary conditions as electrons in atoms.
  • Some participants express uncertainty about the relationship between the measurements made in bubble chambers and the uncertainty principle, with differing views on whether the principle applies to these measurements.

Areas of Agreement / Disagreement

Participants express differing views on the applicability of classical mechanics in bubble chambers and the implications of quantum uncertainty. There is no consensus on the relationship between the measurements in bubble chambers and the uncertainty principle.

Contextual Notes

Limitations include the dependence on specific experimental setups for measuring energy and velocity, as well as the potential ambiguity in interpreting the measurements of particle tracks in relation to quantum mechanics.

jackle
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It is often said that electrons do not follow classical paths, especially in the context of electrons in atoms etc. I have absolutely no problem with this, as I do have a academic background in physics (but extremely rusty).

Non-classical paths, uncertainty etc. being the case, what is then being shown in a bubble chamber if not a classical path? I am a bit embarrassed that I don't know the answer. Is it just that the uncertainty is too small to be relevant in a bubble chamber? I suppose bubbles in a liquid aren't exactly accurate measurements of anything right? So when a particle interacts to make bubbles, what have we actually measured? What happens to the wave function?
 
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jackle said:
It is often said that electrons do not follow classical paths, especially in the context of electrons in atoms etc. I have absolutely no problem with this, as I do have a academic background in physics (but extremely rusty).

Non-classical paths, uncertainty etc. being the case, what is then being shown in a bubble chamber if not a classical path? I am a bit embarrassed that I don't know the answer. Is it just that the uncertainty is too small to be relevant in a bubble chamber? I suppose bubbles in a liquid aren't exactly accurate measurements of anything right? So when a particle interacts to make bubbles, what have we actually measured? What happens to the wave function?

But in a bubble chamber, the charge particles (not necessarily just electrons) are now interacting with many other particles. It is also considered to be "free" particles and is not encumbered by the usual boundary conditions we get in atoms. They are also usually widely separated from each other (no significant wavefunction overlap). So other than the coulombic interactions, they are non-correlated.

Also note that in electron particle accelerators, the electrons are also handled as classical particles. So such treatement isn't unusual.

Zz.
 
jackle said:
It says in Wikipedia that you can't measure the kinetic energy or velocity in a bubble chamber.

http://en.wikipedia.org/wiki/Bubble_chamber

Do you know if this is because of the uncertainty principle?

No, it's because all it can measure are "tracks", i.e. in where and in which direction the particle is moving. If the bubble chamber is also in a magnetic field that bends the charged particle, then it can measure its energy. To measure energy or velocity, you have to SET UP an experiment that measures those quantities. A single measurement does not imply the measurement of ALL properties. This has nothing to do with the HUP.

Zz.
 
the dynamics of a bubble chamber are of sufficient scale that classical mechanics will work just fine
 
OK. Thanks. :blushing:
 
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