How Does the Stern-Gerlach Experiment Illuminate the Electron Spin Problem?

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Discussion Overview

The discussion revolves around the implications of the Stern-Gerlach experiment in relation to the concept of electron spin. Participants explore the nature of electron spin, its classical interpretations, and the challenges in reconciling these with quantum mechanics. The conversation touches on theoretical frameworks, electron-photon interactions, and the nature of electrons as point particles versus extended objects.

Discussion Character

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

Main Points Raised

  • One participant questions the classical model of the electron as a charged rotating sphere, citing issues with electromagnetic energy and size.
  • Another participant suggests that the electron should not be considered as a classical object, implying a need for a quantum perspective.
  • Concerns are raised about the implications of electron spin being 1/2 and the lack of evidence for electrons being anything other than point particles, despite their mass.
  • A participant proposes a mechanism for electron-photon interaction, expressing uncertainty about the electron's motion and its implications for linear and angular momentum.
  • Some participants argue that quantum mechanics provides a more accurate description than classical models, and emphasize the importance of understanding existing theories before proposing new mechanisms.
  • Discussion includes references to quantum electrodynamics as a well-established framework for understanding electron interactions, suggesting that the proposed mechanisms may already be covered by existing theories.
  • There is mention of electron interference experiments as evidence against the notion of electrons being point particles in a classical sense, with references to the Heisenberg Uncertainty Principle.

Areas of Agreement / Disagreement

Participants express differing views on the nature of electron spin and the validity of classical models. While some advocate for a purely quantum mechanical understanding, others challenge the adequacy of existing theories and propose new ideas. The discussion remains unresolved with multiple competing perspectives on the electron's properties and behavior.

Contextual Notes

Participants highlight limitations in classical descriptions of electrons and the need for a quantum framework. There are unresolved questions regarding the electron's motion, momentum, and the implications of its spin, as well as the dependence on definitions of point particles versus extended objects.

Sheldon Cooper
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Hello,
I've been reading the Stern-Gerlach experiment, and where the concept of electron spin is introduced, am facing a problem, i.e., if you consider electron a charged rotating sphere, then the electromagnetic energy and size of the electron becomes huge! So how do you deal with this?
Thanks in advance
 
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Sheldon Cooper said:
So how do you deal with this?

By not considering the electron as a (classically) charged rotating sphere.
 
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I'm pondering the implications of the inherent spin of an electron as not having any classical comparison. The spin is 1/2 yet we have no evidence that an electron is more than a point particle. I have no idea how it is a point particle while it has mass. Yet consider the neutrino which only recently was found to have mass.

I'm working on a mechanism for electron - photon interaction that I'm hoping will describe an electron's "motion" despite having no evidence that they move through space at all. What is the linear momentum if not p=mv proportional to the velocity? Then how may it have angular momentum if there's no volume which may spin?
 
Quantum mechanics gives a good description and does not have all those issues a classical description would have.
cree_be_mee said:
I'm working on a mechanism for electron - photon interaction
That is the wrong approach. Learn about the existing experiments and theories first. To think outside the box you have to know where the box is first.
 
cree_be_mee said:
'm working on a mechanism for electron - photon interaction that I'm hoping will describe an electron's "motion" despite having no evidence that they move through space at all.

That mechanism is already well understood - google for "Quantum Electrodynamics".
It's very hard to discover something new if you don't know what's already been discovered.
 
cree_be_mee said:
The spin is 1/2 yet we have no evidence that an electron is more than a point particle. ...

I'm working on a mechanism for electron - photon interaction that I'm hoping will describe an electron's "motion" despite having no evidence that they move through space at all. What is the linear momentum if not p=mv proportional to the velocity? Then how may it have angular momentum if there's no volume which may spin?

As already mentioned, there is no need to re-invent the wheel. As to the idea that an electron is "only" a point particle: there is plenty of evidence to the contrary. Any electron interference experiment is such evidence (that its position is smeared out across a substantial volume of space). The Heisenberg Uncertainty Principle describes this phenomena.
 
cree_be_mee said:
I'm pondering the implications of the inherent spin of an electron as not having any classical comparison. The spin is 1/2 yet we have no evidence that an electron is more than a point particle. I have no idea how it is a point particle while it has mass. Yet consider the neutrino which only recently was found to have mass.

I'm working on a mechanism for electron - photon interaction that I'm hoping will describe an electron's "motion" despite having no evidence that they move through space at all. What is the linear momentum if not p=mv proportional to the velocity? Then how may it have angular momentum if there's no volume which may spin?

All evidence of electron tells us that it is not a point particle in the classical sense. That's why we describe it with quantum theory (in the most general sense in terms of relativistic quantum field theory within the Standard Model of elementary particles). As far as we know, it is an elementary spin-1/2 Dirac fermion with a mass of around ##0.511 \; \mathrm{MeV}##. That's all you can say precisely about what an electron is, and this is a lot!

The only "mechanism" of electron-photon interaction is, as is implied by the very use of these words, quantum electrodynamics. An (asymptotic) free electron has a momentum ##\vec{p}=m \vec{v}/\sqrt{1-\vec{v}^2/c^2}##. Only in the non-relativistic limit, i.e., for ##|\vec{v}| \ll c##, it's ##\vec{p} \simeq m \vec{v}##.
 
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