Understanding Particle Spins: A Beginner's Guide

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Discussion Overview

The discussion revolves around understanding particle spins, particularly aimed at beginners with limited mathematical background. Participants explore the concept of spin in quantum mechanics, its implications, and seek resources for better comprehension.

Discussion Character

  • Exploratory
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants express a desire for a simplified understanding of particle spins, indicating a preference for resources that do not require extensive mathematical knowledge.
  • One participant suggests that quantum mechanics (QM) is a university-level subject and questions the feasibility of learning about spins without foundational knowledge in classical mechanics.
  • Another participant explains that the classical magnetic moment of a rotating charge is evidence of intrinsic angular momentum, relating this to the concept of spin.
  • Links to external resources are provided, including a website that discusses spin in particle physics.
  • Some participants clarify that while quantum spin contributes to macroscopic angular momentum, it does not correspond to classical spinning objects.
  • There is a discussion about the relationship between electron orbitals and spin, with some asserting that they are related but distinct concepts.
  • One participant notes that spin is an intrinsic quantum number that manifests in an observer's space-time context, emphasizing the mathematical manipulation of spin rather than its intrinsic nature.

Areas of Agreement / Disagreement

Participants generally agree on the complexity of the topic and the challenges of understanding spin without a solid foundation in classical mechanics. However, there are competing views on the relationship between spin and angular momentum, as well as the nature of spin itself.

Contextual Notes

Participants highlight limitations in understanding due to the lack of mathematical prerequisites and the challenges of grasping quantum concepts without a background in classical physics.

ISamson
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Hello.
Could anyone please help me understand particle spins?
I read the 'A Brief History of Time' and now would like to understand them better. Basically from zero.
Any resources?
I have had a look at Wikipedia, but the language is not clear and there is too much information.
Thank you.
 
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ISamson said:
Hello.
Could anyone please help me understand particle spins?
I read the 'A Brief History of Time' and now would like to understand them better. Basically from zero.
Any resources?
I have had a look at Wikipedia, but the language is not clear and there is too much information.
Thank you.

A number of QM books start with spin, but I'm not sure you have the mathematical or physics prerequisites to study QM at undergraduate level. I'm not sure what to suggest. You might try Susskind's lectures:

http://theoreticalminimum.com/courses/quantum-mechanics/2012/winter
 
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No, I do not have much mathematical understanding, unfortunately...
I am not really looking for uni level things and I don't want too much information
I just would like a short and sweet understanding of spins for a high school level.
Thank you, @PeroK.
 
ISamson said:
No, I do not have much mathematical understanding, unfortunately...
I am not really looking for uni level things and I don't want too much information
I just would like a short and sweet understanding of spins for a high school level.
Thank you, @PeroK.

That would be, I suggest, popular science. QM is a university level subject. There's not really a high-school version, as far as I know. One probem would be trying to learn Quantum Spin, Angular Momentum, Harmonic Oscillation before you've learned the much simpler classical versions.

Another problem is that QM is based on Hamiltonian Wave Mechanics (or a more abstract mathematical formulation). You can't really take on Hamiltonian mechanics before you've learned classical mechanics.

It's not clear to me what you would gain by jumping into QM without these prerequisites. Certainly not in the long-term.
 
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Do you know what the classical magnetic moment of a rotating (spinning) charge is? That we can measure magnetic moments of particles is evidence of them having intrinsic angular momentum.

Think of orbiting electrons in an atom. They build up the angular momentum of the atom that generates the magnetic moment. Now consider subnuclear particles and grant them angular momentum. In their rest frame, that angular momentum is called spin (including that of a single electron). Things get a little more complicated if those particles are believed to have no spatial extent, but don't worry about that yet unless you want to get deeply into the math. Just think of spin as intrinsic angular momentum.
 
Although an electron (or other fundamental particle) isn't really a little ball that spins around its axis classically like a spinning baseball or the Earth's 24-hour rotation, its quantum-mechanical "spin" (intrinsic angular momentum) does contribute to an object's macroscopic angular momentum. This is demonstrated by the Einstein-de Haas effect which I discussed in this post:

https://www.physicsforums.com/threa...ntum-object-metaphorical.890175/#post-5600430
 
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Think of it this way: spin is an intrinsic quantum number -- just like charge -- that manifests in an observer's space-time context by contributing to angular momentum. We know nothing of what spin is in a purely intrinsic context (where there are no space-time properties); all we know is how to manipulate the math.
 
mikeyork said:
We know nothing of what spin is in a purely intrinsic context (where there are no space-time properties); all we know is how to manipulate the math
We do know that spin of higher electron orbitals can approach the speed limit "c" in which case, as in the example of Au, relativistic effects apply to even quantum context... which is why gold is golden.
 
  • #10
jerromyjon said:
We do know that spin of higher electron orbitals can approach the speed limit "c" in which case, as in the example of Au, relativistic effects apply to even quantum context... which is why gold is golden.
Spin does not have a linear "speed". Electron orbitals are not electron spin.
 
  • #11
mikeyork said:
Electron orbitals are not electron spin.
But they are related...
 
  • #12
They are related by addition but only in a space-time context because orbital angular momentum has meaning only in a space-time context. Spin has meaning independently of that. I think the OP was interested in spin in particular not angular momentum in general.
 
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  • #13
ISamson said:
Basically from zero.
mikeyork said:
I think the OP was interested in spin in particular not angular momentum in general.
Start from the heart.
 

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