Understanding Particle Spins: A Beginner's Guide

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In summary, the conversation discussed the concept of particle spins and the resources available for understanding them. The conversation touched on the prerequisite knowledge needed to study quantum mechanics and the difficulty of finding a high school level explanation of spins. It also delved into the idea of spin as intrinsic angular momentum and its relationship to orbital angular momentum. The conversation concluded with the suggestion to start with a basic understanding of classical mechanics before attempting to learn quantum mechanics.
  • #1
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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  • #2
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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  • #3
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.
 
  • #4
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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  • #5
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.
 
  • #7
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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  • #8
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.
 
  • #9
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.
 

1. What is a particle spin and why is it important?

Particle spin is an intrinsic property of subatomic particles, which can be thought of as the particle's intrinsic angular momentum. It is important because it helps to characterize and differentiate between different types of particles, and it also plays a crucial role in many fundamental physical processes.

2. How is particle spin measured?

Particle spin is measured using specialized detectors and equipment, such as particle accelerators and magnetic fields. The measurement is based on the deflection of the particle's trajectory in the presence of a magnetic field, which is related to its spin.

3. What are the possible values of particle spin?

The possible values of particle spin are quantized, meaning they can only take on certain discrete values. For elementary particles, the spin can only be an integer or half-integer multiple of the reduced Planck's constant (h-bar). This includes values of 0, 1/2, 1, 3/2, etc.

4. How does particle spin relate to quantum mechanics?

Particle spin is a crucial concept in quantum mechanics, which is the theory that describes the behavior of particles at the subatomic level. In quantum mechanics, particles are described as having both wave-like and particle-like properties, and their spin is one of the fundamental quantum numbers that helps to define their behavior.

5. Can particle spin change over time?

No, the spin of a particle is considered a conserved quantity, meaning it does not change over time. This is a fundamental principle in physics known as angular momentum conservation. However, in certain interactions, such as in radioactive decay, the spin of particles involved may appear to change due to the exchange of other particles.

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