# Tag Info

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The spin of the neutron was measured by the Stern-Gerlach experiment by Sherwood, Stephenson and Bernstein (1954) (sadly paywalled, free links welcome), Abstract: A neutron beam was polarized by total reflection from a magnetized iron mirror. The beam was then analyzed by passing it through an inhomogeneous magnetic field. From the deflection pattern ...

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It is assumed and proven that before measurement there is no distinct spin up or spin down state unless of course it is somehow prepared. General state of a particle is described as a linear combination of spin up and spin down state. If you measure the z projection you get 50 % upz and 50 % downz. If you then take upz particles and measure the x projection ...

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If you prepare many silver atoms in the exact same state each time you might get 1000 out of 1000 to come out spin up. Or if you prepare many silver atoms in the exact same state (but different than the one above) each time you might get 0 out of 1000 to come out spin up. And when I say might it depends on if you pick the right state to prepare them and ...

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No. Let's look at a spin measurement in detail. You can choose any direction $\hat n = n_x\hat x+n_y\hat y+n_z\hat z$ and take any spin, $\alpha |+\rangle+\beta |-\rangle,$ where we define $|\pm\rangle$ by $$\left(n_x\sigma_x+n_y\sigma_y+n_z\sigma_z\right) |\pm\rangle=\pm|\pm\rangle).$$ Then you can send a beam of particles into a small region with an ...

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I think the answers are all correct, but it's worth pointing out that a lot of Earth's rotation came when it was hit by Theia. If Theia had hit the earth's other side, the Earth just might be spinning clockwise, against the spin of all the other planets.

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When our solar system formed it had a certain amount of intrinsic angular momentum. As it collapsed over time it began to spin faster like an ice skater that brings her arms in. Our planet, Earth, was formed in this cloud. It too is the product of that spinning gas cloud long gone. So the Earth retains the angular momentum of the matter that formed it. The ...

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If you're asking why the Earth began rotating, the question isn't particularly enlightening, but the answer is simple: Because some torque acting on the Earth (more likely its constituent particles before gravity pulled them into a single object) in the distant past caused those particles to rotate in the counter clockwise direction. Although as LDC3 ...

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There is a difference between your two cases. When you are talking about a charge passing between magnets you are thinking of it as a uniform magnetic field. But it is not uniform, it gets stronger as you approach the magnets. if it were a uniform field the magnetic dipole you put in the middle would not feel a force along the line of the magnets, although ...

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If my understanding is correct, an electron is an elementary particle which means that it is just a point in space, ... The electron spin is a special case of the general concept of angular momentum, which is a physical quantity generated by rotations. This is completely analogous to energy being generated by time translations and momentum by spatial ...

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We don't know if the electron is an infinitely small object. It may have size and if it does maybe that will make you feel better about the fact that it creates a magnetic field due to its intrinsic spin.

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As the comment above says, the word "spin" should not be taken literally, as in the spin of a beachball. The word spin came about as an attempt to physically understand the differing energy levels an electron can have, due to the magnetic field associated with it. The idea behind it goes back to when the electron was discovered experimentally to have a ...

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An electron does not spin! Its intrinsic angular momentum (the so called spin), should not be confused with the point-like electron rotating in configuration space (then the gyromagnetic factor would be one which is in a way related to charge spinning in configuration space. Actually the gyromagnetic factor of the electron spin is approximately 2.) A black ...

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The question puts the cart before the horse. It is not that you derive that particles described by the Dirac equation have spin $\frac 1 2$. Rather, the Dirac equation is found as the equation for spin $\frac 1 2$ particles. A Dirac spinor $\psi$ is an element of the representation $(0,\frac 1 2) \oplus (\frac 1 2, 0)$ of the Lorentz group.1 In both ...

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