swansont

I knew people in grad school who studied adsorption on solid surfaces, and other surface effects. The forces are different than in the bulk solid, since you don’t have the interaction from all directions. The lack of symmetry makes for some interesting physics. Surfaces of the same material can have pretty strong attraction; the adhesion between metal surfaces is called galling https://en.m.wikipedia.org/wiki/Galling (I “discovered” this problem putting some bolts into a frame in a vacuum system and having one seize up. Right after, I was introduced to the anti-seizing compound molybdenum disulfide)

You’d use QM if there was some interaction involved that required it. You can e.g. use frames of reference to look at what happens to muons and their decay time, without invoking QM.

Frames of reference are important in relativity, where they are tied to a velocity, not necessarily a physical point. All points are at rest with respect to each other in that frame. To rephrase your statement, can you have a valid frame that does not apply to some potential scenario? I don’t know. I can’t think of one at the moment.

I can’t parse “Does a frame of reference have to be applicable to a potential physical scenario to be physically valid?” There’s an adage in particle physics that goes “that which is not forbidden is mandatory” so I can’t imagine a frame of reference that’s valid that would not somehow correspond to a physical scenario, but I don’t know if one exists, or what you might have in mind.

No, not to arbitrary precision. Not exactly sure what you mean here. Physicists have no problem approximating things, so something can be treated as being at rest despite all of the caveats we’ve mentioned.

Yes.

You don’t know what the momentum is, so saying it’s zero isn’t strictly possible, though this might be unimportant for certain problems.

Classically, yes. It loses some meaning in QM, considering the Heisenberg Uncertainty Principle

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At first glance it looks like no more than the expected exponential reduction in intensity with concentration of the absorber predicted by the Beer-Lambert law. Has anyone come across this being used as a counterargument to climate change science, is the implication true that further increases should have a proportionately lesser effect and what relevance does that have to the models used to predict climate change? The radiative forcing is logarithmic in the concentration, i.e. you get a certain effect from doubling the concentration. I’m not sure of the exact number in recent literature, but it’s a few watts each time you double. So each added molecule indeed has a smaller effect. I haven’t seen this as a counterargument, but dishonesty abounds in such discussions. It’s incorporated in the models, so anyone claiming otherwise is pulling a fast one

The wavelength is h/p, so yes, the wavelength tends to infinity as the momentum tends to zero. It can’t actually happen but can be applied as a thought experiment. There are some quantum implications to having zero momentum, and being in the rest frame is a useful approach to certain problems. The spin is not part of this; that’s a separate property. p is the linear momentum.

“The evolution of the individual quantum states in a superposition are accurately described by an appropriate wave equation such as (eg for Dirac fermions) the Dirac equation.” I have no interest in this because my experience with superposition is with the expression of the eigenstates, and not the wave equation or how the wave function was determined. There’s no common ground for me, and so I have no comment. IOW aψ1+bψ2 doesn’t really rely on the wave equation, so I’m not sure where you were going with your post

How does this happen? How was the superposition created in the first place? Does it even make sense to talk about the second law for such a system?

There is no outgoing neutron

Sure. But the superposition also includes the low-entropy state, so the average of the two (weighted by their amplitudes) is less than the entropy of the final state, so there’s no conflict with the 2nd law.

What, precisely, is the problem?

Yes. There’s no violation of the law when you have a superposition.

So in what way is 1/137 “about 1”? What is your source that this is 0.998 of the experimental value?

You did read that, but perhaps you saw that it was disputed and no example was given to support the assertion. In this example, half the energy is in each state.

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To add to Genady’s response: you don’t know the exact trajectory, so the photon passes through both slits and interferes with itself

A stepper motor might be (part of) the solution..

No, because each state has an amplitude, and the probabilities of being in the states add to 1.

Do you have an example? Quantum states I can think of will have an energy, and you need to add energy to put a system in the ground state into a superposition of energy eigenstates (unless they’re degenerate)

In my experience yes. I’ve used commercially-available systems that lasted around 1.5 years or so; generally the failure was degradation of the anti-reflection coating, and the laser wouldn’t stay at the desired frequency, but they would still lase. If it’s a homemade system, it’s critical that the electronics prevent the laser from seeing voltage spikes. Those will destroy a laser diode.