Ok, good. Now, from everyday life, one does not expect that a pointlike mass (in vacuum) undergoing uniform motion or accelerating along a straight line should lead to any rotation-like effects. But this is what seems to happen for charge-carriers such as electrons, since a chiral B-field is...
Let me first say that I was already sufficiently satisfied with the answer in post #6. I still am. I write to hopefully clean up some of the mess that followed post #7.
I understand that there is no rotational asymmetry in the B-field (which I already admitted in post #11). That was never...
All right, I will stop. I think that some of you misunderstood my intentions.
I will treat the B-field as a non-unique mathematical tool, since it is not directly observable. This was a good lesson.
So the direction of the B-field is unambiguous (last post in this thread) but unobservable (post #6 in this thread)?
That requires a good portion of faith I would say.
Ok, I could have been more careful in my use of the phrase 'rotational symmetry'. Perhaps 'clock-/counterclockwise ambiguity' would have been more to the point.
My initial main worry was that a symmetrical situation seemed to give an asymmetric result. I am happy that this isn't the case.
So the magnetic field is essentially just a mathematical crutch, that could possibly be replaced by a simpler alternative? One that does not introduce asymmetries...
An analogy may perhaps help:
Let's say that each time you flush, the water rotates in the same direction. Wouldn't you say that this is an asymmetric situation, and that there should be an underlying explanation?
It has of course absolutely nothing to do with any conventions.
The same...
Ok, I can vaguely understand that. But that doesn't change the fact that there exists an asymmetry. It is possible to measure the (relative) orientation of the magnetic field - a simple test magnet would flip if the current direction was reversed.
I guess that I am looking for a microscopic...
What determines the sense of rotation of the magnetic field around an electric current?
Current through a straight wire is a problem with rotational symmetry, so what is it that breaks the symmetry?
Does the spin of a moving electron have a preferred orientation - or what could it be?
Agreed - I can't directly come to think of any either.
Irrespective of this however, I find it to be a plausible explanation for entropy increase, and a better one than that of a highly improbable initial condition (for logical reasons that we have discussed).
Thank you for your comments...
Can't just the fact that entropy actually decreases be the noticeable effect of an expanding universe?
If I remember right, time-reversibility is a built-in feature of both Newton's and Einstein's equations. Can GR then really be used to disprove this proposition?
I had no idea about that -...
If I carelessly assume that the total number of available states for N particles simply is s^N , then the entropy S becomes
S(t)=k \ln s(t)^N = kN \ln \left[ s(0) V(t)/V(0) \right] , k being Boltzmann's constant.
I do not understand why they aren't affected by cosmic expansion...
It is difficult to achieve uniform and significant diffusion with standard materials - the dominant factor is rather the macroscopic irregularities (required roughness typically about 30 cm for 1 kHz).
Non-uniform acoustic wall impedance is effected by placing many patches of different...
Constructions that do this are commercially available, see for example http://www.rpginc.com/
Not necessarily - variations in acoustic impedance may also produce scattering.
For non-smooth surfaces: The roughness usually needs to be of the same order as the wavelengths for efficient...
If, say, the number of available states s(t) per particle is approx. proportional to volume V(t), then s(t) = s(0) * V(t)/V(0), where t is time.
This is certainly an extreme oversimplification, but the best I could produce in a few minutes I guess.