This account is temporarily suspended to cool down. The suspension period ends on Aug 28 '16 at 0:06.
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494215
bio website
location New York City
age 41
visits member for 4 years
seen Aug 28 at 11:06

I do not participate on this site any longer, except to respond to comments regarding my own text, if that text is unavailable in another form. I do not accept the political moderation atmosphere here, it is not compatible with open science. Unfortunately, this seems to be a recurring pattern on such sites--- they grow with promises of open participation, and then shut down in a phase transition of censorious moderatorship. Hopefully physicsoverflow.org will be the first exception to this rule, as the policies there were crafted specifically to avoid this phenomenon.


Aug
17
answered Deriving Newton's Third Law from homogeneity of Space
Aug
17
comment Why can we treat quantum scattering problems as time-independent?
@Marek--- the critics are right, and your description is not even a good way of describing the time-dependent case.
Aug
17
comment Why can we treat quantum scattering problems as time-independent?
-1 This answer is no good. You are turning off the scattering potential at $t=-\infty$ for no reason, the Hamiltonian in a scattering problem of the sort the OP is asking about is time independent. The answer is ridiculously formal, and all the interesting things are in the "it can be shown...".
Aug
17
awarded  Necromancer
Aug
17
comment Why isn't there a centre of charge?
-1 This answer is totally wrong. The acceleration of a rigid sphere E in response to point/sphere source S is exactly the same as the response of a point mass to the same sphere/point source. The reason is that the point and the sphere make the same outside potential, so a point E and a sphere E have exactly the same reaction force on S, therefore they must feel the same action force from S. There is no way around it. Tidal forces come from shape distortion, like oceans rising and falling, not from the rigid spherical shape.
Aug
16
comment Common false beliefs in Physics
The "glass is a slow fluid" thing is not really fair--- this is derived from an old controversy, only recently understood, over whether an amorphous glass transition is actually sharp, or whether it is a rounded smooth non-phase-transition. It was plausible to believe that it wasn't sharp before recently, so that liquid and solid glass are not separated by a melting transition.
Aug
16
comment Common false beliefs in Physics
Points 3 and 5 are false. Electrons move fast in a metal (although not as fast as the field), and it is completely possible for the trace point of an oscilloscope to move faster than light.
Aug
16
comment Common false beliefs in Physics
It is in no way obvious that statistics and natural selection can produce living things. The theory is not yet at the quantitative level. How would you estimate, even roughly, the order of magnitude of time for evolution? Darwin was able to do it only phenomenologically, by the known rates at which domestication changes animal traits. If you try to estimate the rate of change naively, using modern genetics, you get an estimate which is impossibly long, as was noticed by Pauli many years ago. In this case, the popular belief is pointing out that we don't understand evolution quantitatively.
Aug
16
comment Common false beliefs in Physics
The precise statement is that quantum mechanics implies a fundamental discreteness of state-space, of the position-momentum phase space, in multiples of planck's constant h. The positivist arguments that imply coarse-graining in phase space also imply coarse graining of physical space at the Planck length, and this is born out by theories of quantum gravity. So this is not really a myth. The myth is only that the proper way to do discretization is to replace spacetime by a finite lattice.
Aug
16
comment Common false beliefs in Physics
But this is true in practice--- converting the coal to electricity and running a heat pump is in practice less efficient than just burning the coal directly. I don't think you can call a practical rule of thumb a fallacy.
Aug
16
comment Common false beliefs in Physics
Also, I don't think anyone believes 5, 6 and 7 are arguable at best, and 8 is only stated by people who believe Maxwell's equations, so that the principle of relativity plus the validity of Maxwell's equations implies the constancy of the speed of light.
Aug
16
comment Common false beliefs in Physics
The point of a laser pointer on a far away wall can move faster Regarding point 3, nothing moves faster than light in vacuum, this is not true. Phases of a light wave in a material, virtual particle trajectories contributing to a path integral, a pre-planned crowd "wave" in a large stadium, and other immaterial things. It is material objects and information are constrained by the speed of light.
Aug
16
revised Examples where an ill-behaved function leads to surprising results?
fix reflection error
Aug
16
answered Examples where an ill-behaved function leads to surprising results?
Aug
16
comment Is the S-Matrix the only quantum field observable?
The S-matrix is nontrivial for nonfree models in 2d because it includes the phase shifts.
Aug
16
comment Einstein's postulates $\leftrightarrow$ Minkowski space for a Layman
This is the Minkowski version of the Chinese proof of the Pythagorean theorem.
Aug
16
revised Einstein's postulates $\leftrightarrow$ Minkowski space for a Layman
copy-edit
Aug
16
revised Einstein's postulates $\leftrightarrow$ Minkowski space for a Layman
copy-edit
Aug
16
answered Einstein's postulates $\leftrightarrow$ Minkowski space for a Layman
Aug
16
comment Einstein's postulates $\leftrightarrow$ Minkowski space for a Layman
@Roger: the velocity addition formula, the explanation of Fizeau's experiment, the relativistic E,B transformation formulas, the correct equations of motion, the identity between induced EMF by motion and by changing magnetic fields, and the formulas for the longitudinal and transverse mass of an electron, were all new to this paper. It was considered backward by Poincare because it assumed the symmetry is true and derived the dynamical equations, instead of using the dynamical equations to find the symmetry. History has long ago rendered its verdict on which approach is more fundamental.