35,246 reputation
348120
bio website inspirehep.net/…
location Duchy of Grand Fenwick
age 43
visits member for 4 years
seen 1 hour ago

Experimental nuclear and particle physicist. These days I'm teaching, but I've spent a lot of time on nucleon structure in fixed target electron scattering and neutrino oscillations using reactors and beam sources.


4h
comment Does “normal torque” exist?
The floor exerts friction on the ruler spinning in contact with it and friction always points in the direction opposed to relative motion. The results is a perfectly ordinary torque.
1d
comment Condition for formation of interference pattern
No time to write an answer now. This is a way of arguing about the spacial coherence of the light.
2d
comment What does the Atomic Form Factor means?
"they have fallen out of fashion as a research tool" Hmmm ... well, they've remained important in the transition energy regime (a few GeV scale) exactly because it is hard to do accurate calculation above the nucleon mass but below the perturbative QCD scale. Also in applications like weak-axial scattering where a small signal must be extracted from a large vector background from electromagnetism.
2d
comment How to rebut denials of the existence of photons?
This is really the core of (at least one of) Lamb's point. He doesn't argue against QED, but rather that the word in consistently abused in ways that are not consistent with a modern understanding of quantum optics.
2d
comment What are the hypothetic cases when entropy of a closed system may decrease?
Describe a system in which there is no way to have a change from a micro-state of maximum entropy to another such state. Then anytime the system is in a micro-state of maximum entropy, any change causes a momentary decrease. I believe that a 1-D Ising model is such a system.
2d
comment How to rebut denials of the existence of photons?
@KyleKanos The flip side is---of course---www-3.unipv.it/fis/tamq/Anti-photon.pdf (the paper that user31748 references) and arxiv.org/abs/1204.4616
2d
comment Do time dilation tests prove that it exists or that atomic clocks are faulty?
"Time is what clocks measure" is a tautology. Time is an expression of the fact that two events that happen in the same place can none-the-less be separate from one another. The separation is the time (duration) between them. A device which allows you to compare intervals in that separation is a clock. The phrase can be taken as a definition of a clock as easily as of time, but it is true. To suggest that there is some underlying more correct time you must show that there is a way to measure it.
2d
comment Do time dilation tests prove that it exists or that atomic clocks are faulty?
I'm going to disagree about the it being philosophical. Time is what clocks measure, and all clocks measure the same effect. Without exception. Essentially everyone asks this questions at some point because time dilation is offensive to what we think we know about the way the world works, but we're wrong about that knowledge. Nor can you just wave your hands and blame it on gravity without offering some kind of mechanism that affects all clocks alike.
2d
revised Can a free hydrogen atom constitute ionizing radiation?
speling
2d
comment What are the factors involved to survive an eleven story free fall?
This question appears to be off-topic because it seems to be a invitation to discussion rather than a question with correct answers.
Nov
23
comment The Form Factor in Nuclear physics
See physics.stackexchange.com/questions/57463/…. As I comment there, the core meaning of the term is the same in all kinds of systems.
Nov
23
comment Should a Gaussian Curve Always Be Drawn Symmetrically?
@Jacobadtr I've edited your post to reflect what I perceive to be your actual question (mostly based on your acceptance of Floris' answer). If I have made a mistake please put it back (or better, re-edit to clarify). Editing posts like this is an important feature of stack exchange sites because this question is suppose to help future visitors as well as getting you straightened out. And the fact that several people had to ask and guess what you meant is indicative of a lack of clarity in the original text.
Nov
23
revised Should a Gaussian Curve Always Be Drawn Symmetrically?
Edit to reflect the real question.
Nov
23
comment Stuck on Snell's Law
You seem to misunderstand the underlying algebra here. In particular "I didn't use inverse sin as this would just take me back to 25 degrees." represents a place where you are confused about the math.
Nov
23
comment Should a Gaussian Curve Always Be Drawn Symmetrically?
Of course, if you have asymmetric tails it's worth looking closely at the physics. If there is a resonance there then you expect a Lorentzian to be a better fit, anyway.
Nov
23
comment Should a Gaussian Curve Always Be Drawn Symmetrically?
Again, assuming that Floris hit on the OP's real question it is not about statistics at all. It's about a feature of the graphical plotting of functions. Not really meat for either site, but a side-issue that many students encounter at some point.
Nov
23
comment Should a Gaussian Curve Always Be Drawn Symmetrically?
Assuming that Floris nailed your complaint, you wanted to ask something like: "As plotted the orange line is not symmetric, but it is supposed to represent a symmetric functions (a Gaussian). How can this be right?" It is important to focus our attention on the right feature(s) of the figure. Because you asked about the "fit" several of us were looking at the relationship between your data and the fit-function and trying to figure out what was bugging you.
Nov
23
comment Should a Gaussian Curve Always Be Drawn Symmetrically?
A general word for what has happened with the plotted points of the function not being symmetric is "aliasing" (which has several other, related, meanings in the graphics world). That is, as Floris says, to be expected unless you force the relationship between the mean and the plotted point to be symmetric.
Nov
23
comment Should a Gaussian Curve Always Be Drawn Symmetrically?
Mind you, with the amount of data that you have all those things are to be expected.
Nov
23
comment Should a Gaussian Curve Always Be Drawn Symmetrically?
You may need to specify the question better. A Gaussian function is symmetric about it's mean by construction. It can't help it. So, what is the asymmetry that is bothering you? That the mean is not quite zero? That the fit may be underestimating one tail and over estimating the other. That they data simply have some scatter?