35,921 reputation
350122
bio website inspirehep.net/…
location Duchy of Grand Fenwick
age 43
visits member for 4 years, 1 month
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.


Nov
24
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
Nov
24
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.
Nov
24
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.
Nov
24
revised Can a free hydrogen atom constitute ionizing radiation?
speling
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 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?
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?
Nov
23
comment Why are neutrons present in an atom?
Is the question "Why should it be this way?" or "How do we know that it is this way?". The former can be answered in therms of QHD but because philosophical if pushed to the limit. The latter is clearly a physics question.
Nov
23
comment Energy resolution of LHC Electromagnetic Calorimeter
When you look at a (segmented) calorimeter, you do apply some process to select a bunch of hits which you are treating as belonging together. Then you add up the energy those hits represent and that sum is your $E$. The selection process is important and for a calorimeter in a colider experiment it is unlikely to be "just take it all" the way it might be in a low rate experiment.
Nov
23
comment If a neutrino has a rest frame, why can't a photon have a rest frame as well?
The problem is not using these wonky, almost-right ways of talking, it's trying to answer this question in this way. You give an impression that will only lead the beginning student astray.
Nov
23
comment Determine reactance force of four load cells arranged in two dimensions
You exhibit a system of equations. You solve the reverse problem by inverting the system of equations. It is more compact written in matrix form, which is also the way you will find inverting linear systems of equations addressed in every introductory text on computational methods.
Nov
23
comment Hourglass on the Moon
"Since the force of sand hitting the bottom is only 1/6th as much on the moon, there can only be 1/6th as much sand in the air at any given time. " Doesn't follow. What is canceled is the loss of weight which is proportional to both $g$ and the mass flow rate. But the impact impulse is also proportional to both $g$ and the mass flow rate. I don't think that you can conclude anything from that.
Nov
23
comment If a neutrino has a rest frame, why can't a photon have a rest frame as well?
You are mixing classical wave descriptions with quantum descriptions and doing so incorrectly. In a medium photons are constantly interacting with atoms---being absorbed and re-emitted or undergoing coherent forward scattering. Either process is described by annihilation and creation operators so it it not sensible to talk of a single slower than light photon.
Nov
22
comment “Reality” of length contraction in SR
An observer doesn't have to change the universe, it is the very character of the universe that makes the the actual and correct measurement of lengths to change. It is built-in from the foundation up.
Nov
22
comment Energy resolution of LHC Electromagnetic Calorimeter
BTW -- the tag [accelerator-physics] is for the physics of accelerators, not physics done by taking the beams.
Nov
22
revised Energy resolution of LHC Electromagnetic Calorimeter
edited tags