41,449 reputation
356134
bio website inspirehep.net/…
location Duchy of Grand Fenwick
age 44
visits member for 4 years, 8 months
seen 3 hours 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.

Been reading Zemansky & Dittman's book on thermodynamics recently. Quote: ``The concept of temperature is rich in interpretations and levels of abstraction.'' Nice.


8h
comment Mechanism for inelastic collisions in the particle world
If you are worried about particle "touching" at that level, then I guess you are still stuck in human level thinking. At the deepest level nothing "touch"es in the sense that you mean, all interactions are between fields. See physics.stackexchange.com/q/23797
22h
comment Expression of heat by the Brownian motion
I'm afraid I'm at a loss. You can either try to get hold of the text in question or make some other kind of literature search for "Stratonovich notation". Or abandon the project if you don't expect the reward to be worth the trouble.
22h
comment Will two clocks moving in opposite directions measure the same time as one at rest?
This has the same resolution as the usual twin paradox. Really, it does. Add up the proper time along the various paths.
1d
awarded  Nice Answer
1d
comment Bragg's interference
No, but it is important is making it clear why "parallel" doesn't mean non-intersecting. There is nothing wrong with your answer, of course, but the poster was looking at the diagram we draw and thinking about Euclid and non quite seeing how they come together. Huygens' principle is the answer.
1d
answered What is high energy physics?
1d
comment Charge of $W$-bosons in Feynman diagrams
This would be more complete if you noted that this rules work reliably for time-like $W$'s but is ambiguous for space-like $W$ exchanges.
1d
comment Why are electrons alike but photons not?
@Bort You should make an answer of that.
1d
comment Which centripetal force equation should I use for centripetal motion in uniform magnetic field, and why?
@user132522 The is no "the centripetal force" like there is a gravitational force and a electrostatic force and so on. Instead "centripetal force" is a label applied to some combination of forces---the sum of those pointing inward minus those pointing outward. You figure out this combination when you have circular motion, and ignore it when you don't. Which forces go into the combination depends on the problem. In the case of the free motion of a charged particle in a magnetic field, the only force is the magnetic force and it points in so for that problem $F_c = F_{magnetic}$.
1d
comment Expression of heat by the Brownian motion
I don't suppose the first mention of "Stratonovich notation" was accompanied by a citation? Alternately the authors of the paper may have provided that citation in an earlier, related paper. I'd would be helpful to have a link or at least the bibliographic data for the paper.
1d
comment Bragg's interference
This really isn't complete without mentioning that thought we draw rays as lines, Huygens' principle is in place and each of the ray should be envisioned at outgoing wave-fronts with small but non-trivial angular breadth. It would be even better if you mentioned the size of the detector elements.
1d
comment Can sound waves be made to project 3-D shapes, like a reverse sonar?
The phrase you are looking for is "phased array", and they can---in principle---do all kinds of cool things.
1d
comment Has New Horizons' visit to Pluto taught us anything deeper than mere… facts?
I'd like to a put a word in for the notion that the "mere [] facts" that you're so blasé about are more appropriately known as "data", and are kinda important in the scientific process.
1d
comment Why can't we see light travelling from point A to B?
Here's the rub: compute the intensity needed for the original source when you are talking about length scales on the order of light years. Even with a highly (but not perfectly!) collimated original beam, the scattered light is projected into a lot of solid area and therefore falls off with the familiar dependence. So, design the right detector system and that's not a huge problem, but rely on, say, the Mk I eyeball and you have problems.
1d
comment Showing that a mass moves a half cycle
You've gotten so bound up in the mathematics of the problem that you're not thinking about the system. What kind of behavior does it exhibit if $F=0$ (that is we remove the friction from the system)? How---other than just slapping together a differential equation---can you analyze such systems? In what ways does the reduction of maximum excursion related to the frictional force, assuming the kind of system we have when there is no friction (I know, but start by assuming the friction is small)? And so on.
1d
comment Does an ice cube change its core temperature as it melts?
I've also scrubbed or edited a few comments that were spiraling down into an argument.
1d
comment short circuit an alkaline battery
One of my students works for a specialty battery manufacturer in town and brought us a video of a nail penetration test (that is, they clamp the cell down and shove a nail through the cell with a hydraulic system...) conducted on a LiPo cell. The spray of white-hot fiery stuff was about 2 meters long. Wow!
1d
comment Does an ice cube change its core temperature as it melts?
Right here "When a mass is undergoing phase transition, all invested energy (or radiated energy, depending on the direction it is going) will be used up on the phase transition" you have tripped on the simplification usually taught to students. That is only true if the heat transfer takes place on time scales longer than the thermal-relaxation time of the system. Molecules in the melting zone don't lose their connection to the ones just in from that and all thermal processes are stochastic at a microscopic level. Frisbee's answer is correct.
2d
comment How can the magnetic field surrounding a current-carrying wire ever be uniform?
Secondly, when we want to make a uniform field we don't use a single, long, straight wire to do it. It won't be long before you are shown geometries that can achieve that to a very good approximation indeed.
2d
comment How can the magnetic field surrounding a current-carrying wire ever be uniform?
Two possibilities here, one you are looking at a question of example that says "Assume a wire runs through a region of uniform magnetic field.." in which case it is not talking about the field from the wire but about some externally imposed field.