35,275 reputation
348120
bio website inspirehep.net/…
location Duchy of Grand Fenwick
age 43
visits member for 4 years
seen 14 mins 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.


Mar
11
revised How do we perceive colors outside our gamut?
edited tags
Mar
11
comment What is the minimum optical power detectable by human eye?
There is actualy rather a lot of ambiguity in this question right now. The sensing cells in your eye can respond to single photons (though their QE is not high). However, there is a preprocessing layer (which as a particle experimenter I would describe as a hardware trigger) which discards isolated hits so they never register in the conscience mind. I assume you mean to ask about the dimmest light which can be used to make decisions.
Mar
11
comment Most efficient type of heat pump
"E.g.: $T_{cold} = 30\,°C$ and $T_{cold} = 300\,°C$ yields a high efficency of 0.9." No, it doesn't. You must express these temperatures on an absolute scale. $T_{cold} = 30\,\text{K}$ and $T_{cold} = 300\,\text{K}$ gets a 90% efficiency. As written your situation gets a bit less than 50%.
Mar
11
revised Experiment to measure initial speed of high speed tennis ball?
edited tags
Mar
11
comment Calculating the mass equivalency of a song?
Welcome to Physics.SE. We have the MathJax engine running on the site which allow us to write mathematics in a LaTeX alike language. There are some minimal notes on it in the FAQ.
Mar
11
revised Calculating the mass equivalency of a song?
added latex and some minor spelling; strip "thanks" and repace unicode with MathJax markup
Mar
11
reviewed Edit suggested edit on Most efficient type of heat pump
Mar
11
revised Most efficient type of heat pump
spelling and extended question.
Mar
11
comment Why does Quantum Electrodynamics Allow a Photon to Exist Temporarily as a Positron and an Electron?
@John, this is simply the observed behavior of quantum mechanics. It even has a name: "the totalitarian rule" (totalitarian because everything that is not forbidden is compulsory...). There is a level at which physics explains why (in terms of more fundamental physics), but at it root physics is descriptive not prescriptive and simply says "this is how things are observed to be".
Mar
11
comment Regarding real field Klein Gordon Equations
Please do not remove the content of your question like that.
Mar
11
revised Regarding real field Klein Gordon Equations
rolled back to a previous revision
Mar
11
reviewed Approve suggested edit on Sitting on the bob of a pendulum
Mar
11
comment Experiment to measure initial speed of high speed tennis ball?
"I do know how to work it out when it's inelastic -- the trouble here being a tennis ball doesnt work that way" You have to build some kind of capture system into the pendulum. The variation I used when I was TAing physics 101 (lab low these many years past) had a hollow for the projectile with the aperture guarded by a ratchet: balls check in, but they don't check out.
Mar
11
comment Experiment to measure initial speed of high speed tennis ball?
"The failure of that kind of experiment, though, when measuring a tennis ball's initial velocity is that the tennis ball is inelastic." The ballistic pendulum is always inelastic. Every time. The analysis goes like this: conserve momentum in the inelastic collision between the projectile and the bob to get the initial velocity of the combined projectile--bob system; then conserve energy on the combined system to get the height of the swing. Work it backward to get the initial velocity of the projectile alone. This is the standard means of determining muzzle velocities.
Mar
11
comment A formal procedure for thermodynamic relations
The blog post Good Subjective, Bad Subjective may be useful to readers considering answering this. Unless, of course, you can actually offer a algorithm.
Mar
11
comment Are normal light waves more dangerous than WiFi radiation?
I have asked the bio mods, but no answer yet. There are only three of them and I don't know what timezones they may be in or if they even look in on weekends.
Mar
10
comment Can the path of a charged particle under the influence of a magnetic field be considered piecewise linear?
Note that the momentum of the emitted photons is not opposite the change of momentum of the bending particle in either the quantum or the quasi-classical view, so the presumed piecewise continuous trajectory fails to conserve momentum one way or the other.
Mar
10
comment Are normal light waves more dangerous than WiFi radiation?
If you would like I can inquire of the Biology mods if they want it.
Mar
10
comment Are normal light waves more dangerous than WiFi radiation?
This is basically a human health question, though it should be clear that physics plays a role and that one can reason from fundamental physics to find an envelope in which the answer most lie. Nonetheless I feel that it is not a physics question as such. And, indeed, the answer that it has attracted to date is not a physics answer.
Mar
10
comment What is the formula for calculating the length of any given day (sunrise to sunset)?
Please note that the use of mathematics in a problem does not make it suitable for the [mathematical-physics] tag.