31,883 reputation
341103
bio website inspirehep.net/…
location Duchy of Grand Fenwick
age 43
visits member for 3 years, 8 months
seen 29 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.


Jul
18
revised Can you explain Fermat's Principle to me?
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Jul
18
comment Could Dark Matter particles that don't couple to quarks or leptons have been produced?
@jhobbie WIMPs are popular (at least partly) because we know how to look for them (and because they can cool; I suspect that the OP's guess won't cool right), but this is mostly a matter of "looking for our keys under the streetlight". If we don't even know how to try to detect a particular flavor of dark matter than there is little point in putting a lot of effort into it.
Jul
18
answered Can you explain Fermat's Principle to me?
Jul
17
comment Twin Paradox speed of light
Yes. Do look at the wikipedia article "The general relativity solution for a static homogeneous gravitational field and the special relativity solution for finite acceleration produce identical results." and "the issue is how long the world-lines are, not how bent".
Jul
17
comment Why the original BB84 paper “Quantum cryptography: Public key distribution and coin tossing” has 'withdrawn' status?
One of the reason's for withdrawal in press is "accidental duplicate" which may explain the date issue.
Jul
17
comment Why the original BB84 paper “Quantum cryptography: Public key distribution and coin tossing” has 'withdrawn' status?
Piotr's link is to the DOI page and the withdraw policy link is to the publisher's policy.
Jul
17
comment Twin Paradox speed of light
You do not need general relativity to explain the twin paradox. In some cases GR offers a handy way, but it is not needed. You do need to add up the proper time along the paths of the participants---which you can do with only special relativity and is always sufficient to explain the situation.
Jul
17
comment Understanding gyroscopes
As usual there is much to be gained by reading 'It Has to Go Down A Little, In Order to Go Around'- Following Feynman on the Gyroscope. The short-short version is that our usual classroom explanation is incomplete, and shows that a slightly more complete version reproduces much more of the dynamics.
Jul
17
comment GPS Satellite - Special Relativity
The relative velocity can change. In fact does change. But even at the equator the velocity of the observer is less than 500 m/s relative the center of the Earth, so the range of relative velocities is between 4000 and 5000 m/s. Compute the $\gamma$ for each of those and ask yourself if it matters. (Use the binomial approximation for gamma or a calculating tool with a lot of figures.)
Jul
17
revised How to calculate a collision which is partly elastic and partly inelastic?
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Jul
17
answered How to calculate a collision which is partly elastic and partly inelastic?
Jul
17
comment Changing from potential to kinetic energy
Of course no physicist would use the OP's words to define work, but they would say that "work is the movement of energy from one place or form to another place or form by mechanical means" which is fairly applicable to the OP's question. And, I suspect, pretty unsatisfying.
Jul
17
comment GPS Satellite - Special Relativity
Have you figured the degree of difference (hint: it is non-trivial but not particularly large)? Have you considered averaging over the largest and smallest $\gamma$ that could be involved? How big a difference is it going to make in the final result?
Jul
16
comment How can we detect X-rays?
Re: Xenon. You can also use other Nobel atoms in their liquid state. Liquid argon is quite efficient as long as the nitrogen contamination is kept low. Not very interesting for a stand-alone detector but it is one of the things that makes large scale LArTPCs practical.
Jul
16
comment Was the 2013 meteor over Russia stronger than an atomic bomb?
I've stripped a lot of essentially political commentary. You were a participant and want a copy let me or another mod know, but it wasn't doing anything for the site.
Jul
16
comment Physical reason for annihilation?
Always worth re-re-re-noting the existence of the Totalitarian Rule of quantum mechanics: everything which is not forbidden is mandatory.
Jul
16
comment Book called The Trouble with Physics and current status of superstring theories
And stellar structure and platent formation and dozens of different kinds of condensed matter theorists and the attosecond guys and the non-linear optics guys and the quantum information types who are thinking about computers and communications systems instead of black holes and ... The list goes on and on.
Jul
16
comment Book called The Trouble with Physics and current status of superstring theories
One should also take note that next generation fundamental theories are (contrary to the impression you would get from the media) a small corner of the physics world. They don't even represent a large fraction of the pure theorists.
Jul
16
comment Are the ideas of the speed of light and the absolute top speed inside the universe equivalent?
Note that the LHC does not hold the record for human-created particle beam speed. That distinction belongs to LEP if you count beams in collider systems or some high energy neutrino beam or another in the unlimited open division.
Jul
16
comment Physics of antenna requirements
Er, the best version of the simplest possible design (one conducting stick) may well be a half-wavelength center-driven one, but that is hardly all there to antenna design.