35,911 reputation
350122
bio website inspirehep.net/…
location Duchy of Grand Fenwick
age 43
visits member for 4 years, 1 month
seen 13 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.


3h
comment Relativistic non-linear Walecka model
"And why cannot Google show a satisfactory result to such a simple question?]" Searching based on plain text doesn't deal well with restrictive adjectives because there is a context dependency that is neglected (or treated with fairly rough heuristics). The place to start is in understanding what a Walecka model is in general (a meson exchange based model of nuclear physics, I believe), and only then understand what the adjectives imply.
21h
comment How do we find the accuracy of atomic clocks?
The fundamental reason that atomic clocks are so accurate is that they are just counting devices. You count cycles. And when you count enough of them the bits that you may have missed at the beginning and the end get too small (fractionally) to care about. Then the problem becomes one of checking that you don't miss some as you go along and that is easier to do in comparison mode.
21h
comment Why is Larry Niven's Ringworld Unstable?
@JamesBowery No. For the same reason that gravity isn't a restoring force. Both fall by $1/r^2$, so both are subject to the same math.
1d
comment Why do physics students find vectors so difficult to deal with?
I would hesitate to use the word "component" in that way for fear of students conflating it with the use of the same word meaning the inner-products with the basis vectors of our coordinate space. Students sufficiently confused without adding any ambiguous vocabulary to their difficulties. Perhaps "two properties" would be better.
1d
comment Elastic scaterring of neutrinos - Why does the electron neutrino dominate this channel
The speed of the electron needs to be about 3/4 of c for that to happen. That means a kinetic energy of about 270 keV = 0.27 MeV. Solar neutrinos have energies of about 1 to 10 MeV. In general there is more than sufficient energy.
2d
revised When conserving angular momentum, about which point(s) should it be calculated?
added 2 characters in body
2d
answered Why could the Homestake experiment only detect electron neutrinos
2d
comment What is the temperature of the clear night sky from the surface of Earth?
Mind you "clear" to the mark 1 eyeball means a wide range of absorbtivity as measured by sensitive instruments.
2d
answered When conserving angular momentum, about which point(s) should it be calculated?
2d
comment Can Einstein's 'Theory of General Relativity' exist in Harmony with 'Quantum Mechanics'?
Also related: physics.stackexchange.com/q/71568. You seem to be asking a lot of questions in a hurry without even researching them on this site. Seriously, don't expect us to do your work for you.
2d
comment Why can't dark matter be baryonic?
Duplicate of physics.stackexchange.com/q/26778
2d
comment At what point do researchers in physics make the leap from wild theoretical ideas to physical experiments?
To be blunt, dark matter only appears wild if you don't know the history of what was carefully considered and ruled out before this hypothesis came to the fore nor what evidence accumulated in favor of the idea while other--less unusual--ideas were considered more plausible. In other words dark matter as a serious candidate hypothesis didn't spring fully formed from anyones forehead, it was reluctantly admitted through the servants entrance when nothing more respectable could be found to do the job.
2d
comment Relativistic Kill Vehicle
The drag at those speeds isn't well treated by a viscous parameterization like that. The forces are essentially all inertial.
2d
comment How possible is it that the Large Hadron Collider (LHC) on its second try, could disrupt the gravity of Earth?
As with all these (pop-sci plausible) suggestions, if there was any truth to it the Big Particle Accelerator in the Sky would have done this to us long, long ago. SO relax.
Dec
12
comment Can antimatter-matter collisions generate heat?
"usually high energy gamma radiation" Er ... if hadrons are involved there are a lot of pions which means that a lot of the energy ends up as neutrinos.
Dec
11
comment Do the fields exist without electric charges?
I'm with @John here. The only fundamental neutral fermion is the neutrino and $\nu + \bar\nu$ goes only to $Z^0$ which does not couple directly to photons.
Dec
11
comment What is meant by the temperature of the CMB?
"Temperature usually means the jiggling about of atoms" In an very introductory treatment it does, but that is just to give you a starting place. Serious treatments of temperature are not linked to any given system.
Dec
11
awarded  Good Answer
Dec
10
comment What's the difference between centre of mass & centre of gravity for massive bodies?
Mark, well at least where I see people make a distinction this is the one they make. There are texts that do not distinguish at all.
Dec
10
reviewed Approve What's the difference between centre of mass & centre of gravity for massive bodies?