32,101 reputation
343105
bio website inspirehep.net/…
location Duchy of Grand Fenwick
age 43
visits member for 3 years, 8 months
seen 15 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
22
comment How much could one slow down aging using existing spacecraft?
"the gamma rays emitted by matter anti-matter annihilations in its reacor" The problem with simple matter-antimatter reactions (aside from the bit about getting enough anti-matter together) is that much of the energy is released in neutrinos and pions not photons. In principle you can steer about half the pions to your advantage, but the neutrinos are isotropic and you can't steer them.
Jul
22
awarded  electromagnetic-radiation
Jul
22
comment Why Light and Observers have different laws of physics
Excitations of quantum fields, like photons (and indeed every other fundamental particle), are the things we call particles. These things are what particle physics studies. Photons are particles. And photons travel at the speed of light. And this is OK and not at all a problem. Their path between two non-identical places takes zero proper time and finite time as measured by all observers and this is OK and not at all a problem.
Jul
21
awarded  Good Answer
Jul
21
comment How much could one slow down aging using existing spacecraft?
"and head away from the Earth at top speed" That all depends on your top speed and acceleration profile.
Jul
21
answered Why do hydraulic jumps form?
Jul
21
comment How would an X-ray scanner identify a mirror?
An alternate way (that is a particle physicist's way) to look at it is in terms of the momentum transfer from elastically scattering an x-ray. Even at moderately shallow angle that momentum is more than enough to scatter the electron right off the atom, but that would make the event inelastic which means it is not "reflection" at all. To get reflective behavior you need quite shallow angles indeed.
Jul
21
awarded  Nice Answer
Jul
21
comment How to explain the weak force to a layman?
Wrong in every particular.
Jul
21
comment How does radiation shielding using absorbing materials work?
@Icarus The figure of merit is roughly the number of electrons per unit area in traversing the whole of the shielding. Dense materials allow you to have a high figure of merit in a short distance (which is very often the thing you want), but in other applications the best engineering deal may be found from maximizing electrons per unit area per dollar. That is often when water gets used. For instance, the on-site cooling ponds for spend fuel at reactor facilities are not compact, but they are cheap (and they provide passice cooling as well).
Jul
20
comment Does quark have fixed energy?
Presumably related to the comments here: physics.stackexchange.com/q/127283
Jul
20
answered Does quark have fixed energy?
Jul
20
comment Mathematical model that allows the existence of an infinite number of smallest, but different particles
@HolgerFiedler No (on-shell) photon ever spontaneously pair produces: it requires help from the environment (in a typical discussion this is a "spectator nucleus") and sufficiently high-energy quarks have similar processes. Again, neither photon nor quarks have a fixed energy and they both have fixed mass.
Jul
20
comment Special relativity allows arbitrarily low travel times between two locations
All of this is correct, but what is the question?
Jul
20
comment Electricity production
Oh, I noticed. That's why I suggested a continuous process rather than a one-and-done.
Jul
20
comment Electricity production
Don't leave out chemical sources ... a fuel cell lets you have a continuous process for converting chemical energy to electrical energy.
Jul
20
comment Mathematical model that allows the existence of an infinite number of smallest, but different particles
@HolgerFiedler The points are (1) that it is the mass that is well defined (an intrinsic property of the particle) not the energy (which depends on external factors) and (2) that the mass of the photon is also well defined. Photons are different from quarks because they have different quantum numbers not because one is more entitled to the mantle of "particle" than the other.
Jul
20
reviewed Approve suggested edit on How would an X-ray scanner identify a mirror?
Jul
20
answered How would an X-ray scanner identify a mirror?
Jul
20
comment The physical definition of work seems paradoxical
In point of fact your muscle tissue is doing work when you strain against a immobile object (because individual fibers are contracting and relaxing), but all that energy goes into heat instead of into a larger scale mechanical change.