29,719 reputation
33994
bio website inspirehep.net/…
location Duchy of Grand Fenwick
age 43
visits member for 3 years, 5 months
seen 1 hour 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.


1h
comment What is the meaning behind the neutrino oscillation parameter?
@Danu: the flavor basis and the mass basis are both valid and equivalent descriptions of the system. The flavor states do not have a well defined mass, but just as importantly the mass states do not have well defined flavor.
13h
comment What is an intuitive explanation using forces for the equatorial bulge?
The way to understand it in terms of forces is to use the centrifugal pseudo-force (i.e. work in the rotating frame), but unless you are very clear on the difference between real forces and inertial pseudo-forces this is likely to cause confusion at a later date.
14h
comment If the axis of rotation is fixed, is it ok to say clockwise torque?
Compare to physics.stackexchange.com/questions/71455/…. Just because you are perfectly clear on what you mean does not imply that your listener is perfectly clear on what you mean. In order for "clockwise" to be clear you have to be have agreed on a "forward" first.
14h
comment Protons (as opposed to neutrons) to mediate nuclear fission?
@GODPARTICLE He means the Coulomb force ... the electrostatic interaction between the positively charged nucleus and the positively charged proton is repulsive and quite significant on the scale of kinetic energies in a nuclear reactor.
1d
comment Does the unit of Inertia include radians?
You'll find essentially the same question expressed in different ways in physics.stackexchange.com/q/33542 and elsewhere.
1d
comment Reason for the experiment
Eh?? For the same reason it is important for every other piece of scientific knowledge...
2d
comment Does timbre consist in pitch and volume?
Timbre is almost entirely in the overtones, but this is emphatically not a physics question.
2d
comment Protons and Electrons Occupying the Same Space
The question isn't "What force holds it out?" the question is "What force holds it in?", because quantum states tend to spread out. And the answer is that the electromagnetic interaction (mostly electrostatic) is what holds it in.
Apr
14
comment Loop-the-loop question
As @Floris says, the solution you give is for a slideing block of negligible height. The solution you are supposed to get is for a negligible block of height $2r$ (allowing for the height of it's CoM, and the correct solution must also allow for the angular kinetic energy of the ball (which means it depends on whether the ball is solid or hollow).
Apr
14
comment Precessing gyroscope torque
Yes. There is more when you look at it in detail, but that is how you explain the biggest effect.
Apr
14
comment Precessing gyroscope torque
Look again at the definition of torque. Look in particular at the direction in which it is defined.
Apr
14
comment Why does light seem so slow when compared to everyday observations here on Earth?
The flipped version is "Why is space so big?" (which gives us the chance to bring up Douglas Adams' quote yet again...
Apr
13
comment Mandelstam variables 1 positive 2 negative
@LDC3 The $p$s that appear are 4-momenta. So no, you cannot guarantee that the squares are positive.
Apr
12
comment What can I say about compatibility between predictions and results?
If your uncertainty estimates are good (on both theory and experiment) than the error is 2.5--4 times the uncertainty. The small size of the error makes this a precise measurement but does not change the basic fact that you are several sigma out in three of four channels.
Apr
12
comment Very short decay: A bare quark?
You might find the comments under a post where I relayed this tidbit useful.
Apr
12
comment Very short decay: A bare quark?
Do you know what the word "hadronize" means in this context?
Apr
12
comment Experimental evidence for the relic neutrinos
What should I say that isn't in the Wikipedia article? There are three known flavors of neutrinos with some hints that there might be 1--3 sterile flavors. The cosmology is mostly consistent with 3 flavors early and prefers four at later times. (I'm out of my depth on this stuff but naively I would expect the sterile flavors not to contribute early on, and to start to come in at later times.)
Apr
12
comment Is it possible to look into the beginning of the Universe?
The BICEP experiment has now reported a positive result using the method suggested by @FrankH here.
Apr
12
comment Experimental evidence for the relic neutrinos
There is no direct evidence at this time. We don't even know how to begin.
Apr
12
comment Which is the smallest known particle that scientists have actually *seen with their eyes*?
This question is one that seems obvious and clear to the layman, but is very subtle in the mind of an expert. You have said on one hand that Davidmh's answer is what you want, but on the other hand it fails your own "same photon" test because that is the scan of a long exposure photograph. The question could just as well be "opinion based".