34,571 reputation
347119
bio website inspirehep.net/…
location Duchy of Grand Fenwick
age 43
visits member for 3 years, 11 months
seen 3 hours 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.


4h
comment Should I abandon my thought experiment about time?
The retardation of the signal (the technical word for what you describe here) is separate from time dilation and is not enough to explain what would be observed at high separation velocities.
15h
awarded  Nice Answer
1d
comment What is logical way to calculate percentage error?
It's not of interest outside of teaching laboratories because there is a built in assumption that the right answer is known. Only, we're doing science and trying to learn something new (again once you get beyond leaning exercises in school). Real science has to find a way to quantify precision and uncertainty without reference to a predetermined correct value.
2d
comment What causes the recessed blade of some folding knives to emerge in a kinetic opening?
In at least some dvices the blade starts at a position of stable equilibrium where the centrifugal pseudoforce alone won't cause it to move, but the Euler pseudoforce that develops as you begin the motion is enough to pull it past equilibrium.
2d
comment Two carts connected by spring on frictionless track
Now this is the kind of homework related questions that is good for Physics SE.
2d
comment Is the decay $B\rightarrow K^* \gamma$ decay allowed in the Standard Model?
The branching ratio quantifies it. Singly weak decays are much more common than doubly weak decays (by ratios of 10000:1 or more).
2d
comment Do we exist in multiple dimensions?
You just defined what you mean by "actually exist" by saying that it should actually exist. Define what consequences you think are required for an extra dimension to be "actual". I'm being persnickty about this because I sometimes get the idea that people asking this question don't have a clear idea what it means for a dimension to exist---especially in the context of string theory where the extras are currently presumed to be compact and small.
2d
comment Do we exist in multiple dimensions?
As usual, we'd need to know what you think "actually exist" means before we could answer this question even if we had string theory fully tested and the proper variant identified. Is it sufficient that the theory requires them?
2d
comment Is the decay $B\rightarrow K^* \gamma$ decay allowed in the Standard Model?
Any two-W process is going to be weak-surpressed relative the dominate singly weak decays. Looking is the copy of the particle physics booklet on my desk I see some other double weak decay channels listed with branching ration limits in the $10^{-4}$--$10^{-6}$ range. The listed limit for decay to $K^0 l^+ l^-$ is $3 \times 10^{-7}$.
Oct
22
comment What is the mass of the unstable particle?
Conserve four momentum and rely on the relationship between mass, energy and momentum.
Oct
22
comment Calculating the induced emf without knowing the change in magnetic flux
The problem expects you to engage on more than one level. You're doing fine employing Faraday's law, but you are also expected to deal with the problem in terms of energy.
Oct
22
comment What is logical way to calculate percentage error?
The place where working scientists bother with fractional error is in comparing the size of uncertainties: "neglecting the foo asymmetry is about a 2% error, and we're looking at about 5% counting error anyway so I think it is OK."
Oct
22
comment What is logical way to calculate percentage error?
Assuming that you are going to compute this thing at all, the sign carries useful information. But you certainly don't compute it in the case of an expected value of zero---that case always calls for careful treatment.
Oct
21
comment What is the actual energy content of the Sun?
Most of the hydrogen is ionized, you're low by a factor of roughly two.
Oct
21
comment How can randomness exist?
Right here "However, since it's caused by something," you have presumed your conclusion. The evidence on the ground can't absolutely rule this out, but it comes very close and a deterministic universe is out of favor right now.
Oct
21
comment When a planet is heated through gravitational pull, where is the energy taken from?
Related: physics.stackexchange.com/questions/52132/…
Oct
21
comment Underdetermined forces in a statics problem
@BenCrowell He's right for static friction with a non-deformation assumption (i.e. the sort we teach in PHYS 101). In that case it is always "just enough to prevent relative motion" up to the point where it fails and motion begins. The difficulty here is that examined at high resolution there can be deformation both normal to and across the surface so both the normal force on one side and the static friction on the other can be supporting the cylinder against motion along one direction (i.e. both can have non-zero values in a quiescent state), and ambiguity arises. Time to break out the FEA.
Oct
21
comment How can we tell if a molecule is in thermodynamic equilibrium from scattering data?
I've a (roughly third-hand) story about people assuming equilibrium and later finding it wasn't so. Their system exhibited an anisotropic Doppler broading, which is one way to rule out equilibrium.
Oct
21
revised What Did Nobelaureate Smoot Mean by “Modern Efforts to Find Violations of Special Relativity”
added 539 characters in body
Oct
21
revised Is time not a universal parameter, really, in special relativity?
added 17 characters in body