38,804 reputation
354126
bio website inspirehep.net/…
location Duchy of Grand Fenwick
age 44
visits member for 4 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.

Been reading Zemansky & Dittman's book on thermodynamics recently. Quote: ``The concept of temperature is rich in interpretations and levels of abstraction.'' Nice.


Mar
28
comment What is the particle distribution in Saturn's Ring System?
"Would Newtonian physics not dictate that objects of different masses at the same elevation must travel at different speeds to maintain orbit?" It's worth noting that $m_\text{ring object}/m_\text{planet}$ is a very, very small number. Why don't you compute the difference in circular orbital velocities between, say 1 gram and 100 kg objects in, say, the F ring. It is an instructive calculation.
Mar
27
comment beta minus decay: expression for maximum electron energy
Hmmm ... "because of the mass scales the beta and the neutrino take the bulk of the kinetic energy" is better. Now, that is largely understood when people talk about this problem but being explicit about it can't hurt your understanding. It is also useful to apply the non-relativistic and ultra-relativistic approximation for the kinetic energy where appropriate.
Mar
27
comment Is the lay explanation of the equivalence principle wrong?
More sophisticated arguments at that level include some language equivalent to "in a sufficiently small laboratory", which is strictly correct as the equivalence principle is a local (in the technical sense) statement.
Mar
27
revised X-ray background radiation
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Mar
27
comment X-ray background radiation
BTW, You should edit the data in that comment into the question. That makes the question self contained and does not ask every reading to parse the comment thread to figure out what is going on. Further, comments are transient and subject to deletion.
Mar
27
answered X-ray background radiation
Mar
27
comment X-ray background radiation
A spectrum or a hint about what energies you are seeing in the detector, and some information about what kind of detector you are using would really help. There are several regular users here who have some experience with one or more classes of detectors, but the thing we all know is that there are a lot of possible answers. Give us something to work with here.
Mar
27
comment Is it correct to use $P=\large\frac{V^2}{R}$ for AC circuits?
@MoctavaFarzán Yes, that's the way.
Mar
27
revised Is it correct to use $P=\large\frac{V^2}{R}$ for AC circuits?
added 3 characters in body
Mar
27
answered Could gravity be repulsive at short distances?
Mar
27
answered Background gamma radiation
Mar
27
comment Background gamma radiation
On the other hand, buzsh does have a problem with his units request. Curies is not a dose. It's just a count of events per unit time (and the SI unit of activity is the Becquerel with $1 \,\mathrm{Ci} \approx 3.7 \times 10^{10} \,\mathrm{Bq}$). Sieverts is a measure of biological damage from radiation. They are not at all the same thing. There is no general conversion for $\mathrm{Ci}$ to $\mathrm{Sv}$, and to define one for a particular case requires you to specify radiation type, radiation energy and absorption profile. None of which we have.
Mar
27
comment Background gamma radiation
If he's simply making the distinction between photons (represented with a $\gamma$ at all energies in particle-physics) and massive particle radiation, the meaning is clear.
Mar
26
comment Physics without time
Also, there have been B-decay measurements in which T-symmetry is explicitly violated (and of course all CP-violating measurements are assumed to violate T, as well). And while that's pretty esoteric does it throw a wrench into the whole idea if there are time-non-reversablilties at the level of basic law?
Mar
26
comment Physics without time
In what way would allegedly "time-free" physics be different? I mean, the fact that things can happen in the same place but not coincide would have to be reflected somehow, right?
Mar
26
comment Propagation of uncertainty - which formula?
Note that in certain engineering contexts, the upper bound is regularly used in determining the tolerances that should be demanded. Not exactly a physics answer, but one of some interest to a large subset of people who study physics.
Mar
25
comment Given the quantum Zeno effect, won't continual observations of a photon stop/slow down light?
A second concern is the idea of observing a photon: observation implies interaction and that mean the destruction of the photon. At best you get another outgoing photon, but it is not the same state.
Mar
25
comment Why is the Specific Heat of Helium 36 times greater than Xenon?
In a kinetic gas it is the kinetic energy, but that is proportional to velocity squared. For systems that are not non-interacting there are also potential terms.
Mar
25
comment Why is the Specific Heat of Helium 36 times greater than Xenon?
Start with en.wikipedia.org/wiki/Kinetic_theory.
Mar
25
comment Why is the Specific Heat of Helium 36 times greater than Xenon?
Err ... "Intuitively, temperature equals velocity" Is wrong two ways. First, temperature is proportional to the energy not the velocity, and secondly it is the average energy per mode, not the total (which should be very clear because total energy is extensive and temperature is intensive). So for a change in energy $\Delta E$ the temperature change is proportional to $\Delta E/N$ where $N$ is the number of modes (which reduces to the number of atoms for an ideal gas).