40,854 reputation
356130
bio website inspirehep.net/…
location Duchy of Grand Fenwick
age 44
visits member for 4 years, 7 months
seen 54 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.

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


2h
comment Drag in low earth orbit
Well, look at the leap-frog method which is the simplest integration that will do decent orbits. Don't ask me how to implement it in a spreadsheet, however, I learned "proper" programming early enough to never get any good at spreadsheets.
4h
comment Drag in low earth orbit
Use a better programing environment and a better quadrature (numeric integration; you are using one of the simplest possible ways to go about that and it has some bad failure modes). You might also consider Computational Science as a better home for this. Let me know if you want it migrated.
6h
comment What's the difference between wave equation in PDE form and wave equation in normal form?
Some vocabulary that is often skimmed over in introductory treatments and generally forgotten by students the first anyway. A wave is a traveling disturbance. Any traveling disturbance. A wave the repeats is "periodic". A wave that sinusoidal in form is "harmonic". Not all waves are periodic, nor are all waves harmonic.
21h
comment Constant magnetic field attenuation by µ-metal (mu-metal)
You are encouraged to answer your own questions, but answers that consist of nothing more than a link(s) to some off-site resource(s) are frowned upon on Stack Exchange site. Reproducing the key ideas here would make this into a good and useful answer. Otherwise it is better suited to a comment.
22h
comment How do we measure thermal energy?
"Thermal energy is exactly the average ([...]) of the overall translational kinetic energy of all the particles of your system." Is treating a rather special case as if it defined the general meaning. In general there are non-translational modes and more-over some of the energy in those modes can be potential rather than kinetic.
22h
comment How can radiation be a transverse wave? Does light really resemble a rope? How can a 3D field be a medium for non-spatial 1D waves? Need mental model
CuriousOne is absolutely right that quantum objects don't have trajectories between points of observation. That is one of the reasons not to mix the two points of view until you know each of them separately.
22h
comment How can radiation be a transverse wave? Does light really resemble a rope? How can a 3D field be a medium for non-spatial 1D waves? Need mental model
There is a piece of advice about learning E&M that I give a lot: don't try to understand light in both the classical and quantum picture at the same same time. Pick one and learn it well. Then you can learn the other one on its own merits and without reference to the first. Then look at how they connect to one another. Trying to mix them is a recipe for misunderstanding until you understand both theories.
22h
comment Is light amplitude spacial?
No. The fields are vectors. They have direction. They acquire changing values in directions transverse to the direction of wave propagation. So, the waves are transverse. There just isn't a material substance involved: it is fields that are waving, not matter.
22h
comment Is light amplitude spacial?
No. There is no material thing or stuff that moves in any direction in a pure EM wave. Waves are traveling disturbances. The thing that is disturbed in a ripple on a pond is the position of a lot of water molecules. The thing disturbed in a EM wave is the value of the electric and magnetic fields. That's it. Full stop.
23h
comment How can radiation be a transverse wave? Does light really resemble a rope? How can a 3D field be a medium for non-spatial 1D waves? Need mental model
I think it is important for someone to say that the visualization you are showing show a single "ray" of light (which is why you are talking about it as a 1D structure), but real EM waves are spacing filling entities. The "ray" visualization is a tool for understanding where the energy flows are going, not a literal description of the structure of light.
23h
comment Is light amplitude spacial?
The antenna bit for two reasons: (A) the wave is not a "straight line", it is a space-filling oscillation of the field. and (B) because the response of the field depends on motion of electrons in the antenna to efficiently reproduce the time dependence of the wave. For the Faraday cage the reason is primarily because of Huygens' Principle: you need the retarded and un-retarded wave fronts entering the cage to have a lot of variation on scales less than the wavelength.
23h
comment How can radiation be a transverse wave? Does light really resemble a rope? How can a 3D field be a medium for non-spatial 1D waves? Need mental model
Possible duplicate: physics.stackexchange.com/questions/160042/… Also related: physics.stackexchange.com/questions/184381/…
1d
comment Understanding sine waveform
I haven't time to write a proper answer now, but in the stretched string, the energies in the problem are the simple energy of motion (meaning that you are interested in local velocities) and the elastic energy of stretching the string still further. Just like the in situ oscillation of a mass on a spring these two energies are constantly traded back and force by the elastic forces which set the local acceleration of the system. So it is $\ddot{y}$ that tells you which way energy is flowing and have fast that transfer proceeds.
1d
comment Understanding sine waveform
A surface wave on water in not a simple system and is not actually described by the expression I wrote down. The assignment of energy to various degrees of freedom in surface waves is considerably more complicated than in the case of, for instance, a wave on a stretched string.
1d
comment entaglement experiments in laboratories for atom and photons-how to?
There are a whole host of skills you need (most of which I don't have) from aligning the optics to gain matching the detector systems and setting up the DAQ and reducing the data once you have it. Setting up an experiment like this without some previous experience in experimental optics is going to be a big and frustrating task. I believe that we have some users who have done some benchtop optics but you might get a better response with a more specific questions.
1d
comment Understanding sine waveform
A problem with you question, however, both of your questions are physics questions but you have only described a mathematical wave. If you pick a physical system you will be able figure out what energies are at play and how each of them depends on the relationship between time and space. Likewise you'll see that it is the interaction of those energies that generate the propagation of the wave (or the continuation of the oscillation if that really is the system that you are interested in).
1d
comment Understanding sine waveform
As an aside, what you have written here describes an oscillation in place not a wave which would have a form like $A \sin\left(2\pi ft - 2\pi x/\lambda \right)$.
1d
comment How are determined experimentally the energy levels of the atoms ? How is the calibration done to several decimal points?
This is a better answer to the question in the title than to the x-ray specific version in the body.
2d
comment Prove that negative absolute temperatures are actually hotter than positive absolute temperatures
The one thing that everyone agrees on is that their behavior is a bit surprising, and that is to be expected as we don't encounter systems with temperature ceilings in day-to-day life. In any case, that paper is cited in the comments on most of our "negative absolute temperature" questions. I can assure you that most of the answer authors are aware of it. But the question presupposes the definition of temperature which generates 'negative' values and this post doesn't really address it.
2d
comment Is motion along the $x$ and $y$ axises independent with quadratic drag?
You should look at the link in Qmechanic's comment. The details of this problem have been of interest for a long time and progress on non-numerical solutions has been made in recent decades. Mind you, the numerical solutions have been good enough for gunnery for more than a century.