4,011 reputation
11318
bio website
location
age
visits member for 4 years, 1 month
seen 6 hours ago

21h
comment Violation of conservation of energy?
@WetSavannaAnimalakaRodVance Thanks, the lesson is you run into problems when you try to handwave in answers ;) I guess the core of what I meant was that you have to consider the source emission in the analysis and not just that "there is a photon to start with, now what happens". And as you note in your interesting writeup of maxwell<->one-photon QED states, there are many analysis methods possible to reach the conclusion.
2d
answered How often does a GPS receiver receive microwave signals from satellites?
2d
comment Violation of conservation of energy?
This answer is interesting if you do try to model the source as a classical emitter! I think maybe it ends up in conflict with the premise or spirit of the question as a philosophical question of perfect destructive interference though.
2d
answered Violation of conservation of energy?
Apr
5
awarded  Yearling
Feb
27
comment Is it possible to get the (Pauli) repulsive term in the Lennard-Jones potential from theoretical considerations?
It's not even through experimental fits, it's because it's computationally more cheap to evaluate the power of 12 from the power of 6 you already calculated for the van der waals approximation, and this is good enough for molecular dynamics. This is all explained already in the first paragraphs of the wikipedia entry of the LJ potential (en.wikipedia.org/wiki/Lennard-Jones_potential)
Feb
24
awarded  Enlightened
Feb
24
awarded  Nice Answer
Feb
17
comment Is a CRT / Electron gun in need to be in a closed loop?
@mutiju Hi! Normally no, the negative feed from the power source will keep feeding electrons into the metal. Maybe if you don't connect it anywhere, but just heat it up, maybe you'll shake off some electrons but I guess they will just fall back into the metal.. it's not really an electron gun then anyway..
Feb
17
answered Is a CRT / Electron gun in need to be in a closed loop?
Feb
15
comment What would we see if a camera orbiting close to light speed beamed down images of us on earth?
View along the trajectory (not perpendicular) and a description: youtu.be/0uunSMipnxA
Feb
11
comment How could the “Big Bang” singularity have actually expanded?
I would say the actual existence of singularities is pretty far from established :) It's a sign that the equations break down, that's about as far as the "not disputed" goes I think.
Feb
8
comment Boundaries of holes in a toast burn faster?
I suspect that this is related to that a 90 degree edge around the bread hole has less volume of bread around itself to dissipate the incident radiative heat than a point on a flat bread-piece..
Feb
7
comment Why are atoms of the same element exactly the same?
What I mean is that an atom with say a dozen electrons undergoing absorption of a photon for example, is not interchangeable with a similar atom drifting around in free space. The atom as a whole including all the electrons is only approximately the same as another such atom due to dynamics, even if all the constituents are indistinguishable. I think John's answer contains pretty much what I wanted to add :) But then again, these distinctions are less related to the chemical properties the OP asks about..
Feb
7
comment Why are atoms of the same element exactly the same?
I think your and Lubos answer could be combined in some way :)
Feb
7
comment Why are atoms of the same element exactly the same?
While it's certainly true that for all practical purposes two atoms in steady state are interchangeable, would you really go so far as state that the nucleus and electron cloud are technically identical between the atoms? After all, the simple "orbital" Hamiltonian could be modulated in a possibly non-interchangeable way if you would ever set up an experiment to test this. In other words, the atoms electrons will only seem similar as long as you measure them in a way that allows the hamiltonian to stay time-independent (for example) as the poster alludes to I think.
Feb
4
answered Car “oomph”: power or torque?
Jan
29
answered Are the photons released by trees the same generated by the sun?
Jan
28
revised Why are Green Functions/(Correlation Functions) not on the mass shell?
fixed grammar a bit
Jan
27
comment Can someone explain Planck's constant simply?
@Devin It's just a scalefactor, actually it can be made equal to 1 with proper choice of other units. So the h coefficient by itself isn't important qualitatively in QM really, the underlying structure is the same regardless, so even with h = 1 there will be waves and interference and the other strange QM stuff. You don't see it used in Newtonian physics, because it scales the size of QM waves. The simplest equation using it is probably E = h*f, that is, the scalefactor between energy and frequency for a photon as Peter writes above.