8,566 reputation
1538
bio website sjbyrnes.com
location Massachusetts
age
visits member for 4 years, 3 months
seen 9 hours ago

Oct
3
answered Is “detailed balance” equivalent with a continuity equation in state space?
Oct
2
comment Capacitor's voltage
I'm not sure what the definition of $k$ is. Can you put that in?
Sep
20
comment Can bad guys really hide “dirty bomb” material via bananas?
Gamma radiation can do nothing to a nearby banana except make it slightly warmer and kill mold or pests, as far as I know. It's possible in principle (although I doubt it's likely) that a medical isotope could emit tons of neutrons, in which case nearby objects could become more radioactive (this is called neutron transmutation).
Sep
20
answered Can bad guys really hide “dirty bomb” material via bananas?
Sep
17
answered Are electronic wavefunctions in band gap insulators localized? is a single-particle picture sufficient in this case?
Sep
9
comment Is coherent light required for interference in Young's double slit experiment?
I edited to clarify that "coherent" usually means "spatially coherent". (I do NOT believe that it ALWAYS means spatially coherent. For example, read some descriptions of a Michelson interferometer...) dmckee -- I wish you would not describe things as "coherent" or "incoherent", as if coherence were all-or-nothing. That's what caused the questioner to be confused in the first place. For example, sunlight is not totally incoherent, it's pretty close to collimated, at least when there are no clouds.
Sep
9
revised Is coherent light required for interference in Young's double slit experiment?
clarify the meaning of "coherence" in response to comments
Sep
8
revised Is coherent light required for interference in Young's double slit experiment?
added 34 characters in body
Sep
8
comment Is coherent light required for interference in Young's double slit experiment?
When light is almost-monochromic, it's temporally coherent. When it's traveling more-or-lesss the same direction, it's spatially coherent. Do you agree? As I said, "coherence" means different things in different contexts, and there are certainly times when "coherence" specifically means only "spatial coherence" (as you propose). But I think I'm entitled to refer to temporal coherence as a kind of coherence.
Sep
8
answered Is coherent light required for interference in Young's double slit experiment?
Sep
6
comment Does Gödel preclude a workable ToE?
@babou - When you say "a means to answer all questions", it seems that you're including "a means to rigorously prove or disprove every possible theorem about what will happen to every possible configuration of atoms following the laws of physics for an infinitely long time". Well, if that's what you mean, then I agree, a TOE is NOT "a means to answer all questions". On another topic: Is there a TOE for our universe? I strongly believe "yes", and that we will write it down within the next 100 years. But that's just my belief, it's impossible to know for sure. :-D
Sep
6
revised Does Gödel preclude a workable ToE?
clarify unprovable question
Sep
2
answered Perpetual motion machine of the second kind possible in nano technology?
Aug
27
answered Molecular Hamiltonian
Aug
26
comment Can an AC magnetic field be measured by a hall probe?
"AC" is vague, it could be 0.01 Hz or it could be 1 THz. What frequency range are you asking about?
Aug
26
comment Number density of LO and LA phonons as a function of temperature?
@boyfarrell - Again, each type of crystal has a finite maximum phonon frequency. The highest frequency phonon is usually one of the optical phonons at k=0, although it might be at a different k in some crystals. There are NOT infinitely many phonon bands at higher and higher frequencies. (This is the case for electron bands but not phonon bands.) The number of phonon bands is related to the number of atoms in a unit cell.
Aug
22
comment Four questions on color
@ArtBrown -- Y can be absolute or relative. For example, if you're talking about the color of an LED, Y would be absolute, measured in W/m2. If you're talking about the color of a piece of paper, Y would be relative and unitless, related to what fraction of the light shining on the paper gets diffusely reflected. You're right that I was confused about the horseshoe. I made some corrections, I hope I got it right this time. :-D
Aug
22
revised Four questions on color
more corrections due to comments
Aug
14
comment Four questions on color
@BenCrowell - Thank you, I didn't know about that! I corrected the wording.
Aug
14
revised Four questions on color
correct reference to brain per @Ben Crowell's comment