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bio website lightandmatter.com
location Fullerton, California
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visits member for 4 years, 1 month
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I teach physics at Fullerton College, a community college in Southern California. I have an undergrad degree in math and physics from Berkeley and a PhD in physics from Yale. Back when I was doing research, my field was experimental low-energy nuclear physics.


Oct
4
comment What prevents photons from getting mass from higher order Feynman diagrams
@ACuriousMind: Your quote from the Xiao-Gang Wen paper reads to me as an assertion that it's true, not an explanation of why it's true. Nor does it tell me anything about the specific mechanism proposed in this question.
Oct
4
comment What prevents photons from getting mass from higher order Feynman diagrams
This doesn't seem to me at all like a duplicate of the other question. The answers to the other question tell us that terrible things would happen if the photon had mass. This question gives a seemingly straightforward reason why the photon should have mass, and asks why that reason doesn't hold.
Oct
4
revised source of energy for expansion of the universe
changed title to be a more specific and accurate description of the question
Oct
4
revised source of energy for expansion of the universe
added 9 characters in body
Oct
4
comment Why there is a time gap between the news presenter and the field reporter?
the reporter's image and sound are transmitted back to the studio using the same medium It seems unlikely to me that this is due to the propagation of electromagnetic signals. We don't notice any such propagation delay in a phone call, and the distances involved, even if it's going through a satellite, are too short to explain the delay. Propagation to a geosynchronous satellite is only about 0.1 s round-trip, which is much less than what we observe. And most communications satellites are in much lower orbits than that.
Oct
4
answered source of energy for expansion of the universe
Oct
4
revised source of energy for expansion of the universe
delete "please answer this ASAP, thank you."
Oct
4
comment source of energy for expansion of the universe
@HDE226868: the universe's expansion would have slowed down over time until it was negligible - without dark energy Yes, it would have slowed down, but it wouldn't have stopped by now, for realistic cosmological models.
Oct
4
comment Origin of quark masses
related: physics.stackexchange.com/q/3037 See Lubos's answer and the comment below it.
Oct
4
comment Is the existence of electromagnetic standing waves dependent on the observers reference frame?
I don't understand why you think that the existence of nodes implies that it's a standing wave. The nodes are moving through space, which to me implies that it's a traveling wave.
Oct
3
answered Is this an example of Parity violation?
Oct
3
comment Why did the big bang need to produce equal amounts of matter and antimatter?
This doesn't answer the OP's question, which is why the universe couldn't just always have had an asymmetry, ever since the big bang.
Oct
3
comment Why did the big bang need to produce equal amounts of matter and antimatter?
This doesn't answer the OP's question, which is why the universe couldn't just always have had an asymmetry, ever since the big bang.
Oct
3
comment Does accelerating generate gravitons?
@CuriousOne: There are fundamental reasons for thinking that gravitons must exist, because the other fields are quantized, and it's not possible to couple a classical field to a quantum-mechanical field. We simply aren't ever going to detect gravitons directly with any foreseeable technology.
Oct
3
comment Does accelerating generate gravitons?
An accelerated charge always has a changing dipole moment, so all accelerating (classical) charges radiate electromagnetically. This point turns out to be quite subtle, and your statement is not necessarily true. See physics.stackexchange.com/questions/70915/…
Oct
3
comment Does accelerating generate gravitons?
This is in contrast to electromagnetic radiation, which occurs when the charge distribution has a time varying dipole moment That's the condition for dipole radiation. You can have radiation without a changing dipole moment, e.g., quadrupole radiation.
Oct
3
comment Does accelerating generate gravitons?
conjectured to be, pending direct evidence This is not just a conjecture. It's a firm prediction of GR, already confirmed in quantitative detail by observation of binary pulsars.
Oct
3
comment Is the normal force a conservative force?
In moving reference systems, the normal is coupled to the force that keeps the object on the surface, so the work will be the same as the one by the force that keeps the object on the surface. This is wrong. The first part is wrong because the values of forces are the same regardless of your frame of reference. The second part is wrong because there doesn't have to be any force that "keeps the object on the surface." Think of a tennis racquet hitting a ball.
Oct
3
comment Is the normal force a conservative force?
The concept of conservative versus nonconservative forces is only of interest when the force is a field of force, i.e., a force whose value depends only on the position of the object being acted on.
Oct
2
answered If an antenna must be $\frac{1}{4}$ of the wavelength, how can car antennas be so small?