28,043 reputation
178144
bio website lightandmatter.com
location Fullerton, California
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visits member for 3 years, 11 months
seen May 21 at 15:35

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
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?
Oct
2
comment Does accelerating generate gravitons?
@OscarCunningham: Yes. The system you describe has a varying mass quadrupole moment, so it radiates.
Oct
2
comment Does accelerating generate gravitons?
The real question here would be (1) whether a free-falling object radiates gravitational waves. If so, then it would presumably be true that (2) those gravitational waves are quantized as gravitons, but we don't have a theory of quantum gravity, so we don't really know. The answer to #1 depends on whether the system has a changing mass quadrupole moment. It is definitely possible to come up with scenarios in which there is acceleration but no gravitational radiation, e.g., two parallel, uniform, infinite sheets of mass.
Oct
2
comment Einstein's special relativity beyond the speed of light
There is a no-go theorem by Gorini that shows you can't do this in 3+1 dimensions. V. Gorini, "Linear Kinematical Groups," Commun Math Phys 21 (1971) 150 adsabs.harvard.edu/abs/1971CMaPh..21..150G open access via project euclid: projecteuclid.org/…
Oct
2
comment Can speed be defined in the complex plane?
Another way to see that it can't be of interest physically is to consider the case where $v=c$, which is intermediate between $v<c$ and $v>c$. You get nonsense for $v=c$.
Oct
2
comment What experiment disproved single fluid theory of electricity?
This doesn't address single-fluid versus two-fluid. I doubt that the fluid theories were though of at the time as implying anything about the corpuscular or continuous nature of charge.
Oct
2
comment Vector fields and tensors in E&M
The EM field tensor - as a tensor - does change under change of reference frames. Many people do prefer to describe tensors as invariant. When people adopt that convention, they say that the tensor's components in a particular basis are basis-dependent, but they consider the tensor itself to be invariant.
Oct
2
comment Would an ideal gas be colder at higher altitude due to gravity?
The answer is no. This was a controversy in the 19th century. The putative effect can be referred to as the Loschmidt gravito-thermal effect. Boltzmann, Maxwell, and Guthrie debated the question.
Oct
2
awarded  electromagnetic-radiation
Oct
2
awarded  Nice Answer
Oct
1
revised What is the difference between xrays and ultra violet rays?
added 36 characters in body
Oct
1
answered What is the difference between xrays and ultra violet rays?
Oct
1
comment Can we prove Conservation of Angular Momentum without assuming internal forces are central?
Conservation of angular momentum can't be proved from Newtonian mechanics, because conservation of angular momentum is true in general, but Newtonian mechanics is not true in general. Conservation laws are fundamental. Newton's laws are not.