55,770 reputation
234128
bio website
location Greece
age 74
visits member for 3 years, 11 months
seen 1 hour ago

Retired experimental particle physicist.

The picture is a fayum . It looks like aunts and cousins of mine :).


1h
comment Why do physics students find vectors so difficult to deal with?
I would start the year by tabulating which student had planear geometry with its axioms , trigonometry and solved problems. Nothing like it to give a feeling about the difference between one dimension and two dimensions. If they had not had any then they should be introduced to it, before entering all the complications of higher dimensions. After all we all walk in two dimensions, and every body knows that a diagonal line through a field is faster than going around the two sides.
2h
comment Why do physics students find vectors so difficult to deal with?
Well, I got trigonometry and Pythagoras, planar geometry axioms and all in third grade in highschool back in 1954 . Nothing like drawing circles and computing angles to show the difference between one dimension and two dimensions. Had no difficulty when meeting vectors later.
3h
comment Why do physics students find vectors so difficult to deal with?
I wonder whether they are getting any geometry in their math curriculum in high school? Pythagoras theorem, trigonometry etc?
14h
comment can we detect the photons in the interaction of two charged bodies?
We use the word virtual to differentiate from the real input and output lines ; because Feynman diagrams simplified logically the very complicated integrals one had to solve for scattering theory using the scattering matrix, and it helps keep track of the quantum numbers, an electron always is spin 1/2 , lepton number 1 etc, so the calculations do not get confused.
15h
revised can we detect the photons in the interaction of two charged bodies?
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15h
comment can we detect the photons in the interaction of two charged bodies?
An accelerating particle is a different story, it needs different Feynman diagrams : the electron interacts with an off mass shell photon from the field that gives it the accelerating impulse and a real photon radiates off. There is still a virtual photon from the electric or magnetic field interacting with the electron.
17h
answered can we detect the photons in the interaction of two charged bodies?
18h
comment Why can't dark matter be baryonic?
Have a look at pdg.lbl.gov/2014/reviews/rpp2014-rev-dark-matter.pdf .
20h
comment Why can't dark matter be baryonic?
I am curious, my first impulse would be that baryonic matter would contain charged particles and charged particles interact electromagnetically. Neutral ones are either in atoms, and they also interact and give spectral lines, or unstable. One hypothesizes exotics for dark matter just because in contrast to baryons, electromagnetic interactions are higher order and less probable.
20h
comment Birds and cables: how is the potential difference between two diff. cables established?
Birds usually sit on one cable. If the birds are large enough to touch two live wires they set themselves on fire. My son did his army duty at an outpost where three times crows shorted two cables and set fire to the forest and the soldiers had to rush and put it out. Now in Greece they are slowly replacing the four cables into one braided one and insulated for this reason ( trees too can short two wires)
1d
answered At what point do researchers in physics make the leap from wild theoretical ideas to physical experiments?
1d
comment Schroedinger Equation and Special Relativity
@joshphysics I guess it is the first order derivative in time that does not allow to see the relativistic form while the KG has it explicitly.
1d
comment Schroedinger Equation and Special Relativity
@joshphysics yes, the mass is non relativistic and it is hard to see what would happen at relativistic energies . So I guess my "no" in the answer above is centered on that, as well as the statement in the wiki article. in the KG you know you are dealing with the rest mass.
1d
comment Schroedinger Equation and Special Relativity
@joshphysics I am not disputing QFT. I want a simple demonstration that the S equation is relativistic; I think that the Klein Gordon is the relativistic version of the S. at least the article in wikipedia must also be wrong then.
1d
comment Schroedinger Equation and Special Relativity
@joshphysics the closer I got by searching that the former is relativistic was " it is hard to show that it is" . Do you have a link . I was always of the impression that one needed the Klein Gordon for this , even without spins. ?
1d
comment Schroedinger Equation and Special Relativity
@joshphysics I am assuming the garden variety equation.
1d
revised Schroedinger Equation and Special Relativity
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answered Schroedinger Equation and Special Relativity
1d
awarded  Revival
1d
comment The mass of universe at the point of the Big Bang
@CuriousOne the uniformity of cosmic microwave background radiation could not be explained in the Big Bang. At that time when photons separated the universe could not come to thermodynamic equilibrium because of space time limitations. That is why they invented the inflaton field, to homogenize everything.