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234128
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location Greece
age 74
visits member for 3 years, 11 months
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Retired experimental particle physicist.

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


Dec
9
answered Why are we using water pipe instead of air pipe to warm our houses?
Dec
9
answered Why do we use the Coulomb potential for the hydrogen atom?
Dec
9
awarded  Nice Answer
Dec
8
comment How can we prove that the shape of atom is spherical?
the Van der Waals is a model, useful approximation for certain cases. The orbitals are the measured reality
Dec
8
comment How can we prove that the shape of atom is spherical?
Depending on the ground state , if it is l=0, it is spherical. Higher angular momenta give the various shapes. So it depends on the atom.
Dec
8
revised How does the concept of a “black body” make any sense?
clarification
Dec
8
comment How can we prove that the shape of atom is spherical?
have a look at atomic orbitals , some of them are not even approximately spherical en.wikipedia.org/wiki/Atomic_orbital .
Dec
8
revised How does the concept of a “black body” make any sense?
clarification after comments
Dec
8
comment How does the concept of a “black body” make any sense?
I am sorry but it was a corner stone in discovering the quantization of light. so of course it has to do with the fact that energy levels are discreet.
Dec
8
reviewed Reject How does the concept of a “black body” make any sense?
Dec
8
revised How does the concept of a “black body” make any sense?
addition after comment
Dec
8
comment How does the concept of a “black body” make any sense?
@MattBall reading the links might help. Also questions in comments .
Dec
8
answered How does the concept of a “black body” make any sense?
Dec
8
comment How far back can you trace a photon?
It could make a visible point spot on a film, as with single photon patterns , if I were clever enough and knew enough physical chemistry to design such a film with a potassium content. This was not the point of the question. I assumed I could.
Dec
8
awarded  Nice Answer
Dec
7
comment How far back can you trace a photon?
I am answering the question. The questioner has set potassium acceptors in the detector. For optical light you do not need a photomultiplier. Accumulation of photons will show absorption and emission lines. emission values (as in question) change due to redshift or blue shift and cannot match the potassium the questioner wants in the detector coolcosmos.ipac.caltech.edu/cosmic_classroom/cosmic_reference/… . The standard model comes in to emphasize that the photon is a particle.
Dec
7
comment How far back can you trace a photon?
I should clarify this. there have been "which way" experiments since then that show the importance of the boundary conditions of the slits. It is the total solution photon+slits as boundary conditions. With minimum disturbance the interference does not get destroyed when the slit is known . Anyway I am sure that Feynman is talking of wavefunctions i.e. probabilities, and not of mass and energies in space.
Dec
7
comment How far back can you trace a photon?
Yes for the double slit. Look at these cosmic gamma rays mpa-garching.mpg.de/lectures/ADSEM/WS0203_Obergaulinger.pdf . gamma rays are photons too.
Dec
7
answered How far back can you trace a photon?
Dec
7
comment How far back can you trace a photon?
I am using the standard quantum mechanical interpretation, which assigns probabilities of emission and detection and certainly no energy is spread out all over the universe in any decay.