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Retired experimental particle physicist.

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


Dec
12
comment Simple example showing why measurement & interaction are different
There is a psi**2 of the system crystal+xray, gives the probability to find the xray at some (x,y) on the film. The spot is the "collapse", the accumulation is the probability distribution. The x-ray photons are scattered ( Feynman diagram can be written) by the atoms/molecules in the crystal .
Dec
12
comment Simple example showing why measurement & interaction are different
In the crystal example, the system x-ray+crystal psi "collapsed" each time to give us the information
Dec
12
comment Simple example showing why measurement & interaction are different
Take the simple crystal which is in a quantum mechanical state. X ray studies do not disturb those state, the elastic scattering gives information, but the x rays interacted with the crystal and were measured on the film. So the measurement can be non destructive as far as the isolated wave function goes but still there are real particles measured to get the information. Collapse means that the system interacted , the old wavefunction is no longer valid, an instant on the probability distribution( psi**2) was taken for the particles in the game, and there is a new solution.
Dec
12
revised Simple example showing why measurement & interaction are different
edit after comment
Dec
12
answered Simple example showing why measurement & interaction are different
Dec
12
answered Emission and absorption of photons by electrons
Dec
12
revised Emission and absorption of photons by electrons
format intervention
Dec
12
awarded  wave-particle-duality
Dec
11
answered What's the connection between the spin of the photon and the polarisation of light?
Dec
11
answered Double slit experiment query
Dec
11
answered Universe from nothing
Dec
11
comment Does graviton loops affect the seperately covariant conservation of energy momentum of two noninteracting sectors of matter
you could try asking at physicsoverflow.org , which is graduate level and over physics site.
Dec
11
comment Does graviton loops affect the seperately covariant conservation of energy momentum of two noninteracting sectors of matter
Well, it has been viewed 22 times by now, and none of us seem to want to undertake an answer. My answer would be hand waving :gravitation and quantum mechanics become in numbers commensurate at the very high densities and energies in the beginning of the Big Bang. For usual environments even if there, the terms would be so small as to be ignored.
Dec
10
revised How does a Wavefunction collapse?
clarification for consistency
Dec
10
answered How does a Wavefunction collapse?
Dec
10
comment How does a Wavefunction collapse?
To get at numbers you have to use solutions of the QM equations, the psi one operates on. No?
Dec
10
comment How does a Wavefunction collapse?
It is a signal to future readers to check the physics. If you could see my downvote record you would see that I very very seldom downvote, except at what I consider basic physics misinformation.
Dec
10
comment How does a Wavefunction collapse?
" concentrates the energy previously spread over a huge volume of space into a single silver atom" That one photon from a distant star raises an energy level is a proof of the particle nature of photons and at the same time a vindication of the PROBABILITY wave that describes particles quantum mechanically. The energy /mass etc are NOT described by a wave, but by a single quantum. "concentratin energy" over light years is agains special relativity and the velocity of light.
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?