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age 74
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Retired experimental particle physicist.

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


Apr
3
answered Has the collapse of wave function due to observation been recorded?
Apr
3
comment Energy dependent cross sections for neutrons
neutron scattering against what? protons? you can start with the particle data book pdg.lbl.gov
Apr
3
comment Is Dark Energy Pushing Us Or Pulling Us?
you are making the mistake of visualizing the expansion like a sphere in three dimensions expanding. Even though the gravity we measure creates trajectories and orbits in our three dimensions, dark energy is a phenomenon in the four dimensional space time. "all those particles" are all around us symmetrically in three dimensions. see hyperphysics.phy-astr.gsu.edu/hbase/mechanics/earthole.html as an example of how only the mass internally affects the acceleration, not the external one to the trajectory.
Apr
3
comment When polarized light hits a polarizer, what happens to the polarization which is not transmitted?
It will depend on the material, if it is reflective it could very well be reflected.
Apr
2
answered When polarized light hits a polarizer, what happens to the polarization which is not transmitted?
Apr
2
comment How can a clock work if the uncertainty principle is true?
h_bar is a very small number, and macroscopi energies and time intervals are always way outside the bound.
Apr
2
comment Colliding particles at speeds aproaching c
what are v and u? btw you should add the homework tag
Apr
2
answered How can we detect cosmic background radiation?
Apr
2
answered Could one measure a stick to an arbitrary precision by having its length estimated by enough people?
Apr
1
comment Entropy in biological systems
We have to take in counting entropy as closed system the whole solar system, if we want to count all photons supplying energy to the earth. Then we have to add the positive change in the number of microstates because the system ( in this example) cell + surroundings, through the process of life, i.e. exchange of nutrients etc , increase the number of microstates and thus entropy. For a cell to be alive, it needs, like a crystal, to have symmetries and order, i.e. a smaller number of microstates than the chemicals that give it mass. but cell + suroundings have larger entropy ..
Apr
1
revised How are anti-matter atoms created?
spelling
Apr
1
answered How are anti-matter atoms created?
Apr
1
awarded  Revival
Apr
1
revised Entropy in biological systems
added 132 characters in body
Apr
1
answered Entropy in biological systems
Mar
31
comment How exactly do protons and electrons interact with each other?
In quantum mechanics one no longer talks of "attraction" since the possible positions and energy levels are quantized, not continuous as in classical attractive force physics. The potential is the 1/r potential of electricity but the solutions are the energy levels and two electrons with different spins can be at the same level, and also electrons can be caught at higher energy levels.
Mar
31
comment How exactly do protons and electrons interact with each other?
look at the energy levels of the hydrogen atom hyperphysics.phy-astr.gsu.edu/hbase/hyde.html#c2 . If an electron with the appropriate energy is caught at the lowest n=1 level has two spin states so two electrons can be there. the atom is neutral with one,but the other energy level exists and can catch a second electron if it has the correct energy or if it releases part of its energy in a photon. The electron(s) are in orbitals around the nucleus, i.e. probability distributions in space hyperphysics.phy-astr.gsu.edu/hbase/chemical/eleorb.html
Mar
31
comment How exactly do protons and electrons interact with each other?
It might also be caught into a hydrogen anion en.wikipedia.org/wiki/Hydrogen_anion , if it has the appropriate energy as it scatters.
Mar
31
comment Does Light Ever Cease Once Created
Yes, nothing to scatter on it will go on forever, or as long as the universe lasts according to reasonable models for the universe. There exist cyclic models en.wikipedia.org/wiki/Oscillating_universe , and there in the "big crunch" there will surely be density enough for any original photons to be absorbed.
Mar
31
answered Does Light Ever Cease Once Created