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location Greece
age 75
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Retired experimental particle physicist.

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


Jul
24
answered Why particles don't lose mass when they radiate
Jul
24
answered The observer experiment: quantum mechanics
Jul
23
comment Why does the cloud chamber trails differ in length?
@dmckee I worked for more than ten years with the ALEPH TPC. Started with prototype construction. A beautiful detector.
Jul
23
comment Why does the cloud chamber trails differ in length?
Yes for the low energy tracks, i.e. the ones that stop in the chamber because all their energy was transferred to the ionizing path. For through going tracks we may say whether they are muons or protons but the energy will not be known. In the more sophisticated bubble chambers the "guess" becomes a mathematical fit. New particles were found because the interaction would not fit with the known till then ones. This is old technology though. There are more sophisticated tracking devises with greater accuracies.
Jul
23
answered Why does the cloud chamber trails differ in length?
Jul
23
comment Why does the cloud chamber trails differ in length?
maybe you should link to a picture? Different lengths depend on the energy of the particles, as seeing the tracks is due to the energy loss by ionization. Y shapes means interactions, i.e. the particle scatters strongly off an atom ( instead of just ionizing it)
Jul
23
comment Can a photon excite an electron via the uncertainty principle?
Have a look at this experiment phys.org/news/… . Bye bye, I have chores to do.
Jul
23
comment Can a photon excite an electron via the uncertainty principle?
One always needs an interaction. In the case of the double slit the interaction is "electron (or photon) + screen atom". All of the quantum mechanical probabilistic formulations are about quantum mechanical entities ( particles , atoms, molecules etc) "knowing" within their functional dependence. That knowledge gets manifest by an individual interaction, and a sequence of interactions gives the QM probability distribution for the specific problem.
Jul
23
comment Can a photon excite an electron via the uncertainty principle?
Once again, you are not positing a free electron so that the photon can interact with it. The photon sees the whole construct, cannot "see" the electron in the infinite potential well. It is an unphysical situation your are envisaging. A free electron occupies space with a HUP probability distribution. An electron bound in an infinite potential is in a probability distribution within the space of the potential , mathematically given by the solution of the problem, much more constrained than the HUP, but in a sub world of its own. It cannot see the photon. "electron+potential" see it.
Jul
23
comment Can a photon excite an electron via the uncertainty principle?
still, the photon does not "see" the electron, it sees the whole construct you made, "potential + electron" , it cannot "probe" with its arrival it is a different potential problem. It cannot be fired at the electron , as the electron's position is given by a probability anyway. A high energy photon can disrupt an atom as a whole, and thus its electon, but you are positing an infinite potential well so I do not see how it could be penetrated, except with the new probabilistic solution of the setup "photon +potential well +electron".
Jul
23
answered Can a photon excite an electron via the uncertainty principle?
Jul
22
answered Double-slit experiment: Difference between observing photon path and interference pattern?
Jul
21
answered What is the most common form of antimatter in the universe?
Jul
21
revised Are there any attempts to directly detect dark energy?
correction
Jul
21
revised Are there any attempts to directly detect dark energy?
added 50 characters in body
Jul
21
answered Are there any attempts to directly detect dark energy?
Jul
21
comment Are there any attempts to directly detect dark energy?
the short answer, not at the moment. some people are thinking about it technologyreview.com/view/417243/…
Jul
20
comment Why are tidal forces pointing away from the Moon?
thats right, it is the relative motions we see as tides.
Jul
20
answered Why are tidal forces pointing away from the Moon?
Jul
20
comment How many dimensions does a singularity have?
Not the value of the dimensions, the value of the variable that is assigned to that dimension. It is a clear cut mathematical concept. The x axis is mapped from -infinity to + infinity ( two singular points at the very large positve and negative limit ) on the real numbers, but in between the numbers are real. x is the variable assigned to the x axis dimension