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Sep
20
awarded  Yearling
Sep
20
comment What are the strongest sources of collimated neutrons and protons?
The sun for example must emit a very high number of protons per second (and I bet there are other sources in the universe), but admittedly these are not very focused...
Sep
20
answered What are the strongest sources of collimated neutrons and protons?
Jul
16
comment Is Electromagnetic Mass Possible?
The Meissner effect comes to my mind when I read 'electromagnetism' and 'mass'...
Jul
10
comment Maximum theoretical bandwidth of fibre-optics
I would imagine that some dark fibres (fibres to be used in the future) are installed at the same time
Jul
10
comment Maximum theoretical bandwidth of fibre-optics
also, FTTH is often implemented as a passive optical network (using time multiplexing) meaning that each end user will share the bandwidth of the fibre with other users.
Jul
10
comment Canonical everyday-life example of a technology that could not work without humans mastering QM in analogy to the application of GR in GPS?
this is a quite delicate question: looking at the timeline of the solar cell it looks like the first solar cell was built in 1883 while Einstein postulated the quantum nature of the photoelectric effect only later in 1905. So it could be that without quantum mechanics, we would be able to build certain devices without understanding why they work.
Jul
10
comment Canonical everyday-life example of a technology that could not work without humans mastering QM in analogy to the application of GR in GPS?
I think this applies to semiconductor devices in general (including integrated circuits such as the ones used to type this message)
Mar
27
comment Which units has the relation $E=mc^2$?
I guess you mean $10^{17}\mathrm{m^2/s^2}$
Mar
9
answered The orthogonalized plane waves
Mar
9
comment The orthogonalized plane waves
I guess the $d\tau''$ in the integral should be a $dr''$
Feb
26
comment Why is gravity so hard to unify with the other 3 fundamental forces?
Quantum Gravity is non-renormalizable, see e.g. physics.stackexchange.com/q/3901/671 for what that means
Feb
23
comment Does a Photon leave trace in a silicon tracker?
Yes, I also saw in various places that the probability of photoelectric absorption seems to go with 1/E^3 (where E is the photon energy) while at higher energies one has to think in terms of radiation length as you say. By the way, the CMS detector (ATLAS' direct competitor) actually uses a laser of 1075nm wavelength (i.e. 1.15 eV) to shoot on the silicon tracker where they are detected to monitor the alignment of the different parts of the tracker (see e.g. page 79 of iopscience.iop.org/1748-0221/3/08/S08004)
Feb
22
comment Does a Photon leave trace in a silicon tracker?
that does not really answer why for example photons can be detected in avalanche photo diodes (or photo diodes in general) or Silicon photomultipliers
Feb
22
comment Strong decays of baryons via quark-antiquark pairs
there are two known decay modes, see pdg.lbl.gov/2012/listings/rpp2012-list-xicc-plus.pdf
Feb
21
revised Once I have the eigenvalues and the eigenvectors, how do I find the eigenfunctions?
deleted 39 characters in body
Feb
21
answered Once I have the eigenvalues and the eigenvectors, how do I find the eigenfunctions?
Feb
18
answered Collision of two photons
Feb
18
comment Collision of two photons
see also physics.stackexchange.com/questions/1361/… . They used terawatt pulses of laser light to experimentally demonstrate light by light scattering.
Feb
16
comment Radiation exposure to a child who was briefly in the presence of an adult who had received a 18FDG PET scan
also less than the dose absorbed during a transatlantic flight ($7\cdot10^{-5} $ Sievert) according to this source