According to the latest definition of the SI units in 2019, a second is defined as "$9,192,631,770$ periods of the transition between the two hyperfine levels of the caesium-133 atom (ΔνCs)", and c is fixed as $299792458$ metres per second. However I am puzzled by the fact that all uncertainties ...

The Hamiltonian of a particle described by the Dirac equation neither commutes with the orbital angular momentum nor with the spin angular momentum. However, it commutes with the sum of the orbital and spin angular momentum. This means that neither the orbital angular momentum nor the spin angula...

Since we use AC for domestic purpose, shouldn't Back EMF (Counter-EMF) be produced in household wires? If yes, then the output voltage in the appliances will be less (that's what my stupid brain says! ). But this does not happen in our houses because we don't see bulbs glowing with low intensity ...

(Sorry if I'm spamming your board with Popular Science speculations, but I just thought this could be an interesting thought experiment). There are quite a few videos on youtube about Bell's Experiment. This experiment supposedly disproves the hypothesis of local hidden variables. We split entang...

In special relativity, different observers measure lengths of objects differently, depending on their respective velocities. However, all observers agree on the invariant inner product of two vectors (4-vectors, that is.) But doesn't the norm of a vector correspond to the distance between two poi...