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Wait. I did a physics undergrad but I never asked myself this question. How is it possible that the EM fields from photos can't interact with each other? Doubly

Wait. I did a physics undergrad but I never asked myself this question. How is it possible that the EM fields from photos can't interact with each other? Doubly funny, I did my undergrad research for the PHENIX experiment.

leephillips 5y ago
Fields are abstractions that ease the calculation of the forces on charges caused by the positions and motions of other charges. The charges interact, but the fields don’t; there is nothing “there” to interact. (This is classical EM.) If you are in a room with two charges, the electrostatic field at any point is the addition of the fields from each charge. There is no extra interaction term.
whatshisface 5y ago
Phillips gave you a good answer, but another good answer is that Maxwell's equations are linear; forbidding any interaction between solutions f and g because if L is a linear operator, L[f+g] must = L[f] + L[g].
- earthscienceman 5y ago
  Oooo. Wow. This is a great answer, thanks for explaining it that way.
- acchow 5y ago
  Where do they teach physics like this? Anywhere?
  - whatshisface 5y ago
    I feel like this would be mentioned in a typical undergraduate wave mechanics course taught in a typical American university, but I have not been to enough undergraduate wave mechanics courses in enough American universities to know, really.
- jdbburg 5y ago
  This is what we are taught in high school / college as the super-position principle
at_a_remove 5y ago
Photons are EM fields -- self-propagating ones, like a glider in the Game of Life. The electric field changes, creating a magnetic field, but the magnetic field changes, creating an electric field. Use sines for the functions and you can see how the function just keeps re-appearing. Now, combine that with the superposition principle ... photons pass through one another under most circumstances because of this (unlike gliders).

leephillips 5y ago

Fields are abstractions that ease the calculation of the forces on charges caused by the positions and motions of other charges. The charges interact, but the fields don’t; there is nothing “there” to interact. (This is classical EM.) If you are in a room with two charges, the electrostatic field at any point is the addition of the fields from each charge. There is no extra interaction term.

whatshisface 5y ago

Phillips gave you a good answer, but another good answer is that Maxwell's equations are linear; forbidding any interaction between solutions f and g because if L is a linear operator, L[f+g] must = L[f] + L[g].

earthscienceman 5y ago
Oooo. Wow. This is a great answer, thanks for explaining it that way.
acchow 5y ago
Where do they teach physics like this? Anywhere?
- whatshisface 5y ago
  I feel like this would be mentioned in a typical undergraduate wave mechanics course taught in a typical American university, but I have not been to enough undergraduate wave mechanics courses in enough American universities to know, really.
jdbburg 5y ago
This is what we are taught in high school / college as the super-position principle

at_a_remove 5y ago

Photons are EM fields -- self-propagating ones, like a glider in the Game of Life. The electric field changes, creating a magnetic field, but the magnetic field changes, creating an electric field. Use sines for the functions and you can see how the function just keeps re-appearing. Now, combine that with the superposition principle ... photons pass through one another under most circumstances because of this (unlike gliders).