Let us imagine we have a huge classical body moving in a vacuum and we want to measure its position and velocity. Is it better to bombard this body with electrons or photons?

My uneducated guess from a layman: With electrons because they can convoy more information than photons. Both electrons and photons can be observed at specific places at the sensor (or bubble chamber or whatever), but electrons will change their velocity as a result of the collision. So you have 3d data: change of x velocity, change of y velocity, change of z velocity. But photons only change their frequency as a result of the collision. So you have only 1d data! Am I right?

6 minutes ago, To_Mars_and_Beyond said:

But photons only change their frequency as a result of the collision. So you have only 1d data! Am I right?

No, light can be scattered by massive bodies.

 

Edited March 14, 20214 yr by studiot

Oh but yes. So you still can change individual components of the photon's velocity. So you would have vx^2 + vy^2 + vz^2 = c^2. That eats up one degree of freedom, but you get an extra one from the change of frequency. Nice.

Edited March 14, 20214 yr by To_Mars_and_Beyond