So I've recently read newton's third law violates the principles of relativity. I only know how to prove conservation of momentum if Newton's third law holds. I was hoping someone could explain to me this (proving conservation of momentum when newton's third law is false) without using extremely hefty mathematics, and specifically addressing E&M: " It turns out that we can ``rescue'' momentum conservation by abandoning action at a distance theories, and instead adopting so-called field theories in which there is a medium, called a field, which transmits the force from one particle to another. In electromagnetism there are, in fact, two fields--the electric field, and the magnetic field." source: http://farside.ph.utexas.edu/teaching/em/lectures/node28.html#e311 Thanks.