Can someone explain to me how two parallel electron beams can be attracted to each other according to special relativity. Classical physics says each beam will generate a magnetic field so the beams will be attracted to each other. Relativity says the magnetic field only exists for observers moving relative to the electron beam, hence there is no magnetic field if the beams are moving in parallel and at the same speed. I have been searching for an explanation, here is the closest I got to a discussion of this issue and the so-called expert doesn't even understand the question! http://en.allexperts.com/q/Physics-1358 [Broken] ... -LAW-2.htm I am not concerned with relativistic speeds - relativity should explain magnetism at any speed. There are numerous other discussions explaining how conducting wires are attracted (ie Ampere's experiment), due to the electrons moving relative to the positive metal atoms in the other wire, but there is no equivalent conductive medium in an electron beam!