Here's something that i've been thinking about a while and haven't found a good answer to: Lets say that there're two charges on the x-axis seperated by a certain distance and they're moving upwards along the y-axis. Lets look at charge A (on the right side), when it's at height y2 it's actually feeling the force of charge B from the retarded position y1 which is under y2 because it takes time for the E field of B to get to A(the distance between y1 and y2 is proportional to the distance that light goes in the time that it takes the charge to go from y1 to y2). The force on A at y2 from the charge B at y1 is up and to the right because the field goes out radially from the position of the charge. By the same argument, the force on B from A is up and to the left. so it looks like the charges, one given a little initial speed, will just keep on going faster and faster untill the magnetic force pulls them together and the distance between them is 0. so in the end the speed along the y-axis will be bigger than in the beginning. how is momentum conserved? Thanks.