I am trying to understand magnetism and its relation to electricity: Suppose there are two electrons travelling side by side in deep space at 1 cm distance at .99 c In this article http://academic.mu.edu/phys/matthysd/web004/l0220.htm it is said that the ratio $F_B/F_E$ is $v^2/c^2$ for v << c. According to that formula the magnetic pull sould be .9801 times the electrostatic repulsion. Can you tell me - 1) what is the actual value (applying relativity, since the speed is close to c) ? Is there a big difference? Intuitively it shouldn't be smaller, yet it can't possibly get greater than 1, can it? - 2) what happens to the trajectory of the particles due to the influence of the mutual magnetic field, does if deflect from the straight line?