Magnetism and Special Relativity | Breakthrough Junior Challenge

#breakthroughjuniorchallenge Where does magnetism come from? How and why do we perceive it?

[jhadhiraj]

Why is the wire neutral with respect to the stationary charge ? the electrons are moving with high velocity so wouldn't their length be contracted and thus negative charge density would increase ?

[dheerajabhishek]

if two wires with current flowing in the same direction are kept beside each other then both wires should get positively charged(cause electrons in both wires are stationary and photons density increases in both wires) and should repel each other right? why do they attract practically?