We know that parallel current in two parallel wires causes them to attract. The explanation is that moving charges generate attractive magnetic fields.
If I have two charged pith balls in a space ship, then they should attract more the faster the space ship travels. But relativity says you cannot know your velocity in an inertial frame. In other words you cannot know how fast you are going unless you look outside the space ship. So that means the attraction of two moving charges should only be visible from outside the moving spaceship - which does not make sense to me.
How can a magnetic field not happen in a spaceship but be observed from outside?
There are many questions about the relativistic effects of electrons in a wire, for example
But they all hinge on the velocity difference between the moving electrons in the wire vs the static protons. In my example I am just considering the behavior of two charged pith balls through space. Moving charges should generate a magnetic field, no? Or do moving charges only generate a magnetic field when they are moving relative to protons?