propegation of EM waves WHY DO EM-waves PROPAGATE ? this might sound absurd and stupid...
but i am unable to reason why a time-varying electric and magnetic field must not be localized.
WHY is there a spacial shift in the oscillations instead of being just varying vector fields confined to the same region ?
 A: The electromagnetic force doesn't travel instantly. In Classical physics it would take t=c*d ( where time is the time needed, c is the speed of light and d is the distance) for a charged object to repel or attract the other. The electromagnetic force travels with the speed of light.
So any motion that a charged object does it will actually alter the value of the force it would exert on any other object. Because according to Coulomb's law F=((Q*q)/r^2)*k it depends on the ditance. Since the force travels at the speed of light and not instatly that means that a charged object doing Simple Harmonic Motion would produce a change in the field which would change that way.
In a single close point in space the field would change value but that won't be the case for a very far away point to which the force didn't have enough time to reach yet. A point far away knows that the force has a single value but once enough time passes it will update it's information.
Look at the similarities with a wave in a rope. The molequles of the rope don't propegate, they just move up and down. But what does propegate is the energy. Far away points on the rope do excactly what the previous ones did. This is what happens in the EM wave too. The oscilation of the E vector is localized. But as you get further and further away, the E vector does what in the previous point did.
