What tells to a point that the eletromagnetic field has changed? I'm taking classes in electromagnetism and studying the physics of light. My professor (and everyone says) that a charged body emits light when it's accelerated. Thinking about, I got a problem.
Suppose I have a travelling body A and a point in space B. If this body is approaching the point B, then the intensity of the electric field is going to get bigger and bigger. But what actually tells it to the point B? Isnt it the light? If it isnt, who sent this light, the body? I don't think so, because it would mean that the body is emitting light while travelling with a constant speed, right?
 A: I think it's best to focus on the electromagnetic field in general (rather than on light [classically, a particular type of configuration of the electromagnetic field] )... and its "dynamics".
First, consider a particle.
Specify the initial conditions (initial position and initial velocity of a particle), then use a dynamical law (Newton's Law) to predict the future behavior of that particle.
Next, consider a wave on string.
Specify the initial conditions (initial position and initial velocity of each point on the string), then use a dynamical law (the wave equation) to predict the future behavior of the wave disturbance (displacements) along that string.
For electromagnetism, we do something similar.
At an initial time $t_0$, specify at each point in space
the electric and magnetic fields and their charge and current sources (subject to some constraints: Gauss law for $\vec E$ and for $\vec B$),
then use a dynamical law (Faraday law and Ampere-Maxwell law, and any dynamical laws concerning the motion of the sources)
to predict the electric and magnetic field everywhere at future times $t$.
