I asked myself this question : If you have a hollow sphere with reflective surface on the inside and send light into it what happens to the light? and found a number of places where the question has been asked and answered. One answer : talked about electro magnetic field being everywhere even in vaccuum before any light travels through it and went on to talk about the nature of light. This led me to another question. If light is sent off through vaccuum space to another point, is it possible to detect that light from a point not inline with the path of light? Does the light 'disturb' the electro magnetic field in a way that's detectable? I have only high school physics from 40 years ago but I try to understand. I have no doubt that I use the wrong terms and concepts to formulate the question.