One interesting example of how the very fast but finite speed of light can change what we see when we look at an object over an extended period of time is the observed light echo in V838 Monocerotis system. In the video (which is composed of individual observations over a time base of 2 or 3 years), it looks like we are watching a shell of debris expand out away from the central pair of objects, but this is actually not the case. Rather, what we are seeing is light traveling outward and illuminating successively further layers of a pre-existing but invisible shell of material