I just came across the old cliche that describes a star as a "little candle that shines its light so far," and am curious whether, barring obstruction and interference, one might be able to detect a candle at the distance of a star or more (obviously, using a keener instrument than the human eye).
I understand that we can think of the light from a candle as being a cloud of photons. I know that a photon can potentially travel the greatest distances available in the reachable universe, but it seems to me that from a weak source they must at some distance become so dispersed that even a single photon from the source would be unlikely to hit the earth. Is that right?
