We know how the moon waxes and wanes over a period of approximately 29.5 days. It happens so consistently that we rarely take notice of it.
In this graphic, it lays out the different phases of the moon over 2014, and shows us how the cycle shifts. Doesn't this image look like it is glowing and moving around? It seems hard for us to focus on it, and our eyes prefer to move around the image. Why do we feel that this is happening?
Image credit: Nicholas Ace Wiinikka