The Persian astronomer and poet Omar Khayyam once wrote about the sunrise - "Awake! For Morning in the Bowl of Night Has Flung the Stone that Puts the Stars to Flight!" Now what stone “puts the stars to flight?” The sun, obviously. But why did Khayyam refer to the dark sky as the bowl of night? Is it shaped like a bowl? Often at night when you look up at the sky, it does seem that way. This illusion works because we can't tell how far away the stars are just by using our eyes alone. The stars have different brightnesses, but we can't determine if a star is bright or dim because of distance, or because that star is just naturally bright or dim. So to our eyes, the stars seem to be all the same distance away, kind of like having a huge cereal bowl placed upside down over our heads and with all the stars on the inside surface - the bowl of night.