1. There is an eclipse of the moon as often as the moon runs into
the shadow of the earth. For it is thought to have no light of its
own but to be illumined by the sun, whence it suffers eclipse if the
shadow of the earth comes between it and the sun. The fifteenth moon
suffers this until it passes out from the center and shadow of the
interposing earth and sees the sun and is seen by the sun.