In the Earth, the sky is blue because the blue rays of the sun bounce off the gases in the atmosphere, making it look like blue light is coming from the sky. But on the moon, because there is no atmosphere, the sky looks black, even in the daytime. There is no atmosphere to protect the moon from the rocks that fall from outer space, and these meteorites crash right into the moon and make wide, shallow holes called craters. The moon has thousands of them. Newer craters gradually wear away the older ones.