Galileo & the Moon

, the great Italian astronomer and physicist Galileo Galilei sat down to write a letter. He wanted to describe some of the observations he had been making over the previous few months with his self-built “optick tube” (the name ‘telescope’ had not yet been devised). As some others were already doing, though with much less powerful aid, he pointed the instrument not at objects on Earth but toward the night sky. What