You sure y have ooked up at the sky before. Humans a ways have. Maybe you can f nd the B g D pper and even Or on—or at east h s Be t—but, for the most part, a the stars ook pretty much the same to you, and you can’t te a star from a planet.

The f rst chapter of th s part takes a ook at the conste at ons the second ntroduces the te escope and some bas deas about ght as a wave and the third moves through the e ectromagnet c spectrum and beyond visible light.