The spectacular advances in astronomy during the 21st century can’t be fully appreciated without knowledge of the equally spectacular advances in the 20th century. That century answered questions like: “How do stars shine?” “How far away is the Milky Way?” “How did the solar system form?” These questions were answered by exploiting advances in physics and engineering, many related to the electromagnetic spectrum. Astronomy uses radio frequencies, microwaves, and X-rays as well as visible light. We’ll look at blinking stars. We’ll explore the hubbub caused by Hubble. And, of course, babble about the Big Bang.