The spectacular advances in astronomy during the 21st Century can’t be fully appreciated without an understanding and knowledge of the equally spectacular advances in the 20th Century.

That century answered many important questions posed in the 19th Century — “How do stars shine?”; “What’s the nature of a nebula?”; “How far away is the Milky Way?”; “How did the Solar System form?”. These questions were answered by exploiting theoretical advances in Physics and practical advances in Engineering, many of these related to the electromagnetic spectrum. Not all of astronomy relies on visible light, but uses radio frequencies, microwaves, and X-rays.

We’ll look at the impact of the discovery of blinking stars and revel at the Hertzsprung-Russell sequence of star lifetimes. We’ll explore the hubbub caused by Hubble and the eye-opening theories of Einstein; we’ll Ooh! over the Oort Cloud, and look with awe at the Van Allen belts. And, of course, babble about the Big Bang and Hans Bethe.