General relativity | James Kennedy

Excellent modern physics primer that’s mostly a biography of Einstein
203 pages, ★★★★

Author Michio Kaku is a very talented science writer. He is one of the few science writers who achieves the near-impossible goal of communicating advanced science accurately, in a way that’s easy to understand, and with added humour throughout. Most writers can’t do that!

In Einstein’s Cosmos, Kaku explores how Einstein’s life story shaped almost all of modern physics. The question of uniting two seemingly incompatible theories is a recurring theme in this book (and in physics itself). The first instance is on page 11, where we learn how Einstein was faced with the problem of reconciling Newton’s forces and Maxwell’s fields. “One of them had to fall”, Kaku writes. Einstein would topple Newtonian forces and replace them with something beautifully simple.

Kaku’s analogies are very easy to understand. To illustrate length contractions and time dilations using cars, he slows the speed of light down to 20mph and describes what each observer would see.

We’re now faced with an incompatibility between general relativity and quantum field theory. Both hold true at different scales, but they don’t seem to overlap properly as part of a grand “unifying theory”. Just as Einstein unified Newton’s and Maxwell’s equations, physicists are now faced with the task of unifying general relativity and quantum field theory—and the book almost exactly as it started.

Beautiful! ★★★★