This year we give thanks for an idea that is central to our modern understanding of the forces of nature: gauge symmetry.
When you write a popular book, some of the biggest decisions you are faced with involve choosing which interesting but difficult concepts to tackle, and which to simply put aside. In The Particle at the End of the Universe, I faced this question when it came to the concept of gauge symmetries, and in particular their relationship to the forces of nature. It's a simple relationship to summarize: the standard four "forces of nature" all arise directly from gauge symmetries. And the Higgs field is interesting because it serves to hide some of those symmetries from us.
So in the end, recognizing that it's a subtle topic and the discussion might prove unsatisfying, I bit the bullet and tried my best to explain why this kind of symmetry leads directly to what we think of as a force. Part of that involved explaining what a "connection" is in this context, which I'm not sure anyone has ever tried before in a popular book. And likely nobody ever will try again!
