Stephen Hawking's A Brief History of Time is about the universe, both the grand-scale universe of stars and planets, general relativity, and the tiny universe of atoms and subatomic particles, quantum mechanics. The reason the book covers both dimensions is that understanding both is the only way to understand the way the universe works as a whole. Some theories explain the workings of the grand scale of the universe and others the workings of the minute scale, but they tend to contradict one another. And, currently, there is no theory that explains both...