It is difficult to write a review after concurrently finishing The Edge of the Universe, The Particle at the End of the Universe, and Brian Clegg's fine book Gravity--the latter two books are highly recommended both deserving of forthcoming reviews. One will find a large crossover between the contents Clegg's book and the Caroll's The Particle at the End of the Universe.
Brian Clegg has written a very interesting and popular level book for semi-initiated science readers. Indeed, most of the contents of this book should be familiar as gravity has been the driving force behind the success of Newtonian physics and Einstein's subsequent general theory of relativity. And, of course the Holy Grail for gravity is now the "search" for a quantum theory of gravity, a theory of everything by another name. What makes Clegg's standout from other books that mention the same issues, however, is written in an enjoyable and logical style. As the previous review does not say too much by way of the contents of the chapters, it is here that I will briefly turn my attentions.
The book is premised on the importance of gravity, not only for our daily lives but for the history of science, both issues that comprise chapter 1. The chapters are small and self-contained, meaning that a subsequent chapter is not premised on reading the previous chapter.
Chapters 2 through 5 look at the development and treatment of the gravity and the cosmos, from Aristotle to Ptolemy to Galileo until the reader reaches Newton. Most of this information can be gleaned from other popular level science books, but that in no way detracts from Clegg's writing style which enables the reader to easily follow the contents, and easy to memorize which is unspoken goal for many readers.
Chapter 5 talks about action-at-a-distance and Newtonian physics, focusing on his theory of gravity. This lays the foundation for Newton's detractors and the introduction to alternative views about gravity as Newton has brought the entirety of the cosmos down to earth (no pun intended). Clegg also makes mention--and this is true throughout the entire book--of interesting and collateral issues that Glegg calls "gravitational mysteries" such as the moon and tidal forces. Returning to action-at-a-distance, Clegg paves the way for Einstein's revolution.
Chapters 6 and 7 Clegg iterates Einstein's miracle year, 1905, and unpacks the topics of each one of Einstein's works, focusing on STR. The focus shifts from STR to the general theory of relativity. Clegg provides simple illustrations regarding the POE (principle of equivalence), the nature and properties of spacetime eventually getting to Minkowski's spacetime (4-D ontology) that Einstein subsequently accepted. Clegg focuses on simple examples for spacetime aside from the same "ball in a rubber sheet analogy," and why and where such analogies breakdown. Clegg discusses popular issues such as gravitational waves, gravitational lensing, and the bending of light (which he returns to later). Again, Clegg writes on these matters in an easy top digest fashion making them easy to memorize.
In Chapter 8 the book begins to turn towards quantum physics, the structure and utility of atomic particles, and the four fundamental forces. The issue of gravitons turns the reader back to events in spacetime such as black holes, the singularity, hawking radiation and other issues. These issues are somewhat of an outline for Chapters 9 and 10.
In Chapter 9 we "enter the quantum" where Clegg discusses the hunt for a quantum theory of gravity and the main theories for a new quantum theory of quantum theory of gravity such as string theory, M--theory, loop quantum gravity, and twistor theory. Each alternative is subsequently unpacked throughout the remainder of the chapter. Chapter 10 reverts back to spacetime, looking at phenomena that back up the general theory of relativity.
The final chapter unpacks the history of antigravity proponents and their failed attempts at creating artifacts (e.g., ships that can fly close to the speed of light, gyroscopes, etc.). Clegg includes an interesting discussion about the history of flying saucers. There are many more issues that are touched upon in the book, but many of these issues care also found in other books such as the two mentioned about. Again, Clegg's book gets a good rating for the reasons above and because of the collateral scientific facts that one does not usually find in other books in the same genre such (e.g., flying saucers, and pseudoscience).
Of particular import for this reviewer is his commentary following the final chapter, statements that are not uncommon when reading academic journals, overhear at seminars or when reading graduate level textbooks. For example, taking a cue from the iconic Richard Feynman, Clegg has an honest moment about the nature and limitations of science, which follow logically from the final chapter of the book that highlights attempts to create antigravity that Clegg presently assigns to the category of "science fiction."
After quoting Feynman at length, Clegg points out that Feynman "was explaining . . . physics is never going to be able to answer the ultimate question: `Why?' We can describe how nature behaves with more and more accuracy. We can observe apparent laws and constants of nature. But we can never observe questions like, `Why does gravity attract?'" In popular level reading one rarely is confronted by such honesty, which is welcome for those of us who are more inclined towards second-order disciplines such as the philosophy of physics, where both scientists and avid readers would do well in reading books by Tim Maudlin et seq.
Clegg broadly addresses the idea of multiverse (not any specific multiverse theory) in conjunction with the "weak" anthropic principle concluding, "So given the multiverse, the simple answer to `Why are things like they are?' is that they have to be or we wouldn't be here. Many people (including me) find this answer facile. Even if you accept it, all we've done is push back the `Why' a stage to ask instead `Why does the multiverse exist?' At this level we move away from science and get to metaphysics or theology." (Pages 283-84). As a reviewer my job is not to preach, but this makes Clegg's book all the better. I simple offer a hearty--bravo! A very enjoyable book.