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Reinventing Gravity Review

Chalkboards are the Physicist's greatest tool. Moffat is win for having his book title depicted on a chalkboard.

Reinventing Gravity is a physics based pop-science book by Dr. John Moffat. Its primary focus deals with Moffat’s Modified Gravity (MOG) theory (his is technically called Scalar-Tensor-Vector Gravity (STVG)), how it holds up as a theory of gravity, and the story leading up to his creating of it.

Overall, I have to say that I found this book to be a quite good read. Though I must point out from the start, that I personally had some trouble with understanding some portions. There is very little math, however some of the topics he deals with a rather high-end in the physics spectrum, and requires at least some knowledge on the matters, as he does not do all that much explaining. Even so, you can still get by with no foreknowledge; you just may have some troubles in understanding his explanations at some points.

Basically, I found Moffat’s book to be more or less typical in the style and setup of his writing, but that is actually quite a good thing. The entire book is really more of a history than anything, as he goes through basically all of the 20th century of theoretical physics, mainly that of cosmological. His explanations for Special and General Relativity are quite good, but very specific. And for the most part, he really does not deal with Quantum Mechanics. But both of these reasons are simply due to what he is concentrating on in his book: gravity. More specifically, the problems with our current interpretation of gravity.

This book goes through the modern understandings of gravity, and the problems facing them. He explains different viewpoints on different matters throughout the years, what they solve, and what problems that they have as gravitational theories. He also includes his theories where they are applicable, and, while not really being completely unbiased, still gives a good look at his own.

Eventually he comes finally to his MOG (it actually takes quite some time for him to get into it in detail, not until the second half of the book), and goes into quite a bit of detail (though not really any math) explaining how his theory fixes many of the various problems in Einstein’s gravity (the gravity theory we still use).

So what exactly are these problems in gravity? Well, there are several. Ranging from mathematically infinities (which prove in themselves that there is a problem) at the big bang and black holes, to the “missing” matter in the Universe, these problems are very realizable, yet to most people, they are not problems at all. In fact, many of these “problems” are things that most people believe to be acts. For instance: the Big Bang. It is still a theory that the Universe began in an infinitesimally small, infinitesimally dense object. Other theories, such as Moffat’s MOG predict other possibilities (his essentially suggests that space existed, and the galaxies then morphed into being. This has some interesting consequences, including the fact that at t = 0 (beginning of the Universe), time could have moved in the negative direction, just as likely as the positive direction (and who’s to say which way it IS moving?)). Another, related problem is that of black holes. They most likely exist, but perhaps not in the way that we currently think they do, such as them not actually having a Schwarzschild radius (event horizon, point of no return for light). Finally, and most dealt with in his book, is that of dark matter. Dark matter is just a theory, made up to solve the odd problem of, by Einstein’s equations, the Universe missing over 90% of the matter it should have. Once again, by Einstein’s equations.

Basically, astronomers have looked at the rotation and pull of various galaxies, and calculated the amount of mass that should be in and around those galaxies for them to be moving the way they do. The observed amount of mass is less than 10% of the mass required by these calculations, using equations from Einstein.

So, not wanting to believe that Einstein could be wrong, Physicists leapt into action, and theorized that we simply cannot observe the rest of the matter; that it was not reflecting any light. And so, dark matter was born.

While it is indeed quite possible that this is true, it is at least equally likely that Einstein’s equations simply do not hold at the magnitude that we are now looking at. They work perfectly for smaller masses with smaller distances, however at such a massive degree, it is possible that the laws of Physics change from what we currently understand.

And so, this is where Moffat came in, and developed his MOG. And while he is only one of the many people to attempt this (other famous examples include Modified Newtonian Dynamics (MOND)), his seems to be holding well against tests of its validity.

Overall, I have to say that I really quite liked this book, and I highly suggest it to anyone, whether they be a Physics major like myself, or merely a interested reader with little to no background in Physics. Like many Physics books, there are notes in the Appendix for more details for the more Physics learned reader, and the overall book is written at a level that most will have very little difficulty understanding.

And finally, reading this may be very important, as it just may be history in the making. If MOG continues to succeed, Moffat just may well go beyond Einstein, just as Einstein went beyond Newton. And we will have a new understanding of the Universe.