Reinventing Gravity: A Physicist Goes Beyond Einstein,   ISBN:9780061170881

Customer Rating: 

Personal background: I took general relativity as a grad student something over thirty years ago. Even at that time there were questions about extending general relativity, and various theories floating about for doing so. (The issue of quantizing gravity was, of course, also open, as it has remained.) Since those days a variety of theories have come and gone. I have read some on the MOND theory mentioned in the book, but not much on Moffat's own MOG theory.

Moffat takes his own, somewhat quirky, approach to laying out the physics and astrophysics background to his theory. I had no trouble following it, but it was all material I already knew. How successful his approach is in informing a non-physicist is hard for me to judge. I will take the liberty of laying in--from my viewpoint--some history for those considering this book:

For several centuries physics was built, very successfully, upon the coordinate transformations Galileo developed for adjusting how motion is viewed by two observers moving relative to each other, and upon the laws of dynamics and gravity put forth by Newton. But in the nineteenth century problems began to arise. On a large scale, the equations of electromagnetism proposed by Maxwell were inconsistent with the transformation of Galileo, and the motion of the planet Mercury was not quite as described by Newton's laws. On a smaller scale, the emission of electrons from a surface with a bright light shining on it didn't make sense based on classical physics, and attempts to calculate the emission of heat (light) from of a warm object failed to give a finite answer. Clearly some adjustments needed to be made.

The solution to both problems lay in papers Einstein published in 1905. His special theory of relativity explained motion at high velocities but with small accelerations (or gravitational force); his general theory of 1915-16 extended the understanding to include acceleration (which is equivalent to gravity in the the general theory). His paper on the photoelectric effect led to the development of quantum mechanics. Eventually the special theory and quantum mechanics were merged into a relativistic theory of quantum mechanics; general relativity, however, has never successfully been combined with quantum theory.

Over the years various issues with general relativity have arisen: It allows for mathematically singular solutions (as at the center of black holes); the hope is that quantum mechanics will somehow solve this problem. The isotropy of the universe requires an early, rapid "inflation" of space, which has no obvious cause. The recently observed accelerating expansion of the universe requires large amounts of dark matter and dark energy, no source for which is known. And some observations of spacecraft leaving the solar system seem slightly at odds with general relativity.

Whew! What now? Many physicists think this will all be sorted out by string theory or brane theory, once someone figures out how to tease any prediction from them. At the moment they seem to be pliable enough to predict anything, which means they predict nothing; not very "sciency"!

Another approach is to modify general relativity. MOND was an approach to this that looked promising, but an observation of colliding galaxies has dimmed it star (so to speak). Moffat has his own theory of modified gravity (MOG), which aims to finally untie the cosmological knot. And his narrative in this book does offer interesting hints as to what his theory might offer. Unfortunately, that's all the book offers.

Because he's aimed the book at a general audience, there is none of the math or physics detail that would allow a physicist to evaluate his theory. And while he'll pull the general reader along thinking he's on to something, most readers will lack the background in general relativity and cosmology to critically evaluate his claims.

This is an interesting book, and when I have time I hope to find some papers on MOG and learn more. But the level of detail in the book is of little value to a physicist, and the appealing, folksy tone is likely to lull non-physicists into believing they understand things they really don't.

Because I found the level of detail in the book frustrating it took me a while to finish it. The average reader may find it more interesting and informative than I did, but please don't close the cover thinking you know the whole story.

Customer Rating: 

I have just finished reading this book. It was a great read and invites the reader to think on key issues in astronomy today.

I would wholeheartedly agree with the review of Parmenides, but I would not hesitate to give this book a 5 out of 5. For a book that suggests that we should investigate possible alternatives to dark matter and that we should (perhaps) consider modifying Newtonian and Einsteinain gravity (slightly) in order to deal with astrophysical phenomena such as flattened galactic rotation curves and galaxy clusters that seem to rotate too fast to stay together, I felt that the author presented his suggestions very fairly and in a strikingly unassuming, non-antagonistic manner. It shows the wisdom of this author's years - a true old-school "gentleman" physicist interested in the real pursuit of science. Whether his theory of modifed gravity is right or wrong (and who can honestly tell at this point until we get more convincing data), I got the feeling throughout the text that the author was more interested to add to the dark matter/dark energy debate and to the ultimate pursuit of truth, than to necessarily promulgate a single point of view. I give him very high marks for his approach throughout the text.

I also give the author very high marks for how clearly he was able to convey his thoughts in a very straight-forward manner. As Parmenides says, there was no mathematics included in the text. But I found this quite re-freshing all-in-all. Too often I have found that scientists seem to fall back into mathematics, unable to express an idea coherently enough to convey their ideas to an educated person interested in science. Rarely do you see a physicist so able to express himself or herself in non-mathematical terms as this author has been able to do in this case. No doubt mathematics is the language of science, but language itself is the method of mass communication of new ideas. I really give the author very high marks for how he articulated his theory (right or wrong).

I believe that anyone would enjoy reading this book, but it probably would help to have at least a passing familiarity with current astronomical issues.

Customer Rating: 

First off, I have to say I really enjoyed the flow of this book. The first two thirds was a fabulous progression of the thoughts and aches of the physicists of yore that went through the processes of getting their theories created and accepted, and of the more recent progession of discoveries and theories to explain the reason why most current scientists feel dark matter exists. The gravitational lensing effect (excessive bending of light ) of galactic clusters, the flat rotation curves of galaxies (why a "year" for an outer star is the same as a "year" for an inner star), the pioneer 10 and 11 decelleration anomolies and so on are each explained in enough detail to tie the whole dark matter paradigm into a nicely understood package. If you are fairly new to dark matter and yearning for some history and some explainations, then this portion of the book is worth the entire price.

In addition the author has an appreciated style of inserting tons of tidbits of extra information that are worth knowing, regardless of your level of expertise on the general subject, throughout the entire book. You get little pieces of physics trivia for free and great starter "wiki" words and phrases to further your knowledge. I was especially appreciative of the insertion of the Abell 520 cluster train crash anomaly which contradicts the Bullet Cluster conclusions about dark matter. Wow!!! I think this little bit of information for me was worth the price of the book alone! Wiki this one yourself for a big surprise!!

Now for the cons: The MOG theory, which is at the core of the entire book is a decent theory and is easy to understand. There was good supportive references and was believably presented. I don't lean toward or away from this theory, and even though I have serious reservations about the dark matter theory that has been too eagerly accepted in the community, I don't think the author fully convinced me to accept his theory as the final answer. Using a dart board as an analogy, I think dark matter is somewhere on the perimeter, MOG is somewhat closer, but no-one has yet shown me anything I'd consider in the bulls eye area. I hope they keep trying.

I would have liked to see the author throw in the exact details of the MOG theory, presented of course in a layman style, that included what constants and newtonian formulas that were used (and in what way) to create the theory so the reader could get a better sense of the "meat" in all of this. There are plenty of references and text describing the authors lectures, previous submissions to scientific journals, and corespondences that lead me to beleive he really is working on something substantial, but I was left feeling like there was one more act to the play that wasn't in the book.

This book is a "keeper", especially as a reference, and I recommend it.

Customer Rating: 

I've been a fan of pop science for years but when it comes right down to it I'm totally a layman. To my layman brethren I offer this warning, Reinventing Gravity is not an easy read. There are no formulas but quite often I found myself zoning out.

What the book is about is the authors attempt to resolve some of the great mysteries of cosmology including the apparent expansion of the universe and the possible existence or non-existence of dark matter and dark energy. The author's theory is that some of the constants of the universe including the speed of light and the force of gravity aren't so constant. In particular he presents a hypothesis that the speed of light during the early moments of the universe was much much faster than the current speed in our corner of the universe. With regards to gravity he proposes that the force of gravity actually increases as objects move apart up to a certain point and then begins to diminish. He calls these ideas modified gravity or MOG.

Let me get this right out of the way. The author lost me. I don't understand how adjusting the speed of light at the early moments of the universe solves the strange smoothness of the universe or how having gravity increase and then decrease can be anything but an ad hoc solution to observation. If the author offered up an explanation as to why gravity might behave this way I somehow missed it. MOG also gets rid of singularities particularly those that form Black Holes and the singularity that preceded the Big Bang. As to how MOG gets rid of singularities I couldn't say because I couldn't follow. Maybe I'm just dense so if the following sentence makes sense to you, "the vacuum fluctuations in MOG's varying G and phion fields in the neighborhood of t = 0 generate the scale-invariant primordial power spectrum that is required to explain the WMAP power spectrum data..." If that sounds perfectly logical and understandable then this is the book for you.

When I read pop science books I like to be informed and entertained and in this case I don't think the author managed either. I was slightly amused by his critique of superstring theory in which he stated that, "one prominent feature of sting theory is the use of the word "super" which enhances its attraction for physics students and media alike" I have to admit that was funny but that was one brief moment in the book. It's possible that Professor Moffat may have discovered the next great revolution in physics but my suspicion is probably not. I guess I would have been swayed more had his theory contained a little more meat on the bone or didn't feel so contrived. Maybe the problem was in the author's delivery but I just didn't feel as if I was reading something revolutionary. Or maybe I was just too dopey to follow.

Customer Rating: 

I was thoroughly enjoying this book on my Kindle 2. The first 50 pages or so, don't use any math. When the math began, I noticed that many four digit numbers began with "10". So we get 1070, 1036, etc. Then we get 10 -23, 10 -36, etc. I realized that the author intended to write 10 raised exponentially, eg...10^70 etc. I phoned the Kindle people at Amazon and explained the situation. They were very nice, and they refunded the cost of my purchase. I got the impression that they would advise the Kindle team and changes would be made.

I don't think this is happening. I do some proofreading for another ebook website, and I know this can be done. Some of the non-scientific books on Kindle are replete with errors (called "scanos" as in "typos") which even beginner proofreaders catch and correct.

As a shareholder in Amazon.com, I sincerely hope that management looks into this matter. Maybe they can pay the proofreaders at Project Gutenberg or [...] to give their books a smooth-scan. These folks could use the money.