Reinventing Gravity: A Physicist Goes Beyond Einstein

by John W. Moffat

Einstein's gravity theory—his general theory of relativity—has served as the basis for a series of astonishing cosmological discoveries. But what if, nonetheless, Einstein got it wrong?

Since the 1930s, physicists have noticed an alarming discrepancy between the universe as we see it and the universe that Einstein's theory of relativity predicts. There just doesn't seem to be enough stuff out there for everything to hang together. Galaxies spin so fast that, based on the amount of visible matter in them, they ought to be flung to pieces, the same way a spinning yo-yo can break its string. Cosmologists tried to solve the problem by positing dark matter—a mysterious, invisible substance that surrounds galaxies, holding the visible matter in place—and particle physicists, attempting to identify the nature of the stuff, have undertaken a slew of experiments to detect it. So far, none have.

Now, John W. Moffat, a physicist at the Perimeter Institute for Theoretical Physics in Waterloo, Canada, offers a different solution to the problem. The cap­stone to a storybook career—one that began with a correspondence with Einstein and a conversation with Niels Bohr—Moffat's modified gravity theory, or MOG, can model the movements of the universe without recourse to dark matter, and his work chal­lenging the constancy of the speed of light raises a stark challenge to the usual models of the first half-million years of the universe's existence.

This bold new work, presenting the entirety of Moffat's hypothesis to a general readership for the first time, promises to overturn everything we thought we knew about the origins and evolution of the universe.

Genres: Physics, Science, Nonfiction, History

288 pages, Kindle Edition

First published September 20, 2008

About the author

John W. Moffat has been a professor of physics for more than three decades. He is currently Professor Emeritus at the University of Toronto, a member of the Perimeter Institute for Theoretical Physics in Waterloo, Ontario, Canada, and adjunct professor in the physics department at the University of Waterloo. Moffat is well known for his alternative theory of gravity to Einstein's general relativity. He is the author of Reinventing Gravity: A Physicist Goes Beyond Einstein and Einstein Wrote Back: My Life in Physics.

Reviews

[Voyt · Rating 4 out of 5]

Models and physics of the Universe.
POSTED AT AMAZON 2009
..yes, we have quite a few and none of them is for sure. There are physicists like Victor Stenger ("The Comprehensive Cosmos") who believes that we know almost everything about it based on standard inflationary model. But it cannot be further from the truth. This model is FULL of riddles! Flaws of Big Bang scenario have been discussed by several cosmologists in their books and John Moffat does it as well. They propose different scenarios. We may read about string (superstring-brane) models in "Endless Universe" (Steinhardt, Turok), "Universe Before the Big Bang" (Gasperini). New topology unique idea appears in "The Wraparound Universe" by Luminet. Moffat's book cannot be missed by anybody searching for truth in cosmology and about possible ways of Universe creation and development! All these "not main stream science" models cannot be disproved at least for now. Moffat's work concentrates on dark matter (and dark energy to certain extent), whether there is a real need to incorporate it into Einstein's gravity theory so that the theory can fit astrophysical and cosmological data. His conclusion: not realy. Perhaps we are too preoccupied with both shadowy dark "fudge factors". How can we verify who is right and reject certain propositions? Hope exists in analyzing Cosmic Microwave background ("The Music of the Big Bang" by Balbi) - at least for now. We have to wait for results coming from Planck mission and CERN experiments. For those who will live long enough radiotelescope SKA project will push our knowledge and verifications even further. For know, it is essential to know what we expect from variety of different theories (like the one in John Moffat's book). Author represents great deal of talent in explaining difficult topics and physical phenomena by using "easy going", straight language and building clear analogies without any abstract mathematics. Simply: "Reinventing Gravity" is a classic popular cosmology book about above mentioned theoretical models and extra lessons presenting MOND, VSL and MOG theories that has not been explored so far in popular science publications (IMO). Glossary therms are very appreciated and notes to each chapter are very helpful for those who want to explore beyond the main text. Must read for all cosmology enthusiasts!

[Mike · Rating 2 out of 5]

This book does not actually explain the authors theory very well. The first half of this book is basically a brief history of gravity. Obviously it's important to have that background, but anyone reading this book is probably going to know most of it already, and it's covered in many other books. The rest of the book talks about various theories and the observations that either reinforce or disprove them. We don't get into the author's MOG or MSTG or whatever it's real name is until two-thirds of the way through! Even then, there is only a brief, vague description of additional fields, a fifth force and its new particle called a phion. There is hardly any discussion on these remarkable additions, which are surely a big factor in why MOG is struggling for acceptance. I mean, a new force? A new boson not in the Standard Model?! And how is that different from dark matter, anyway? There's much excitement about how well MOG fits the observations and avoids singularities, but very little in the way of new, testable predictions. Can we detect phions? Do they change the mass-energy equivalence? Are there quantum mechanical consequences? Finally, while equations can be scary, there's so much maths-speak anyway it would be nice to actually see the MOG/MSTG equations somewhere in this book. Is there no equivalent to E=mc2 or Einstein's field equations? Somewhat disappointed but keen to learn more.

[David · Rating 3 out of 5]

Interesting effort by a physicist from U. Toronto to explain his modified (from Einstein's theory) theory of gravity. He sets it against the prevailing (I gather) wisdom that Einstein's model can be patched up to account for anomalous data by proposing that most of the matter in the universe is invisible "dark matter" that no one has been able thus far to detect. He's also skeptical about string theory and black holes.

I understood the philosophy of science aspects (e.g., emphasis on testable, falsifiable predictions; preference for point predictions rather than models with many fudge factors allowing retrofit to observations.....) and the sociology of science aspects (e.g., difficulties getting his stuff published at first when it was too far outside the mainstream, trendiness of string theory among young physicists). What I had a really hard time tracking was the actual science science part of it.

The book is ostensibly aimed at layperson, which is me as it pertains to physics for sure, and he does a good job of keeping the text uncluttered with equations, but I still wasn't right on top of it. Here's a relatively tame sample excerpt (p. 157):

"My new theory....MSTG, was different from NGT in that the spacetime geometry I used was the purely symmetric spacetime of Einstein gravity. The antisymmetric part, the "skew," of NGT was no longer part of the geometry, but now occurred as an additional field in the equations of the theory. In other words, the skewness came not from spacetime itself but from a new field in the theory tha in fact constituted a new fifth force."

If you are able to evaluate whether demoting the antisymmetric part from "part of the geometry" to merely "an additional field in the equations" is a good idea, a big difference, etc., then you will likely get more out of this book than I did in terms of the physics itself.

[Bill Leach · Rating 4 out of 5]

The author starts with a review of the development of physics from the Greeks, through Newton and Einstein to modern particle physics and cosmology. Galileo is noted to be the first scientist to emphasize the importance of experiments in checking out theories. Of note is the history of how Einstein was able to show that relativity accounted for the perihelion advance of Mercury, doing away with the hypothesized Vulcan and ending the major search for the planet.

Modern cosmology has invoked the presence of a dark matter to explain the motions of the universe as otherwise it is not consistent with Einsteinian physics. Efforts to find the dark matter particles, WIMPS and axions being the most likely, have so far failed. Also notable are black holes - singularities that fall out of Einsteinian physics. While the physics of black holes have been explored extensively, the only evidence is the irregular motion of nearby stars. Einstein was not happy with the singularities inherent in the theory of relativity.

Early inflation of the universe has been hypothesized to account for the flatness and uniformity of the current universe. Such inflation requires a huge cosmological constant where the vacuum energy density if about 10^70 times as large as presently observed. Numerous variations on inflation theory have been proposed to get around this and other problems. Moffat has proposed a Variable Speed of Light (VSL) theory as an alternative to inflation, which resolves many of these problems. VSL could be tested against inflation as the two models predict different spectrums of gravity waves. Current experiments to detect gravity waves have not so far produced results.

Cosmic Microwave Background (CMB) radiation from the Cosmic Background Explorer (COBE) has provided detailed information on angular power spectrum of acoustic waves. These same data plus observations of the galaxies provide detail on the matter power spectrum. In order for these observations to be consistent with the standard model of cosmology (Einsteinian physics), it is concluded that the universe must be 4 percent baryons, 24 percent dark matter and 72 percent dark energy.

Physics have been trying to combine general relativity with quantum mechanics by finding a way to "quantize" the gravitational field. Much work has gone in to string theory, but it has become complicated with many dimensions and an infinite number of solutions. The theory produces no predictions that are testable and many consider it to be anti-science. Moffat terms the huge time and resource allocation to string theory as the "lost generation". Other groups are working on an approach termed Loop Quantum Gravity (LQG), which sees spacetime as being quantified at distances of the order of the Plank length. While this theory does a better job of respecting a number of principles of relativity including the dynamic geometry of spacetime, it is not clear that it can be tested.

It is very difficult to develop a modified gravity theory which avoids instabilities that are clearly incorrect. Mordehai Milgrom's Modified Newtonian Dynamics (MOND) and subsequently, Jacob Bekenstein's Tensor-Vector-Scalar (TeVeS), sees the gravity changing below a certain threshold. These theories have produced some good results, but have instabilities and are not fully relativistic.

Moffat has developed a series of theories termed Modified Gravity (MOG) - Nonsummetrical Gravity Theory (NGT), Metric-Skew-Tensor Gravity (MSTG) and Scalar-Tensor-Vector Gravity (STVG). All see a variable gravitational constant. The three theories can only be distinguished by their predictions for strong gravitational fields. There are are completely relativistic, devoid of instabilities (except NGT) and in good agreement with all astronomical observations to date. STVG postulates a fifth force, the phion field / particle.

In 2004, the bullet cluster was discovered in the constellation Carina. Two clusters of galaxies had collided. Interpretation using the standards model indicates that dark matter was associated with the visible galaxies rather than the gaseous areas, to create the gravitational observed lensing. This was largely hailed as a proof that dark matter exists. STVG predicts the gravitational lensing without the need for dark matter. Additionally, it predicts the temperature of the larger cluster (179 million degrees C) in agreement with observational data.

In 2007, another complicated collision of galaxy clusters, named Abell520, was discovered in Orion. In this case, however, it appeared that the dark matter was associated with the gaseous areas rather than the galaxies. This is not easily explained, some scientists suggesting there may be two types of dark matter. The author claims MOG predicts the observed lensing without requiring dark matter.

More recent work on MOG has eliminated any free parameters, making all predictions exact. The theory (STVG?) reduces to Einsteinian mechanics within the solar system. MOG shows agreement with globular clusters, galaxies, galaxy clusters and satellite galaxies without invoking dark matter. MOG indicates that at very low accelerations a body's inertial mass should differ from it's gravitational mass, a test that could be carried out in space. Calculation of the matter power spectrum with MOG shows an oscillating curve while the standard model with dark matter shows a uniform curve. It is expected that observational data will provide the detail required to distinguish the two in coming years.

The author describes a new solution to Einstein's field equations that does not lead to singularities, but leaves it nameless. (This chapter is somewhat vague). It appears that a negative field energy is implicit in this solution, which implies that massive objects would not collapse into the singularity of a black hole and would not have an event horizon. The body would allow the loss of tiny amounts of matter, avoiding the information loss problem. Moffat terms such objects Grey Stars.

MOG has a solution for an expanding universe without the need for dark energy, but it is unclear whether any experiment could verify it.

MOG provides a unique model of the early universe. It does not suggest a cyclic universe which is at odds with the Second Law of Thermodynamics. Standard inflation is not needed. CMB arises at about 400,000 years. The various theories have different predictions as to the amplitude and intensity of gravity waves that arise at t = 0. They also differ in their predictions of the polarization of the CMB. Experimental data may allow these to be tested in coming years.

A fascinating book.

[Mike · Rating 2 out of 5]

This book does not actually explain the authors theory very well.

The first half is basically a brief history of gravity. Obviously it's important to have that background, and it's quite well done, but anyone reading this book is probably going to know most of it already, and it's covered in many other books.

The rest of the book talks about cosmological anomalies and various alternative theories that try to account for them. We don't get into the author's MOG or MSTG or whatever it's real name is until two-thirds of the way through!

Even then, there is only a brief, vague description of additional fields, a fifth force and its new particle called a phion. There is hardly any discussion on these remarkable additions, which are surely a big factor in why MOG is struggling for acceptance. I mean, a new force? A new boson not in the Standard Model?! And how is that different from dark matter, anyway?

There's much excitement about how well MOG fits the observations and avoids singularities, but very little in the way of new, testable predictions. Can we detect phions? Do they change the mass-energy equivalence? Are there quantum mechanical consequences?

Finally, while equations can be scary, there's so much maths-speak anyway it would be nice to actually see the MOG/MSTG equations somewhere in this book. Is there no equivalent to E=mc2 or Einstein's field equations?

Somewhat disappointed but keen to learn more.

[Yankey · Rating 4 out of 5]

Don't let the subject matter scare you off. Even if you are not a science, math or other kind of Geek, this will be a good read.

John Moffat spends the first half of this book detailing the history regarding mans understanding of gravity. His style is patient, grounded and understandable to laymen.

Archimedes, Newton and Einstein all conceived concepts of gravity that were generations ahead of their time. The theories these geniuses put forward have been used in the development of all types of math and science developments. Yet, there are inconsistencies, "plugged in" factors and missing proofs. Is it time to make the next big step in understanding nature? Space telescopes, particle collider's, new gravity sensing experiments and more are bringing lots of new information on the subject to the forefront of research.

[Maurice Williams · Rating 4 out of 5]

I have often heard of a singularity, better known as a black hole, being described as a situation in which all the known laws of nature no longer apply. I always had a hard time visualizing such a situation. John W. Moffat in his “Reinventing Gravity: A Physicist Goes Beyond Einstein” presents a different, more easily understood, description. A singularity is a theoretical situation arrived at mathematically where the mathematical numbers become extremely large, too large to calculate, so large that, if a computer were used to make the calculations, the computer would crash.

A mainstream cosmologist with outstanding credentials, Dr. Moffat is professor emeritus of physics in the University of Toronto and adjunct professor at the University of Waterloo. He is also a resident affiliate member of the Perimeter Institute for Theoretical Physics in Toronto. Here is a man who knows what he is talking about.

Cosmologists describe the workings of the cosmos through a combination of Newton’s gravity, Einstein’s relativity, and quantum mechanics, resulting in identification of four basic forces in nature: gravity, electromagnetism, weak nuclear force, and strong nuclear force. So far, all have mathematically been proven reliable; but recent observations from orbiting telescopes show distant galaxies rotating at very fast speeds, so fast that if gravity were the only force holding these galaxies together, they would have spun apart long ago. Observations from orbiting telescopes also indicate that the expansion of the universe is accelerating, implying that there is an unknown force causing the acceleration.

To provide some means to explain both of these unexpected observations, cosmologists have proposed dark matter to provide sufficient mass within distant galaxies and also proposed dark energy to explain the acceleration. Neither has ever been detected, yet cosmologists opine that the two of them comprise 96% of the entire universe. Moffat proposes his Modified Gravity hypothesis, which adds a fifth force to the four already recognized. The fifth force is a gravitational degree of freedom and is part of the overall geometry or warping of space-time. He proposes that Newton’s gravity constant would now be a variable force and, together with the new force, strengthens the pull of gravity in far away galaxies and in clusters of galaxies.

Mathematical equations describing Moffat’s concepts do not require dark matter and dark energy and do not result in singularities, like black holes that current theories predict whenever a star collapses under its own gravity, where there is a reversal of time and space at the “event horizon.”

John Moffat describes a difficult subject that is usually understood only by mathematicians. He wrote “Reinventing Gravity” so that the average reader could follow his arguments, and provides technical end-notes for those wanting more detail. His book is very interesting. John Moffat's book can probably bring an untrained reader to a better understanding of what holds the cosmos together.

[Alejo.Tobon · Rating 4 out of 5]

If I had to choose a word for the book I’d pick “provocative”. Is not common to find books outside of the mainstream theories in science and a different theory of gravity without Dark Matter and a different cosmology model is very interesting. Although the book is not new and has a lot of chapters for the background and only a few specific of the Modified Gravity, it does well explaining different features and approximations. The theory itself has some intriguing features (VSL, phion field and variable G) not explained in this book but I think is worth exploring deeply to understand better such proposal. What I didn’t like much during the reading, is the biased opinions of the author towards his theory, although is normal, I think it was too much.

I found a lot of value exploring ideas (mainstream or not) looking for the explanation of the universe and I’d definitely recommend this book for those who want to be provoked by different ideas.

[Lesley · Rating 3 out of 5]

The subject matter was fascinating. My background in this consists of a graduate course in general relativity but this is far outside of my present field of physics so I have not kept up to date with recent developments. The explanations of the various theories and their associated problems was very interesting, as were the summaries of the experimental data to date and how these relate to the theories. However, without being aware of current literature on the subject, one does have to wonder how much of this book is self-serving and biased. That may just be the cynic in me talking, and I still did enjoy the subject matter very much. The book was challenging at times, but I was glad to push through to the end.

[Dan Zarfati · Rating 5 out of 5]

Very interesting book, analyzing Einstein gravity , black holes and dark matter.

[Rossdavidh · Rating 3 out of 5]

What to say about a physicist who decides that maybe his entire profession is wrong about gravity? Whatever you may think of his theory, he is not an obvious crank, who you can safely disregard. But then, neither is he an obvious genius, correct when (nearly) all others are wrong. He is in that nebulous gray area between the two. Reading his book, gives you a lot of food for thought, and not only about physics.

Nowadays, we can take it for granted that when Newton, or Kepler, or Copernicus, or Einstein proposed their world-shaking new theories, they had opposition. However, what is not as obvious is that, at around the same time, there were others who had new and radical theories. Those people's new and radical theories turned out to be wrong, even though some of them might have been intelligent and thoughtful. That's the way humanity is; even among the smart ones, most of the ideas are wrong. So while it is obvious now, looking back, that the opposition to the ones who were right was based more on an aversion to new ideas than it was to any flaw in Newton's or Einstein's ideas, it wasn't obvious at the time.

The reason why we might take somebody like Moffat, who thinks that our current theories of gravity are wrong, seriously, is that astrophysics does seem to be in a bit of an odd spot. It was awkward enough when we had black holes, which seem to behave in very odd ways. Worse yet, we have dark matter, and then dark energy, which basically amount to the most gargantuan fudge factors in the history of calculating anything. According to mainstream astrophysics, over 90% of all the matter and energy in the universe is "dark", that is not perceptible to us in any way (except for how it impacts other through gravity, and similarly indirect ways). I don't know if Moffat's theory is any good, but he is right to be calling out physics on this. If your theory needs a fudge factor greater than the known universe to make your sums come out right, maybe you need to make a better theory.

The problems of astrophysics call to mind the similar problems, I think it is not too strong a term to call it a crisis, which besets the physics of the very small, where string theory has gone from being the proposed savior to the proposal that we need 10 or more dimensions in order to get anywhere mathematically, without much of any good way to verify that they exist. These problems collide when we get back to the Big Bang and the instant thereafter, where the realm of astrophysics is also the realm of the very small. But how do you test your theory for how the Big Bang worked?

The answer, largely, is that you don't. You can, however, come up with some mind-bending theories about it. Then, you can write books about it. If you feel like having a good time having your mind bent, this is a good book to do it.

[Travis · Rating 4 out of 5]

If you are at all interested in physics, astronomy, and cosmology, then you should take the time to peruse this book. Moffat looks at some of the most exotic and complicated issues in present day physics--dark matter, dark energy, inflation, the accelerating growth of the universe, black holes, the cosmological constant--and proposes a new theory that quite simply does away with these puzzles.

Moffat is particularly motivated by the problem of dark matter. Rather than accepting the orthodox view of dark matter, Moffat plays the role of the child pointing out that the emperor has no clothes: dark matter has never yet been detected and is said, by the physics establishment, to interact--if at all--with normal matter only very, very weakly, but Moffat argues that there is no dark matter. Dark matter was posited around 30 years ago to try to account for the problem of the gravity at the edges of galaxies appearing to be too strong for the amount of visible matter that could be observed. Moffat, in taking on his peers, asserts that the solution is not to propose this esoteric and so far completely undetectable dark matter; instead, he proposes that the gravity at the edges of the galaxies actually is as strong as it appears, but in making this assertion, Moffat is claiming the Einstein's theory of gravity is wrong; it stands in need of modification. Thus, Moffat proposes a new theory of gravity: MOG (modified gravity).

This is a fascinating read, and if the future empirical observations are consistent with Moffat's MOG rather than with the dark matter approach used in Einstein's theory of gravity, Moffat may well be hailed as the successor of Newton and Einstein in revolutionizing our view of gravity and of the cosmos.

[William Schram · Rating 3 out of 5]

The author spends a lot of time telling us the reason why a paradigm shift for our thoughts on gravity is necessary. Most of it is about how a lot of the data doesn't agree with the theory anymore. Also, it is difficult to observe a lot of the things predicted in the theory and to accommodate it, it is necessary to invent things like Dark Energy and Dark Matter, which can't really be observed.

Thus, the author wants to simplify the current paradigm of gravity. To do this he develops a modified gravity theory or MOG.

So most of the book is the history of gravity theories starting Aristotle and going on to the Cosmological ideas of Claudius Ptolemy and finally getting on to Copernicus and Newton and Kepler. Of course it was found that some things did not follow in this theory, so they thought another planet existed that was between the Sun and Mercury, but was not found.

Then along comes Einstein with his General Theory of Relativity which had proof, but was contested. This is mostly due to the fact that combining it with the Special Theory of Relativity causes the equations to break down, and that it was hard to view gravitational lensing with the technology at the time. However, his equations seemed to fit the data so they were accepted.

Then he finally gets into his MOG. Not much else to say about it.

I liked the book, I thought it was pretty good. I am not sure of the current state of Physics though since this book is not exactly cutting edge, and I was wondering if a lot of these issues are still issues. In any case, if I had the time I would read it again.

[Benoit Galarneau · Rating 2 out of 5]

Je n'ai pas fini ce livre.
Il s'ouvre sur une très belle histoire de la science physique. De Newton à Einstein en passant par Maxwell, on saisit bien l'enjeu fondamental d'unifier les concepts de physique. On y explique comment sont apparu les théories modernes du Big Bang, de l’expansion de l’univers et de la mécanique quantique. On y retrouve une certaine ironie dans l’exposition de concepts qui n’ont pas tenu la route (comme l’éther) mais qui faisaient office de vérité pendant un temps.
Le but du livre est de présenter une nouvelle théorie quant à la gravité — force étrange dans notre compréhension actuelle de l’univers.
Pour y parvenir, l'auteur dénonce les visions du modèle expansionniste de Guth and all, et là, il me perd.
Si les prétentions de Einstein sont assez "matures" pour être vulgarisées avec aisance, ce n'est pas le cas des théories émergentes et Moffat sombre vite dans des détails destinés aux initiés.
On comprend que le débat est lourd de conséquences (fin de la matière noire et des trous noirs, révision du modèle standard) mais il est impossible de se faire une idée. Peut-être que la ré-édition de 2050 sera passionnante.
Je vous le recommande pour les 150 premières pages.

[Josh Ronsen · Rating 4 out of 5]

A very well-written history of our evolving ideas about gravity. However, Moffat is somewhat vague about his own revolutionary theory that posits a 5th force of nature. Perhaps it is too complicated to describe to the general reader, but after reading the book I cannot tell you any details about it.

Moffat unfairly criticizes Inflation theories for inventing a new particle, the Inflaton. But in modern (quantum) field theory, every field has a particle associated with it. When Moffat gets around to vaguely talking about his new theory of gravity, he neglects to mention that he invents a new particle to go along with his new field. I think he deliberately confuses the general reader on this issue; both Inflation and Moffation (if I can call it that) both call for a new field AND a new particle. Moffat can't dismiss Inflation for this reason without dismissing his own theory.

[Kevin · Rating 4 out of 5]

Though this book avoids any formulas and equations, its description of theories of gravity and concerning gravity get rather technical. I liked the history of the planet Vulcan and the descriptions of how science works.

What I liked most was to find that a real physicist has conceived a theory that avoids dark matter, dark energy, black holes, and possibly even the Big Bang. As a scientist, but not a physicist, I have not felt comfortable with these concepts. It appears that Dr. Moffat's new theory does not need them to account for astronomical phenomenon. He even suggests ways to test his theory.

I am looking forward to seeing his ideas get acceptance within the scientific community.

[Zoffix Znet · Rating 1 out of 5]

Torture. I feel completely exhausted after reading this book. While the beginning is somewhat entertaining, the book quickly slides into the "Brief History of Time" motif exhibited by virtually every other popular cosmology book. The later half can be summed up in a single sentence: "MOG theory conforms to experimental data and avoids dark matter". Some pages could be ripped out of the book without its losing any of information value. The idea of MOG theory avoiding dark matter is repeated probably 20-30 times over and over. Considering the book has 223 pages of main content, it's quite sad that the only info it tells about the theory can be summarized in a single paragraph. While the MOG theory sounds interesting, I would strongly recommend you find a better source of its description.

[Carl Schmidt · Rating 4 out of 5]

Some of the other reviews were critical of this book for spending too much time regurgitating the history of gravity theories, and treading somewhat lightly on the topic of MOG (Modified Gravity) itself. However, as a layperson interested in the world of physics, I found the balance about right. Had the author delved into MOG's equations, I think the appeal of the book to a wider audience would have been more limited. It's well written, well-researched, and enjoyable to read. In short, if you've been reading things like "The Universe in a Nutshell", or "Brief History of Nearly Everything", and perhaps following news of the LHC, then there's a high probability you'll enjoy this book as well.

[Rod · Rating 1 out of 5]

First few chapters are a good review of progress toward a unified theory of quantum gravity. Goes downhill from there with the author arguing for his own theory, which repudiates Einstein's General Theory of Relativity.

AFAIK, the General Theory predicts all know experimental results, and is accepted by virtually all workers in the field. Except for this author. The non-specialist reader should be aware the the last two thirds of the book represents a distinctly minority position among workers in the field.

[Glyn Longden · Rating 3 out of 5]

Moffat, who is at the Perimeter Institute in Waterloo, has always been a maverick in the world of cosmology and physics. He makes a case that dark matter, which supposedly makes up about 25% of the universe, doesn't
really exist and that his own modified gravity theory(MOG) can explain many of the mysteries in the universe. Is Moffat right? Probably not, but at least he's not afraid to throw out some new ideas in light of the apparent failure of string theory to provide explanations for the operation of the cosmos.



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[Faith · Rating 2 out of 5]

I understand that this book is made for the general public.. but to write equations in sentences really put me off. Other than that i prefer MOG than the dark matter candidate to explain the "missing masses". Also in this book he explains how MOG could compliment in the standard models, giving few physical examples (including brief literature) on galaxies blackhole space time etc.. i'm still little put off with the literature... I get bored before going into how MOG could provide an alternate solution.

[Genessa]

While I respect Dr Moffat's creativity in searching for a way to reconcile quantum mechanics and general relativity, he has been spending a lot of page space so far on mocking previously held or alternative theories to his own. This as he ignores the rather large leap (a fifth major force? hmm) entailed in his Modified Gravity theory.
however, I'm interested enough in how he came up with said theory and his proofs and justifications to keep reading. and also I'm doing a presentation on modern gravity theory for a physics class.. so, the more you know...

[Yutaka · Rating 4 out of 5]

巨大渦巻銀河の外縁を動く恒星の実際の公転速度は、アインシュタインの理論から予測される値よりも2倍近く早い。その質量のギャップを埋めるために「ダークマター」が仮定されていて、一般的な前提になっている。筆者はダークマターが存在するという仮定ではなく、重力定数が距離によって可変とすることで一般相対性理論を含有しつつ、ダークマターが存在しなくても公転速度を説明できるという理論（修正重力理論(MOG)）を考案している。

本書では、ニュートンからアインシュタイン、そして現代に至るまでの重力理論の変遷をたどりつつ、MOG理論の内容とその優秀性を紹介しています。第五の力の場である「ファイオン場」を想定しているがそれに対応するファイオン粒子はまだ発見されていないこと（期待される候補はあるみたい）や、（宇宙の加速膨張に必携の）ダークエネルギー（真空が持つエネルギーとも）についてはまだ説明できないことなど、但し書きはつくものの、現時点では有力な理論ではないかと感じました。

[Michael · Rating 3 out of 5]

Moffatt is really trying to start something. He presents provocative arguments against such theories as the Big Bang, dark matter, the cosmological constant (speed of light), black holes, and string theory (he calls string theorists a "lost generation"), and offers a "modified gravity theory" to reconcile the mess he makes of modern physics' favorite concepts.

[Steve · Rating 3 out of 5]

Interesting alternative to dark matter and dark energy, explanations for faster galaxy rotation than matter in galaxy will allow and accelerating expansion of our universe. More data and testing will be required to validate his approach.

[Julian Haigh · Rating 3 out of 5]

Didn't understand much, but enjoyed it as a current (and not talking down to me) book on physics: gravity, cosmology and string theory. Interesting: I endeavour to be able to come back to the subject material with more understanding a second time.