Status
Available
Collection
Publication
New York : Smithsonian Books/Collins, 2008.
Description
A bold revision of one of the most successful theories of all time: Einstein's general theory of relativity. Physicists have long known that something is wrong with gravity. Einstein's relativity and the theory of quantum mechanics are fundamentally incompatible, which has prompted the last 30 years of work in string theory and quantum gravity. However, John Moffat has identified a bigger problem: not only does Einstein's theory not work in the world of the very small; it does not seem to work in the world of the very large either. Moffat has developed a modified theory of gravity, or MOG, that can explain the behaviour of our universe as well as Einstein's, without resorting to dubious, yet long-claimed excuse for the existence of invisible "dark matter." As John Barrow of the University of Cambridge asserts, the simplicity of Moffat's model demands that physicists take this daring new theory seriously. Now, for the first time, Reinventing Gravity introduces general readers to Moffat's groundbreaking new ideas about the universe.… (more)
User reviews
LibraryThing member fpagan
No crackpot, Moffat was long in Toronto U's physics department and is now with the Perimeter Institute. His Modified Gravity theory (MOG), an extension of general relativity, involves a varying G and a fifth force mediated by "phions." It does away with the universe's postulated dark matter. It
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also leads him to question the conventional understanding of dark energy, black holes, and the Big Bang. Great stuff, but I would bet he is wrong. (In not being a fan of string theory, though, he may be right.) Show Less
LibraryThing member MauriceAWilliams
Dr. Moffat, a mainstream cosmologist with impeccable credentials, is also professor emeritus of physics in the University of Toronto and a resident affiliate member of the Perimeter Institute for Theoretical Physics in Toronto. He has authored many professional papers, has worked with many
One of the many items that impressed me is Moffat’s description of a singularity, like a black hole. I had already picked up a definition from the media that a singularity is a situation where all known laws of physics no longer apply. I always wondered about that. Moffat describes a singularity as 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. Cosmologists are in the habit of describing the cosmos through mathematics because mathematical computations can be precise enough to predict hitherto unknown behavior in the cosmos (and in physical nature), behavior that can subsequently be searched for and authenticated by observation. This is how science progresses.
The present understanding of what holds the cosmos together is a combination of Newton’s theory of gravity, Einstein’s relativity, and quantum mechanics. All three theories have been proven reliable, but attempts to unify all three into a single Grand Unified Theory have failed. These theories of cosmology propose four basic forces in nature: gravity, electromagnetism, weak nuclear force, and strong nuclear force. Moffat’s work indicates that there is another force to consider.
There is much new information obtained from telescopes orbiting the Earth. Distant galaxies show evidence that they are rotating too fast for the galaxies to hold together. If current understanding of gravity is the only force holding these galaxies together, they would have spun apart long ago. There simply isn’t enough mass within those galaxies to counteract the centrifugal force of the outermost stars orbiting at observed speeds. To make the current understanding of gravity sufficient to counteract observed centrifugal forces, cosmologists have presumed that there must be unseen dark matter within the galaxies. Recent observations also indicate that the expansion of the universe is accelerating, implying that there is an unknown force causing the acceleration. Cosmologists propose that, in addition to dark matter, there must also exist dark energy, a proposed undetected energy that serves to explain the acceleration. Dark matter and dark energy have never been observed even though there have been very expensive experiments performed to detect both.
Moffat spent many years studying whether gravity really is a force of uniform and constant strength throughout the universe or might it be a variable-strength force, especially outside the solar system. He proposes a modified gravity hypothesis that adds a fifth force to the four already recognized. The fifth force can be thought of as a “gravitational degree of freedom: part of the overall geometry or warping of space-time.” Newton’s gravity constant would now no longer be a constant but a variable force in time and space. This variable force of gravity, together with the new force, strengthens the pull of gravity in far away galaxies and in clusters of galaxies.
Moffat relates that mathematical equations based on the addition of his new force can explain all current and past observations without singularities or the need to propose dark matter or dark energy. In addition, his hypothesis holds that, when a star collapses under its own gravity, it does not form a black hole (a singularity where there is a reversal of time and space at the “event horizon”). A collapsed star forms, instead, a very massive and very small object that he calls a “grey star.”
Moffat has described a very difficult subject, usually understood only through mathematics. He describes his position in plain English easily understood by the average reader. This is a very informative and interesting book written by someone who has the credentials to know what he is talking about. “Reinventing Gravity” may well be the book that will introduce you to the new frontier on cosmology.
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cosmologists, and even discussed cosmology with Albert Einstein. He points out many inconsistencies in the current theory about gravity and suggests his own thoughts on how to correct those inconsistencies. His suggestion is not a totally new hypothesis but a modification in the understanding of gravity. His book is written for the layperson and is easy to understand, but he provides detailed end notes for readers more versed in cosmology.One of the many items that impressed me is Moffat’s description of a singularity, like a black hole. I had already picked up a definition from the media that a singularity is a situation where all known laws of physics no longer apply. I always wondered about that. Moffat describes a singularity as 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. Cosmologists are in the habit of describing the cosmos through mathematics because mathematical computations can be precise enough to predict hitherto unknown behavior in the cosmos (and in physical nature), behavior that can subsequently be searched for and authenticated by observation. This is how science progresses.
The present understanding of what holds the cosmos together is a combination of Newton’s theory of gravity, Einstein’s relativity, and quantum mechanics. All three theories have been proven reliable, but attempts to unify all three into a single Grand Unified Theory have failed. These theories of cosmology propose four basic forces in nature: gravity, electromagnetism, weak nuclear force, and strong nuclear force. Moffat’s work indicates that there is another force to consider.
There is much new information obtained from telescopes orbiting the Earth. Distant galaxies show evidence that they are rotating too fast for the galaxies to hold together. If current understanding of gravity is the only force holding these galaxies together, they would have spun apart long ago. There simply isn’t enough mass within those galaxies to counteract the centrifugal force of the outermost stars orbiting at observed speeds. To make the current understanding of gravity sufficient to counteract observed centrifugal forces, cosmologists have presumed that there must be unseen dark matter within the galaxies. Recent observations also indicate that the expansion of the universe is accelerating, implying that there is an unknown force causing the acceleration. Cosmologists propose that, in addition to dark matter, there must also exist dark energy, a proposed undetected energy that serves to explain the acceleration. Dark matter and dark energy have never been observed even though there have been very expensive experiments performed to detect both.
Moffat spent many years studying whether gravity really is a force of uniform and constant strength throughout the universe or might it be a variable-strength force, especially outside the solar system. He proposes a modified gravity hypothesis that adds a fifth force to the four already recognized. The fifth force can be thought of as a “gravitational degree of freedom: part of the overall geometry or warping of space-time.” Newton’s gravity constant would now no longer be a constant but a variable force in time and space. This variable force of gravity, together with the new force, strengthens the pull of gravity in far away galaxies and in clusters of galaxies.
Moffat relates that mathematical equations based on the addition of his new force can explain all current and past observations without singularities or the need to propose dark matter or dark energy. In addition, his hypothesis holds that, when a star collapses under its own gravity, it does not form a black hole (a singularity where there is a reversal of time and space at the “event horizon”). A collapsed star forms, instead, a very massive and very small object that he calls a “grey star.”
Moffat has described a very difficult subject, usually understood only through mathematics. He describes his position in plain English easily understood by the average reader. This is a very informative and interesting book written by someone who has the credentials to know what he is talking about. “Reinventing Gravity” may well be the book that will introduce you to the new frontier on cosmology.
Show Less