Reinventing Gravity

Moffat's work culminates in his nonsymmetric gravitational theory and scalar–tensor–vector gravity (now called MOG).[1] His theory explains galactic rotation curves without invoking dark matter. He proposes a variable speed of light approach to cosmological problems, which posits that G/c is constant through time, but G and c separately have not been. Moreover, the speed of light c may have been much higher (at least trillion trillion times faster than the normal speed of light) during early moments of the Big Bang.[2] His recent work on inhomogeneous cosmological models purports to explain certain anomalous effects in the CMB data, and to account for the recently discovered acceleration of the expansion of the universe.

The theory is based on an action principle and postulates the existence of a vector field, while elevating the three constants of the theory to scalar fields. In the weak-field approximation, STVG produces a Yukawa-like modification of the gravitational force due to a point source. Intuitively, this result can be described as follows: far from a source gravity is stronger than the Newtonian prediction, but at shorter distances, it is counteracted by a repulsive fifth force due to the vector field.

STVG has been used successfully to explain galaxy rotation curves,[3] the mass profiles of galaxy clusters,[4] gravitational lensing in the Bullet Cluster,[5] and cosmological observations[6] without the need for dark matter. On a smaller scale, in the solar system, STVG predicts no observable deviation from general relativity.[7] The theory may also offer an explanation for the origin of inertia.[8]

The book was well received, although not uncontroversial, within scientific circles.[9] Publishers Weekly, in particular, said of Moffat:[10]

If his theory stands the test of time, Moffat will have created a paradigm shift not seen since Newton.

• Einstein Wrote Back, another book by Moffat