Gravity

On this part of our site, we present peer-reviewed, published evidence that gravity propagates faster than light. The observational evidence and related consequences appear in the following articles. But in our "Primer on Lorentzian relativity", we find out why speeds faster than light in forward time are still allowed by physics, despite strong rumors to the contrary. That is now supplemented by our article on Lorentz contraction, which provides a physical interpretation of that illusion produced by time dilation.

We also discuss the derivation of the relativistic perihelion advance formula from both classical and Lorentzian principles. The latter is shown in detail, and is much simpler. See links in box at left to preferred format.

Does the equivalence principle mean that gravity is just geometry? What is the origin and nature of inertia? What is the "transparency principle", and what does it tell us about gravity? These are the main issues addressed in "Does gravity have inertia?", a question we answer in the negative.

Does relativity require that space be curved? We show that it does not in "Does space curve?" This is material extracted from the previous article because it is of interest apart from the broader issue of inertia.

Particle models of gravity in flat space-time can yield all the familiar Newtonian and general relativity properties of gravity, but imply additional properties -- faster-than-light propagation, finite range, shielding, frictional losses, heating of masses -- that go beyond standard gravity. To see a discussion of these and how the new properties fare with observations and experiments, read Possible New Properties of Gravity. This was preprinted in v. 5 of the Meta Research Bulletin and then published in Astrophysics & Space Science, v. 244, pp. 249-261 (1996).

What the Global Positioning System Tells Us about Relativity discusses what aspects of general and special relativity are experimentally verified and which are subject to interpretation or uncertainty. The results are based on analysis of the behavior of super-accurate atomic clocks launched into orbit and compared with other orbiting and ground clocks. This is published in Open Questions in Relativistic Physics, F. Selleri, ed., Apeiron, Montreal, pp. 81-90 (1998). A companion paper is "What the Global Positioning System tells us about the twin's paradox", which explains some of the weirdness of special relativity and its most famous paradox.

Does "gravitational field" refer to "gravitational force" or "gravitational potential"? The former is covered by the equivalence principle, the latter is not. Yet only the latter affects clock rates. See a PowerPoint presentation of the key experimental results shedding light on these often-confused concepts. Don't have a PowerPoint viewer? It's a free download from Microsoft.

The Speed of Gravity - What the Experiments Say discusses all the experimental evidence that bears on the intriguing question of the speed of gravity, concluding that it must be many orders of magnitude faster than light in forward time (i.e., no causality violations). This was preprinted in v. 6 of the Meta Research Bulletin and then published in Physics Letters A, v. 250, pp. 1-11 (1998). A technical comment dealing with subsequent discussion of the Lienard-Wiechert potentials is published in Physics Letters A, v. 262, pp. 261-263 (1999).

Discussion of the first "speed of gravity" paper led to a follow-up paper to answer questions and issues raised by the community of relativists in response to the first paper. The most important of these issues is whether the proof that nothing can propagate faster than light in forward time is still valid. That is answered in the negative in The Speed of Gravity -- Repeal of the Speed Limit. This preprint is currently undergoing peer review. Specific technical commentary may be sent to the author at This email address is being protected from spambots. You need JavaScript enabled to view it..

Readers of Pushing Gravity may be interested in a supplement to the chapters by Tom Van Flandern and Victor Slabinski: The Meta Cycle. It shows where some of the numerical constraints came from, and how energy and number density are conserved for gravitons.

Anomalies have been seen in pendulums and gravimeters during solar eclipses. This so-called "Allais effect"is explained in an off-site paper published in Phys.Rev.D. Some later, more general work on gravity is preprinted here.