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
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
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 <email@example.com>.
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