Tom Van Flandern
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Tom Van Flandern is a credentialed astronomer with Ph.D. from Yale in 1969, specializing in celestial mechanics. He worked at the U.S. Naval Observatory for 20 years. In 1991, he founded the Meta Research organization in Washington, D. C. He has since found himself at the center of a scientific debate on his problem with the standard model of gravitation, General Relativity.
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Background
In a 2002 paper. Van Flandern and co-author J. P. Vigier argue that the conservation of momentum would be non-conserved under General Relativity given a speed of gravity equal to that of light. Specifically they note that orbits would not "close", and would be unstable. For instance, the orbit of the Earth would double in size over a period of about 1200 years.
To understand the argument, consider the conceptual model of Newtonian gravitation. In this system the Sun basically "pulls on the Earth" using an unknown mechanism, the same mechanism causing the Earth to pull on the Sun. Given any particular snapshot in time, the force between the Earth and Sun lies along the line between them. If this were not the case, for instance, if the Sun pulled slightly to one side, then there would be a leftover torque and the angular momentum of the Earth would change over time. This effect is not seen, in fact it is the conservation of angular momentum that leads to the original statements of celestial mechanics, Kepler's laws of planetary motion.
There is a "twist" that needs to be considered. From the Sun's perspective the Earth is moving about it. In modern physics all forces are transmitted at, or below, the speed of light. Given this wrinkle a problem arises: if the Sun pulls on the Earth then the direction of the force when it arrives 8 minutes later will be in the wrong direction -- it will be where the Sun was and not where it is now. This leads to the problems noted above, it is exactly the same as if the force is not directly along the line between the two bodies. For this reason, Newton felt that the speed of gravity must be instantaneous, although he was at a loss to provide a model for this interaction.
In the 19th century a new conceptual model evolved, one that indirectly addressed these problems. Under these so-called field theories, gravity does not work as a force directly between two bodies, but on the surrounding space itself. In the case of the Sun-Earth system, the Sun does not pull on the Earth, but instead creates a potential field in space, which the Earth interacts with by following the path to the lowest potential, toward the Sun. The implications of this change in model are profound. In the same "heliocentric" view of the Sun-Earth system, the force the Earth feels is always directed towards the Sun because it is interacting with the spherically symmetric field set up by the Sun. In a moving case the potential field that is set up is "sloped" in the direction of the Sun's motion, and once again the Earth moves towards the Sun. Field theories have since become the standard model for most of physics. Similar models are used to explain electromagnetism for instance.
Under a field theory the introduction of a maximum speed of propagation is of no serious concern. There are effects if the source is accelerating, but the magnitude of the effect is directly related to the speed of propagation relative to the acceleration. When relativity suggested a finite speed for all things, this presented no particular problem, notably given the fairly high speed of light. Astronomical evidence of the era had no counterexamples to demonstrate a problem. Note that similar effects occur in the electromagnetic force as well, but, for a variety of reasons, the resulting effects are much different, we call them magnetism.
General Relativity, the currently accepted model of gravitation, works on a field basis. However it proposes a different nature to the field, which many interpret in a geometric fashion; the field is actually the "bending" of space as opposed to some sort of potential. The Earth moves around the Sun because that it the shortest path between today and tomorrow, not because it is being pulled on.
Tom Van Flandern's non-standard theory of gravity
Van Flandern, with co-author J. P. Vigier have argued that the field model does not truely explain the lack of momentum exchange. They base this conclusion on the logical impossibility of gravity changing a target body's motion by space-time curvature alone in the absence of a force acting, and on the logical impossibility of creating new momentum for the target body out of a gravitational field that cannot itself be a source of radially-directed new momentum because of its symmetry and static character. [6] It is now well known that, if the gravitational potential field is an optical medium, the simple mechanism of refraction reproduces all the first-order effects special to GR exactly and with no adjustable parameters. [7]
In the same article [6], Van Flandern and Vigier cite all six experiments sensitive to the propagation speed of gravitational force. All six of those experiments indicate that the speed of gravity must be far greater than the speed of light, because a speed as slow as light could be detected by relatively large changes in the angular momentum of the planets and binary pulsars, in the times of solar eclipses, and even in laboratory experiments. [8] The most severe limits are set by the binary pulsars, indicating that gravity must propagate at no less than 20 billion times the speed of light.
In his conclusions, Van Flandern argues that the no-longer-popular interpretation of general relativity (GR) in which gravity is a force of nature (the interpretation preferred by Feynman [3], Dirac [4], and Einstein himself [5]) is the correct one, rather than a pure geometric effect of curved space-time (which readily explains the apparent equivalence of inertial mass and gravitational mass).
To put these logical and experimental results into a coherent picture consistent with GR while not invoking the logical absurdity of instantaneous action at a distance (one entity occupying two places at the same time), Van Flandern proposes a Le Sage-like mechanism for gravity, with the momentum transferred by super-fast, vastly sub-quantum particles. [9, 10] In this simple model, the apple falls from the tree, not because of anything from the Earth pulling it and not because of "curved space-time", but because more of the gravitons arriving from all directions hit the apple from above than from below because the Earth blocks some of them from hitting the apple's underside.
Van Flandern points out that, while faster-than-light force propagation speeds for gravity violate Einstein's special relativity (SR), they are in accord with Lorentzian relativity (LR). The latter had never been experimentally distinguished from special relativity until the speed of gravity results effectively falsified SR in favor of LR. [6] Even if a different interpretation of the experiments could be found, the mere existence of LR as a never-falsified theory demonstrates that faster-than-light propagation and communication in forward time remain possible in physics and in reality.
Van Flandern notes that, in both Newtonian gravitation and even in general relativity, gravitational force speed is already taken to be infinite, although changes in gravitational potential fields are taken to propagate at the speed of light. If gravitational force propagated at light speed also, the orbits of planets would spiral rapidly outward because of this propagation delay. Even computer experiments show that Earth's orbit would double in radius in just 1200 years. Faster-than-light ‘gravitons’ are the simplest way to explain why this does not happen.
Counterarguments
A serious problem with Van Flandern's argument is contained within the formulation of general relativity itself. Moving bodies set up fields that effectively encode their motion into them. The force a remote body feels due to that field reacts in accordance to that encoded motion, that is, they "know" the source body is moving. This is not something that is forced into the model or added on, it is a natural consequence of the GR formulation. This effect fully explains (to everyone else at least) the problems that Van Flandern claims exist. His "experiments" all require one to ignore this, that is, the force of gravity will be directed at the source regardless of motion. Each of the sections makes a statement similar to this: This is because the retarded position of any source of gravity must lie in the same direction relative to its true position as the tangential motion of the target body—a statement which is simply false under basic general relativity.
Just because a statement is false does not mean that it is not a problem. However in this case the statement directly addresses the issue. For instance, an orbital simulator programmed to simulate GR fully will indeed work perfectly, and the orbital expansion Van Flandern claims is a problem simply doesn't exist. In fact GR does predict small measurable effects that an infinite-speed gravity would not, effects which appear in several of the examples Van Flandern himself uses for evidence against GR.
This has been pointed out on many occasions, but both Van Flandern and his supporters continue to reject this conclusion. To date Van Flandern's refutation of these issues has always come down to either re-stating his original objections, or claiming that people do not understand his theory. The latter may indeed be true because he has never stated it in complete form. Repeated calls for such a statement, preferably mathematically, have not been answered to date. In fact the only statements to date have been simple thought experiments, with little that one could call theory. Many conclude that there is no such theory, just his "feelings" that something is wrong with the standard model.
Many in the scientific community consider Tom Van Flandern's theories to be crankish. It is inevitable that Van Flandern's competence would be criticized because in 1990 he founded an organization, Meta Research, specifically to examine anomalies and puzzles that challenge mainstream theories. The Meta Research web site [14] is filled with reports on puzzles solved conventionally, but also with anomalies that stand up to scrutiny and demand theory revision or outright rejection. In addition to the origin and nature of gravitation, other leading theories that Van Flandern and Meta Research have advanced include the exploded planet hypothesis to replace a dozen conventional models for how asteroids, comets, meteoroids, and moons evolved to their present state, the satellite model for comets to replace the "dirty snowball" model and the Oort cloud hypothesis, the fission hypothesis to replace the primeval solar nebula hypothesis with a common mechanism for the origin of planets and major moons, including Earth's Moon, and the Meta Model to replace the Big Bang cosmology and all its multitudinous supporting hypotheses. While Van Flandern was a research astronomer at the U.S. Naval Observatory from 1963-1983, he was frequently joined by his late USNO colleague Robert Sutton Harrington. These various theories and many others in the field of astronomy are covered in Van Flandern's popular book, now in its fifth printing. [15]
External links
[1] short bio (http://metaresearch.org/home/about%20meta%20research/vanflandern.asp)
[2] full resume (http://metaresearch.org/home/about%20meta%20research/resume.asp)
[3] R.P. Feynman (1995), Feynman Lectures on Gravitation, Addison-Wesley, New York, section 8.4, 113.
[4] P.A.M. Dirac (1951), “Is there an aether?”, Nature 168: 906-907.
[5] A. Einstein (1920), Ether and the theory of relativity, Springer, Berlin, reprinted Dover (1983), 23.
[6] T. Van Flandern and J.P. Vigier (2002), “Experimental Repeal of the Speed Limit for Gravitational, Electrodynamic, and Quantum Field Interactions”, Found.Phys. 32(#7), 1031-1068. Preprint available at The speed of gravity – Repeal of the speed limit (http://metaresearch.org/cosmology/gravity/speed_limit.asp).
[7] Fernando de Felice (1971), “On the gravitational field acting as an optical medium”, Gen.Rel.&Grav. 2#4: 347-357.
[8] T. Van Flandern (1998), “The speed of gravity – What the experiments say”, Phys.Lett.A 250: 1-11. Also at The speed of gravity – What the experiments say (http://metaresearch.org/cosmology/gravity/gravity.asp).
[9] T. Van Flandern (1996), “Possible new properties of gravity”, Astrophys.&SpaceSci. 244: 249-261; also at Possible new properties of gravity (http://metaresearch.org/cosmology/gravity/possiblenewpropertiesofgravity.asp).
[10] T. Van Flandern (2002), “Gravity”, in Pushing Gravity: New Perspectives on Le Sage's Theory of Gravitation, M. Edwards, ed., Apeiron Press, Montreal, 93-122. See also V. Slabinski (2002), “Force, heat and drag in a graviton model”, M. Edwards, ed., Apeiron Press, Montreal, 123-128.
[11] G.E. Marsch, C. Nissim-Sabat (1999), “Comments on ‘The speed of gravity’”, Phys.Lett.A, 262: 103-106.
[12] S. Carlip (2000), “Aberration and the speed of gravity”, Phys.Lett.A, 267: 81-87.
[13] T. Van Flandern (1999), “Reply to comments on ‘The speed of gravity’”, Phys.Lett.A, 262: 261-263.
[14] Meta Research web site (http://metaresearch.org)
[15] T. Van Flandern (1993; 2nd ed. 1999), Dark Matter, Missing Planets and New Comets, North Atlantic Books, Berkeley.
[16] aberration animation (http://metaresearch.org/media%20and%20links/animations/animations.asp)