Gravity as Radiation Pressure

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Le Sage's Theory of Gravity

Daniel goes on to state (or report, as the case may be), that this effect is “in fact identical with a gravitational field.” If this statement is correct, it suggests that the gravitational field is simply the Poynting vector force which results when one object occludes some of the radiation flowing from cosmic sources that is directed at a second object, ie, when a radiation pressure differential exists across an object. This concept is roughly approximated by the Le Sage theory of gravitation, which is also known as ‘shadow gravity,’ and ‘push gravity.’

It is uncertain at this point whether the modern understanding of quantum physics can provide satisfactory solutions to the problems currently associated with Le Sage gravity theory (which originally postulated ubiquitous material ‘corpuscles’ rather than photons as a gravitational force mechanism). Perhaps the answers to the problems with a photonic model of Le Sage gravity can be found in modern physical theories, or in the nontrivial reinterpretation of General Relativity that Daniel Fry describes in ‘Atoms, Galaxies and Understanding’ and ‘Steps to the Stars.’ Richard Feynman examined Le Sage gravitational theory in 1965 and concluded that the Le Sage theory implies a drag on moving objects which effectively discredits the idea.[1] Further research may determine if the unsupportable notion of a drag effect on all moving bodies is a necessary implication of post-relativistic Le Sage models.[2] Although a definitive analysis of this question has remained elusive, others are investigating the subject in some detail: The Electro-Magnetic Radiation Pressure (EMRP) Gravity Theory

There are a number of compelling facts which seem to support a Le Sage gravitational theory which are difficult to dismiss. For example, from Fatio’s earliest formulation of the model circa 1690, the theory predicted that matter consists almost entirely of empty space - long before kinetic theory made this a mainstream view (see ‘Matter and Particles: Porosity of Matter’ section of the Le Sage wiki article cited above). Also, it appears that the ‘speed of gravity’ is approximately (or perhaps exactly) equal to the speed of light, which seems suggestive of a photonic mechanism of gravity. Furthermore, Le Sage theories predict that the resultant mass of two bound objects will be smaller than the sum of the two unbound masses, which is observed in nuclear reactions, and is well-established through calculations of chemical reactions. And the inverse square law is a natural product of the theory.


In conclusion, it seems clear upon close examination that the gravitational field mechanism described in Daniel Fry’s 1966 book is directly related to electromagnetic waves, the Poynting vector, and radiation pressure. What is less clear is how these factors can model gravitational field interactions without predicting runaway heating of matter and an inertial drag effect, and how the model can predict the observed coupling of gravity and energy.

There may yet be solutions to the many problems raised with Le Sage gravity theories, and if so, then Daniel Fry’s gravity model would be validated. But this effort would entail a refutation of many challenging arguments posed by some of the greatest minds in physics history.

  1. Feynman, R. P. (1967), The Character of Physical Law, The 1964 Messenger Lectures, pp. 37-39, ISBN 0-262-56003-8
  2. It does seem encouraging, however, to note that the similar problem of orbital decay, which was associated with a finite propagation velocity of gravitational fields, was overcome in General Relativity (which limited the speed of gravity to the speed of light) by defining simultaneity as a condition of both time and space coordinates: Relativity 4 Engineers - The Speed of Gravity?