View source for Georges-Louis Le Sage

{{Infobox scientist
| name = Georges-Louis Le Sage
| alt = Georges-Louis Le Sage
| birth_date = 13 June 1724
| birth_place = Geneva, Republic of Geneva
| death_date = 20 November 1803 (aged 79)
| death_place = Geneva
| residence = Geneva
| nationality = Genevan
| fields = [[Physics]], Mathematics, Chemistry, Gravitation
| workplaces = Private tutor, Geneva
| known_for = Le Sage's theory of gravitation, ultramundane corpuscles, push (shadow) gravity, early anticipation of the kinetic theory of gases, an early electric telegraph
}}

'''Georges-Louis Le Sage''' (13 June 1724 &ndash; 20 November 1803) was a Genevan physicist and mathematician best known for the ''kinetic'' or ''shadow'' theory of gravitation, in which gravity is not an attraction at all but the residual '''push''' of an omnidirectional flux of tiny, fast-moving particles &mdash; his "ultramundane corpuscles" &mdash; which bodies partially screen from one another. He also devised one of the earliest electric telegraphs and anticipated important elements of the kinetic theory of gases, for which he was later praised by Maxwell and Clausius.

Le Sage matters on this wiki because his programme is the direct ancestor of the modern '''pushing gravity''' research tradition. Where mainstream physics abandoned mechanical explanations of gravitation &mdash; first for Newtonian action at a distance, then for the geometry of general relativity &mdash; a continuous line of dissident researchers has held that gravity must have a physical cause, and has kept working on Le Sage-type models. That line runs through [[Quirino Majorana]]'s absorption experiments and [[Tom Van Flandern]]'s gravitational-shielding arguments to the present-day [[Particle Model]] of [[Bob de Hilster]] and [[David de Hilster]].

==Biography==
Le Sage was born in Geneva on 13 June 1724. His father, also named Georges-Louis Le Sage, was a schoolmaster originally from Couches in Burgundy; his mother was Anne Marie Camp. He was educated in Geneva, studying mathematics under Gabriel Cramer and physics under Jean-Louis Calandrini, before going to Basel and then Paris to study medicine. In Basel he came into contact with Daniel Bernoulli, whose treatment of gases as swarms of moving particles left a permanent mark on his thinking.

On returning to Geneva he was refused permission to practise medicine, because his father was not a native of the city. Barred from that career, and unable to obtain the chair of mathematics he sought at the Geneva academy, Le Sage supported himself for the rest of his life by private tutoring in mathematics. Among his pupils were the physicist Pierre Prévost and the mathematician Simon Lhuilier; Jean-André Deluc was a friend from his student years. He never held a salaried academic post, and pursued the cause of gravity as an independent investigator &mdash; a circumstance that will be familiar to many contemporary readers of this wiki.

Le Sage suffered from a notoriously poor memory and difficulty sustaining attention. He compensated by writing his thoughts down as they occurred on scraps and on the backs of playing cards; more than 35,000 of these survive in the library at Geneva and remain a major source for historians of his work. An accident in 1762 left his eyesight severely impaired. Despite his marginal professional position he was widely respected: he became a Fellow of the Royal Society and a correspondent of the French Academy of Sciences, and maintained a very large scientific correspondence; Euler was among the contemporaries who took an interest in the gravitational part of his work. He died in Geneva on 20 November 1803.

==The theory of gravitation==
Le Sage claimed to have arrived at the essentials of his theory by 1743 and to have satisfied himself of it in 1747, recording the moment with the exclamation "Eureka, Eureka." He set it out in the unpublished ''Essai sur l'origine des forces mortes'' (1748), first published an account in the ''Mercure de France'' in 1756, developed it at length in ''Essai de chymie méchanique'' (1758), and made it accessible to a general readership in ''Lucrèce Newtonien'' (1784) &mdash; the title announcing his aim of joining the atomism of Lucretius to the mechanics of [[Isaac Newton]].

===The mechanism===
The model is simple and entirely mechanical:

* Space is permeated by an enormous number of exceedingly small, exceedingly fast particles &mdash; Le Sage's '''ultramundane corpuscles''' &mdash; streaming in every direction, arriving from beyond the visible world.
* An isolated body is struck equally from all sides and therefore feels no net force.
* When two bodies are present, each intercepts a small part of the flux that would otherwise have struck the other. Each body therefore sits in the other's faint "shadow" and is struck slightly less hard on the facing side than on the far side.
* The imbalance pushes the two bodies together. What is observed as gravitational ''attraction'' is in fact an unbalanced ''push''.

The inverse-square law follows directly from the geometry: the shadow cast by a body spreads over spherical surfaces whose area grows as the square of the distance, so the deficit in momentum per unit area falls off as the inverse square. Proportionality to mass follows from Le Sage's assumption that ordinary matter is overwhelmingly empty space &mdash; a sparse cage-like lattice of matter through which nearly all corpuscles pass unimpeded. Because the screening is very slight, the force is nearly proportional to the total quantity of matter rather than to surface area, and gravity is essentially unshieldable in ordinary circumstances.

The same picture was proposed in the 1690s by Nicolas Fatio de Duillier, a fellow Genevan and a friend of Newton and Huygens, whose manuscript ''De la Cause de la Pesanteur'' remained unpublished. Le Sage learned of Fatio's work at some point and edited some of his papers, and the question of independence has been debated ever since; what is not in dispute is that Le Sage developed the idea furthest, named its particles, and made it a subject of serious European discussion for a century.

===The classic objections===
Two objections dominated the nineteenth-century debate, and any modern Le Sage model must answer them.

'''Drag.''' A body moving through an isotropic flux meets more corpuscles head-on than from behind, and should feel a resistance proportional to the product of its own speed and the corpuscle speed. Since the gravitational force itself goes as the square of the corpuscle speed, the ratio of drag to gravity is set by the ratio of the body's speed to the corpuscle speed. Keeping planetary orbits stable over geological time therefore requires corpuscles travelling at velocities enormously greater than that of light &mdash; a requirement Le Sage and his successors accepted, and which was only felt as fatal after special relativity forbade it.

'''Heating.''' The more serious problem is thermodynamic. For a net force to arise, collisions must be at least partly inelastic: some of the corpuscles' momentum must be absorbed. But the corpuscles carry kinetic energy vastly greater than the momentum imbalance that produces gravity, and that energy has to go somewhere. Maxwell and later Poincaré calculated that the absorbed energy would raise the temperature of the Earth catastrophically &mdash; Poincaré's estimate was on the order of 10<sup>26</sup> degrees per second &mdash; and Poincaré concluded dryly that "the earth could not long stand such a regime." Lord Kelvin, who revived the theory in 1873, proposed that the absorbed translational energy is taken up by internal vibrational and rotational modes of the corpuscles themselves, which then recover their translational energy in distant collisions, so that the flux is continually regenerated rather than degraded. Kelvin's version drew serious attention from Peter Guthrie Tait, Samuel Tolver Preston, Caspar Isenkrahe, and others, but he himself remained cautious about how much of physics the model could carry.

A third and testable consequence is '''gravitational shielding''': if matter is not perfectly transparent to the flux, a large intervening mass should very slightly reduce the weight of a body behind it, and the combined shadow of two bodies should be marginally less than the sum of their separate shadows. This prediction is what made [[Quirino Majorana]]'s absorption experiments of the 1920s so important to the tradition, and it remains the sharpest empirical point of contact between Le Sage models and observation.

==Other work==
Le Sage's mechanical picture of gases &mdash; particles in ceaseless motion whose impacts produce pressure &mdash; anticipated the kinetic theory later developed by Clausius and Maxwell, both of whom acknowledged him. In 1774 he built an electric telegraph using twenty-six wires, one for each letter of the alphabet, with pith-ball electroscopes as receivers: one of the first working electrostatic telegraphs. His posthumous ''Physique mécanique'', assembled from his papers by his pupil Pierre Prévost, appeared in 1818, fifteen years after his death.

==Modern reception among dissident researchers==
Mainstream physics set Le Sage aside, first because of the thermal objection and then because general relativity replaced the search for a mechanism with a geometrical description. Within the dissident and critical-thinking community, however, the reasoning has gone the other way: a description of gravity is not an explanation of it, and Le Sage's programme is the most developed attempt at an explanation ever offered. Pushing gravity is consequently one of the most active research lines on this wiki.

The modern reference volume is '''''[[Pushing Gravity: New Perspectives on Le Sages Theory of Gravitation|Pushing Gravity: New Perspectives on Le Sage's Theory of Gravitation]]''''', edited by [[Matthew R Edwards]] (Apeiron, Montreal, 2002), a collection of twenty-two papers covering the three-hundred-year history of the theory, gravitational shielding and the Majorana experiments, and new Le Sage models. Papers from that volume and its milieu that are catalogued on this wiki include:

* [[Matthew R Edwards]], "[[Le Sage's Theory of Gravity: the Revival by Kelvin and Some Later Developments]]"
* [[Halton C Arp]], "[[The Observational Impetus for Le Sage Gravity]]" &mdash; the astronomer of anomalous redshift arguing that observation, not theory, points back to Le Sage
* [[Paul A Stowe]], "[[Dynamic Effects in Le Sage Models]]"
* [[Paul A Stowe]] and [[Barry Mingst]], "[[Derivation of Newtonian Gravitation from LeSage's Attenuation Concept]]"
* "[[Gravitational Absorption According to the Hypotheses of Le Sage and Majorana]]"
* [[Boris I Kolesnichenko]], "[[Today?s View on the Lesage Hypothesis]]" (''[[Galilean Electrodynamics]]'', 2003)

Other wiki authors working in the same tradition include [[Walter C Wright]], whose book ''[[Gravity is a Push]]'' argues the case at book length, and [[Tom Van Flandern]], who used Le Sage-type reasoning in his arguments about the propagation speed of gravity.

===The de Hilster particle model===
The most sustained current development on this wiki is the [[Particle Model]] of [[Bob de Hilster]] and [[David de Hilster]], in which gravity is produced by a particle &mdash; the G1 &mdash; whose impacts push matter together, exactly in the Le Sage manner. Bob de Hilster's work began with a variation of the Cavendish experiment proposed by [[Ricardo Carezani]] and filmed for [[Einstein Wrong - The Miracle Year]], and led him to compute gravitational forces by summing the individual impulses delivered by particles entering, striking, and leaving extended bodies of real geometry, rather than treating them as Newtonian point masses. The resulting curves reproduce the shape of Newton's gravity curve. His book ''[[Gravity is Not Free]]'' (2015) states the central objection to the orthodox account in its title: an attractive force acting endlessly across empty space, drawing on no source, is not a physical mechanism, whereas a push has a supply and a cost. The model is developed further in ''[[Principia Mathematica 2]]'', which the authors describe as extending Newton's ''Principia'' using concepts from Newton, Le Sage, [[Glenn Borchardt|Borchardt]] and others.

[[Raymond H Gallucci]], whose usual role in CNPS is to test other dissidents' proposals by direct calculation, has examined the tradition in "[[Gravity – When Push Comes to Shove?]]" (2015), a paper explicitly keyed to Le Sage, Fatio, shadowing, and the question of push versus pull.

==Discussed in CNPS talks==
* [https://www.youtube.com/watch?v=d723ZlL2Ln0 "Dark Matter Versus G"] by [[Bob de Hilster]] (27 June 2018) &mdash; argues that dark matter was invented to preserve Newton's gravity equation for galactic rotation curves, and revisits Le Sage's proposal that gravity has a shielding property, together with [[Quirino Majorana]]'s experiments to detect it.

==Works==
* ''Essai sur l'origine des forces mortes'' (1748, unpublished)
* "Lettre à une académicienne sur le sujet de la gravitation universelle", ''Mercure de France'' (May 1756)
* ''Essai de chymie méchanique'' (1758) &mdash; crowned by the Academy of Rouen in 1758
* ''Lucrèce Newtonien'', in ''Nouveaux Mémoires de l'Académie Royale des Sciences et Belles-Lettres de Berlin'' (1784)
* ''Physique mécanique'' (1818), edited posthumously by Pierre Prévost

==External links==
* [https://en.wikipedia.org/wiki/Georges-Louis_Le_Sage Georges-Louis Le Sage] at Wikipedia
* [https://gallica.bnf.fr/ark:/12148/bpt6k110507m ''Essai de chymie méchanique'' (1758)] at Gallica (Bibliothèque nationale de France)
* [https://archive.org/details/pushinggravityne0000unse ''Pushing Gravity: New Perspectives on Le Sage's Theory of Gravitation''] at the Internet Archive

[[Category:Scientist|Le Sage Georges-Louis]]
[[Category:Gravity|Le Sage Georges-Louis]]
[[Category:Theory & Models|Le Sage Georges-Louis]]