Le Sage's theory of gravitation

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Le Sage’s theory of gravitation is a historical attempt to explain gravity as a mechanical effect, not as a mysterious force. It was first proposed in a form by Nicolas Fatio de Duillier in 1690 and then developed by Georges-Louis Le Sage in 1748. The idea is that the universe is filled with countless tiny, invisible particles (called corpuscles) moving in all directions at high speed.

How the theory supposed gravity works
- If you stand alone in space, particles push on you from every direction with equal force, so there’s no net pull.
- When two bodies come near each other, each one blocks some of the particles that would have hit the other. This shielding creates a slight imbalance: more particles hit from the side away from the other body, pushing the two bodies toward each other.
- In short, gravity is a shadowing effect or “push gravity,” not an actual attraction between masses.

Turning shadow into a real pull
- To get an overall attraction (instead of two bodies just pushing away and toward empty space), the theory requires that when corpuscles bounce off matter, the reflections are not perfectly elastic. If some momentum is lost or slowed during collisions, the reflected particle flow is weaker, and a net push toward the other body remains.
- The amount of shadowing is linked to the surface area of matter, and by assuming matter is mostly empty space with many tiny, similarly structured opaque elements, the shadow effect ends up roughly proportional to mass.

A look at the historical line and the problems
- Fatio laid out the core ideas and even did some early math to connect the shadow idea to how gravity might fall off with distance.
- Le Sage popularized the view and worked out more details, but the theory faced serious problems. If collisions are too elastic, there’s no net force; if they’re inelastic enough to create gravity, huge amounts of energy would be absorbed as heat. That leads to energy and heat problems that many scientists found unacceptable.
- The model also predicts drag on moving bodies (extra resistance in motion) and distortions in the way gravity should behave at various speeds and distances. To avoid these issues, the required corpuscle speeds would have to be absurdly high, even conflicting with relativity.
- Over the centuries, many respected thinkers (including Laplace, Kant, Maxwell, and Poincaré) pointed out fundamental difficulties with the idea, especially around energy conservation, the speed of gravity, and how it fits with modern physics.

From then to now
- The idea never became the mainstream explanation for gravity. With Einstein’s general relativity, gravity is understood as the effect of curved spacetime rather than a shadowing force from a flux of particles.
- Some later writers revived or toyed with Le Sage-like ideas, often to explore the concept or to connect it with other questions, but these views are not part of accepted physics today.
- The core prediction of Le Sage’s theory—that matter is extremely porous and that a huge, invisible flux mediates gravity—has echoes in modern discussions about how forces might work at a fundamental level, but the simple Le Sage mechanism itself does not match experiments and established physics.

In short, Le Sage’s idea offered a bold, mechanical way to think about gravity, but serious energy, drag, and relativistic problems kept it from being viable. Today, gravity is explained by general relativity, not by a shadowing flux of fast-moving particles.