Mechanical explanations of gravitation
This theory is probably[1] the best-known mechanical explanation, and was developed for the first time by Nicolas Fatio de Duillier in 1690, and re-invented, among others, by Georges-Louis Le Sage (1748), Lord Kelvin (1872), and Hendrik Lorentz (1900), and criticized by James Clerk Maxwell (1875), and Henri Poincaré (1908).
The theory posits that the force of gravity is the result of tiny particles or waves moving at high speed in all directions, throughout the universe.
Criticism: This theory was declined primarily for thermodynamic reasons because a shadow only appears in this model if the particles or waves are at least partly absorbed, which should lead to an enormous heating of the bodies.
[4][5][6] This idea on the formation of the cosmos by vortices of matter was preceded by the ancient pre-Socratic atomists Leucippus and Democritus.
At this time, Newton developed his theory of gravitation which is based on attraction, and although Huygens agreed with the mathematical formalism, he said the model was insufficient due to the lack of a mechanical explanation of the force law.
Newton's discovery that gravity obeys the inverse square law surprised Huygens and he tried to take this into account by assuming that the speed of the aether is smaller in greater distance.
Whereas Descartes had outlined three species of matter – each linked respectively to the emission, transmission, and reflection of light – Thomson developed a theory based on a unitary continuum.
[11][12] In a 1675 letter to Henry Oldenburg, and later to Robert Boyle, Newton wrote the following: [Gravity is the result of] “a condensation causing a flow of ether with a corresponding thinning of the ether density associated with the increased velocity of flow.” He also asserted that such a process was consistent with all his other work and Kepler's Laws of Motion.
Gravity must be caused by an agent acting constantly according to certain laws; but whether this agent be material or immaterial, I have left to the consideration of my readers.On the other hand, Newton is also well known for the phrase Hypotheses non fingo, written in 1713:[15] I have not as yet been able to discover the reason for these properties of gravity from phenomena, and I do not feign hypotheses.
For whatever is not deduced from the phenomena must be called a hypothesis; and hypotheses, whether metaphysical or physical, or based on occult qualities, or mechanical, have no place in experimental philosophy.
In this philosophy particular propositions are inferred from the phenomena, and afterwards rendered general by induction.And according to the testimony of some of his friends, such as Nicolas Fatio de Duillier or David Gregory, Newton thought that gravitation is based directly on divine influence.
Like Newton, Leonhard Euler presupposed in 1760 that the gravitational aether loses density in accordance with the inverse square law.
Furthermore, James Clerk Maxwell pointed out that in this "hydrostatic" model "the state of stress... which we must suppose to exist in the invisible medium, is 3000 times greater than that which the strongest steel could support".
[21] Criticism: Maxwell objected that this theory requires a steady production of waves, which must be accompanied by an infinite consumption of energy.
[24] In 1748, Mikhail Lomonosov assumed that the effect of the aether is proportional to the complete surface of the elementary components of which matter consists (similar to Huygens and Fatio before him).
[26] However, it was shown by Taylor that the decreased density due to thermal expansion is compensated for by the increased speed of the heated particles; therefore, no attraction arises.
[20] These mechanical explanations for gravity never gained widespread acceptance, although such ideas continued to be studied occasionally by physicists until the beginning of the twentieth century, by which time it was generally considered to be conclusively discredited.
Le Sage's theory was studied by Radzievskii and Kagalnikova (1960),[27] Shneiderov (1961),[28] Buonomano and Engels (1976),[29] Adamut (1982),[30] and Edwards (2014).
