page_title: History of gravitational theory
section_title: Mechanical explanations
hierarchical_section_title: History of gravitational theory / European Enlightenment / Mechanical explanations
caption_attribution_description: Portrait of Isaac Newton (1642-1727)
context_page_description: In physics, theories of gravitation postulate mechanisms of interaction governing the movements of bodies with mass. There have been numerous theories of gravitation since ancient times. The first extant sources discussing such theories are found in ancient Greek philosophy. This work was furthered by ancient Indian and medieval Islamic physicists, before gaining great strides during the Renaissance and Scientific Revolution, culminating in the formulation of Newton's law of gravity. This was superseded by Albert Einstein's theory of relativity in the early 20th century.
  Greek philosopher Aristotle believed that objects tend toward a point due to their inner gravitas. Vitruvius understood that objects fall based on their specific gravity. In the 7th century CE, Brahmagupta spoke of gravity as an attractive force. The Aristotelian concept of gravity began to be rejected, initially by Islamic physicists, starting in the 11th century with Ibn Sina's theory of impetus. The following century, Abu'l-Barakāt al-Baghdādī described gravitational acceleration. The works of Ibn Sina and al-Baghdādī were translated into Latin by the 14th century, influencing Jean Buridan and Albert of Saxony.
context_section_description: In 1644, René Descartes proposed that no empty space can exist and that a continuum of matter causes every motion to be curvilinear. Thus, centrifugal force thrusts relatively light matter away from the central vortices of celestial bodies, lowering density locally and thereby creating centripetal pressure. Utilizing aspects of this theory, between 1669 and 1690, Christiaan Huygens designed a mathematical vortex model. In one of his proofs, he shows that the distance elapsed by an object dropped from a spinning wheel will increase proportionally to the square of the wheel's rotation time. In 1671, Robert Hooke speculated that gravitation is the result of bodies emitting waves in the aether. Nicolas Fatio de Duillier (1690) and Georges-Louis Le Sage (1748) proposed a corpuscular model using some sort of screening or shadowing mechanism. In 1784, Le Sage posited that gravity could be a result of the collision of atoms, and in the early 19th century, he expanded Daniel Bernoulli's theory of corpuscular pressure to the universe as a whole. A similar model was later created by Hendrik Lorentz (1853–1928), who used electromagnetic radiation instead of corpuscles.
  English mathematician Isaac Newton utilized Descartes' argument that curvilinear motion constrains inertia, and in 1675, argued that aether streams attract all bodies to one another. Newton (1717) and Leonhard Euler (1760) proposed a model in which the aether loses density near mass, leading to a net force acting on bodies. Mechanistic models fell out of favor because most of them lead to an unacceptable amount of drag, which was not observed. Others violate the energy conservation law and are incompatible with modern thermodynamics.
  Some mechanical explanations of gravitation (including Le Sage's theory) were created between 1650 and 1900 to explain Newton's theory, but they were overthrown because most of them lead to an unacceptable amount of drag, which is not observed. Other models violate the energy conservation law and are incompatible with modern thermodynamics.
caption: Portrait of Isaac Newton (1642–1727) by Godfrey Kneller (1689)
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