Gravitational constant

The gravitational constant, G, is the proportionality constant in Newton’s law of universal gravitation. It sets the strength of gravitational attraction between masses and appears in Einstein’s field equations.

Newton's law of universal gravitation: A law stating that two masses attract with force proportional to their product and inversely proportional to the square of their separation. G sets the force scale in this inverse-square relation.
Gravitational force: The attractive interaction between objects with mass or energy. Newton’s law uses G to quantify this force between two bodies.
Isaac Newton: The English mathematician and physicist who formulated the laws of motion and universal gravitation. Newton’s force law introduced the proportionality later represented by G.
Standard acceleration of gravity: The exactly defined reference acceleration 9.80665 metres per second squared used in measurement and engineering. Unlike G, it is a conventional reference value, not a universal force-law constant.
Torsion balance: An instrument that detects small torques through the twisting of a suspended fiber. The Cavendish-style apparatus detects the tiny attraction needed to measure G.
Mass: A physical property measuring inertia and, in gravity, the source and response to gravitational interaction. The product of two masses determines the force scale alongside G.
Henry Cavendish: The English natural philosopher whose torsion-balance experiment measured the attraction between laboratory masses. His 1798 experiment enabled a determination of Earth’s density and, in modern terms, G.
Gravitational field strength: Force per unit mass at a location in a gravitational field. Field strength varies with position and nearby masses; G is universal.
Gravitational potential: Potential energy per unit mass in a gravitational field. For a point mass, G determines the potential’s strength and spatial profile.
Inverse-square law: A relation in which a quantity decreases as the square of distance increases. Newton’s gravitational force follows this distance dependence, leaving G as its constant factor.

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