Gravitational Constant

The gravitational constant (also known as "universal gravitational constant", or as "Newton's constant"), denoted by the letter $G$ , is an empirical physical constant involved in the calculation of gravitational effects in Sir Isaac Newton's law of universal gravitation and in Albert Einstein's general theory of relativity. Its measured value is 6989667408000000000♠6.67408(31)×10⁻¹¹ m³⋅kg⁻¹⋅s⁻².

According to Newton's law of universal gravitation, the attractive force ( $F$ ) between two point-like bodies is directly proportional to the product of their masses ( $m 1$ and $m 2$ ), and inversely proportional to the square of the distance, $r$ , (inverse-square law) between them:

The constant of proportionality, $G$ , is the gravitational constant. Colloquially, the gravitational constant is also called "Big G", for disambiguation with "small g" ( $g$ ), which is the local gravitational field of Earth (equivalent to the free-fall acceleration). The two quantities are related by $g=GM_{\rm {E}}r_{\rm {E}}^{-2}$ (where $M_{\rm {E}}$ is the mass of the Earth and $r_{\rm {E}}$ is the Earth radius).

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