View source for Gravitational constant

[[File:NewtonsLawOfUniversalGravitation.svg|thumb|right|300px|The gravitational constant ''G'' is a key quantity in [[Newton's law of universal gravitation]]]]

The '''gravitational constant''', called <math>G</math> in [[physics]] [[equation]]s, is an  [[empiricism|empirical]] [[physical constant]]. It is used to show the force between two objects caused by [[gravity]]. The gravitational constant appears in [[Newton's law of universal gravitation|Isaac Newton's universal law of gravitation]].

<math>G</math> is about {{val|6.67430|e=-11}} N⋅m<sup>2</sup>/kg<sup>2</sup>,<ref name="physconst-G">{{cite web |url=http://physics.nist.gov/cgi-bin/cuu/Value?bg |title=2018 CODATA Value: Newtonian constant of gravitation |date=20 May 2019 |work=The NIST Reference on Constants, Units, and Uncertainty |publisher=[[National Institute of Standards and Technology|NIST]] |access-date=2019-05-20}}</ref> and is denoted by letter <math>G</math>. In the [[International System of Units|SI system]], the constant is equal to the force in newtons that two objects, each with a mass of 1 kilogram, exert on each other at a distance of 1 meter.

It usually appears in [[Sir Isaac Newton]]'s [[Newton's law of universal gravitation|law of universal gravitation]], and in [[Albert Einstein]]'s [[general theory of relativity]]. It is also known as the '''universal gravitational constant''', '''Newton's constant''', and colloquially as '''Big G'''.<ref>{{cite web |first1=Jens H. |last1=Gundlach |first2=Stephen M. |last2=Merkowitz |title=University of Washington Big G Measurement |work=Astrophysics Science Division |publisher=Goddard Space Flight Center |date=2002-12-23 |url=http://asd.gsfc.nasa.gov/Stephen.Merkowitz/G/Big_G.html |quote=Since Cavendish first measured Newton's Gravitational constant 200 years ago, "Big G" remains one of the most elusive constants in physics.}}</ref> It should not be confused with "small g" (''[[Gravity of Earth|g]]''), which is the local gravitational field of the Earth (equivalent to the free-fall acceleration).<ref>{{cite book| last1 = Halliday| first1 = David| last2 = Walker| first2 = Jearl| last3 = Resnick| first3 = Robert| title = WIE ASE Fundamentals of Physics Extended, Eighth Edition, Asian Student Edition| year = 2007| isbn = 978-0-470-04618-0| page = 336 }}</ref>

== References ==
{{reflist}}

{{Clear}}


[[Category:Relativity]]
[[Category:Gravitation]]


{{physics-stub}}