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I know very little about physics. So, please forigve me if I ask anything wrong. I just read an article about gravitation. Where I saw an equation $$F = \frac {Gm_1m_2}{r²}$$ where $F$ is gravitational force, $m_1$ and $m_2$ are masses of two bodies, $r$ is the linear distance between the bodies and $G$ is gravitational constant. What is this gravitational constant? Can someone will explain it to me? A good explanation will be really appreciated.

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  • $\begingroup$ Not sure about this question. It's interesting to think about and explain what $G$ is, but the wiki page is quite good already en.wikipedia.org/wiki/Gravitational_constant $\endgroup$
    – innisfree
    Jun 3 at 8:33
  • $\begingroup$ My only issue with the wiki page is that it calls it all sorts of things (Cavendish constatant etc) apart from what I ever hear anyone actually calling it: big G or Newton's constant. $\endgroup$
    – innisfree
    Jun 3 at 8:35

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$G$ is a value inserted to make the two sides of the equation equal. If everything else on the right hand side has a value of $1$ (for example, you have two one kilogram masses separated by a distance of one metre) then $G$ is the numerical value of the gravitational force between them. In SI units the value of $G$ is about $6.674 \times 10^{-11}$.

As far as we know, the value of $G$ cannot be found from theory - it has to be measured in experiments such as this one. Also, as far as we know, the value of $G$ is constant - it is the same everywhere in the observable universe, and does not vary with time.

For more details see this Wikipedia article.

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