# What is the constant $G$ in Newton's law of gravitation?

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.

• 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 Jun 3 at 8:33
• 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. Jun 3 at 8:35

$$G$$ 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.