Where Does the Gravitational Constant Come From?

[NewDescartes]

I was wondering where the Gravitational Constant comes from. As far as I know it has been measured with a tension line and weights. I also understand that Newton uses it his gravitational formula, but he didn't measure it. Did he just guess the number? Also is G the proportionality or distribution of gravity per kg?

 

[atyy]

http://www.leydenscience.org/physics/gravitation/cavend.htm

 

[JesseM]

http://www.leydenscience.org/physics/gravitation/cavend.htm

As for the other part of NewDescartes' question, it says here that Newton couldn't actually establish any good estimate for the value of the gravitational constant (and it says here that when calculating things like planetary orbits, Newton used equations 'with ratios so that the constant would cancel out'). So, the Cavendish experiment really was the first to give it a value.

 

[NewDescartes]

So the gravitational constant is approx. 6.67428 * 10^11 Newtons??

 

[NewDescartes]

By the way thanks for everything. I enjoy this immensely, even debates.

 

[jtbell]

So the gravitational constant is approx. 6.67428 * 10^11 Newtons??

To be picky, the units are Newton m^2 / kg^2.

 

[buffordboy23]

So the gravitational constant is approx. 6.67428 * 10^11 Newtons??

Don't forget the minus sign in the exponent.

According to the Constants section of PF's Latex Reference,

$$G\ =\ 6.673(10)\ \times\ 10^{-11}\ m^{3} kg^{-1} s^{-2}$$

I prefer the units representation given by jtbell much more though.