[alancalverd]

Newton's gravity equation is based on this erroneous and incredulous measurement. Shame.

Newton died 50 years before Cavendish's experiment. Always check the obvious before opening your mouth, lest people take you for a fool.

[Colin2B]

Always check the obvious before opening your mouth, lest people take you for a fool.

Too late for that 
Poor soul, brain overheating, needs a sabbatical, let’s give him one on us.

[jeffreyH]

Newton's gravity equation is based on this erroneous and incredulous measurement. Shame.

Newton died 50 years before Cavendish's experiment. Always check the obvious before opening your mouth, lest people take you for a fool.

LOL. That.creased me up!

[happy6666]

I think alright is right where Newton created Newton's equation and Cav supported Newton's equation with his experiment. However, if alright1234 is right than would he not be the greatest physics that ever lived even greater than Newton which I doubt but I could be wrong since didn't Einstein think that the planets revolved around the earth in 1905.

[Kryptid]

didn't Einstein think that the planets revolved around the earth in 1905.

No.

[happy6666]

How did Newton derive the constant G?

[happy6666]

didn't Einstein think that the planets revolved around the earth in 1905.

No.

Is Einstein translational velocity constant or does it vary? If the translational velocity is constant then it can only occur with the earth at the center of the Universe. Golly I thought everyone new that. I learn that in high school. Gee I feel smart!!! I am cute too. He he he

[Kryptid]

Is Einstein translational velocity constant or does it vary? If the translational velocity is constant then it can only occur with the earth at the center of the Universe. Golly I thought everyone new that. I learn that in high school. Gee I feel smart!!! I am cute too. He he he

Nothing about relativity requires Earth to be at the center of the Universe. It's the opposite, in fact: relativity says that there are no absolute reference frames and thus no absolute coordinates in space.

[Bored chemist]

How did Newton derive the constant G?

I'm not sure he did.
You can do most of the orbital mechanics calculations by knowing that it is constant.

[alancalverd]

How did Newton derive the constant G?

Newton's equation F = GmM/r^2 solves Kepler's observed orbital motion of the planets, so in principle anyone who could measure or estimate F, M, m and r could derive a value for G.  The practical problem in the 1700s arose from not knowing the density of any other heavenly body, or having sufficiently sensitive apparatus to measure F for laboratory-sized bodies.

As it turned out, Maskeleyne's use of a  mountain and Cavendish's use of a torsion balance solved the problem by brilliant astronomical technique and engineering respectively, and came up with reasonably similar values.   

[evan_au]

How did Newton derive the constant G?

You can solve Newton's law of gravity if you measure the radius of the planetary orbits, know the mass of the Sun & Earth, can measure the force between the Sun and Planets and/or know "G".

In practise, Newton didn't know any of these parameters.

There was a transit of Venus across the face of the Sun in 1769 which was observed by astronomers in various places around the world; when the measurements were collated, this determined the size of the solar system and resolved one of the unknowns in Newton's law of gravitation.
- It also allowed determination of the speed of light, since it was observed that the transits of the moons of Jupiter occurred later when Jupiter was on the other side of the Sun from Earth, due to the finite speed of light...

Cavendish used known masses at known distances; he measured the force of attraction and then could solve for the remaining unknown: G.
- This knowledge could then be used to "weigh" the Sun and the Earth (and other bodies with moons).

See: https://en.wikipedia.org/wiki/1769_transit_of_Venus_observed_from_Tahiti