Re: [Phys-l] How did Newton estimate the Gravitational constant?

[Daryl Taylor <daryl261@gmail.com>]

Newton didn't. Cavendish did; in one of the most famous experiments of all
time. Newton knew of the proportions, but not the value of 'G'. Cavendish
performed a very delicate and intricate experiment to actually measure the
attraction between large masses in his lab. He's the one who found 'G'.

-Daryl Taylor

On Thu, Oct 28, 2010 at 6:00 AM, Brian Blais <bblais@bryant.edu> wrote:

> Hello,
>
> A student asked me this question in class yesterday, and I wasn't sure
> (haven't looked at the Principia in a long time, but always found the
> arguments a bit hard to follow).  I imagine he could do it from a rough
> estimate of the mass of the Earth, mass of the Moon, and distance to the
> Moon.  With the Moon's period you could get a value for G.  Is this how he
> did it?  I know that the direct measurement wasn't done until later, by
> Cavendish.
>
> Further, did he have any way of estimating the distance to the Sun?  I
> couldn't think of one that was available at his time, but he was more clever
> than I.  :)
>
>
>                                thanks,
>
>                                        bb
>
> --
> Brian Blais
> bblais@bryant.edu
> http://web.bryant.edu/~bblais <http://web.bryant.edu/%7Ebblais>
> http://bblais.blogspot.com/
>
>
>
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-- 
Daryl L Taylor
(Sent from my Droid using 100% certified recycled electrons...)