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*From*: Daryl Taylor <daryl261@gmail.com>*Date*: Thu, 28 Oct 2010 08:04:14 -0400

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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Forum for Physics Educators

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--

Daryl L Taylor

(Sent from my Droid using 100% certified recycled electrons...)

**References**:**[Phys-l] How did Newton estimate the Gravitational constant?***From:*Brian Blais <bblais@bryant.edu>

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