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

[Bernard Cleyet <bernardcleyet@redshift.com>]

That estimate was done, IIRC, in medieval times by using quadrature of the earth-moon-sun system -- of course it just gave the solar distance in terms of lunar units.

bc tho taught intro. astronomy, remembers only Aristarchus (Earth size) and Leonardo (Earth shine)

p.s. further reading gives this:   [Not bad estimates of earth size and lunar distance and ~ half to the sun.  Those Greeks were rather sharp!  Note the intuition for the solar centric system.]


http://galileoandeinstein.physics.virginia.edu/lectures/gkastr1.html

p.s.  read recently, tho, their rejection of "zero" set back maths for a millennium.



On 2010, Oct 28, , at 03:00, Brian Blais 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://bblais.blogspot.com/
>
>
>
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