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# Re: Yes, I'm back

From: Tim May Tuesday, January 21, 2003, 6:22
Christophe Grandsire writes:
> En réponse à Tim May <butsuri@...>:
>   (Okay, you can still call
> > the derived Newtonian version "Kepler's third law" if you like, but
> > Kepler never wrote it, and it's not what Peter was referring to.)
> >
>
> By this kind of arguments, we shouldn't call Newton's laws of
> movement Newton's! Their current form has little to do with what
> Newton originally wrote. Yet the basis is still the same and the
> application too. It's the same for Kepler's third law. The fact
> that we can now derive the proportion constant doesn't mean the law
> has changed in any substantial way, or that we should make a
> difference between Kepler's third law as he originally wrote it and
> as we know it now. By Jove! It's only a matter of a constant that
> has become calculable!
>

Whether or not Kepler's 3rd law remains Kepler's third law when you
replace the constant of proportionality with
$\frac{2\pi}{\sqrt{Gm_{s}}}$ is a semantic argument in which I have no
interest.  I merely suggest that it is legitimate to refer to the
third of the laws formulated empirically by Kepler as "Kepler's third
law", that this contained no mention of the mass of the sun, and that
this is almost certainly what Peter was referring to.