> The 8pi is merely a specific choice of units. Einstein used traditional
> CGS/MKS units of course, but nowadays most authors use units with 
> G=1 or 8piG=1; with the latter units one simply writes:
>
> G = T
>
> So the 8pi is not of major significance (except possibly historical
> interest).

Wrong again, Tom.  The 8 pi is not simply a unitary choice -- it follows
from the choice of units.  It is not itself a choice of units.  The strength
of the gravitational 'couple' was taken from Newton's equation.  GR -- being
fundamentally a pure math theory -- requires a way to set the constants to
connect them to observations in the real universe.

The speed of light -- for example -- is physically the same... whether we
use units in mks, cgs, cubits per tic or whatever.

greywolf42
ubi dubium ibi libertas