> I believe that 5 decimal places is enough to calculate the circumference
of
> the earth to within a handspan. Sorry don't have a reference, I just
> remember being told it at one stage.

Earth's circumference close to 4E10 mm
        (40,075.02 km at equator except on bank holidays.)
Or about 5E12 handspan - so early advice and/or memory a bit low.

_________

> If your limit is measuring one cycle of
> earth's orbit to within 1mm, then the zeros start at the 16th digit past
> the decimal point.

Length ("Circumference") of earth's orbit is about 9.4E14 mm
Close enough to what Olin said :-).

_______


Distance to Alpha Centauri Proxima*** ~= 4E19 mm
So 10 billion* times around the earth = distance to the 2nd closest star
(after Sol).

Or about 3 billion years for a point on earth's equator to travel the same
distance due to spin.
But, only about 500 years at earth's (believed**) absolute velocity.


  Russell McMahon
  E&OE !!!!!!!!!!!!!!!!!

* US billion
** Flame shields up.
*** Alpha Centauri is the outer of the two pointers to the Southern Cross.
AC Proxima is quite a lot dimmer and slightly below it - both are almost the
same distance away from earth.
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