🚀 go-pugleaf

R.W.Dirksen (R.W.Dirksen@caiw.nl) wrote:
: Dik T. Winter wrote:
: > 
: > In article <5heh6s$ooa@raven.cc.ukans.edu> ipsifend@eagle.cc.ukans.edu (Greffindel) writes:
: >  > So, it's pi x 1000 light-years, right?
: >  > Speed of light: 3x10E8 m/s
[ snip snip snip ]
: >  > 18 decimal digits of pi gives you the distance correct down to the
: >  > millimeter.  How much more pi do you need?
: > 
: > Are you sure?  I think the error in the speed of light and in the number
: > of days in a year is much too large to warrant this assertion.

Well, presumably anyone who was doing the calculation for real would want 
as many significant figures for the speed of light and the number of
seconds in a year; I just picked easy numbers to facilitate doing the
multiplication by hand... (in fact, odds are there's at least one
error in my multiplication as big as any caused by c being
2.9something x 10E8 rather than 3.  

: > 
: > It is true, in real life 22/7 is mostly good enough, and if not you
: > go to 355/133 which probably is excellent (it would be good enough
: > in the calculation above).  On the other hand, there are indeed
: > situations where you need an extremely good approximation of pi, or
: > your calculations can go wrong.  There are highly unstable calculations
: > (like some of the higher zeros of the Riemann zeta function) that
: > require this.  (In the latter case to verify that all non-trivial zeros
: > are on a particular line, you need to separate them.  The problem is
: > that they can get arbitrarily close to each other.  And the calculations
: > involve cosines.)

Cool.  I can buy that.

: > --
: > dik t. winter, cwi, kruislaan 413, 1098 sj  amsterdam, nederland, +31205924131
: > home: bovenover 215, 1025 jn  amsterdam, nederland; http://www.cwi.nl/~dik/

: The speed of light is known very exact because it is a constant value.
: They actually made it a definition:

: 1 meter = the distance that light travels in 1/299792458 seconds
: Therefore, the light speed c is defined as 299,792.458 km/s.

Ah, there's the number. :)

: p.s. why celebrate pi-day anyway. I personally like the number
: 0.3157894736842105263157894736842105263157894736842105263157894736... 
: or 6/19. That's why I celebrate that day instead!

: Gerben Dirksen

Happy 6/19 day, then! :)

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