If astronomers think they can nail down astronomical distances outside
our solar system, and especially outside our galaxy, to better than 6 %
they are too proud of themselves. That's why I gave the 10 Pm figure
"near enough for astronomical math". I find it handy to have a mental
number for conversions of non-metric figures that I encounter.
Given the precision of calculating the length of a mean solar year and
given the exact value now used for the speed of light, you could go out
past the four significant figures that you cited, Bill.
Jim
Bill Hooper wrote:
On 2008 Mar 22 , at 7:34 PM, James Frysinger wrote:
Near enough for astronomical math, a light year is 10 Pm.
The more precise figure is 9.460 Pm. I agree that 10 Pm is a good
approximate value. It's only off by about 6%. If a 6% error is too much
in some situation, then using 9.5 Pm would reduce the error to about
0.4% which isn't bad.
--
James R. Frysinger
632 Stony Point Mountain Road
Doyle, TN 38559-3030
(H) 931.657.3107
(C) 931.212.0267
