On 06/17/2016 06:19 PM, Steven D'Aprano wrote:
On Sat, 18 Jun 2016 09:49 am, Ian Kelly wrote:
If I tell you that the speed of light is 300,000,000 m/s, do you think
that measurement has 9 significant digits? If you do, then you would be
wrong.
Hmmm.
If I tell you that some physical phenomenon [let's call it the speed of
light] is 299,999,999 m/s, how many significant digits would I be using?
I know! I know! 9!
What if I tell you that it's 300,000,001 m/s?
Oh! 9 again!
What if the figure to nine significant digits *actually is* three followed
by eight zeroes?
Hmmm... thinking.... thinking... oh yeah! You put a bar over the last
significant digit -- or you use scientific notation:
30e7 has two significant digits.
For all that it is in widespread use, I think the concept of "significant
figures" is inherently ambiguous.
Not at all -- just have to keep your notations correct*.
--
~Ethan~
* Mine might be 30 years out of date, but maybe not.
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