value of pi and 22/7
Ethan Furman
ethan at stoneleaf.us
Fri Jun 17 22:27:08 EDT 2016
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* Mine might be 30 years out of date, but maybe not.
More information about the Python-list
mailing list