<story><title>How Many Decimals of Pi Do We Really Need?</title><url>http://www.jpl.nasa.gov/edu/news/2016/3/16/how-many-decimals-of-pi-do-we-really-need/</url></story><parent_chain><item><author>drewolbrich</author><text>If you know the diameter of the observable Universe and you want to calculate its circumference with the accuracy of the diameter of a proton, the number of digits of pi that you need is 43.</text></item></parent_chain><comment><author>gmuslera</author><text>The smallest possible distance is the Plank lenght, 1,6&lt;i&gt;10^-35 (1&lt;/i&gt;10^-15 is the diameter of a proton). And for that you only need around 60 digits of pi to calculate the circumference of the universe.&lt;p&gt;Of course, that is just for the simple operation of calculate the circumference given the diameter, more complex operations with pi may require more precision.</text></comment>
<story><title>How Many Decimals of Pi Do We Really Need?</title><url>http://www.jpl.nasa.gov/edu/news/2016/3/16/how-many-decimals-of-pi-do-we-really-need/</url></story><parent_chain><item><author>drewolbrich</author><text>If you know the diameter of the observable Universe and you want to calculate its circumference with the accuracy of the diameter of a proton, the number of digits of pi that you need is 43.</text></item></parent_chain><comment><author>mabbo</author><text>I&amp;#x27;ve always heard the number is around 50, but do you have any references to show that as being correct?</text></comment>