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posted by Fnord666 on Wednesday August 14 2019, @11:59PM   Printer-friendly
from the that's-the-combination-to-my-luggage! dept.

https://www.jpl.nasa.gov/edu/news/2016/3/16/how-many-decimals-of-pi-do-we-really-need/

Earlier this week, we received this question from a fan on Facebook who wondered how many decimals of the mathematical constant pi (π) NASA-JPL scientists and engineers use when making calculations:

Does JPL only use 3.14 for its pi calculations? Or do you use more decimals like say: 3.141592653589793238462643383279502884197169399375105820974944592307816406286208998628034825342117067982148086513282306647093844609550582231725359408128481117450284102701938521105559644622948954930381964428810975665933446128475648233786783165271201909145648566923460348610454326648213393607260249141273724587006606315588174881520920962829254091715364367892590360

We posed this question to the director and chief engineer for NASA's Dawn mission, Marc Rayman. Here's what he said:


Original Submission

 
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  • (Score: 2) by Immerman on Friday August 16 2019, @02:45AM

    by Immerman (3985) on Friday August 16 2019, @02:45AM (#880845)

    Now you've got me wondering why he didn't use 29,001 feet instead, and half the error or the same result.

    I suppose measuring to a fraction of a foot in those days would be rough, leaving 29,000.0 as unacceptable.

    It does bear mentioning that I've seen a convention in many science and engineering books of representing such an "exact" integer with a trailing decimal point - e.g. as 29,000. - but it's far from ubiquitous. It also isn't generally flexible - it doesn't help you if your measuring method is accurate to 10 feet.

    Plus, as your link indicates, he was actually off by 29 feet, so clearly he was overestimating the precision of his measurement technology by 1.5 orders of magnitude.

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