What field do you work in, and how many digits of pi do you use?

This article says that NASA uses 15 digits after the decimal point, which I’m counting as 16 in total, since that’s how we count significant digits in scientific notation. If you round pi to 3, that’s one significant digit, and if you round it to 1, that’s zero digits.

I know that 22/7 is an extremely good approximation for pi, since it’s written with 3 digits, but is accurate to almost 4 digits. Another good one is √10, which is accurate to a little over 2 digits.

I’ve heard that ‘field engineers’ used to use these approximations to save time when doing math by hand. But what field, exactly? Can anyone give examples of fields that use fewer than 16 digits? In the spirit of something like xkcd: Purity, could you rank different sciences by how many digits of pi they require?

Vanth, (edited )
@Vanth@reddthat.com avatar

deleted_by_author

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  • absGeekNZ,
    @absGeekNZ@lemmy.nz avatar

    This

    HaywardT,

    Design metal parts. I’m a welder so a number between 2-4 is close enough.

    SuckMyWang,

    You hear that? “Normal” units

    SamsonSeinfelder,

    That is 0.025 Millimeter in normal units

    towerful,

    You can say 25 micrometers

    noughtnaut,
    @noughtnaut@lemmy.world avatar

    Yes, it’s technically correct (which we all know is the best kind of correct) and engineers would understand.

    Using mm means most everyone (who knows metric) understands that in much more practical terms. A quarter of a tenth of thiiis much is a pretty damn tight fit.

    taladar,

    Bold of you to assume that anywhere close to everyone who understands metric would know that 0.25 is a quarter of something.

    TheRaven,
    @TheRaven@lemmy.ca avatar

    Bold of you to assume that the country that still uses the Imperial system is the one that better understands fractions.

    cbc.ca/…/how-failing-at-fractions-saved-the-quart…

    taladar,

    I didn’t say that imperial countries understand them better.

    towerful,

    Micrometers is actually so common that it has a colloquial non-SI name of “micron”

    According to wiki:

    The micrometre is a common unit of measurement for wavelengths of infrared radiation as well as sizes of biological cells and bacteria,[1] and for grading wool by the diameter of the fibres.[3] The width of a single human hair ranges from approximately 20 to 200 μm.

    agamemnonymous,
    @agamemnonymous@sh.itjust.works avatar

    because it rhymes.

    With?

    nycki,

    Answering my own question: I work in web development and my usual value for pi is the standard JavaScript Math.PI. JavaScript uses 64-bit floats, which are accurate to about 15 decimal places. But that’s how many digits the computer uses. For practical math, I don’t think I’ve ever needed more than 2 digits of accuracy in an equation involving pi.

    Asidonhopo,

    Retail, and to my knowledge among all my coworkers we have used zero digits of pi.

    When I code in C++ I use 15 digits of pi after the decimal point (double float) but I have only rarely coded for money and have never used pi for those work products, so again, zero digits on the clock.

    Ditto for restaurant work, although 2 decimal points would be more than enough if I needed the volume of a cake or other round food.

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