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?
You must log in or # to comment.
Molecular biology. 4 digits.
This probably won’t play well with this audience, but I’m a management/strategy consultant. “~5” (technically one decimal place but also rounded to the nearest interval of 5) for any C-level decks ;)
That’s less than one significant digit! Even just to one significant bit, pi is 4.
That’s a crime 😭
Oof :D
I’m a programmer and I remember 33 digits, but in practice I never use pi because I never have to deal with geometry
I’m British, not American, so I use 7/22.
Rub it in, metric π, you imperialist rebel.
Embedded engineer, working in education. I use 3 for mental estimations and whatever is stored in the calculator, I have happened to grab, for “precision” work. Sometimes I’ll even round pi to 4, to build in some tolerance when calculating materials.
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.
Back in middle school I memorized this much of pi (for no good reason):
3.14159265358979323846264338327950288419716939937510
That’s far more accurate than I’ll ever need.
Mechanical engineer here - Matlab uses 16 digits for pi(), so that’s my go-to. When doing some larger thermodynamic simulations, I sacrifice some digits of pi to get more computational headroom. But that’s only after I get really annoyed at the code, and it almost never helps (but rarely hurts, as well)
I’m a nothing in particular, and I used to remember 100 digits. I could probably remember again in an hour.
3.14159
Design of mechanical parts, specifically machined. 0.001" is a fairly tight tolerance for my applications, 0.0001" is going to cost a pretty penny and is used judiciously. We don’t really need to go to 3.14159 but I honestly think we do because it rhymes.
This
That is 0.025 Millimeter in normal units
You can say 25 micrometers
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.
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.
Bold of you to assume that anywhere close to everyone who understands metric would know that 0.25 is a quarter of something.
Bold of you to assume that the country that still uses the Imperial system is the one that better understands fractions.
I didn’t say that imperial countries understand them better.
because it rhymes.
With?
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.
As a mathematician, I don’t use any digits, but the symbol π.
As a computer scientist, same, but it’s called
PI.It’s the computer that does the thing with the digits, not me. 🙃
In which case you’re probably using a predefined 64-bit floating point number, which I think is accurate to 15 digits.
Well, you know what’s funny, after writing the comment above, I double-checked what the π constant is called in Rust, as that’s what I’m mostly coding with these days.
And well, it actually makes you choose. There’s
f32::consts::PIandf64::consts::PI. Which I guess, makes sense. If you’re calculating with 32-bit floats, you should be aware that π is going to be less precise.
So, yeah, I’m a hoax, computer scientists do need to decide between 32-bit and 64-bit.In fact, the one time I needed π in Rust, was as a 32-bit float. I built a tiny gravity simulation in a game engine and game engines generally use 32-bit floats…
I’d like to agree, but writing π with capital letters is heresy.
Yeah, math conventions and programming conventions don’t always align. As in, basically never…
If anyone here wants a fun way to memorize more digits, enjoy this song!
Really glad I have a legit reason to share this old thing
I am a farmer who has to graft pipe cuts at various angles. i use 3.14159. which is plenty since i am measuring my cuts to the nearest eighth of an inch and i am not sending this ish to the moon.
I would like to hear more about rice farming and if the rice is tall or you are.
hmm rice can get pretty tall. i guess my username should be talltallricefarmer
In Biostatistics - only ever use pi in the variance of the logistic density. Using 3.14 gives substantially equivalent results to using arbitrarily large precision. But I use whatever my calculator or R give me.
