this post was submitted on 12 Mar 2024
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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?

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[–] [email protected] 7 points 8 months ago

I rarely use pi. But when I do I only use 3 digits. I wish I could use less, but we still need to use change when we make purchases.

[–] TheRealKuni 7 points 8 months ago

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.

[–] pranz 6 points 8 months ago (3 children)

This probably won’t play well with this audience, but I’m a management/strategy consultant. β€œ~5” (technically one decimal place but also rounded to the nearest interval of 5) for any C-level decks ;)

[–] [email protected] 5 points 8 months ago
[–] [email protected] 4 points 8 months ago

That's less than one significant digit! Even just to one significant bit, pi is 4.

[–] Feathercrown 3 points 8 months ago

That's a crime 😭

[–] [email protected] 6 points 8 months ago

Chip R&D. We only use 1's, 0's if management is feeling generous. There are no circles, no need for pi.

[–] [email protected] 6 points 8 months ago

The digital field, and we use the first ten digits, especially when those first ten digits is some person's password with the password hint "easy as pi".

[–] [email protected] 5 points 8 months ago (1 children)

I don't use Pi but I do use GPS fairly often and try to get down to 7 digits after the decimal point. Our equipment probably isn't quite that accurate though lol so the seventh digit is likely a guess. Probably even the 6th digit.

[–] [email protected] 6 points 8 months ago

Well I’m an uber driver and I’m requesting you start using 9 or 10 digits because my passengers are all over the place when I’m supposed to be able to see where they are.

[–] [email protected] 5 points 8 months ago

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.

[–] LowtierComputer 5 points 8 months ago

Equipment engineering. Usually 2 if I'm doing math by hand. 5 for more accurate calculations.

[–] [email protected] 4 points 8 months ago

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)

[–] j4k3 4 points 8 months ago

I can't say "professionally" but I learned CAD design with FreeCAD, and know the topological naming issue thoroughly.

Almost all "mystery" problems in CAD are due to a combination of the hacks that get around the Topological Naming Issue and Ο€.

In CAD, you cookie, you brownie, you might even salad, but you stay the hell away from importing Ο€ as a reference on anything complex. For 3D printing, I never need better than 0.05mm so 3.1416.

[–] viralJ 4 points 8 months ago

Molecular biology. 4 digits.

[–] [email protected] 3 points 8 months ago

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.

[–] [email protected] 3 points 8 months ago

I work in the Bakery field and our specialty is Pie.

[–] snausagesinablanket 3 points 8 months ago
[–] [email protected] 2 points 8 months ago

I'm a nothing in particular, and I used to remember 100 digits. I could probably remember again in an hour.

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