this post was submitted on 01 Oct 2023
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Science Memes

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PI is what (i.imgur.com)
submitted 1 year ago by [email protected] to c/[email protected]
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[–] [email protected] 2 points 1 year ago (1 children)

I get it now. I was taking exception to your characterization of 3 and 5 being equally inaccurate in the sense of how close they are to the actual true value, which, of course, can never be known, except in every more accurate approximations.

In that case, I guess we still have a difference of opinion. I think that using approximations that are closer to their true value are more useful in teaching, despite (and maybe because of) the greater difficulty. If the student is not yet ready for that level of difficulty, then perhaps a different problem should be presented.

To that end, I actually think that there are several things to teach. That PI is not 3 or 3.14 or any other decimal expansion. That 3 is close enough for most casual encounters outside school. That 3.14 is close enough for most engineering work. That 3.1416 is close enough for most scientific work. That 15 decimal places is close enough for rocket scientists. That 37 decimal places are enough to calculate the circumference of the universe to within the diameter of a hydrogen atom. (https://www.jpl.nasa.gov/edu/news/2016/3/16/how-many-decimals-of-pi-do-we-really-need/ is my reference for the last two items. The others are just wild-ass guesses.)

[–] [email protected] 1 points 1 year ago* (last edited 1 year ago) (1 children)

What I mean is, if you're using 3, you're approximating, heavily. If you do anything critical using that value, it's as bad as using 5 really, imo. Is it really the case that 3 can be used casually? Like in what, workmanship, crafting or something else?

Personally, I would say that pi should be presented as 3.14 and calculators should be used, there's no reason to fear less than elegant numbers xD. And no, that's not close enough for most engineering work, as an engineer we don't usually approximate that much despite the memes, since you have to reduce the margin of error as much as practical. You generally don't even approximate, just leave it as pi the symbol for the most part since in the end you won't calculate it manually. The errors stack up the more you use the value. Eg, multiply an inaccurate value of pi by pi and the error you get is exponential.

That aside, I think 5 is more elegant than 3 so if youre approximating to avoid the cumbersome numbers why not go for elegance instead of accuracy? xD

[–] [email protected] 2 points 1 year ago (1 children)

When I'm figuring the buoyancy of a 20 litre pail or, alternatively, how much it'll weigh when filled with sand, 3 is easier to work in my head for off-the-cuff estimates so I know about how many pails I need.

That said, I do typically use the π button on my calculator when it comes time to actually execute on the project. :)

[–] [email protected] 1 points 1 year ago (1 children)

That's interesting. I imagine if you do that long enough you'll just approximate with pi intact as well intuitively.

Anyways nice conversation.

[–] [email protected] 1 points 1 year ago

Yes! Thank you. It's always nice to see other perspectives.