this post was submitted on 08 Nov 2023
94 points (95.2% liked)

No Stupid Questions

35220 readers
1853 users here now

No such thing. Ask away!

!nostupidquestions is a community dedicated to being helpful and answering each others' questions on various topics.

The rules for posting and commenting, besides the rules defined here for lemmy.world, are as follows:

Rules (interactive)


Rule 1- All posts must be legitimate questions. All post titles must include a question.

All posts must be legitimate questions, and all post titles must include a question. Questions that are joke or trolling questions, memes, song lyrics as title, etc. are not allowed here. See Rule 6 for all exceptions.



Rule 2- Your question subject cannot be illegal or NSFW material.

Your question subject cannot be illegal or NSFW material. You will be warned first, banned second.



Rule 3- Do not seek mental, medical and professional help here.

Do not seek mental, medical and professional help here. Breaking this rule will not get you or your post removed, but it will put you at risk, and possibly in danger.



Rule 4- No self promotion or upvote-farming of any kind.

That's it.



Rule 5- No baiting or sealioning or promoting an agenda.

Questions which, instead of being of an innocuous nature, are specifically intended (based on reports and in the opinion of our crack moderation team) to bait users into ideological wars on charged political topics will be removed and the authors warned - or banned - depending on severity.



Rule 6- Regarding META posts and joke questions.

Provided it is about the community itself, you may post non-question posts using the [META] tag on your post title.

On fridays, you are allowed to post meme and troll questions, on the condition that it's in text format only, and conforms with our other rules. These posts MUST include the [NSQ Friday] tag in their title.

If you post a serious question on friday and are looking only for legitimate answers, then please include the [Serious] tag on your post. Irrelevant replies will then be removed by moderators.



Rule 7- You can't intentionally annoy, mock, or harass other members.

If you intentionally annoy, mock, harass, or discriminate against any individual member, you will be removed.

Likewise, if you are a member, sympathiser or a resemblant of a movement that is known to largely hate, mock, discriminate against, and/or want to take lives of a group of people, and you were provably vocal about your hate, then you will be banned on sight.



Rule 8- All comments should try to stay relevant to their parent content.



Rule 9- Reposts from other platforms are not allowed.

Let everyone have their own content.



Rule 10- Majority of bots aren't allowed to participate here.



Credits

Our breathtaking icon was bestowed upon us by @Cevilia!

The greatest banner of all time: by @TheOneWithTheHair!

founded 1 year ago
MODERATORS
 

xkcd: Coordinate Precision but pi (π)?

I tried looking for some answer but found mostly

  • People reciting pi
  • People teaching how to memorize pi
  • How to calculate pi using different formula
  • How many digits NASA uses

Update question to be more specific

In case someone see this later, what is the most advanced object you can build or perform its task, with different length of pi?

0, 3 => you can't make a full circle

1, 3.1 => very wobbly circle

2, 3.14 => perfect hole on a beach

3, 3.142 => ??

4, 3.1416 => ??

5, 3.14159 => ??

Old question below

In practice, the majority of people will never require any extra digit past 3.14. Some engineering may go to 3.1416. And unless you are doing space stuff 3.14159 is probably more than sufficient.

But at which point do a situation require extra digit?
From 3 to 3.1 to 3.14 and so on.

My non-existing rubber duck told me I can just plug these into a graphing calculator. facepalm

y=(2πx−(2·3.14x))

y=abs(2πx−(2·3.142x))

y=abs(2πx−(2·3.1416x))

y=(2πx−(2·3.14159x))

Got adequate answer from @dual_sport_dork and @howrar
Any extra example of big object and its minimum pi approximation still welcome.

you are viewing a single comment's thread
view the rest of the comments
[–] dual_sport_dork@lemmy.world 68 points 10 months ago (6 children)

On the NASA front, I believe I read somewhere that NASA determined that only 40 decimal places of pi are required to define a sphere the size of the observable universe to the accuracy of +/- the width of one hydrogen atom. It seems like you could file that under "close enough."

Just using 3 is certainly too low of a precision -- unless you're writing a major work of religious literature, of course. 3.1 is likewise unlikely to result in acceptable accuracy on a terrestrial scale. I've always used 3.14159 which is conveniently exactly what I can remember without looking it up and it's always been good enough for me. I don't think I've ever in my life needed to scribe a circle much larger than a couple of feet across at any rate.

You may be interested in reading this: https://blogs.scientificamerican.com/observations/how-much-pi-do-you-need/

[–] HonoraryMancunian@lemmy.world 20 points 10 months ago

And if my maths is correct, 63 decimal places gets that universe circle's precision to within a Planck length

[–] user45178@lemmy.world 4 points 10 months ago (3 children)

Then why did we need to put in so much effort to get to the 100 billionth or so? When all we could ever need are 40, maybe 50 if you want?

[–] Pons_Aelius@kbin.social 12 points 10 months ago* (last edited 10 months ago) (2 children)

It is not about actual use when they calculate pi to tthese numbers.

It is about finding out if pi is actually irrational or is it recurring on some level.ie: does it start repeating at some point.

[–] vrighter@discuss.tchncs.de 3 points 10 months ago (1 children)

nope, just for testing computers. We know pi is transcendental. Which implies it is irrational. This has been mathematically proven.

We don't need to check. We know that it does not repeat.

[–] Chobbes@lemmy.world 6 points 10 months ago

There’s facts about pi we don’t know, though. We have not proved whether or not pi contains every finite sequence of digits. A breakthrough about this will probably have little to do with brute force computing billions of digits of pi, but maybe there can be a clue there. As far as I know we basically just calculate a bunch of pi to flex. It’s the mathematical equivalent of walking around shirtless to show off your abs.

[–] jasory@programming.dev 1 points 7 months ago

Nope. Alexander Yee literally just wrote the program for shits and giggles. (Even the mathematical routines aren't generally useful).

Pi can be proven to be irrational with a pen and paper.

[–] hperrin@lemmy.world 6 points 10 months ago

For the sheer unadulterated thrill of calculating pi.

[–] Alexstarfire@lemmy.world 1 points 10 months ago

Why do most records exist?

[–] AmidFuror@kbin.social 4 points 10 months ago* (last edited 10 months ago)

Upvoted for religious text reference. Another way to put it would be if you are OK with being off by 33% for insect leg count, you can use 3 for pi.

[–] g6d3np81@kbin.social 3 points 10 months ago

Thank you, I already skimmed through that article before posting. Maybe I failed to put my question into words properly.

I want examples similar to pool/fence circumference in the article. Along the line of "We're building x, and this is the worst rounding we can go, one fewer digit and it will be off by y"

[–] AA5B@lemmy.world 2 points 10 months ago

When we round pi to the integer 3 … to estimate the circumference of an object with a diameter of 100 feet, we will be off by a little over 14 feet.

It seems like ‘3’ is sufficient for real life. It’s probably more precise that I can freehand draw a circle. If I really did need to measure the fencing for a circle with diameter 100’, it’s within the window of padding I would estimate

[–] angrystego@lemmy.world 1 points 10 months ago (1 children)

Now I'm imagining the Holy Pinity.

[–] dual_sport_dork@lemmy.world 4 points 10 months ago

For those still in the dark, I'm referencing the bible in 1 Kings 7, 23-26:

And he made a molten sea, ten cubits from the one brim to the other: it was round all about, and his height was five cubits: and a line of thirty cubits did compass it round about. And under the brim of it round about there were knops compassing it, ten in a cubit, compassing the sea round about: the knops were cast in two rows, when it was cast. It stood upon twelve oxen, three looking toward the north, and three looking toward the west, and three looking toward the south, and three looking toward the east: and the sea was set above upon them, and all their hinder parts were inward. And it was an hand breadth thick, and the brim thereof was wrought like the brim of a cup, with flowers of lilies: it contained two thousand baths.

Those measurements would only work if either the cauldron were not actually circular, or if Pi were equal to 3.