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[-] BedbugCutlefish@lemmy.world 98 points 1 week ago* (last edited 1 week ago)

Nah, that's silly. Asia obviously has the longest coastline.

Sure, based on that paradox, the specific measurement of a given coastline will differ. But if you pick a standard (i.e., 1km straight lines), Asia is easily the longest. Doesn't matter what standard you pick.

The only way the paradox matter here is of you pick different standards for different coastlines. Which, os obviously wrong.

[-] TropicalDingdong@lemmy.world 36 points 1 week ago

Some infinites are larger than other infinites.

[-] cynar@lemmy.world 15 points 1 week ago

It's not a true fractal, so the length has some finite bounding. It's just stupidly large, since you are tracing the atomic structure.

[-] TropicalDingdong@lemmy.world 5 points 1 week ago* (last edited 1 week ago)

Let F be a geometric object and let C be the set of counterexamples.

F is a True Fractal ⟺ F satisfies all properties P₁, P₂, ..., Pₙ

Where for each counterexample c ∈ C that satisfies P₁...Pₙ: Define Pₙ₊₁ := "is not like c"

The definition recurses infinitely as new counterexamples emerge.

Corollary: Coastlines exhibit fractal properties at every scale... except they don't, because [insert new property], except that's also not quite right because [insert newer property], except actually [insert even newer property]...

□ (no true scotsman continues fractally)

[-] Triumph@fedia.io 4 points 1 week ago

This motherfucker coming correct with subscripts.

[-] GraniteM@lemmy.world 5 points 1 week ago

That's a fair point. I forgot that some infinites are larger than other infinites.

[-] Triumph@fedia.io 9 points 1 week ago

Did you also forget about Dre?

[-] Lemmyoutofhere@lemmy.ca 2 points 1 week ago

Did you forget about the game?

[-] SmoothOperator@lemmy.world 5 points 1 week ago

Isn't it a bit like saying "there's obviously more real numbers between 0 and 2 than between 0 and 1"? Which, to my knowledge, is a false statement.

[-] clay_pidgin@sh.itjust.works 4 points 1 week ago

If between 0 and 1 are an infinite number of real numbers, then between 0 and 2 are twice infinite real numbers, IIRC my college math. I probably don't.

[-] village604@adultswim.fan 7 points 1 week ago

In math they'd both be equal

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[-] Capricorn_Geriatric@lemmy.world 3 points 1 week ago* (last edited 1 week ago)

It isn't.

When you look at the number of real numbers, you can always find new ones in both - you'll never run out.

That being said, imagine (or actually draw) two number lines in the same scale. One [0,1] the other [0,2]. Choose a natural number n, and divide both lines with that many lines. You'll get n+1 segmets in both lines.

When you let n run off into infinity, the number of segments will be the same in both lines. This is the cardinality of the set.

But for practical purposes of measuring a coastline, this approach is flawed.

Yes, you'll always see n+1 segments, but we aren't measuring the number of distinct points on the coastline, but rather its length, i.e. the distance between these points.

If you go back to your two to-scale number lines and divide them into n segments, the segments on one are exactly two times larger than on the other.

This is what we want to measure when we want to measure a coastline. The total length drawn when connecting these n points (and not their number!) as the number of points runs off towards infinity.

The solution to this "paradox" is probably closer to the definition of the integral (used to measure areas "under" math functions) than to that of the cardinality of infinite sets (used to measure the number of distinct elements in a set).

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The cardinality of the two intervals [0,1] and [0,2] are equivalent. E.g. for every number in the former you could map it to a unique number in the latter and vice versa. (Multiply or divide by two)

However in statistics, if you have a continuous variable with a uniform distribution on the interval [0, 2] and you want to know what the chances are of that value being between [0,1] then you do what you normally would for a discrete set and divide 1 by 2 because there are twice as many elements in the total than there are in half the range.

In other words, for weird theoretical math the amount of numbers in the reals is equivalent to the amount of any elements in a subset of the reals, but other than those weird cases, you should treat it as though they are different sizes.

[-] SmoothOperator@lemmy.world 1 points 1 week ago* (last edited 1 week ago)

Sure, the length of the intervals is easily compared. But saying

there are twice as many elements in the total than there are in half the range

is false. They are both aleph 1. In other words, for each unique element you can pick from [0,2], I can pick a unique element from [0,1]. I could even pick two or more. So you can't compare the number of elements in the two in a meaningful way other than saying they both belong to the same category of infinite.

This is the whole crux of the coastline problem, isn't it?

[-] bryndos@fedia.io 3 points 1 week ago

Funny that so many uses of maths depends on measurement, and yet so many pure mathematicians seem to be clueless about how we actually measure things and why its useful. It doesn't even matters about all this bullshit about infinities , were talking about the real world. It's all about the precision of the tape measure. Here's a true story from back in the day:

English Mathematician: You'll need an infinite number of bricks to build a wall around any island's coastline. French guy: come on over and see Mont Saint Michel it's vraiment genial!

English Mathematician: Oh that wall is infinitely far away from the true coastline, those bricks are not regulation infinitesimal length. If they'd started from the other corner they'd have got a different shape, and for sure needed infinite number of infinitesimal bricks to actually build that wall. Sloppy french masons. I can prove it I'll blast them all away with cannon fire until the glorious mathematical truth is revealed underneath.

One year later French inhabitants: fuck off english maths whore!

Ten years more laterer Hi french dudes! I'm back with a greater number of even bigger state of the art truth seeking cannon. I will prove this if its the last thing i do.

One year later . . .

[-] nublug@piefed.blahaj.zone 39 points 1 week ago

i hate the coastline 'paradox' and every other 'paradox' that's just a missing variable. "if we measure with a big resolution it's a smaller number of units and a small resolution is a bigger number!?" that's not a paradox. that's just how that variable works always. it's not confusing or interesting at all.

[-] scott@lem.free.as 10 points 1 week ago

But if you shrink the "yardstick" down to an infinitesimally small size, the length, effectively, becomes infinite... and it's the same for all coastlines. They're all infinitely long.

... but some are longer than others. ;)

[-] Fredthefishlord 17 points 1 week ago* (last edited 1 week ago)

Literally no. Very hard to measure, but strictly still a finite length. Limits and all that jazz.

[-] kartoffelsaft@programming.dev 4 points 1 week ago

Limits can resolve to infinity. The coastline paradox is just the observation that the (semi-reasonable) assumption that landmasses are fractal shaped implies the coastline tends towards infinity with smaller yardsticks.

[-] Fredthefishlord 4 points 1 week ago* (last edited 1 week ago)

They can.. I wasn't saying they couldn't... I meant that as to point to the logic you'd use to prove it finite

My bad for the poor wording though.

[-] spicehoarder@lemmy.zip 2 points 1 week ago

If you're going to talk about paradoxes, you should also know you're committing a presupposition fallacy

[-] MrPoopyButthole@lemmy.world 8 points 1 week ago

Max Planck says no...

[-] Lemming6969@lemmy.world 5 points 1 week ago

Didn't calculus solve this stuff?

[-] spicehoarder@lemmy.zip 2 points 1 week ago

Surely the distance approaches some finite value.

[-] theunknownmuncher@lemmy.world 26 points 1 week ago* (last edited 1 week ago)

Not all infinities are equal, friend. Asia does have more infinite coastline than other continents.

[-] BetterDev@programming.dev 2 points 1 week ago* (last edited 1 week ago)

Its true that not all infinities are equal, but the way we determine which infinities are larger is as follows

Say you have two infinite sets: A and B A is the set of integers B is the set of positive integers

Now, based on your argument, Asia has the largest infinite coastline in the same way A contains more numbers than B, right?

Well that's not how infinity works. |B| = |A| surprisingly.

The test you can use to see if one infinity is bigger than another is thus:

Can you take each element of A, and assign a unique member of B to it? If so, they're the same order of infinity.

As an example where you can't do this, and therefore the infinite sets are truely of different sizes, is the real numbers vs the integers. Go ahead, try to label every real number with an integer, I'll wait.

[-] Atlas_@lemmy.world 1 points 1 week ago

I'll label every real number with the integer 1.

[-] theunknownmuncher@lemmy.world 1 points 1 week ago* (last edited 1 week ago)

Go ahead, try to label every real number with an integer, I'll wait.

Why would I be trying to do this though? You've got the argument backwards.

Is the set of all real numbers between 0 and 100 bigger or equal to the set of all real numbers between 0 and 1?

It seems like I'm wrong though and these sets are the same "size" lol

[-] BetterDev@programming.dev 2 points 1 week ago

Exactly! It is unintuitive, but there are as many infinite elements of the set of all real numbers between 0 and 1, as there are in the set between 0 and 100.

I hope this demonstrates what the people here arguing for the paradox are saying, to the people who are arguing that one is obviously longer.

Just because something is obvious, doesn't make it true :)

[-] almost1337@lemmy.zip 1 points 1 week ago

And then aleph numbers get thrown into the conversation

[-] theunknownmuncher@lemmy.world 1 points 1 week ago

Alright, I concede. I did it wrong but still ended up with the right answer. There are other responses in this thread with correct explanation for why Asia has more coastline

[-] BetterDev@programming.dev 2 points 1 week ago* (last edited 1 week ago)

Yeah, if you use an arbitrary standardized measuring stick, the problem goes away, as it is no longer infinite.

Still a fun thought experiment to demonstrate how unintuitive infinities are!

Anyway, major kudos to you for engaging with this thread in good faith! That is so rare these days, I barely venture to comment anymore. Respect.

... and thank you for the opportunity to share a weird math fact!

[-] theunknownmuncher@lemmy.world 2 points 1 week ago* (last edited 1 week ago)

Hmm I've consulted a mathematician that I know, and they say that cardinality isn't really the same as "size", but comparing the two infinite sets of the same cardinality is basically meaningless because infinity is not a "number", even though one set is provably "bigger" than the other set

[-] BetterDev@programming.dev 1 points 1 week ago

And it may very well be true, but we can't prove it mathematically.

[-] solarvector@lemmy.dbzer0.com 21 points 1 week ago

If your unit of measurement is 1 Asia coastline, all others would be some changing fraction thereof. Mathematical equation paradox maybe but hardly over that disproves the answer.

[-] RattlerSix@lemmy.world 19 points 1 week ago

But how do we know Asia's coastline isn't more jaggedy?

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[-] DragonTypeWyvern@midwest.social 12 points 1 week ago
[-] yermaw@sh.itjust.works 6 points 1 week ago

So when that kid said "well I hate you infinity plus a million" he was on to something mathematically?

[-] tias@discuss.tchncs.de 8 points 1 week ago

No, but if he said "well I hate you two to the power of infinity" he would be.

[-] cattywampas@midwest.social 6 points 1 week ago

Unless they're assuming a certain resolution of measurement.

[-] m4xie@lemmy.ca 2 points 1 week ago

Surely the coast of a continent of a given area can only have a finite theoretically maximum length even if the whole coast is a Hilbert Curve filling that area, because the minimum feature size is determined by the surface tension of water m

[-] bryndos@fedia.io 1 points 1 week ago

My new years resolution will be to solve this paradox.

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this post was submitted on 20 Nov 2025
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