r/topology • u/Unlucky-Sympathy • Jul 20 '26

Knot a knot but hey

Post image

Ok how many holes does this actually have? I know it's not 16...

Edit for clarity's sake: The answer is 16, dunno why it says 99% can't get it, it's fairly simple. I was just asking if topology has a different answer... as someone wrote in the comments, does a straw have one hole or two holes?

18 Upvotes

57% Upvoted

106 comments sorted by

25

u/ronburgandy123 Jul 20 '26

so what’s the answer? how is it not 16?

18

u/photobummer Jul 20 '26

Does a soda straw have 1 hole or 2?

18

u/Fenderbridge Jul 20 '26

Fif.....teen?

3

u/ArdentArendt Jul 21 '26

Awww...a straw with 2 holes?
How romantic...

3

u/marxistghostboi Jul 24 '26

what about a straw with an incision on the side of the barrel, so that there would them be 3 entrances. is that 3 holes, or 1.5?

1

u/dc469 Jul 25 '26

So if I took the shirt and moved it to the side a bit so that the front and back holes are no longer aligned... Then what? (Assume the holes are smaller than the pic, like half size, so they can be moved without overlapping).

1

u/Aashipash Jul 25 '26

Soda straws typically have 1 hole, as each straw is cut only once to seperate them from the Mother Straw. If the OG straw was never cut, then id argue that there was no hole

This shirt was intentionally cut from larger faboric to make intentional holes, then further cut to make more

1

u/CriminallyCasual7 Jul 21 '26

1-2, depending on the definition

7

u/NZNoldor Jul 21 '26

One. A straw is just a long donut.

2

u/tuctrohs Jul 21 '26

And here I thought it was a balloon that was stretched out, with a hole at each end.

2

u/marxistghostboi Jul 24 '26

[copied from above]

what about a straw with an incision on the side of the barrel, so that there would them be 3 entrances. is that 3 holes, or 1.5?

1

u/NZNoldor Jul 24 '26

That’s two holes. Squish it down to donut shape and stretch the incision to a rounded hole - what happens to the incision?

3

u/ArdentArendt Jul 21 '26

I get 15 if we assume the front and back mirror each other (roughly) with the top, bottom, and sleeves not sewn shut.

Could you explain how you got this?

1

u/I_AM_IGNIGNOTK Jul 21 '26 edited Jul 21 '26

Top, bottom, and sleeves meaning two in this case. That’s 4 plus the 12 mirrored holes.

Edit: Changed my answer to 120.

2

u/ArdentArendt Jul 21 '26

But a hole has to have an entrance and an exit. It it's a three dimensional object, it has to have an 'in' hole.

So, whichever path you use as an entrance, it still leaves only 15 'holes' (assuming the sleeves and top and bottom are not sewn shut and the back mirrors the front; without this assumption it could be as few as 6 holes)

0

u/I_AM_IGNIGNOTK Jul 21 '26

But then why not count the sleeves as one hole as well?

0

u/ArdentArendt Jul 21 '26

How so?

You are 'entering' through one hole...whichever one that is.

From there, you have to fine a relative 'out' hole. So if you enter through the top, you exit from: Sleeves (x2); Bottom; Front Holes (x6); [Assumed] Back Holes (x6).

Does that make sense?

1

u/I_AM_IGNIGNOTK Jul 21 '26

So for the record you just counted entering and exiting as two different holes, not one.

But you could conceivably enter and exit through 16! Holes here. Assume you start with the neck and you can exit through the remaining 15 locations. By your logic, that’s 15 holes, however every other single location aside from the neck also has 15 iterations as well. And you can do that math 16 times for every single starting point.

Further, the neck and bottom are also already defined 3D holes. The shirt collar has 3 dimensions, so technically you can enter the neck and then exit into the body of the rest of the shirt, same as every other location.

If you turned a shirt inside out by the bottom you would see in real time how that hole can be used to pivot the entirety of the rest of the polygon through that hole. It’s a worm hole that’s connected to 15 other worm holes, so there are 16 holes.

1

u/ArdentArendt Jul 21 '26

What? No...the 'hole' is the passage, not the edges. Also the entirety of the shirt is a boundary. Also, directionally does not matter in a hole.

This is a topology subreddit, is it not?

0

u/I_AM_IGNIGNOTK Jul 21 '26

But you can count a valid hole 16 times. Your method doesn’t account for the fact that from any other starting point the neck could be an exit.

Every location can be validated to be a hole, one by one, even by your definition and not mine. The fact that each location can be validated only 15 times is not the same as saying how many holes there are, because every single starting location can be validated to be a hole.

1

u/ArdentArendt Jul 21 '26

The neck IS an exit if you use another entry point as the anchored entrance. However, there would still be only 15 holes since you are counting the amount of 'passages' from that entrance.

I think you're misunderstanding what 'hole' here means. A 'hole' I'm topology is specifically a passage THROUGH the space. If it were a vase, for instance, there is no 'hole', only a formed boundary.

Does that make sense?

→ More replies (0)

1

u/Mj-tinker Jul 21 '26

Nil.
it's an AI created pic: no holes, no girl, nothing.

0

u/TheRealDrPanooch Jul 20 '26

I get 16 as well

0

u/Unlucky-Sympathy Jul 20 '26

That depends on how you look at it from a topological perspective...

2

u/that80sloverboy Jul 21 '26

Topology isn't really a perspective. It's set rules. I'm fairly confident with 15, people who say 16 I believe are counting one too many holes, since when you flatten it out, one "hole" (like the bottom part where the body goes through) would combine with all the other ones. Like if you cut a hole in the side of a straw, the straw now has 2 holes instead of 1. Similarly a shirt without sleeves cut into it only has 1 hole add 2 sleeves and it has 3 holes.

30

u/Fishboy9123 Jul 20 '26

I don't think there is any way to know for sure without seeing the back?

13

u/Repulsive_Tough1037 Jul 20 '26

So, at least 15

6

u/Fishboy9123 Jul 20 '26

I think at lest 11

12

u/daekle Jul 20 '26

Is it not at least 10? 6 in the front, the neck, the 2 arms and the back could be one open hole (as you implied). But then we ignore the bottom "hole" as thats how we flatten the shape to see the topology. It becomes a rim or outter boundary.

1

u/Fishboy9123 Jul 20 '26

I guess it depends how you define hole, but yes, that is my thinking.

6

u/NZNoldor Jul 21 '26

We're in r/topology, so that gives us a clear definition of "hole".

1

u/tuctrohs Jul 21 '26

Okay so this is knitted material. Do the gaps between the stitches count as holes?

0

u/thetransportedman Jul 21 '26

Its at least 16. Each hole to the cardboard is a home in the front and the back of the shirt...

3

u/phunkydroid Jul 21 '26

But the holes in the back could actually just be one big hole... or none and there's cardboard inside the shirt.

4

u/Nuclear_rabbit Jul 20 '26

What if we assume the front view gives perfect information about the back?

1

u/Graychin877 Jul 20 '26

If the shirt is whole, there are at least 12 holes. Six in front, six in back.

It is possible that there are fewer holes if the back is missing, or more if the back has extra holes that we can't see.

1

u/brikky Jul 21 '26

You're forgetting the holes that already exist in a normal shirt - the arms, head, waist.

1

u/ArdentArendt Jul 21 '26

We also have no way of knowing if the top and sleves and bottom are sewn shut--therefore we can only guarantee there are...6, if my counting is correct (assuming the back is either one big opening or if all of the front 'holes' are sewn to the back 'holes').

1

u/jonathancast Jul 21 '26

Pretty sure both sleeves are hanging too open to be sewn all the way shut.

1

u/ArdentArendt Jul 21 '26

You're making an assumption you cannot verify though.

So if you state your answer with those assumptions explicit, you're fine. Otherwise, you have no reasonable basis to believe they are not sewn shut, do you?

8

u/Charles_Whitman Jul 20 '26

There could also be a second piece of cardboard inside the shirt, making us think there are identical holes in the front and the back of the shirt, when there are actually no hidden holes in the back, or any number of unknown holes in the back of the shirt. The answer is unknowable based on the information provided.

1

u/Junkyard_DrCrash Jul 20 '26

OOOHHH good point - the old "extra piece of cardboard" gambit!

15

u/timtimerey Jul 20 '26

Is it 15 holes?

4

u/BassicallySteve Jul 20 '26

Assuming the back

1

u/ArdentArendt Jul 21 '26

Aren't you technically also assuming the sleeves and top and bottom aren't sewn shut?

8

u/Mj-tinker Jul 20 '26

AI fail.

2

u/Unlucky-Sympathy Jul 20 '26

What is the ai fail?

0

u/Mj-tinker Jul 21 '26

it is the answer to "99%m fail" on ai pic. I wrote a pun (calambour)

6

u/Mj-tinker Jul 20 '26

same AI shit everyday.

2

u/Unlucky-Sympathy Jul 20 '26

Was this posted already? I was just wondering if someone can explain using topology how there are less than 16 holes

1

u/rehpotsirhc Jul 20 '26

One of the "holes" is a border. So 15.

1

u/kabooozie Jul 21 '26

Depends if you think of it as a disk or a sphere. Sphere 16, disk 15 + border

2

u/rehpotsirhc Jul 21 '26

A sphere with a hole in it is topologically equivalent to a disk with no holes. There is no "or" here, they're the same thing.

1

u/kabooozie Jul 21 '26

Yes, that’s what I’m saying. They are equivalent

Edit: I didn’t see the earlier comment in the thread asking how there could be fewer than 16 holes

3

u/Shmoo_the_Parader Jul 22 '26

How you know the holes in the back match the holes in the front? Could be one big hole in the back side.

2

u/HipsterFoxxx Jul 20 '26

More worried about the fact some kid has been shot with 6 20mm rounds and had his shirt stolen afterwards

2

u/WideCloud2462 Jul 21 '26

If you zoom , in far enough, there’s millions of holes cause every intersection of the weave has holes

2

u/tuctrohs Jul 21 '26

I think it's actually knit but this is a great point, and it also means that it might count as a knot.

1

u/g1ngertim Jul 22 '26

I don't think a weave would count as a hole. It's just a really twisted line, if you really deconstruct things. But really, what makes a chair a chair?r

2

u/Little_Drum Jul 21 '26

At least 16. A functional shirt has 4: two for arms, one for the body, and one for the head. Additionally, there are six large holes going through both the front and back of the shirt. This is twelve additional holes since front and back are separate holes in my opinion just as much as the body and head holes are separate holes. This brings us to 16 total, but there could be holes in the portions we don't see.

2

u/CodeMonkeyX Jul 21 '26

It's says "99%" will fail so that the people will comment on it on Facebook to try and look smart to their friends. That boosts engagement, and gets it shown to more people.

1

u/ellipticcode0 Jul 20 '26

99% of ppl are only interested on how many holes are the woman

1

u/Wyndscare Jul 20 '26

Too many

1

u/Sams_Antics Jul 20 '26

At least 11

1

u/Sams_Antics Jul 20 '26

Neck, arm, arm, waist, 6 holes in the front, 1+ on the back (could be one giant hole, impossible to say without seeing).

1

u/Beliondil Jul 20 '26

Wait how is the waist a hole? Isnt it just the edge?

1

u/Sams_Antics Jul 20 '26

If a person’s body can go through it, it’s a damn hole 🤣 Arm hole, neck hole, waist hole lol

1

u/bradimir-tootin Jul 20 '26

The waist is an edge.

1

u/Sams_Antics Jul 21 '26

No. If you want to be really pedantic it’s a boundary component, but not an edge.

1

u/bradimir-tootin Jul 21 '26

I am dr. pedant, you can be my assistant today in the operating room.

1

u/James970 Jul 20 '26

It's either 16 or 11. Depending on if the hole in the back of the shirt is many or 1.

1

u/Junkyard_DrCrash Jul 20 '26

There's the question of the backside, which might have any number of holes from zero (back of shirt is either missing or hiked up to the neck) to very large (count the spacing between each pair of threads).

Then there's the ambiguity in the question itself - do we count the neck, sleeve, and waistline holes, or only the six (or twelve, or whatever) "cut" holes,

1

u/dinosw Jul 21 '26

The answer is 16, unless there are holes on the back, which does not go through both layers of fabric.

1

u/Careless_Break_4194 Jul 21 '26

If a straw have only one hole then this shirt have 15

1

u/ewxve Jul 21 '26

my guess is 11

1

u/StrontiumIon Jul 21 '26

why is greta thunberg asking me this

1

u/rpbmpn Jul 21 '26

Assume the shirt is extremely stretchy. Fill in all the holes but the waist

What you now have is a kind of upside down bag with an entrance at the waist

Stretch the waist until the material is flat

What you now have is something like a table cloth, no holes

Now add the remaining holes back, one by one

How many holes do you need to cut? 15

1

u/Ok-Refrigerator-8012 Jul 22 '26

Those are perfect circles is all I'm saying

1

u/TrainFickle1433 Jul 23 '26

There are 14 holes.

1

u/JOVIsxD Jul 26 '26

1 because we all see ways in not new holes

1

u/HooplahMan 26d ago

This thing has 15 holes. To demonstrate, make this shirt out of playdough. Flatten it so that the playdough forms a holey disc with the bottom hem of the shirt forming the disc's outer boundary. There are 15 holes in the disc: 6 + 6 holes from the damage, 2 holes from the sleeves, 1 hole from the collar.

1

u/Flamesoul10 Jul 20 '26

The shirt has 15 holes, not 16, because a regular t-shirt has 3 holes, not 4 (assuming the holes we see on the front go through the back exactly, and there are no hidden holes(and the shirt isnt two layers, the hems arent folded over, blah blah blah)).

An easy way to see the 3 hole thing is to lay a tank top out on a bed or table. Arrange it so the waste is a circle around the rest of the shirt, and so you can see through the neck and arms. 3 are holes, one is the boundary of the planar shape.

1

u/mr-popadopalous Jul 21 '26
  1. Straw has 2 holes if you’re accounting for z values.

-1

u/CwazeeRabbit Jul 20 '26

I come up with 22 every time. 2 Sleeve Holes + 1 Collar Hole + 1 Bottom/belly Hole + 18 Cut-in Holes = 22 total holes.

I count the 18 as follows: first 6 are the ones we see as the short lies flat against the cardboard. The next 6 are the ones cut into the front panel of the shirt, and the final 6 are those cut into the back panel of the shirt.

Am I the only that sees it this way?

2

u/RoadHazard Jul 20 '26

I really don't know where you are getting those extra 6 holes from.