this post was submitted on 04 Jul 2023
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At work we somehow landed on the topic of how many holes a human has, which then evolved into a heated discussion on the classic question of how many holes does a straw have.

I think it's two, but some people are convinced that it's one, which I just don't understand. What are your thoughts?

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[–] [email protected] 3 points 1 year ago

If you make the straw less long, it’s a donut. And a donut obviously has 1 hole. So a long donut only has one hole. Q.E.D

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

1 'hole' if you can call it that. Imagine if the straw started life as a solid cylinder and you had to bore out the inside to turn it into a straw: if that were the case, you would drill 1 hole all the way through it.

Another analogy is a donut. Would you agree that a donut has just 1 hole? I would say yes. Now stretch that donut vertically untill you have a giant cylinder with a hole in the middle. That's basically now just a straw. The fact you stretched it doesn't increase the number of holes it has.

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

So as you begin to bore, that is one hole. But when you go through the other side, you have in fact made two holes. I think a donut can actually be thought of either as one hole or two holes, or more correctly; two holes that are the same hole.

Back to the straw; if you make another hole in the side of the straw half way up, would it still have one hole? Or two holes? Or three holes?

A bit like thinking of the human digestive tract, most of us would agree that your mouth is a different hole to your anus, but we agree that they are in two ends of the same system

[–] [email protected] 0 points 1 year ago (1 children)

Imagine if the straw started life as a solid cylinder and you had to bore out the inside to turn it into a straw

This would mean a straw has a hole, yes. It would be like a donut indeed - donuts are first whole, then have the hole punched out of them. This meets a dictionary definition of a hole (a perforation). A subtractive process has removed an area, leaving a hole.

But straws aren't manufactured this way, their solid bits are additively formed around the empty area. I personally don't think this meets the definition.

Your topological argument is strong though - both a donut and straw share the same topological feature, but when we use these math abstractions, things can be a bit weird. For instance, a hollow torus (imagine a creme-filled donut that has not yet had its shell penetrated to fill it) has two holes. One might not expect this since it looks like it still only obviously has one, but the "inner torus" consisting of negative space (that represents the hollow) is itself a valid topological hole as well.

[–] [email protected] 0 points 1 year ago* (last edited 1 year ago) (1 children)

On the matter of the doughnut: If you make them at home, you're almost always just rolling a cylinder and then making it a circle. I have never actually punched a hole out of a doughnut. That would mess up the toroidal shape.

But also: So you're saying a straw has 0 holes?

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

Maybe she's not, but I am. An intact straw has zero holes. If you stick a pin in the side, it has one. If you stick a pin all the way through, it has two.

[–] [email protected] 2 points 1 year ago

Classic topology question. Absolutely one hole; it goes all the way through.

Of course, connotatively, two is a fine assessment, but not in topology.

How many holes does a donut have? Now just try to image the real difference between a straw and a donut. Is there one, aside from deliciousness?

[–] [email protected] 2 points 1 year ago

How many holes does a donut have?

Now make the donut higher. A lot higher. Now you have a donut-tunnel. Now make the walls thinner. Now shrink it. Now you have a straw.

One hole.

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

It's just one long hole.

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

Does a doughnut have two holes?

Because a straw is just an elongated doughnut.

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

Mathematically It's one. Think of a disk, like a CD, does it have one hole or two? One, right? Now imagine you can make it thicker, I.e. increase the height, and then reduce the outer radius... Making it progressively more straw-like. At what point does it stop having 1 hole and begin to have 2?

Topologically they're the same shape.

I'm sure Matt Parker has a video on this topic in YouTube. Here

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

The specific field is topology fyi

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

A regular straw has zero holes. The central cavity, through which beverages flow, is not part of the straw, and hence it's endpoints are not holes in the straw.

[–] [email protected] 3 points 1 year ago (1 children)

A straw is topologically the same as a donut. It absolutely has one hole.

[–] [email protected] 0 points 1 year ago (1 children)

It has two exits, one hole.

If you drill a hole in a block of wood you create one hole not two, note that whether or not the drill exits the opposite side, only one hole has been created despite differing numbers of exits.

[–] [email protected] 0 points 1 year ago (1 children)

What if you drill through a book?

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

You'll be banned from the bookstore

[–] [email protected] 0 points 1 year ago (1 children)

A straw is geometrically the same as a circular piece of paper with a z depth of zero and a hole in the middle. Because the z depth is zero there is only one hole. As you add thickness the one hole remains. Therefore, a straw has one hole.

[–] [email protected] 0 points 1 year ago (2 children)

so, using this logic, how many holes does a human have? 2? 2 1/2?

[–] [email protected] 0 points 1 year ago (1 children)
  1. Two ears, two eyes, two nostrils, one mouth, all connected to the anus.
[–] [email protected] 0 points 1 year ago (1 children)

ears? tell me this story...

[–] [email protected] 0 points 1 year ago (1 children)

You have to rip through a membrane unless you've had tubes implanted for the ears I think?

[–] [email protected] 0 points 1 year ago (1 children)

Yes I google it and discovered my mistake

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

I'm a weirdo who learned how to 'click' their ears (opening eustachian tubes on demand) on their own possibly before Google existed, and have done a little research between now and then :p

[–] [email protected] 0 points 1 year ago (1 children)

one hole is going through the straw

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

No it's two holes

[–] [email protected] 0 points 1 year ago (1 children)
[–] [email protected] -1 points 1 year ago

Then how does the liquid go through it

[–] [email protected] 0 points 1 year ago (1 children)

By the logic of most of the comments in here, does this mean most people are wrong when they say they are digging a hole???

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

I'm Diggy Diggy crater