How Many Holes Does A Straw Have? The Correct Answer Explained

This question has generated a lot of debate online. BuzzFeed's video has 450,000+ views already. But the question has a mathematical interpretation with a correct answer: in topology, how many holes does a straw have? I explain and animate the answer in the video. It's great to see topology go viral!

My blog post for this video

BuzzFeedVideo

Drinking Straws: How Many Holes? Kevin Knudson, professor of mathematics at the University of Florida

2016 Nobel Prize in Physics

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[MindYourDecisions]

Happy 2 year anniversary! At the time my channel was very small and people asked why I would even make a video, so let me share the history. The topic was trending and Buzzfeed posted a reaction video that racked up 450, 000 views. I thought the topic was a great way to teach some math and topology. It is now 2 years later...Buzzfeed's video has 566, 000 views, my video has 800, 000 views, and a video by VSauce on the topic is trending right now with over 3 million views (search for how many holes does a human have). It is often said math is not popular, but it seems math and science are Buzzworthy topics after all!

[milandavid]

I think the main confusion comes from the fact that "hole" can mean different things.
If you think about a hole as an opening, it's 2
If you think about a hole as a tunnel, it's 1
If you think about a hole as a defect, it's 0.
Of course mathematically there's 1 hole.

[Querez]

Before I watch: one.

After I watch: yes

[iHoRst-duvv]

1903: i bet there will be flying cars in the future
2018: how many holes does a straw have?

[LimeGreenTeknii]

Here's how I explain it: A donut has one hole, right? Imagine you could stretch a donut so it's taller so that it looks like a straw. If you believe a donut has one hole and a straw has two holes, at some point when you stretch that donut, it must go from having one hole to two, which doesn't make much sense.

[NA-ckcz]

Never thought a straw could stir such a philosophical conversation

[dellmix]

Normal person: 2 holes
Mathematician: 1 hole
Philosopher: 0 holes

[billvojtech]

I've listened to 1:56 and have this to say: It depends on your definition of "hole" and of "straw." If you start with a rod and drill a hole through its center along its long axis, then it has one hole, (like a reusable metal drinking straw). If the straw is formed by winding a flat material in a spiral and glueing the edges where they meet, (as in a paper drinking straw), you could say it has no holes.

[garychap]

Here's ALL the correct answers :

Straws have one hole, topographically speaking - but only because, in the field of topology, a hole has a very specific meaning and we're considering the straw to be an ideal mathematical surface (which it clearly isn't)

Then there's semantics... one can dig a hole in the ground but it is not (topographically speaking) a hole - however it IS still a hole according to the english language. How many of these non-topological holes a straw has is merely a question of scale... since the surface of a straw is not an ideal surface. So, the answer is likely to be between zero and trillions.

Then there's the functional answer. Having defined the object to be a straw - how many holes does the STRAW have? None... it is a perfect straw. If it had a hole it wouldn't work very well. This is a logical statement based upon types, equivalent to asking whether a bicycles inner tube has a hole in it ... the concept of the item itself establishes the baseline of form, and this ideal conceptual form is then compared to the item under test.

Then there's the material sciences answer. A straw has enough tiny (and, indeed, also properly topological) holes in it to lose water/gas molecules by osmosis, so again the answer is trillions. This IS still a topological answer, but one properly recognising that the straw is NOT some ideal mathematical surface as those weird beardy mathemagicians would have you believe.

Then there's a pragmatic materialists answer... there IS no straw, just a collection of atoms which are held in proximity but never touch. The concept of holes cannot be reconciled with this view.

Which brings us neatly to the Zen answer: Mu!


Clearly one needs to first :

- define a straw that we can all agree on.
- define a hole that we all can agree on.
- define a scale that we can all agree on.

Only then, can a proper answer be attempted.

To hold out that a hole is a strictly topographic feature and that we should imagine a straw to be an ideal surface - is a cartoonish simplification. Similarly, one could establish how many sheep can fit in a field by first considering all sheep to be perfect spheres...

... by doing so, we answer an *entirely different question* - and usually one which is more comfortable to work on.

But yes, I'd also default to claiming that a straw only has one hole... and, probably, later get arrested for brawling with pragmatists in the car park.

[potatomanW]

I explain it like this. If you cut a hole in a paper it makes one hole. It you thicken the paper, say a block of wood and cut a hole, there will still be one hole. So a straw is basically a super tall but skinny piece of paper with 1 hole.

[singhanmolpreet]

It also depends on how you define a hole.

[jamesnabors]

From a manufacturing standpoint, a paper straw has zero holes. It is a rhombus spindled around a cylinder and glued into place. The rhombus remains intact, thus no holes.

[colorad]

Wait-wait-wait
Do you really expect Buzzfeed to do something reasonable?

[syver]

0 holes proof: "Waiter! My Straw has a hole in it!" - Waiter brings new straw. Q.E.D.

[RJTheBikeGuy]

If I have a piece of wood, and drill a hole through it, it has one hole. If I carve the outside of the wood down until it's a tube (a straw), it still only has one hole. Not too complicated.

[robertheal]

The reason why people "debate" about it, is because it is a debate about the meaning of language words, which is defined by the people, and not by experts. What is a "hole", anyway.

[FlamingFoxProd]

Me at 2 AM: I need to go to sleep

My brain: No, you need to find out how many holes a straw has

[tamlynburleigh]

My first thought was to define a hole. It must have some height, so any solid with a change in surface height downwards must be a hole. After that I struggled with all sorts of counter definitions. It was a really interesting exercise. Thanks.

[sadhlife]

Does this mean that if i fold a piece of paper into a cylinder and tape it, I've just made a hole in it?

[heinenrby]

I think much disagreement comes from how hole is defined in regular language and how it is defined in mathematics. In real life you can dig a hole in the dirt, but a mathematician would say it is not a hole, but an insignificant dent. Likewise the interpretation of the word hole can lead to disagreement in this conundrum.

But the straw has 1 mathematical hole, that is for sure.