How to Slice a Bagel into Two Linked Halves (2009)

http://www.georgehart.com/bagel/bagel.html

by _xs0j • 8 years ago

415 61 8 years ago

I didn’t know what I was getting into with that click, but now I’ve added bagels to our grocery list so I can do this.

Bagel, lox, cucumber and cream cheese has become my new favorite thing lately (bonus points for a squeeze of lemon, capers or some red onion if those things are to be found).

However, I of course have no bagels or bagel accessories on the one day I read about mathematically correct bagels :(

So yeah, added to my grocery list too!

geoffreyhale• 8 years ago

That was my dinner of choice throughout childhood. Love it still.

troysandal• 8 years ago

This is the best article ever posted to Hacker News.

pvorb• 8 years ago

Sharing stories like these with the world is what the world wide web was made for.

mabbo• 8 years ago

I wonder if it's possible to repeat the process in such a way that you make a chain. I'm trying to visualize how but I'm not certain whether it could only make more links all attached in the same place.

cwmma• 8 years ago

you'd need a very thick bagel

rcthompson• 8 years ago

I believe every link would be linked to every other link.

delecti2• 8 years ago

Not necessarily. Just as you could take a chain and stack the links such that the holes lined up, with enough precision, and a strong enough baked good, you could cut the bagel such that there were a chain of linked rings.

ihaveajob6• 8 years ago

Exercise to the reader: How do you slice the bagel so that you can spread cream cheese continuously along both sides. In other words, can you make a Möbious bagel?

jcoffland• 8 years ago

Leave it uncut. It already has a continuous surface.

ihaveajob6• 8 years ago

But then you can't spread on the soft side.

ihaveajob6• 8 years ago

I should document this and make it my first HN post.

dumbfounder• 8 years ago

Don't you have a job?

sp3322• 8 years ago

Yeah, I think you can just make a half-twist instead of a full twist like the article does. Or any number of full turns + 1/2.

wlesieutre2• 8 years ago

Make a cut through it shaped like a mobius strip - that is, a single 180 degree rotation instead of going the whole 360 degrees shown here.

To think about it another way, imagine if you took a mobius strip and constructed a semicircular lump of bread on the surface, extending it around until it connects back to itself. You've made a bagel!

Now take the mobius strip out of the middle, and the gap it leaves is the cut you're asking to make.

jnordwick2• 8 years ago

Sounds like a job for some parchment and my weekend.

I wonder if I could sell bagel-sized silicone mobius strips for baking.

pbhjpbhj• 8 years ago

I definitely saw a Mobious bagel on Youtube, perhaps about 5 years ago - my attempt to copy it failed, my bagel was too soft.

epistasis• 8 years ago

Haven't attempted or vetted yet, but perhaps this? https://m.youtube.com/watch?v=NRvK_07KRV8

jmgrosen• 8 years ago

This article is the best thing since sliced bread.

mi100hael• 8 years ago

OUT.

hmate9• 8 years ago

I never knew I needed this information. I’m gonna go buy some bagels now.

hawktheslayer2• 8 years ago

My team at work thinks of every excuse possible to get bagels. Recently for a birthday, a work anniversary, and being restacked into new cubes. But this is the best possible excuse for bringing in bagels again on Monday.

Declanomous• 8 years ago

The resulting workers comp report when someone slices their hand is going to be really interesting.

hawktheslayer2• 8 years ago

Of course if we could make a bagel cutter in the spirit of the popular bagel guillotine slicer that cuts a linked bagel we could be millonaires.

phkahler• 8 years ago

Don't share it. Just wait until the next batch comes in and then cut a few like this while no one is watching.

tzahola3• 8 years ago

Now do it with a mug.

ihaveajob6• 8 years ago

All the pictures in that link already show a mug.

delecti2• 8 years ago

A mug is topologically equivalent to a bagel or donut or torus.

tzahola3• 8 years ago

T-topologically w-what??

I mean yeah, that was the point of my remark.

To write something on topic as well:

There was a fun little challenge on puzzles.stackexchange I think, which relied on the same construction as this article. I couldn’t find it, but it went like this:

“You’re stuck on top of a tall building with nothing but a saw. There’s a ladder fastened to the side of the building, but it’s unfortunately not long enough to reach the ground; in fact it goes about half the height of the building from the top. Challenge is to get on the ground “safely”. You can cut into the ladder with your saw in any way you like and you can assume that the resulting pieces will be rigid, but won’t break under load.”

yeukhon• 8 years ago

Is it a sin to put pineapple on it?

Someone please ask Professor Shewchuk (UC Berkeley) and Professor Demaine (MIT) to look at this! Perfect geometric problem for both of them.

sizzzzlerz• 8 years ago

Clearly, a candidate for inclusion in one of the fine academic journals on mathematics. Or the Martha Bakes cookbook.

Either way, bravo!

joncrane• 8 years ago

It turns out there's a sequel! http://www.georgehart.com/bagel/knot.html

DrScump• 8 years ago

"Waiter, my bagel has black magic marker all over it. I think I'll just have the omelette instead."

jweather• 8 years ago

Numberphile video on this topic, including 3d-printed examples of some higher-order slicings: https://www.youtube.com/watch?v=3_VydFQmtZ8

Whitespace• 8 years ago

Here's George Hart's daughter Vi Hart making a Mexihexaflexagon, which is a kind of three-sided flat quesadilla: https://www.youtube.com/watch?v=GTwrVAbV56o

That family must have the best picnics!

sp3322• 8 years ago

Here's a short series on math-based Thanksgiving foods. https://www.youtube.com/watch?v=F5RyVWI4Onk&list=PLaNzoFtkQ7... It's hard to know where to stop recommending Vi Hart projects, I find them consistently cool and fascinating, so I'll just mention her blog http://vihart.com/ and Patreon https://www.patreon.com/vihart

kakarot• 8 years ago

Hexaflexagons are great and Vi Hart is great. Nice share.

netcraft• 8 years ago

ah, I never put it together that they were related! That would be a fun family.

tritium2• 8 years ago

The manner of delivery is reminiscent of Steve “Protopod” Sutton’s [0] famous iced tea video. [1]

[0] https://www.youtube.com/user/protopod

[1] https://www.youtube.com/watch?v=hSkT77010fE

earenndil• 8 years ago

I prefer his other daughter, Vim Hart.

qrbLPHiKpiux• 8 years ago

Video tutorial please.

julioneander• 8 years ago

There's an addendum at the bottom of the page linking to a how-to video: http://www.youtube.com/watch?v=dN8AwGUaqDA

eschneider• 8 years ago

I'd rather just have a mimosa. :/

gowld• 8 years ago

I've tried never been able to achieve this with my hands and knives.

tkahnoski• 8 years ago

Just had a brief discussion at work about bagels that started with a complaint about how they're never sliced all the way through.

After a couple minutes of back and forth an epiphany was realized that if they were pre-cut all the way through they'd get jumbled up and then we'd spend way too much time rifling through halves to find a matching one.

blurbleblurble• 8 years ago

Villarceau circles!

https://en.wikipedia.org/wiki/Villarceau_circles

JacobHenner• 8 years ago

Video of the process: https://www.youtube.com/watch?v=2T5FrZl04JY

How to Slice a Bagel into Two Linked Halves (2009)

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