
How to Slice a Bagel into Two Linked Halves (2009) - jakegarelick
http://www.georgehart.com/bagel/bagel.html
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Whitespace
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](https://www.youtube.com/watch?v=GTwrVAbV56o)

That family must have the best picnics!

~~~
sp332
Here's a short series on math-based Thanksgiving foods.
[https://www.youtube.com/watch?v=F5RyVWI4Onk&list=PLaNzoFtkQ7...](https://www.youtube.com/watch?v=F5RyVWI4Onk&list=PLaNzoFtkQ7rZo-
HKloTHnhpimhfEzDlFl) 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/](http://vihart.com/) and Patreon
[https://www.patreon.com/vihart](https://www.patreon.com/vihart)

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joncrane
It turns out there's a sequel!
[http://www.georgehart.com/bagel/knot.html](http://www.georgehart.com/bagel/knot.html)

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

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ihaveajob
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?

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jcoffland
Leave it uncut. It already has a continuous surface.

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

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Splines
Lazy answer: Cut it almost in half and leave it connected. Fold hinge around.

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ihaveajob
Clever.

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troysandal
This is the best article ever posted to Hacker News.

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

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hawktheslayer
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.

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

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hawktheslayer
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.

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needcaffeine
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.

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curiousGambler
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!

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

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

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mabbo
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.

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

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delecti
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.

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tritium
Well, if you cut the bagel according to this particular linked torodial
method, to produce two links, you’d then be able to perform the traditional
bagel slice on one of the linked halves, and that would produce a chain with
three links...

But deriving from a single original torus, a chain with an arbitrary or
infinite number of links, whereby each individual link is bound to no more
than two other links? I’ll have to think about that one...

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tkahnoski
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.

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

Either way, bravo!

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hmate9
I never knew I needed this information. I’m gonna go buy some bagels now.

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JacobHenner
Video of the process:
[https://www.youtube.com/watch?v=2T5FrZl04JY](https://www.youtube.com/watch?v=2T5FrZl04JY)

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macawfish
Villarceau circles!

[https://en.wikipedia.org/wiki/Villarceau_circles](https://en.wikipedia.org/wiki/Villarceau_circles)

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yeukhon
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.

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

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tzahola
Now do it with a mug.

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

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tzahola
_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.”

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chopin
As far as I can tell this challenge would not require a twisted cut.

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tzahola
Please elaborate!

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Crespyl
I think it would be possible to slice the ladder exactly in half, down its
length, right?

Each rung would go from a cylinder to a half-cylinder, but should still be
rigidly connected to either side of the ladder all the same.

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Retra
The problem is then you have two short ladders. You throw your two half
ladders off the roof and they don't magically stand end-to-end for you. You
have to cut with a twist to ensure the last rungs are entangled with each
other so the half-ladders are hooked together. Then you can hang one off the
other and reach the ground.

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Crespyl
See I was envisioning one of these:
[http://www.bates.co.za/BMS_Product_Images/ROUND%20TUBE%20LAD...](http://www.bates.co.za/BMS_Product_Images/ROUND%20TUBE%20LADDER%20C-W%20HOOKS%202.5M.jpg)

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eschneider
I'd rather just have a mimosa. :/

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jmgrosen
This article is the best thing since sliced bread.

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mi100hael
OUT.

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qrbLPHiKpiux
Video tutorial please.

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

