How to Slice a Bagel into Two Linked Halves | Hacker News Reader

How to Slice a Bagel into Two Linked Halves

georgehart.com

198 pointsmsvan34 comments

Neat, but academic, because as everyone undoubtedly knows slicing bagel into a Mobius strip is far more practical. Not only does it give you a surface for jam-and-buttering, but also keeps the construct in a single piece ensuring an unbeatable simplicity and predictability of the user experience. It's the same technique as in the article, but the knife needs to rotate at the half of its angular speed as it goes along bagel's diameter.

The OP structure can be reassembled into a sandwhich after dressing. Key feature.

Not only does it give you a surface for jam-and-buttering...

Yeah, but if you drop it on the floor it is guaranteed to land jam-side-down 100% of the time.

It will fall jam side down 100% of the time even if it's not a Mobius strip. It's the law.

> It is much more fun to put cream cheese on these bagels than on an ordinary bagel. In additional to the intellectual stimulation, you get more cream cheese, because there is slightly more surface area.

I believe this is winning on all fronts here.

trivia: vi hart is child of george hart. i guess awesome runs in that family.

And Erik Demaine is the son of the prodigal Martin Demaine. It seems that some mathematicians are good at communicating their passion to their children.

This construction shows Villarceau circles[1], which are the nontrivial circle sections of a torus. This can be also seen on the POV raytracer hall of fame[2].

    [1]: http://en.wikipedia.org/wiki/Villarceau_circles
    [2]: http://hof.povray.org/Villarceau_Circles-CSG.html

Oh man, if ever I lose my wedding ring, I know what I'm going to commission to replace it.

And they say topology is useless!

We expanded the utilty from teacups and donuts to now include bagels!

I have a number of friends who are middle and high school math teachers. I have asked them to demonstrate this for their students and report back on how utterly blown their students' minds are.

Stuff like this makes me wish I had continued on the path of becoming a math teacher myself rather than returning to the world of software.

The rest of George Hart's site is interesting as well, especially his encyclopedia of virtual polyhedra [1]. There is also a part 2 of "Mathematically Correct Breakfast" (this time a trefoil knot) [2], and his sculptures are worth looking at as well [3].

[1] http://www.georgehart.com/virtual-polyhedra/vp.html

[2] http://www.georgehart.com/bagel/knot.html

[3] http://www.georgehart.com/sculpture/sculpture.html

Previous discussions:

http://news.ycombinator.com/item?id=982249 http://news.ycombinator.com/item?id=1234503 http://news.ycombinator.com/item?id=1967930

This story has allotted a total of 656 karma, interesting.

I felt a great disturbance in the Force, as if millions of bagels suddenly cried out in terror, and were suddenly silenced.

> … and were suddenly silenced.

You misspelt 'sliced'.

Now if they could bake them like this, I could see that fad taking off...

I suspect you could bake two interlocked bagel rings with a little help from a baking sheet that had angled U-shaped cutouts. You'd mold the rings while the dough was soft, and the baking sheet would help support the rings, as separate but interlocked, during baking. (To me, this feels like less of a challenge than the cutting trick.)

That won’t work, as the dough isn’t soft enough before it is baked. By that time, the dough has been shaped, risen for 36 hours and boiled. Baking is a pretty minor step in the process.

http://www.genuineideas.com/ArticlesIndex/bagels.html

Presumably, OP meant pre-boiling.

I don’t see how that could work. You’d either have to split the bagels before boiling, which would turn them into Frankenbagels while boiling, or you’d have to forego the boiling step, which would make it a roll with a hole – not a bagel.

Thanks for the reference... seems the proper accessory would need to be something that helps hold the two in the proper position through rising/boiling. Maybe something in high-temperature silicone? (And yes, it'd certainly force a different hole-to-ring proportion...) Needs experiments!

Sure, that could work. I think it comes down to the definition of a bagel. Most bagels you can buy in the store don't meet my definition, that's partially why this exercise is so challenging for me. I will definitely try to find a solution, though. The idea appeals to me.

—Ashkenazi Jew, my grandmother taught me how to make bagels. It's quite a process, when done properly.

Been waiting for somebody to explain how that could be possible.

Normally you take a knife slice a bagel down the middle and you end up with 2 half's but part of that action ends up cutting both sides of the hole at the same time.

Instead take a knife cut to the center but not the other side then as you cut around the edge rotate the cut so by the time your around the full bagel the knife is upside down. If you picture it at one point knife handle is on the above the bagel and after a little while it's below the bagel. The only trick is to make you cut line up when your done.

Great. Now I have the urge to dissect bagels at 2 AM :)

I have tried these cuts a dozen times, never with success. What kind of knife/dough do you need to make clean cuts? 10 year olds can do it in two tries, why can't I?

Missed the Hacker News on this one ..

I know I'm not heavily karma'd and so my opinion counts for less, but this isn't the sort of thing I'm expecting on HN. This belongs over in Reddit (where I promise I'll still see it .. probably reposted a dozen times)

This technique has been posted before on reddit already many many times. It definitely shouldn't be here.

Not everyone who reads HN reads reddit.

The Internet is a much bigger place than some people realize.

title: Includes phrase 'Mathematically Correct'

submission title: Includes phrase 'Linked'

Contains everything necessary for hip pseudo-hacker karma.

"Please don't submit comments complaining that a submission is inappropriate for the site." http://ycombinator.com/newsguidelines.html

Complaining is just noise.

Thanks for pointing me to those.

I also missed this one: > If your account is less than a year old, please don't submit comments saying that HN is turning into Reddit. (It's a common semi-noob illusion.)

I'm only up to 326 days, so I'll go back to my corner and apologize (genuinely) for not being aware of these rules.

Though I still don't think it belongs here ;-D

Check the What to Post guidelines again: "anything that gratifies one's intellectual curiosity"

http://ycombinator.com/newsguidelines.html

Reply on news.ycombinator.com