Main content

### Course: Math for fun and glory > Unit 1

Lesson 7: Thanksgiving math# Borromean onion rings

Borromean Onion Rings, the perfect way to top your Green Bean Matherole! Borromean onion rings were invented by special guest Marc ten Bosch (http://marctenbosch.com). Also shown are gelatinous cranberry cylinder, bread spheres and butter prism, mathed potatoes, apple pie, and pumpkin tau.
Mathed Potatoes: http://youtu.be/F5RyVWI4Onk
Green Bean Matherole: http://youtu.be/XwIs1nlDQ2I
Turduckenen-duckenen: http://youtu.be/pjrI91J6jOw. Created by Vi Hart.

## Want to join the conversation?

- So is 4D time?

Thanks for all the answers to my question. xD(4 votes)- Not necessarily. You can measure anything you like on any dimension. It is quite common to have three spatial dimensions with time as the 4th, as that is useful when measuring things in our universe. In this context however, I think Vi was referring to a 4th spatial dimension, which would allow you to create the Borromean rings without cutting them.(16 votes)

- Isn't that how the Olympics rings are designed (minus the onion)?(6 votes)
- The Olympic Rings are just 5 rings linked in a line, while these are not actually linked.(6 votes)

- did anyone see on2:02the pi and the tau?(6 votes)
- who's she cooking with at0:11?(5 votes)
- Marc ten Bosch, the 4 dimensional Frenchman who invented the Borromean Onion Rings.(4 votes)

- How come there isn't a video for the cranberry cylinder or the pi and tau pies?(2 votes)
- I would guess there is one, but she didn't post it on Khan Academy. If you search YouTube for "vi hart thanksgiving cranberry cylinder" it should come up. But there might not be one, so don't hold me responsible. I'm not allowed on YouTube, so I couldn't tell you for sure.

--Blue Leaf(3 votes)

- Can you make a mobius strip using onion rings?(3 votes)
- Yes you can! Make it the same way you would make a Mobius strip out of paper -- make a loop and twist it halfway -- then connect it with a toothpick. After you fry your Mobius onion ring, it will stick together and you can remove the toothpick. The final product will hopefully be delicious.

--Blue Leaf(0 votes)

- At1:53, what is a "gelatinous cranberry cylinder"? Dose anyone know how she made it?(2 votes)
- You can buy a can of cranberry in the store. Personally, I don't like it but thats beside the point. When she refers to it as a "gelatinous cranberry cylinder", she is just giving it a fancy, mathematical name.

Hope that helps!*Ben Doucette*(2 votes)

- That actually looks good. What would make it better is if you added garlic (to me it would taste better anyway)?(2 votes)
- how can she move so fast(2 votes)
- So, if you can make them, doesn't that mean they're 3D?(1 vote)
- They are 4D only while you are putting them together. Once they are completed, however, they are 3D(3 votes)

## Video transcript

So say your vector field green
bean casserole is in the oven, and now it's time to think about
a nice, crispy onion topping. Normal people might
just use, for instance, French's French fried
onions in a can, put super awesome people
use a real French person, and real fresh onions, to make
their own fresh onion toroids. And they fry free linked
with the Brunnian property to get Borromean onion rings. The Borromean rings
show up in many forms, they come flat and in 3D,
round, rectangly, triangly. But, the important thing is
not the way the rings appear, but the way they are
connected to each other. The thing about
the Borromean rings is that no two of the rings
are actually linked together. Ignore the pink and look at
just the green and brown. They're sitting on top of
each other, not linked. And if you just look
at the green and pink, or pink and brown,
it's the same thing. And yet, all three together
are linked inseparably. So to make your Borromean
rings out of onion rings, you will have to cut
one of your rings and then fasten it back together
with a toothpick or something, which can be removed
after frying. Or you can use the
fourth dimension. And luckily I have a
four-dimensional guest to help me out. If you're stuck in
three dimensions, you can think of it like this. Here I've got an outside
ring and an inside ring. Now, the third ring
which I have cut, is going to go outside
of the outside ring, but inside of the inside ring. Each ring is wholly out of, and
wholly inside of the other two rings so that no two are
linked, but all three are. You can also think of laying
two on each other flat, one on top of the other. And then having the
third weave through them, so that it goes
over the one on top, and under the one on bottom. The result can be made to be
flatter or more spherical, in some you can see the
relationship that Borromean rings have with braids. Sure the orange,
yellow, and red ribbons are all twisted together,
but no two strands are twisted together. If I pull out the orange one,
the other two fall apart. Some people and
cultures and stuff think of this
togetherness property as a metaphor for unity. So when you eat
Borromean onion rings, you get to feel all
deep and symbolic. But don't forget to
save enough to put on top of your green
bean matherole. And there we go. At this point I've got a
gelatinous cranberry cylinder, bread spheres with butter prism,
masked potatoes, a vector field green bean matherole with
Borromean onion rings, apple pie, and pumpkin tau. All I need is a
double helix cut ham, and of course, the
crowning glory of this feast which I will tell
you about next time.