The Mobius Bagel

The mathematical field of topology—the study of qualitative properties of certain objects that are invariant under certain kind of transformations—has fascinated me ever since I heard the joke that topologists can’t tell the coffee cup from which they are drinking from the doughnut they are eating.

(Okay, I admit it’s not a funny joke. But I’m a sucker for mathematical humor. And donuts.)

Now a professor and artist George Hart has shown how to cut a bagel into a Mobius strip: two congruent, linked halves—they “pass through each other’s holes, like two links of a chain.”

Hart provides step-by-step instructions for how, using a single knife cut, you can transform an ordinary bagel into a topological marvel. And the best part? “[Y]ou get more cream cheese, because there is slightly more surface area.”

(Via: Serious Eats” New York )

Update: In the comments, Beatrix points out that the bagels aren’t a Mobius strip after all but rather “a pair of linked annuli, each with a full twist. a mobius strip has a half-twist only. if this were a mobius strip, one could not spread cream cheese on one side.” Also, over on Postmodern Conservative, uber-math nerd Will Wilson has more topological goodness .