Fix your floppy pizza slice with Gaussian curvature


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Yay, I love Numberphile videos !!

This one on Graham’s number is one of my favorites:

(Computerphile is also awesome)


As an engineer and mathematician, this seemed a bit convoluted. And kind of neglects that pizza bends in explaining why folding pizza doesn’t bend. Easier to just say you are increasing the area moment of inertia of the beam. i.e. Thin stuff flexes, thick stuff not as much. You could hold pizza sideways and do even better. We just fold it so stuff doesn’t fall off.

Making things thicker (and stiffer) without making them heavier is why I-beams are I beam shaped. The farther you get stuff from the middle, the stiffer the the beam will be.


Try cutting up some paper and taping it together in positive, negative, and zero curvature configurations. Thickness may be important in I beams, but in the regime of mostly-planar, flexible items it doesn’t seem to do much.


Now you’re halfway to getting the joke in this XKCD comic.

That one made a definite fan. Though it DID take an hour and a half of online research to finally get the punchline.


Doesn’t everyone fold their pizza in half to stop it drooping? I thought this was just obvious - in the way that throwing a ball is obvious but if you think about it from a math/physics perspective it’s crazy-complicated. I always fold my pizza in half if it’s sloppy. Or I use a knife and fork - I know, I know, horrors!


Hey - thanks! I assume it’s obvious that I was having fun in m’kitchen.

Afterwards, I realized that I hadn’t defined the principal curvatures – showing that I’m more of a physicist than mathematician.


Every single person in New York City has been doing this since the Dawn of Mozzarella, and a fair number of them are mathematicians.


That alt-text got me.

I just spent two and a half weeks in Utah, and I was sorely tempted to find some temple garments to walk around in. Clearly visible under a croptop and booty shorts.

Of course I have a figure roughly resembling Jabba the Hutt, so, all the more fun in the prank.


We New Yorkers feel this geometrical property viscerally.


Thankfully we haven’t had a Chicogoan in here yet to try to rewrite the laws of pizza, or give a mathematical “proof”.



Or you do a less common maneuver that a friend of mine loves, place two slices cheese-to-cheese and eat it like a sandwich.


Not often, no.

Good pizza doesn’t droop.


just use a knife and fork like a civilized person!


Is he some kind of socialist?


Yes, a knife and fork. And a plate. However, approximately three centimeters from the edge, I switch to by-hand. After cutting the eighth (or whateverth) of a pizza in half, along a radius:

Doesn’t everyone eat pizza this way?


Oh, that’s not right.


We have a local pizza joint that’s somewhere between what most people call pizza, and a Chicago deep-dish. Eating with a fork is a given, as folding it would make it too large for most people’s mouths.


Now, Chicago deep-dish, that I eat by hand. :smirk: