Gaussian Curvature and its Practical Consequences

Wired has a very cool article about manifolds and curvature.

I have used ice cream cones (and the act of unrolling them) to help explain curved versus straight geodesics for one of the problems our student had to do in calculus of variations. I then "assigned" my students to do this the next time they went to the local ice cream place.

(Tip of the cap to Jeremy Kun.)