Dave Richesonさんのイラストまとめ

In her @G4GCelebration talk Doris Schattschneider shared the link to the web app "[John H.] Conway's Magic Pen," which allows you to generate various tilings such as this one. She was the mathematical consultant behind it. https://t.co/yNBrgSXYWI

For a function of one variable there's a test called ``the only critical point in town.'' It says that if a differentiable function has only one critical point and it's a local max (or min), then it's a global max (min) (proof: Rolle's Theorem). However, as these images and [1/2]

Took this old NY Times 25-question language quiz. It correctly identified my home town—Rochester—where I haven't lived in 30+ years. Most distinctive answer: "What do you call the rubber-soled shoes worn in gym class or for athletic activities?" Sneakers.
https://t.co/a5vSK2bZpN

TIL about Hilma af Klint (1862–1944), a Swedish artist who was painting abstracts before Kandinsky, Mondrian, etc. What caught my eye was the geometric images in some of them—cubes, spirals, circles, etc. Beautiful!

Two Sierpinski curves of order 4. Continuing the iterations, these curves would limit on the filled-in square and the Sierpinski triangle. https://t.co/6VUNu6poJ1

Applied topology: in 2007 de Silva and @robertghrist discuss how to use homology to detect holes in coverage in a network of small, scattered, local sensors. https://t.co/vmAJyFcEDP

In particular, if you take the inverse image of a circle of latitude on S^2, you get a torus in S^3. The preimage of each point on the circle is a Villarceau circle on the torus like one of the metal rings in the previous photo. 5/7

Today's rabbit hole: I've been reading about homotopy groups of spheres, the Hopf fibration, etc. Homotopy groups are a way of describing how spheres of one dimension can be mapped into spheres of other dimensions. The first homotopy group, the fundamental group, is easy to 1/7

TIL about Dandelin spheres. These spheres are tangent to both a cone and a plane. The spheres intersect the plane at the foci/focus of the conic section formed by the intersection of the plane and the cone.

Thanks, @PaulaKrieg for suggesting gluing instead of taping. I've added tabs to my template for making your own paper real projective plane: https://t.co/Ay8JVJY4gL