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Henry Segerman @henryseg@mathstodon.xyz

An optical illusion, made with a spherical ("360") camera. With Alexa Meade and Dan Ariely. youtu.be/EahZSQmcs_s mathstodon.xyz/media/TJODzd57-

I have been playing at generating snowflakes using cellular automata.

Just in time for Christmas (if they're into this kind of thing), a new kind of expanding mechanism! shpws.me/Pi30 . More info: youtu.be/bEVHVzrQ_PM

Sneak preview of a mechanism project I’ve been working on for a while.
mathstodon.xyz/media/xo09DAkqb

Send/Receive

Stereographic projection of the latitude/longitude grid on the sphere.

Source code: community.wolfram.com/groups/- mathstodon.xyz/media/6W6BEU7iT

New @numberphile video up with me talking about - you guessed it - juggling: youtube.com/watch?v=7dwgusHjA0 - 45 minutes, over 2k views. Wow!

And finally, the dramatic conclusion to my series on Heesch numbers: does there exist a convex pentagon that can be surrounded, but doesn't tile the plane, and admits a surround that's edge-to-edge? Heesch's original 1968 shape does all of the above except the edge-to-edge part. isohedral.ca/heesch-numbers-pa mathstodon.xyz/media/a0bUlDZY_

The story of Heesch numbers continues in two posts. In isohedral.ca/heesch-numbers-pa, I compute Heesch numbers of polyominoes and polyiamonds in search of interesting new examples; in isohedral.ca/heesch-numbers-pa, I present a new family of simple polygons, all with Heesch number 1.

I had to reconstruct this gif by Bill Gosper in GeoGebra to believe it.
Construct the tangent to a given point on a circle without using a compass.

ggbm.at/GJAkqvTb mathstodon.xyz/media/ekv6ASMGa

Matt Parker made a video about our Brilliant Geometry exhibition in Edinburgh: youtube.com/watch?v=LOVzytir7b

Intertwine

Stereographic projection of 30 congruent spheres centered on equally-spaced points along a trefoil knot in the 3-sphere.

Source code: community.wolfram.com/groups/- mathstodon.xyz/media/WZXefyrbf

Topographical topology at the Arches National Park in Utah! youtu.be/-1_VYcJGvKU

Time to justify my presence here...

The Heesch number of a shape is the maximum number of layers of copies of that shape by which you can surround it. Heesch's Problem asks which positive integers can be Heesch numbers. I'll show a few fun new results over a series of blog posts; today, I offer a basic introduction to the topic. isohedral.ca/heesch-numbers-pa

mathstodon.xyz/media/qc0LaKFTr

Come spend a semester illustrating mathematics with us, Fall 2019 at ICERM! icerm.brown.edu/programs/sp-f1

Here's one of the default fractals from the fractal explorer I just tooted, entitled "Sponge": mathstodon.xyz/media/bKKj6ruFA