When drawing train track diagrams in geometric topology, it's important to get the signals right so your trains don't crash into each other.

"Squaring the circle" illusion. This one is a vertical format video, trying out YouTube shorts. youtube.com/shorts/KYMYshbhKcw

it's kind of funny how there's a bunch of mathematical problems of the form "a collection of death row prisoners are given the ability to to free themselves by doing X"

Hilbert's space filling curve evaluated at 2048 uniformly random points.

A less symmetric cyclic scissor grid. I like the way this one winds around as it furls and unfurls! Joint work with Kyle VanDeventer, full video at youtu.be/76XIrm91Ra0

A grid of scissor linkages can move if the quadrilaterals corresponding to the scissors are cyclic! Joint work with Kyle VanDeventer. Full video: youtu.be/76XIrm91Ra0

Video of a talk I gave yesterday at the MoMath Moves 2022 conference, on some of the puzzles I've been working on recently. There are one or two things in here that I haven't got around to making a proper video of yet! youtu.be/SDZlsUHGhGM

The 2022 spherical conference photo, in stereographic and equirectangular projections.

New video with @saulsch explaining Cannon-Thurston maps. These are "naturally occurring" space-filling curves associated to certain hyperbolic manifolds. Full video at youtu.be/FpeeFcK3lTk

Behind the scenes of an upcoming video with @saulsch: how to get a smooth dolly shot with minimal equipment.

Experimenting with some CNC engraving of @saulsch's and my Cannon-Thurston paths with
my brother Will Segerman.

When I think about climate change, I think about the Great Stink.

By 1830, London was the largest, richest city in the world. But the city's waste management systems had not changed appreciably since medieval times. Most human waste was handled quite simply: it was just dumped into the River Thames.

The result was a slow-growing crisis that lasted three decades. Cholera outbreaks (from drinking tainted water, though nobody understood that then) periodically wracked the city, killing tens of thousands. The stench from the river gradually grew worse and worse, making life in riverside districts increasingly intolerable. The government was too hesitant to take dramatic action, though; it tried instead to mitigate the problem, by pouring lime into the river to cut the stench.

It all came to a head in the summer of 1858. A dry spell caused the level of the river to drop, leaving the banks coated with mounds of what the newspapers delicately called "impure matter." The stench was so bad that it became known as "the Great Stink." Parliament, whose halls were right on the river, could not conduct business. The smell in the chambers was so strong that all the curtains were soaked in chloride of lime to try and block it. (It didn't work.)

Parliament was now faced with a simple, stark choice: do something to clean up the river, or move itself out of London altogether. Members seriously discussed relocating to Oxford and St. Albans, but in the end, they decided to act. Municipal engineer Joseph Bazalgette was authorized to build a network of new sewers, at the then-staggering cost of £3 million, to be paid for by taxing every London household three pennies for the next 40 years.

Bazalgette's sewers solved the problem. They solved it so well they're still in use today. But democratic government had to be dragged kicking and screaming into making them happen. Only when the problem made their own lives intolerable did they finally act.

How all this relates to climate change, I shall leave as an exercise for the reader.


Susan Goldstine, Liz Paley, and I wrote an article about Mathemalchemy, a whimsical 24 math-artist installation exploring the beauty of mathematics. ams.org/journals/notices/20220

A handful of projects use it to manage dependencies among user-installable plugins.

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