This is YBC 7289, a Babylonian tablet from 1800 BC – 1600 BC showing the sides and diagonals of a square with a very accurate sexagesimal approximation to the square root of two, "the greatest known computational accuracy ... in the ancient world". Now a Good Article on Wikipedia,

The Cal Poly ag students have started selling these blood oranges at the local farmer's market, as they do every year around this time, only $1 for five. In the summer they sell sweet corn on the cob.

Holes and their reflections. (The reflections are in the curved surface of an espresso portafilter.)

The view from my desk. Actually my office has lots of windows with a nice view of a well-used plaza, outdoor coffee shop, trees, and distant mountains. But to see that, I have to get up and go over to one of the windows. If I stay at my desk and look up at the window, I see this interesting geometric pattern instead.

This is not a cinnamon bun. It's actually a 160 million year old fossil snail shell from Madagascar, roughly the size of a large fist (or cinnamon bun). I don't think it's particularly rare or valuable; I picked it up because I liked its shape.

Spotted on the Cambridge University Press display table at SODA...

Matsya And The Great Deluge, street art from Fort Bragg illustrating an ancient Indian folk tale. For a more complete view of this piece and more information about it, see

It feels like I haven't been taking and posting enough photos. So here's a cell phone shot from yesterday that I took to illustrate the Wikipedia article

The Beacon hasn't actually lived there for nearly 20 years, but their old sign still hangs on the building.

Amazon trained a sexism-fighting, resume-screening AI with sexist hiring data, so the bot became sexist:

A Problem Fit for a Princess:

A post on the history of the Apollonian Gasket, a fractal formed by tangent circles, inspired by its use as the logo of the San Joaquin Math Teachers’ Circle.


A Mastodon instance for maths people. The kind of people who make \(\pi z^2 \times a\) jokes.

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