The four points, two distances problem: theguardian.com/science/2019/o

Can you find all of the ways of arranging four distinct points in the plane so that they form only two distances? The link is not a spoiler but it has a separate link to the solution. "Nearly everyone misses at least one" says Peter Winkler; can you guess the one I missed?

Because I just spent 15 minutes trying to remember how to find out what variables a CMake find_package call sets:

cmake --help-module Find<name>

Goddammit. Why is this information so hard to find?

Robert MacKay's Chaos Machine. Its configuration space is a genus three surface. The dynamics of the machine are equivalent to geodesic flow on the surface, which is Anosov, hence chaotic.

Very happy to notice that Erich's Packing Center (www2.stetson.edu/~efriedma/pac) is still being updated! Two new (and very pretty) packings have been added this year: www2.stetson.edu/~efriedma/tri, www2.stetson.edu/~efriedma/lin

The problem with transiting though Shanghai airport is that all the staff try to talk to me in Chinese

I sure do love when the metro makes an announcement they say only once so by the time you start paying attention all you catch is "The inconvenience is regretted"

Compact packings of the plane with three sizes of discs: arxiv.org/abs/1810.02231, Thomas Fernique, Amir Hashemi, and Olga Sizova

Here, "compact packing" means interior-disjoint disks forming only 3-sided gaps. The circle packing theorem constructs these for any finite maximal planar graph, with little control over disk size. Instead this paper seeks packings of the whole plane by infinitely many disks, with few sizes. 9 pairs of sizes and 164 triples work. Here's one from Fig.3 of the paper.

shitpost about 90s TV

Here's a 1965 RAND report demonstrating a conversational interface with an algebraic processing system. They determine that a conversational user interface vastly improves usability in their tests.

New blog post: Motorcycle graphs and the eventual fate of sparse Life, 11011110.github.io/blog/2018/1

Of course Mac OS X's Calendar interprets "IST" as Irish Standard Time and not Indian Standard Time. The fool is me for expecting different.

I got the urge to start singing "Domo Arigato Mr. Roboto" the moment I landed in Tokyo and I'm pretty sure that's extremely culturally insensitive

A recent Learned League question asked for the name of the infamous Leni Riefenstahl film which documented the second Nazi Party Congress. Some brilliant wrong answers shared on the forums:
- Das Jackboot
- 2 Fascist 2 Fuhrerious
- Dude, Wehrmacht Car?

$r=\sqrt{1+\alpha\cos2\theta}.$ All these curves enclose the same area.

cw: shitpost

cw: shitpost

The quality of a Fourier approximation of a closed curve $$\gamma:\mathbb S^1\to\mathbb R^2$$ depends heavily on its parametrization. Below: a square approximated with 1, 2, and 3 nonzero Fourier modes.

Fun fact: The hairy ball theorem doesn't apply to black holes because black holes have no hair

Spam texts in India are amazing.
"ACCOUNTS IS THE FUTURE OF YOUR CHILD."
wtf

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