robinhouston

Maths etc.

Location: England

Last Notes

2026-03-11 13:37:14 UTC

TIL. In April 1974, in the middle of the night, a small group of conspirators secretly installed a large tensegrity icosahedron made from discarded telephone poles on the campus of Twente University in the Netherlands.
It’s still there. People call it Het Ding (“the thing”).
https://www.utwente.nl/en/alumni/inspiring-alumni/ut-canon/stories/het-ding/
https://media.mathstodon.xyz/media_attachments/files/116/210/792/392/176/399/original/fcf8215535988335.png

2025-12-03 03:54:22 UTC

I would not have guessed this was possible!
Vladan Majerech has found a one-dimensional spaceship in the Game of Life: a pattern just one cell high and 3,707,300,605 cells wide that, after 133,076,755,768 generations (during which it is not confined to the one-dimensional line, of course) recreates the starting pattern but translated two cells to the right.
https://conwaylife.com/forums/viewtopic.php?&p=222136#p222136

2025-08-16 09:30:47 UTC

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Interesting: they all decode ok on my iOS phone. I wonder what's different.
https://media.mathstodon.xyz/media_attachments/files/115/037/733/716/846/552/original/c94e02ebade25015.jpeg

2025-08-11 20:47:32 UTC

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No, it's still open! He did say a little sadly that it has proved harder to resolve than he hoped it would be.

2025-07-06 08:14:42 UTC

Did you all know that there is a SECOND rhombic dodecahedron whose faces are all congruent rhombuses, that is less symmetrical than the normal rhombic dodecahedron?
https://media.mathstodon.xyz/media_attachments/files/114/805/287/168/448/878/original/8072f205cfafb67a.png

2025-05-02 07:48:48 UTC

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Yes, that fits with what I imagined it meant. I haven't thought about it seriously. I suppose another possible interpretation of the first condition would just be that the rings are pairwise linked, but knowing Conway the automorphism interpretation seems more likely.

2025-05-02 07:30:06 UTC

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I think the prize was only offered for correct solutions submitted on the day itself (2016-03-14), so unfortunately you wouldn't even get pizza for it now.

2025-05-02 04:06:41 UTC

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Here's the third, unsolved, problem:
My key-rings are metal circles of diameter about two inches. They are all linked together in a strange jumble, so that try as I might, I can’t tell any pair from any other pair.
However, I can tell some triple from other triples, even though I’ve never been able to distinguish left from right. What are the possible numbers of key-rings in this jumble?

2025-05-02 04:05:58 UTC

In 2016, as a publicity stunt for Pi Day, the US chain restaurant Pizza Hut announced a trio of mathematical puzzles written by John H Conway, offering prizes of Pizza Hut gift cards.
The first two problems were successfully solved, and prizes presumably awarded, but the third was not and seemingly remains unsolved to this day!
https://blog.pizzahut.com/pizza-hut-partners-with-mathematician-john-h-conway-for-national-pi-day-math-contest/
https://blog.pizzahut.com/national-pi-day-math-contest-problems-are-here-2/

2025-04-30 12:04:04 UTC

Happy Gauss's Birthday, everyone! I hope you're having a good one.

2025-02-15 16:34:53 UTC

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I thought the list of still-unsolved problems at the end of the paper was interesting:
* Is a three-piece dissection still impossible if flipping is allowed?
* Are there only a finite number of rectangles that can be dissected into three pieces from a triangle? If so, how can they be enumerated?
* Are there any other four-piece dissections between an equilateral triangle and a square, aside from the solution proposed by Dudeney?
* Are there any pairs of regular n-gons and m-gons that can be dissected into three pieces, where n ≠ m?
* Is a three-piece dissection still impossible if we allow nonpolygonal (curved) pieces?

2025-01-31 17:08:20 UTC

If you're interested in algorithmic art, and within striking distance of London, I'd recommend the Electric Dreams exhibition at Tate Modern
https://media.mathstodon.xyz/media_attachments/files/113/924/064/098/742/522/original/6464770bfe441a3c.jpeg
https://media.mathstodon.xyz/media_attachments/files/113/924/064/278/494/129/original/57e92aaacc6c3dfd.jpeg
https://media.mathstodon.xyz/media_attachments/files/113/924/064/704/269/390/original/74ed8ba1b92b5713.jpeg
https://media.mathstodon.xyz/media_attachments/files/113/924/065/015/801/331/original/cd6fa4daf14a9dd4.jpeg

2025-01-19 04:58:45 UTC

I've recently discovered that there's at least one creator who posts amazingly high-quality mathematical visualisations to TikTok. Sorry Americans.
https://media.mathstodon.xyz/media_attachments/files/113/853/245/635/213/620/original/03e1c45e44c37324.mp4