@robinhouston@mathstodon.xyz avatar

robinhouston

@robinhouston@mathstodon.xyz

Interested in things

This is where I post half-baked ideas & mistakes. Please don't assume that anything I say here is right.

This profile is from a federated server and may be incomplete. Browse more on the original instance.

robinhouston, to random
@robinhouston@mathstodon.xyz avatar

I have two tickets for @emf which unfortunately I can't use. I'm happy to give them for free to a friend, or at face value to a trustworthy-seeming stranger. Any takers?

christianp, to random
@christianp@mathstodon.xyz avatar

A weird oversight: the email I get from Google Groups telling me that someone wants to join the group is in their preferred language, not mine.

robinhouston,
@robinhouston@mathstodon.xyz avatar

@christianp I get the impression Google don't place a very high priority on Google Groups

robinhouston, to random
@robinhouston@mathstodon.xyz avatar

Is anything known about optimal packings of quarter-circles into a square?

robinhouston,
@robinhouston@mathstodon.xyz avatar

Several people have suggested putting them in sideways.

A) The tin isn't tall enough.

B) I'm more interested in the mathematical question that this real world problem suggested than I am in the actual real world problem.

robinhouston,
@robinhouston@mathstodon.xyz avatar

The absence of this problem from Erich Friedman's ‘Packing Center’ makes me think it probably hasn't been extensively studied

ColinTheMathmo, to random
@ColinTheMathmo@mathstodon.xyz avatar

In something of a rush this morning, going for fastest rather than error-free.

711

⬜⬜⬜⬜⬇️⬜⬜⬜⬜⬜⬜⬜⬜⬜
⬜⬜⬜➡️⏹️➡️➡️➡️➡️➡️➡️⬇️⬜⬜
➡️➡️➡️⬆️⬜⬜⬜⬜⬜⬜⬜➡️➡️➡️

https://www.andrewt.net/puzzles/cell-tower/?p=711

Current streak: 57 (Lanthanum)

Best streak: 93

robinhouston,
@robinhouston@mathstodon.xyz avatar

@ColinTheMathmo In following my usual strategy of going for fast rather than error-free, today I managed neither! I took a wrong turn, got stuck, and the whole thing took 5 minutes.

⬛️⬛️⬛️⬛️⬛️➡️➡️➡️➡️➡️⬇️⬛️⬛️⬛️
➡️➡️➡️➡️➡️⬆️⬛️⬛️⬛️⬛️➡️➡️➡️➡️

ColinTheMathmo, to random
@ColinTheMathmo@mathstodon.xyz avatar

I found this one straight forward. Every now and again there's one that "just works".

709

➡️➡️➡️➡️➡️➡️➡️➡️➡️➡️➡️➡️➡️➡️

https://www.andrewt.net/puzzles/cell-tower/?p=709

Current streak: 55 (Caesium)

Best streak: 93

robinhouston,
@robinhouston@mathstodon.xyz avatar

@ColinTheMathmo I got this one in less than a minute, which is unusually quick for me. (I aim for two minutes, and only manage it about half the time.)

hartkp, to random Norwegian
@hartkp@mathstodon.xyz avatar

707

➡️➡️➡️➡️➡️➡️➡️➡️➡️➡️➡️➡️➡️➡️➡️

https://www.andrewt.net/puzzles/cell-tower/?p=707

robinhouston,
@robinhouston@mathstodon.xyz avatar

@hartkp @ppscrv @ColinTheMathmo @christianp No! I don't worry about it at all any more; i optimise for time-to-completion instead. Much more fun.

MLE_online, (edited ) to random
@MLE_online@social.afront.org avatar

The only body parts that get their own special word for hurting are head, tooth, heart, ear and stomach.

There's no elbowache, legache, or noseache, for example

robinhouston,
@robinhouston@mathstodon.xyz avatar

@MLE_online Heartache. Ballache?

robinhouston,
@robinhouston@mathstodon.xyz avatar

@MLE_online Used metaphorically to refer to something annoying. Possibly a Britishism?

robinhouston,
@robinhouston@mathstodon.xyz avatar

@MLE_online I don't know how I missed heart in your list!

simon, to random
@simon@simonwillison.net avatar

Anyone know how to get iPhone keyboard to stop correcting plugin to plug-in? None of the tips I've found online about setting up a text replacement rule actually work

https://support.apple.com/en-us/104995 says "In iOS 17 and later, Auto-Correction temporarily underlines words that it corrects. To quickly edit an auto-correction, tap the underlined word and choose an option from the pop-up menu" - but that doesn't help, it rarely shows for plugin and when it does it only lets me revert, not add-to-dictionary

robinhouston,
@robinhouston@mathstodon.xyz avatar

@simon Mine does not do this. I wondered if the difference might be that I'm using the English (UK) keyboard, but I tried changing it to English (US) and that doesn't do it either.

I don't know what that means, but it seems relevant. Plugin plugin plugin.

robinhouston, to random
@robinhouston@mathstodon.xyz avatar

There was a brief but glorious flowering of geometric surrealism in meme culture a few years ago

image/png
image/png
image/png

robinhouston, to random
@robinhouston@mathstodon.xyz avatar

I am confident enough in the truth of this claim that I have not yet dared to take it apart.

robinhouston, to random
@robinhouston@mathstodon.xyz avatar

Another strong candidate for best toy I discovered last week is George Bell's amazing exploding egg

video/mp4

robinhouston, to random
@robinhouston@mathstodon.xyz avatar

A recent remark by @simontatham has prompted me to wonder about cuboids.

I was taught as a child – and I assume this must be usual in British schools, or at least used to be – that a ‘cuboid’ is a brick shape, i.e. the product of three line segments.

On the other hand, the Wikipedia page https://en.wikipedia.org/wiki/Cuboid defines a cuboid in a more general way, to be any polyhedron that is combinatorially equivalent to a cube.

robinhouston,
@robinhouston@mathstodon.xyz avatar

And it seems that there is no universally-accepted name for what I was taught to call a cuboid: I recently read a paper that used “rectangular parallelepipedon”, which is charming but rather a mouthful.

Sometimes ‘box’ is used for the n-dimensional generalisation, so we could say 3-box, but I've never seen that. I've seen rectangular prism, which … okay, but also come off it.

Can we have a universally-understood simple term for this simple shape??

robinhouston, to random
@robinhouston@mathstodon.xyz avatar

Is there a principle behind the design of this pattern? Clearly it is too symmetrical to be random; but can more be said? (This is an open-ended question. I don't have an answer in mind.)

robinhouston, to random
@robinhouston@mathstodon.xyz avatar

Possibly the coolest toy I discovered at G4G – definitely in the top three – is Andreas Hoenigschmid's Shashibo Cube.

It's a kaleidocycle of length 12, fitted with magnets so the tetrahedra snap together in a satisfying way, and it's just preposterously fun to play with. Everyone I showed it to wanted to get one.

robinhouston,
@robinhouston@mathstodon.xyz avatar

@simontatham That's very interesting! Thanks for the information. I agree that the shape is the really magical thing.

robinhouston,
@robinhouston@mathstodon.xyz avatar

@simontatham How did you come across this originally, by the way? I would have liked to have known about it sooner, and I'm wondering where I ought to have been looking.

robinhouston,
@robinhouston@mathstodon.xyz avatar

@simontatham I will check for you, if I can ever work out how to make that shape!

robinhouston,
@robinhouston@mathstodon.xyz avatar

@simontatham This feels as though it might be half of a √2 × √2 × 1 cuboid, but I don't have a second copy about my person right now. Also it doesn't appear to be the same as your polyhedron‽

robinhouston,
@robinhouston@mathstodon.xyz avatar

@simontatham Ohh, I see! Yours is the mirror image of that:

robinhouston,
@robinhouston@mathstodon.xyz avatar

@simontatham Also, it turns out I did have a second one on me. And yes, they make a lovely cuboid!

mcc, to random
@mcc@mastodon.social avatar

For the last year I've been semi-daily posting "What I'm Listening To Today" links in this thread:

https://mastodon.social/@mcc/108199886340178151

The thread is now so long it is increasingly breaking Mastodon, so I am making a new thread, starting here.

To recap, here's the entirety of the year-one thread in the most impractical possible format: A YouTube playlist containing 246 songs and running for just over 47 hours:

https://www.youtube.com/playlist?list=PLLIjft6ja7DP_GwDs3XuTbiFmHYTwJWa7

robinhouston,
@robinhouston@mathstodon.xyz avatar

@mcc I have never told you that i love your music posts, but i love your music posts & i think you should know that

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