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/
A funny detail, via @11011110:
In 2008, the university temporarily removed Het Ding for maintenance – and they accidentally put it back the other way up!
See before and after photos here, taken from https://www.utoday.nl/campus-life/74074/student-prank-and-artwork-het-ding-exists-50-years
@11011110 I wonder if we can find before and after photos to compare.
*Edit*: Yes, this article has comparison photos: https://www.utoday.nl/campus-life/74074/student-prank-and-artwork-het-ding-exists-50-years
I can see why he called it ‘mirrored’ – the transformation applied is equivalent to reflection in a horizontal plane – though it is also equivalent to a rotation.
Exactly 50 years ago, students placed artwork 'Het Ding' near the university's main entrance as a joke. Today, the structure of six discarded telephone poles and steel wire still stands there, but mirrored since 2008. Read an article from our archive on the unusual history of Het Ding here.
@11011110 @robinhouston I was even more confused when I read the Dutch Wikipedia article in Firefox's translation, because it said
"Together they form a twenty-plane with fourteen equilateral and six equilateral triangles."
That seemed like a strange way of saying "twenty equilateral triangles"! But reverting to the Dutch, it's actually using two different words, fourteen "gelijkbenige" and six "gelijkzijdige". According to Wiktionary, the first of those means "isosceles", not "equilateral". Firefox's translation made a goof.
So this is apparently not a _regular_ icosahedron. Does that affect the question of whether it's chiral, perhaps?
@robinhouston that would explain why I couldn't quite see some of the icosahedron edges in the photos! I found it quite hard to work out what was going on, because the wires are so thin and often the same colour as the background.
I did remember a construction I'd seen in a Johnny Ball book as a child, in which you make a regular icosahedron by slotting three 1 × φ rectangular cards together and then connecting the 12 corners of the cards with string. If you changed the aspect ratio of those cards, that would also be a way to make an icosahedron with 14 isosceles faces and 6 equilateral which was still not chiral.
@mjd @simontatham @robinhouston yes, and the article that Wikipedia cites has another photo; the poles are perhaps not as heavy as what I have on my street.
@11011110 @robinhouston on reflection, I also don't believe those counts! If this sculpture has the form of Jessen's icosahedron, then surely it has _twelve_ isosceles triangles and _eight_ equilateral ones?
An easy mistake; clearly the equilateral triangles have something to do with a cube or its dual octahedron, and all you have to do is forget whether it's the faces or the vertices. I didn't spot it yesterday for that reason. But I got there in the end!
@xan You might think so! But when some people did something similar recently in San Francisco there was no such overreaction. (It had been removed by the following day, though: I don't know by whom.)
Attached: 3 images Some of the Zometool crowd made a large sculpture of a projection of a tesseract and yesterday, in the tradition of Drop Art from which zometool was born, installed it guerilla-style in a nearby park.
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