MonostableTetrahedron
Created Thursday 26 June 2025
Recently there has been a paper announcing:
- A new pyramid-like shape always lands the same side up
It was written up in Quanta:
The paper is here:
- Building a monostable tetrahedron :
In it they say:
"What did appear as a challenge, though, was a physical realization of such an object. The second author built a model (now lost) from lead foil and finely-split bamboo, which appeared to tumble sequentially from one face, through two others, to its final resting position."
Well, I have the model.
- https://www.solipsys.co.uk/images/MonostableTetrahedron_00_Standing.jpg
- https://www.solipsys.co.uk/images/MonostableTetrahedron_01_AfterRolling.jpg
- https://www.solipsys.co.uk/images/MonostableTetrahedron_02_Closeup.jpg
Bob Dawson and I made this in the 1980s during our overlap in Cambridge.
The paper at the apex was cut to specific angles to create the shape we needed. And it really is unstable on all but one face, and will "roll" from one face, through two others, and come to rest on the fourth.
The first photo shows the shape standing without rolling because it's on a slope to make it stable. If it's on the flat, it will roll.
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