Greg Eganさんのイラストまとめ

A sphere knotted in four dimensions (rotating in R^4 and projected down to R^3), built by taking trefoil knots in R^3 scaled by sin u, and given a 4th coord of cos u.

This construction was discussed by @stevenstrogatz and Colin Adams in this fun podcast:
https://t.co/FrmrYjv3Lx

Glue a tube to the midline of a Möbius strip, looping around to join up with itself. The result is not 1-sided — but the fun thing is you can have a fast-moving particle traverse the whole tube, held up by centrifugal force.

Here unneeded parts of the tube have been cut away.

[1/3] You can carve a tunnel through a cube that another cube the same size can pass through.

All the Platonic solids share this property, and so do all n-cubes:

https://t.co/oIeERcDtmm

Wallis credits Prince Rupert of the Rhine with noting this of the cube, so mathematicians

As the world turns, but the map stays still. Peirce's projection based on an elliptic function, wrapped on a torus. https://t.co/YjljFZCz7w