by wendy » Sun Apr 14, 2019 12:55 pm
As in 3d, there is half the earth in daylight, and half the dusk-area would be rising.
So in 3d, you have the gimble of a globe acting as sunrise (or any other time of day), in 4d, the gimble is a half-sphere.
The half-sphere is rooted at the toruses of zero thickness, and it rotates around these, one with the sun, and the other against it.