The movie depicts a rotating spacetime hypercube,
projected from 4 dimensions on to the 2 dimensions of the screen
in the same way as the
rotating 4D hypercube.
The prototypical example of a hypercube
is the 4-dimensional geometrical object with corners at
(
A spacetime hypercube differs from an ordinary 4-dimensional spatial hypercube
in that one of the dimensions, the time dimension, is, essentially, imaginary.
That is, the time dimension behaves in many ways as if it were
What is a spacetime rotation? It is a Lorentz transformation, the combination of an ordinary rotation in space with a Lorentz boost by some velocity in some spatial direction. Just as a spatial rotation transforms two spatial directions amongst each other, leaving one spatial direction (the rotation axis) fixed, so also a Lorentz boost transforms time and one spatial direction, the direction of the velocity, as illustrated for example on the Centre of the Lightcone page. In the movie, the direction of the Lorentz boost has been chosen to be the same as the direction of the spatial rotation axis. The diagram at left shows the direction of this boost/rotation axis, together with the direction of the time axis. |

- Rotating 4D hypercube (46K GIF movie).
- Rotating 4D spacetime hypercube (this page; 47K GIF movie).
- Both 4D hypercube movies together.

Back to The Postulates of Special Relativity

**Updated** 3 Apr 1998