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This movie is analogous to the previous one in that it shows the
threedimensional shadow of a hypercube folding together in fourspace. We
start with the unfolded hypercube made from eight cubes in a flat
threespace at the bottom of fourspace. The central (yellow) cube stays
in place as we rotate the other cubes through the fourth dimension. The
portions of them that move closer to the light source appear to get
larger, and the cubes appear to distort into pyramid shapes. Note how this
corresponds to the twodimensional shadows of the sides of the cube
folding in th eprevious movie.
Once the sides are folded together, we fold the top over. It turns inside
out (just as the shadow of the top of the cube did) and closes up by
doublecovering the rest of the hypercube. Compare this to the end result
in the case of the threedimensional cube in the previous movie.
