However, since we do not currently have a model of the 120-cell anywhere around the house, before starting the project tonight we took a look at two of Henry Segerman’s movies:

(1) Half of a 120-cell

and

(2) Toroidal Half 120-cell

With Segerman’s videos as background, we now calculated what “” would be for the 120-cell:

We approached the 600-cell the same way – starting with a video from Henry Segerman:

After that quick introduction we discussed the shape and calculated the value of “” for it. Turned out that it was the most 4-d spherical of the shapes that we looked at. That was a fun fact, and thinking about that fact caused my son to ask what a 4-d sphere actually looked like!

Well, I couldn’t end this week-long project with the question about the 4-dimensional sphere hanging in the air. We talked about the shape for about 5 min and then took the dog for a walk 🙂

As we walked up the street at the end of the walk my son turned to me and said:

“Wait a minute, all of the spheres would have to differ by infinitesimal amounts . . . . but, oh, there are infinitely many of them so I guess that’s ok.”

The project couldn’t have ended on a better note! Thanks to Patrick Honner for the great Pi day exercise which inspired this project. Thanks also to Henry Segerman for his videos about the 120- and 600- cells. I hope to own a few more of his 3d prints soon!

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