Fr. Magnus Wenninger was an astoundingly prolific polyhedron model builder, having built many thousands of models during his life. He is best known for his trio of model-building books: *Polyhedron Models,* *Spherical Models,* and *Dual Models.* Ask anyone who is an enthusiastic model builder, and I will bet that they own at least one, if not all three.

These books were important because they opened up the world of polyhedron model building to a much wider audience, giving detailed instructions on how to build dozens of models, as well as discussing the mathematics underlying polyhedra (although to a limited extent).

But perhaps equal to Fr. Wenninger’s model-building capabilities was his ability to connect polyhedron enthusiasts with one another. Because of his books, other model builders would correspond with him describing their particular interests, and he would connect them with others who had written to him with similar interests. In 1996, he created a mailing list where those interested could exchange ideas about all aspects of polyhedra. It was very active for several years, but because of the proliferation of sites about polyhedra in recent years, it is somewhat less so now. It is now maintained by Dr. Roman Mäder.

I was first introduced to Fr. Wenninger’s books by finding them among the stacks at the mathematics and science library at Carnegie Mellon. I don’t recall how many times I checked out *Polyhedron Models;* I was completely engrossed. I would page back and forth, over and over, looking for similarities between the various models and underlying geometrical patterns.

I began corresponding with Magnus in the summer of 1993. I still have all of our correspondence — I made sure to photocopy any letter I sent him so I would have a continuous record of our polyhedral conversations.

Sadly, Magnus Wenninger passed away last February at the age of 97. When I heard about this, I thought it would be fitting to organize an Invited Paper Session at the Joint Mathematics Meetings (on 12 January 2018 in San Diego) in his honor. I invited some of his colleagues from the polyhedron mailing list, and others as well.

This morning, I began reading through the letters exchanged with Magnus in preparation for a talk I will be giving in the session. Yes, this was in the day when people wrote *letters**,* and moreover, wrote them *by hand.* Amazing! Such an interesting treasure trove of ideas and thoughts.

For my talk, I am excerpting text from Magnus’ letters to me, taking pictures of the text, and using these excerpts as the main body of slides. I am not sure how many others had an extensive correspondence with Magnus, but I thought this would provide a unique glimpse into Magnus’ life.

And so begins this series of posts commemorating Fr. Magnus Wenninger. I’ll continue this post by giving an overview of our relationship. Then later, I’ll share with you some excerpts from his letters to me, as well as provide commentary when appropriate. It is fitting that he should be remembered; organizing the Invited Paper Session in his memory as well as writing about him in my blog will serve as my contribution.

I was simply fascinated by the beauty, intricacy — and to an extent, simplicity — of three-dimensional polyhedron models. But I was *also* a graduate student at Carnegie Mellon in mathematics, which was not insignificant.

And just what *was* the significance of being a graduate student? Well, I was being trained to think rigorously, mathematically. At the time, however, all the accessible books on polyhedral geometry were at a relatively elementary level.

What I mean is this. When you study a polyhedron, there are many metrical features evident, such as edge lengths and various angles; for example, the angles between two faces of a polyhedron (like the 90° angles between faces of a cube). And in many of these books, these lengths and angles were given — but in most cases, only in tables with approximations to enough significant figures necessary to build reasonably accurate models.

I started to wonder *how* all those numbers were calculated. I wasn’t satisfied with *approximate* results; I wanted *exact* results. Thus began my polyhedral self-education, some thirty years ago.

So I began playing around, and when I finished graduate school, mustered up the courage to write Magnus. I was rather intimidated at the time — I had just started learning about polyhedra, and he had published at least three books on the subject! But it turns out Magnus was unusually generous with his time and talent, and replied within a few weeks.

My introductory letter was dated 5 July 1993, and the last letter I have from Magnus bears the date 22 October 1997. I am quite sure that this is because we continued our correspondence online. However, virtually all of that correspondence is lost, since most of it was conducted through a university email address I no longer have access to.

There are a few lingering emails in my gmail account, since my correspondence with Magnus waned after I left my first university position. But in addition to maintaining an active correspondence with Magnus, I did visit him a number of times at St. John’s Abbey in Collegeville, MN. I would stay in a guest room at the Abbey, and join Magnus for lunch and dinner. Throughout the day, I would visit Magnus’ room where we would talk about polyhedra, or perhaps I would work on my own, or just take a walk around the campus.

My interactions with Magnus were absolutely inspirational. Looking back at notes from those years, I am amazed at how much I accomplished — and this at a time when computer graphics were much less sophisticated than they are now. I would often share results with Magnus in my letters, and he would provide his unique perspective on my current work. Even when he was critical, he was unfailingly kind.

So in my next post, I’ll begin sharing excerpts from Magnus’ letters to me. That is, after all, how you get to know a person — one interaction at a time. Hopefully you will be able to get a sense of the humble, brilliant, generous man Magnus was and continues to be for those who knew him well. His legacy lives on through us, as we strive to be for others who Magnus was for us.

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