## Fr. Magnus Wenninger, O.S.B., V

This is the final installment about my correspondence with Magnus Wenninger.  I didn’t realize I had so much to say!  But I am glad to take the opportunity to share a bit about a friend and colleague who contributed so much to the revitalization of three-dimensional geometry in recent years.  Talk to anyone truly interested in polyhedra, and they will know of Magnus.

As I mentioned last week, I’ll begin with Magnus’ memoir on the Symmetry Congress (as you can see in the title of his memoir).  His friend Chuck Stevens lived near where the Congress was held, and so met him at the airport and was his tour guide for the duration of his visit.  (Note:  the Society is still active — just google it!)

In this excerpt, Magnus remarks (start in the middle of line 4) that people who don’t know much about polyhedra always ask the same two questions:  how long did it take you to make that model, and what do you do with them?  I have had similar questions asked of me over the years as well; you just learn to be patient and hopefully enlighten….  Of course Magnus was always kind and generous with his responses.

You might be surprised by Magnus talking with a 10-year-old boy at the conference.  Of course it may have been that Josh just happened to be staying at the same hotel, though that is unlikely since he was visiting relatives.  More likely is that his aunt or uncle was a conference participant and brought him to the conference.  I should remark that it is a common occurrence for a participant in an international conference to plan a family vacation around the trip, so you regularly see children of all ages at such conferences.

I direct your attention to last seven lines here.  Magnus was perfectly happy to have his brandy, building polyhedra in an air-conditioned room rather than braving the summer heat to be “cultural.”  For me, this emphasizes the simplicity of Magnus’ life.  He did not need much to make him happy — some paper and glue, his building tools, his Bible, and perhaps a few other books on philosophy and theology.  The quintessential minimalist life of a Benedictine monk.

Here, the second paragraph is interesting.  In rereading it, I think I could imagine the exact expression on Magnus’ face when he heard “I’ll take it.”  I know that this was a rare occurrence for Magnus.  Perhaps it might be less so now; because of Magnus’ influence, as well as the explosion of computer graphics on the internet, people are generally more informed about polyhedra than they were in 1995.

Moreover, more and more high school geometry textbooks are moving away from exclusively two-column proofs, and some even have chapters devoted to the Platonic solids.  I don’t think we’re at the point yet where “dodecahedron” is a household word…but we’re definitely moving, if slowly, closer to that point.

The final excerpt I’d like to share is from December 1995.  I include this as another example of my collaboration with Magnus — our discussions of “perfect versions” of polyhedra.  I’ll go into this example in more detail since it’s a bit easier to understand, but I note Magnus was not a fan of the adjective “perfect.”  (And as a historical note, I had used the term “perfect version” and had also corresponded with Chuck Stevens, so Chuck must subsequently have talked to or corresponded with Magnus and used the term, and so Magnus thought Chuck came up with the term.)

I now agree, but have yet to come up with a better term.  The basic idea is that some polyhedron models are very complicated to build.  But for many of them, there are ways to make similar-looking polyhedra which are still aesthetically pleasing, but a bit easier to construct.

Let’s look at an example I mentioned a few weeks ago:  the stellated truncated hexahedron, shown below.

Notice the blue regular octagrams.  Now consider the octagrams shown here.

On the left is a regular octagram.  If you draw a square around it, as shown, you divide the edges of the square in the ratio $1:\sqrt2:1.$  Notice that the octagram is divided into 17 smaller pieces by its edges.

However, if you start with a square and subdivide the edges into equal thirds, an interesting phenomenon occurs — there are four points where three edges intersect, resulting in a subdivision of the octagram into just 13 pieces.

You will note that this variation is not regular — the horizontal and vertical edges are not the same length as the diagonal edges.  So any polyhedron with this octagram as a face would not be a uniform polyhedron.

However, it would be what Magnus referred to as a “variation” of a uniform polyhedron. So if we took the stellated truncated hexahedron, kept the planes containing the pink triangles just where they are, but slightly move the planes containing the blue octagrams toward the center, we would end up with the following polyhedron:

Note that the octagrams are now the octagram variations.  Also notice how the pentagonal visible pink pieces are now rhombi, and the small blue square pieces are completely absent!

Such simplifications are typical when working with this kind of variation.  Of course many polyhedra have such variations — but now isn’t time to go into further details.  But these variations were among the polyhedra Magnus and I wrote about.

As I mentioned, there is little left of my correspondence with Magnus, since several years of emails have been lost.  But I hope there is enough here to give you a sense of what Magnus was like as an individual, friend, and colleague.  He never let his fame or reputation go to his head — all he was ever doing, as he saw it, was taking an idea already in the mind of God, and making it real.

He truly was humble, gentle, and kind — and of course a masterful geometer who significantly influenced the last few generations of polyhedron model builders.  He will be missed.

## Fr. Magnus Wenninger, O.S.B., IV

Last week I ended with a remembrance of my wonderful visits to see Magnus at St. John’s Abbey in Collegeville, MN.  These were certainly unique among my visits with other friends and mathematicians.

I left off with an excerpt from 10 June 1994; this next one is dated 18 June 1994.

This is another excerpt describing elements of our collaboration together; I point your attention to the first few sentences, where “stellations of two cores” are mentioned.  Again, since the focus is on my work with Magnus, I will elaborate a bit on this idea without giving all the necessary background.  (If you’re really curious, the internet has all the answers to your questions about stellations.)

Consider the following uniform polyhedron, called the stellated truncated hexahedron.

This name is perhaps a misnomer, since careful observation reveals that the octahedron bounded by the eight pink triangles in fact lies entirely inside the cube (hexahedron) bounded by the eight octagrams.  So the octahedron does not actually truncate the cube.

Here is a partial figure from a paper I’m currently writing based on the notes referred to in the above excerpt.

Notice in d) how the red square truncates the black square to create a regular octagon.  So this figure shows how the lines containing the edges of an octagon (analogous to faces of polyhedra in three dimensions) divide the plane into different regions.

But in h), we have a figure bounded by lines containing edges of two squares, but one lies entirely within the other.  So we cannot choose a single polygon as generating this diagram.  Therefore, we say this figure is generated by two cores — the two squares which do not intersect each other.

Of course there are many other polyhedra which may be thought of in this way, but hopefully these two examples illustrate this polyhedral thread in my collaboration with Magnus.

This excerpt is from November 1994.  I include it as it illustrates how industrious Magnus was in building polyhedra.  He would build polyhedron models and sell them at craft fairs to raise money for the Abbey or other related causes.

“Sales average only about a dollar an hour for my work.”  Now 1994 was not all that long ago…a dollar an hour hardly seems fair for the work of a world-renowned model builder!  But most people just see a few brightly colored bits of paper held together with a few drops of glue, and have no real idea about the mathematics behind the models or what it takes to build them.

So building polyhedra really was a labor of love for Magnus; he would have built them just to give them away.  I recall one trip where I brought back three large trash bags filled with models which Magnus built but had no room to store.  I kept some for myself, but then freely distributed them to mathematics teachers and students of all levels so they could take pleasure in holding and studying them.  I hope some were inspired to build a few models on their own….

Again, Magnus stayed rather busy!  Note that in 1995, he had already been a priest for 50 years.  Also notice the reference to the ISIS Congress in Washington, D.C.  Magnus wrote a fairly detailed “memoir” about his attendance at that conference.  I’ll show you several excerpts from that memoir in next week’s post, as it comes rather later in the year (and so there isn’t room for those excerpts this week).

This is another example of a figure Magnus sent me as part of our ongoing collaboration.  At the beginning of our correspondence, I had begun a textbook on polyhedra based on spherical trigonometry, which I used for a course I taught at the college level.

In particular, I was investigating the mathematics in Spherical Models.  Recall that I wasn’t satisfied with numerical approximations — I wanted exact mathematical expressions for the angles used to build geodesic models based on polyhedra.

The above figure is based on one I used for designing spherical models where some of the faces of the polyhedron are pentagons.  When projected onto a sphere, you needed to draw geodesics (great circles) connecting the vertices and calculate the individual segments in the spherical pentagram just created.

Now in the plane, when you join the vertices of a pentagon with diagonals, the diagonals are subdivided into the ratio φ : 1 : φ, where φ is the golden ratio.  But the angles into which the diagonals of the spherical pentagram are subdivided isn’t a matter of calculating a simple ratio — there is a lot of trigonometry involved.  Moreover, the ratio varies with the size of the original spherical pentagon.

In any case, here it not the place to discuss all the mathematical details.  I just wanted to illustrate again one aspect of my correspondence with Magnus.  I feel certain I must have sent him all my draft chapters, but likely he gave me his commentary when I visited, or perhaps somewhere in those emails that have been lost forever in some virtual black hole….

This last excerpt shows Magnus’ gentle nature.  Perhaps you are not aware of the difference between the geometrical terms trapezoid and trapezium (see this article for a brief history) — but the meanings in the UK and US are swapped.  What is a trapezoid here is a trapezium in the UK, and vice versa.

In any case, I made a reference to “Those crazy Brits!” when discussing this difference in nomenclature, and Magnus was sympathetic to their cause, as shown in the last few sentences of the excerpt.  I can honestly say I cannot recall him ever saying a disparaging word about anyone (try counting the number of people you can say that about).  He was always keen to understand all sides of an issue — and this always made philosophical and theological discussions so interesting.

I’ll stop with this comment today.  Next week, we’ll begin by looking at Magnus’ memoir on the ISIS conference in Washington, D.C.

## Fr. Magnus Wenninger, O.S.B., III

I just returned yesterday from the Joint Mathematics Meetings in San Diego, where I gave my talk commemorating Fr. Magnus Wenninger.  Last week, I posted several excerpts from my correspondence with Magnus which I included in that talk.  Today, I’ll continue that discussion, again adding commentary as appropriate.

I included this quote because of Magnus’ translation of Kepler:  “Beyond doubt there exists in the mind of God the eternal form of all these shapes, which we call its truth.”  Magnus had a very philosophical approach to mathematics, and always considered that his work was some manifestation of the Divine.

Is mathematics invented or discovered?  This age-old and unresolved question has sparked much debate over the centuries.  But for Magnus, the answer is clear:  mathematics is discovered.  The polyhedra he created all existed in the mind of God long before he reimagined them with a few pieces of paper and a little glue.

So Magnus’ vocation as a Benedictine monk strongly influenced how he thought about his life’s work.  Having personally held and studied some of Magnus’ models, it is not a stretch to say that perhaps they were in fact touched by the Divine….

This excerpt again shows how very active Magnus was during the 1990s.  But this particular letter is part of a thread in our correspondence where I was planning my first visit to see Magnus.

What made the trip a little more challenging is that I also wanted to visit Peter Messer in Wisconsin as well.  Magnus introduced me to Peter as someone very interested in studying stellations of polyhedra, both from concrete and abstract viewpoints.  (I also have a folder of correspondence from Peter, but that for another time!)  Also, Peter was using Mathematica, which I was quite familiar with.  So it seemed appropriate that we should meet.

Peter just recently retired, but was a dermatologist at the time, and hence had a busy professional schedule.  So I was trying to juggle three schedules to arrange a series of visits — all through written correspondence!  Now we would consider this approach somewhat anachronistic, but at the time, it was perfectly reasonable.

The title of my talk at the Joint Mathematics Meetings was Working with Magnus Wenninger.  So in addition to excerpts which documented our getting to know each other, I also included excerpts which illustrated various aspects of our collaboration.

If you look back at the very first excerpt from last week’s post, you’ll notice the second paragraph begins “I’m in no hurry to get information about barycentric coordinates.”  In my introductory letter to Magnus, I mentioned that I had begun work on finding coordinates of polyhedra using a barycentric coordinate system.

But over the next several months, I did send Magnus notes on barycentric coordinates, and he did study them.  Now is not the time to go into a detailed discussion of barycentric coordinates — the point is that Magnus occasionally included diagrams in his correspondence to present his perspective on different aspects of our collaboration.

The first figure shows barycentric coordinates relative to a six-frequency triangle.  The second figure shows how he would use this abstract idea to create a template which he would use to make what would be called a six-frequency geodesic icosahedron.  Again, now is not the time to go into details, but I did want to include a brief description for those who are a little more familiar with polyhedra and geodesic structures.

Although, as I mentioned just a few moments ago, I began arranging my first visit with Magnus through letters, I must have finalized arrangements with him and Peter over the telephone.  This excerpt from 10 June 1994 was the first letter since February which mentioned my visit; I must have realized that calling both Magnus and Peter was ultimately more efficient than writing them.  I should mention that Magnus had difficulty hearing over the phone, and so we never had any substantial conversations on the telephone; our chats were confined to arranging logistics of visits or other such details.

I always enjoyed my visits with Magnus.  I would stay in a guest room in the Abbey at St. John’s University in Collegeville, Minnesota — this was a spartan room with a simple bed, a small desk and chair, and I think maybe another chair to sit in…it’s been too many years to remember the exact details.

I’ll recall a typical day during one of our visits — although the individual visits tend to blur together.  I’d say I made a half-dozen visits while I lived in the Midwest, including a time when Magnus visited me and I drove him to a conference at the University of Illinois Urbana-Champaign.

In any case, there was a common room for guests in the abbey for breakfast.  Nothing too elaborate, but enough to get you going.  I’d be on my own in the morning — working on polyhedral pursuits, or perhaps just walking around the beautiful campus.  My visits were usually during the summer, so I was spared the cold of Minnesota winters.

Magnus would then find me around lunchtime.  He had permission for me to have lunch and dinner with the other monks — a real treat, since this was not the usual protocol.  But Magnus and I often had philosophical and theological discussions as well as conversations about polyhedra, and so I was welcome at meals.  I can’t remember details, but the conversations were always quite stimulating.  The Benedictines at St. John’s were rather liberal.

In the afternoon, we’d meet to discuss various aspects of polyhedra or perhaps work on some models.  Often Magnus would be building while we talked.

Then I’d be on my own for a bit.  Often I would go to one of the Offices in the Abbey church before dinner, and I’d meet Magnus after the service (the monks sat in their own section) and we’d walk down to dinner and more interesting conversation.

Our evening sessions were a bit more informal, and our discussions would often be more philosophical rather than polyhedral in nature.  Magnus would have his nightly brandy — or perhaps a little Grand Marnier, since I would usually bring him a bottle when I visited.

Then it was early to bed for Magnus, although I was up a little later.  I am not sure when the first Office was in the morning, but I am fairly certain I was always in bed at the time….

We must have made arrangements for future visits either by phone or email, since this is the only correspondence I have which includes any details of visits with Magnus.  But they were wonderful times which I shall always remember fondly.

I’ll continue with excerpts from my correspondence with Magnus next week…so stay tuned!

## Fr. Magnus Wenninger, O.S.B., II

In this next installment of my commemoration of Fr. Magnus Wenninger, I’ll excerpt various snippets from our correspondence together which illustrate Magnus’ unique perspective as well as highlight our collaboration together.

This is by no means meant to be a complete biography of Magnus’ life; rather, I hope you get to know Magnus a little through our particular correspondence.  Of course everyone who knew Magnus had a slightly different experience.

I have about 65 letters in my folder of correspondence, which includes both letters from Magnus and my replies.  I had to be selective in preparing my talk for the Joint Mathematics Meetings, and what follows are the excerpts I chose (in chronological order), along with some personal commentary.

I chose this excerpt for a few reasons.  First, Tom Banchoff will also be giving a talk at the JMM in our session commemorating Magnus.  But I also wanted to highlight the fact that Magnus, although already in his early seventies, was still very active.  He was routinely invited to give talks and presentations, and also published papers occasionally.

And, as he indicated, when not otherwise occupied, he was always building models of one sort or another.  And I really do mean always — even at conferences, he would often have a table set up where he would build models and discuss polyhedra with anyone interested enough to stop by and see what he was up to.  Which was usually very many people….

This excerpt is from a letter dated 30 August 1993.  It would take too long to set the stage for what this letter discusses, but I want to draw attention to the words “eye-balling” and “guessing” here.

Magnus’ focus was on building models, not on studying their precise mathematical properties.  So if he didn’t actually know exact coordinates for a model, he would approximate, and build what he called a variation of the abstract mathematical model.

But here, Magnus is being somewhat humble — for his eye-balling and guessing is scaffolded on decades of model-building experience.  It’s like giving a chef who graduated from Le Cordon Bleu a bowl of soup, say, and asking him or her to “guess” what spices were used.  You’d get a lot more than just a guess….

This intuition about three-dimensional geometry was absolutely key to Magnus’ model-building success.  If a spike on a model was too “pointy,” Magnus would simply design a variation with the features he wanted.  And somehow, almost magically, they always turned out wonderfully.

This next excerpt is dated 13 September 1993.  The important quote here is the last complete sentence.  As I mentioned last week, Magnus is best known for his trio of books Polyhedron Models, Spherical Models, and Dual Models.

Magnus is not the first to have enumerated all the uniform polyhedra; this had been done by a few others earlier — Coxeter (et al.) published a complete enumeration in 1954, Sopov proved completeness of the list in 1970, and Magnus’ Polyhedron Models was published in 1971.

And even though Polyhedron Models was always the most popular of the three books, Magnus’ felt that Dual Models was more significant since it was the first time all the duals of the uniform polyhedra were published.

I also note his use of words:  “more significant.”  I don’t think Magnus would never had said “I am more proud of Dual Models.”  He was not a prideful man, always giving credit to his God for his insights and abilities.

But I think significance here is all relative.  In terms of popularizing polyhedra and model building, Polyhedron Models was certainly the most significant of the three books. But in terms of a contribution to the mathematics of polyhedral geometry, I would agree with Magnus that Dual Models was the most significant of the three.

Of course Spherical Models is quite wonderful, too….  But in this book, Magnus indicated how to build (or approximately build) a wide variety of spherical models.  However, moving in this direction is much more difficult mathematically and in some sense broader than just considering the uniform polyhedra or their duals, since there are many ways to build a spherical model based on a given polyhedron.  So there would be little hope of being so comprehensive when discussing spherical models.

I include this next excerpt since it is one of the few times Magnus has mentioned his own abilities in his letters — it also echoes the excerpt from 30 August 1993.  So there is little more to say here, except to note that he mentions his intuitive abilities are derived from building over a thousand models, not to any inherent ability.  Again, an instance of his humility.

In this excerpt, I point to the phrase, “…holding a real model in my hands is still my greatest thrill.”  Those of us who knew Magnus absolutely knew he felt this way about model building.

Because of his extensive polyhedral network, he had connections with mathematicians who helped him with precise, computer-generated diagrams to help him make models for his books.  But he was less interested in the details of how the diagrams were made than he was in diving right into building the models themselves.

He was also well aware that computer graphics were an excellent tool which could be used to discover new and wonderful polyhedra — changing a parameter here or there would result in a different polyhedron, and it is easy to look at parameterized series of polyhedra with a computer.

But, this was all in aid of model building, not an end in itself for Magnus.  There are plenty of others who focus on the computer graphics — as it should be, since any polyhedral enthusiast will have their own particular areas of interest and expertise.

Only five excerpts, and it’s time to finish!  I didn’t realize I had so much to say about these snippets of correspondence.  But I hope you are beginning to have some insight into who Magnus was and what he accomplished.  I’ll have still more to say as in the next installment of excerpts from my correspondence with Magnus.