Why Lustrum14?

At present this blog has no readers. Zip. None. Not a soul. That may change or it may not: we shall see.

But for all you non-existent readers I should explain why I have called this blog "lustrum14". Until this morning I did not know that a "lustrum" is a word that means a "period of 5 years". I learned this because I am reading (just finishing) Siobhan Robert's book on the English mathematician (now at Princeton) John Conway which is called Genius at Play. She quotes Conway explaining what is a lustrum. Conway says he has seen it used in Disraeli's Sybil "where it says of a young man that he had not yet finished his fifth lustrum". This means he was not yet 25. I have read Sybil but do not recall this; I have a habit of seeing new words and just skimming over them rather than looking them up.

Anyway, be all that as it may, I am now 65 and therefore in my fourteenth lustrum. Hence the name.

Siobhan Roberts also wrote King of Infinite Space which is a biography of H S M (Donald) Coxeter. Coveter is another English mathematician who ended up on Canada. He wrote An Introduction to Geometry which I always say is the one book I would take with me to a desert island. My link between Coveter and Conway (and Conway admired Coveter greatly) is Euclidean. Coveter has a wonderful group theoretic proof in his book about why you cannot trisect and angle with ruler and compass. The Conway book contains Conway's beautiful proof of Morley's Trisector Theorem. This was one that Euclid missed: Frank Morley found it in 1904 and it says that "the points of intersection of the adjacent trisectors of the angles of any triangle are the vertices of an equilateral triangle".

Each vertex of the outer triangle is trisected. Morley's trisector theorem states that the purple triangle is equilateral.

Every now and then I expect this blog to wander into the mathematical realm: I used to be a mathematician but now I struggle to get much of it. That is an unavoidable consequence of being in one's 14th lustrum!!