Editorial

Spring is here in the UK at last! I am always glad when winter is on its way out. I have just returned from a two-day IUCr Finance Committee meeting in the city of Lund (Sweden), where I heard about the creative work carried out by our new Marketing Executive, Kezia Bowman. Kezia will be involved in developing marketing strategies to promote the IUCr and its publications and initiatives, and creating engaging content for diverse audiences. I wish her success in this important role.

In this issue of the Newsletter, we have two articles from the Hargittais, one on the Russian crystallographer Vladimir A. Koptsik, who was an important contributor to symmetry groups, especially the so-called Shubnikov groups. These groups, sometimes called colour groups, explore all the possible symmetry operations in which alternating colours (say black and red) can be included. Most crystallographers will already be familiar with the 230 space groups, which relate possible atomic positions subject to symmetry constraints in three dimensions. The Shubnikov groups add the possibility of positions for species with alternating properties, such as up and down electron spins. This is important for the study of magnetic crystal structures. There are 1651 such groups, and these were tabulated and illustrated by Koptsik in a weighty book (Шубниковские группы, published by Moscow University in 1966). I actually have a copy in front of me and I have to admire the enormous body of work that Koptsik achieved.

The other Hargittai article is on Johannes Kepler, he of planetary fame. Whereas his work on planetary orbits is well known, he was also interested in crystals and why they formed such symmetric shapes. Why, for example, were snowflakes hexagonal in shape? In 1611, he conjectured that there must be some underlying regularity in their internal structure, though he could not know what this structure actually was. He, along with others, such as Robert Hooke, considered the close packing of spheres as a way of explaining the external morphology of crystals: today we know that it is periodic arrangements of atoms and molecules that are responsible for the external shapes of crystals. Kepler famously considered, for instance, the three-dimensional packing of spheres (this was related to the problem of how to keep cannon balls from rolling around the deck of a warship). Kepler’s conjecture was that the so-called cubic and hexagonal close packings were the most stable arrangement (think of the way oranges can be stacked together on a fruit stall). Surprisingly, his conjecture was not fully proved until very recently by T. Hales, S. M. Adams, G. Bauer et al. ["A Formal Proof of the Kepler Conjecture" (2017). Forum Math. Pi, 5, e2]. So that took just over 400 years to solve!

I was intrigued when a friend of mine in India sent me a poem that she had found that mentioned a famous scientist who played an important role in our understanding of X-rays and atomic physics, namely Harry Moseley. He was killed in battle at Gallipoli in 1915 and this poem was published 10 years after. Many years ago, I went into the office of one of our secretaries and noticed a cardboard box in the corner behind the door. I also saw that every time someone entered the room, the door was slammed against the box. I looked inside the box, and there was one of Moseley’s original X-ray tubes, very similar to the one seen being held by Moseley in my article about the poem. Miraculously, despite its fragility, it had survived despite its rough treatment. It can now be seen in the small museum at the Clarendon Laboratory.