chalkdust been directly detected. There are alternatives: one could, for example, modify the laws of gravity on large scales, an approach that Stewart believes shouldn’t be neglected. “I think modified gravity is the way forward. I don’t think the impetus of dark maer is that strong.” Physicists would lead you to believe that “it is dark maer; we know it’s there”, but Stewart doesn’t find the evidence convincing: “there are a lot of neglected alternatives: that’s bad.” From his airy oﬀice, it was to a more visible sign of the wonders of our universe that Stewart went with his family for Christmas: the northern lights. A well-deserved break for one of mathematics’ most famous and best communicators. Trupti Patel is a PhD student at the London Centre for Nanotechnology at UCL. She works on superconducting quantum interference devices. Mahew Wright is a PhD student at the Department of Mathematics at UCL. He works on cosmology and modified theories of gravity.
My favourite shape Everyone loves a good shape. You may think that you learnt all the shapes at primary school, but there are plenty still around that mathematicians find interesting. We have spread some of our favourites throughout this issue. We’d really love to hear about yours! Send them to us at chalkdustmag, and you might firstname.lastname@example.org, @chalkdustmag or just see them on our blog!
Penrose tiles Rudolf Kohulák
My favourite shape is a rhombus that has been split into two pieces called ‘kite’ and ‘dart’. These shapes might not look interesting, but the British physicist Roger Penrose discovered an unusual feature of these objects. They can be arranged to cover the whole plane without any gaps or overlaps. However, the resulting image is highly unsymmetrical. For instance, it lacks translational symmetry (ie you cannot shi the paern such that the result would end up being identical to the original picture). The discovery revolutionised the field of crystallography and led to the identification of quasicrystals.