chalkdust orem, and they think about close and related mathematical ideas to keep it alive. Whereas some people, such as Terence Tao, constantly do fiy pieces of work simultaneously in what appear to be totally unrelated areas of mathematics and so oen put them together.” He thinks it is good for mathematicians to move out of their comfort zones, as in doing so you oen find spin-oﬀs back into your own area, and it helps you avoid geing stuck in a rut. Although he concedes that for some people this doesn’t work: “you may end up geing distracted by several things but end up doing nothing!”. What does Stewart think of the relationship between research and popularisation? He believes mathematical research does help with popularising science and maths, and gives authority to his writing. Most people who write about pop science usually work in the field and have developed a skill of being able to write in a way others would understand. But there are exceptions, and there are some excellent journalists who spend a lot of time talking to scientists and trying to understand what is going Ian posing in a Chalkdust T-shirt. on; Stewart believes both approaches work. The relationship between popularisation and research can work both ways however; in fact, he has oen found that popularising something has helped his research. “Writing for a diﬀerent audience makes you rethink everything—oen you find that as you try to explain things to an audience who do not understand things perfectly well, you realise you don’t understand it as well as you thought. And so you get feedback in both directions.” Popularisers also get exposed to diﬀerent areas of maths that can inspire new research ideas. It was having to review a book on robot locomotion for New Scientist, for example, that got Stewart thinking about how animals walked, spawning a whole new area of mathematical inquiry in which he has subsequently published many papers.
Writing for a diﬀerent audience makes you rethink everything. Stewart’s next book, due out at some point in 2016, is called Calculating the Cosmos, and will look at cosmology and astronomy through the window of maths. He sounds particularly excited about this book, and believes it potentially is his best yet. In 17 Equations that Changed the World he was quite outspoken about cosmologists’ current ideas about dark maer, dark energy and inflation. We asked him what his thoughts were now. “I still am outspoken!”, he exclaims. There is a large amount of energy missing from the universe, and the dynamics of objects such as galaxies don’t seem to agree with our theoretical predictions. To account for this, physicists have to add extra energy components to the universe: dark maer, dark energy and the inflaton. This certainly works: the maths can now accurately describe the dynamics of the universe we observe, although these extra components have never chalkdustmagazine.com