Sabine Hossenfelder (No one in physics dares say so, but the race to invent new particles is pointless, 26 September) has missed the point of a big part of particle physics, and indeed fundamental research as a whole. While we’d all like to revolutionise our respective fields by discovering a new particle or otherwise, in reality, winnowing out the impossible – the particles that don’t exist – is an equally important, if painstaking, function of science. Nature has an infinite capacity to surprise, and our scientific forebears learned long ago to take nothing for granted. Every impossibility proved gets us closer to a deeper understanding of the real universe; it’s just as important to know that faster-than-light travel is impossible as it is to understand that light is made up of photons, for instance.
It would of course be tremendously tedious to rule out every last outlandish possibility (Hossenfelder’s octopuses on Mars, for example), and so we need a set of principles to guide us on where to look. There is general disagreement about what works best, but many of the hypothetical particles mentioned in the article have been designed with useful functions in mind – breaking cherished principles of the standard model for instance, or adding new features to it. What we’re testing are the principles themselves, not the particles; while some of them might really exist, others are simply straw men to help us formulate useful tests.
Dr Phil Bull
Reader in cosmology, Jodrell Bank Centre for Astrophysics
