Irradiate maize, and it will begin frantically shuffling its chromosomes. Starve E.coli and it will accelerate its mutation rate. Many organisms have this response to stress. They throw the wildest possibilities at the wall to see what might stick, which is to say, what strange version of themselves might survive. They create disorder that might restore order.
From a chaotic disk of gas, a planet forms and migrates into a stable orbit. Twin moons are brought into resonance. For every turn Enceladus takes around Saturn, Dione takes two. Tidal interactions with the planet keep this ratio steady. Disorder has coalesced into order.
A group of Oxford professors have undertaken to bring these types of phenomena together. In a series of lectures and a book, they explored from fields as diverse as musicology, physics and group theory the symmetry in the universe, especially that between order and disorder. Despite some excitement that they might be approaching a grand theory of everything, the results are loosely connected and, so far, half baked, but it’s the kind of half-baked that reminds you how good cookie dough tastes. It’s what you might imagine goes on at a university until you actually work at one.
Symmetry can refer to reflections, or else objects that are well-proportioned in the way that Leonardo da Vinci envisioned the proportions of the universe. Benedict Rattigan, who introduced me to the symmetry project, gave a tour within the British Museum to show that cultures vary in their acceptance of disorder, decay, and death. They express that through how rigidly symmetrical their art and architecture are, and whether they exclude disorder, or else depict it in a battle with order. Some cultures rather celebrate disorder (think: mardi gras or various days of the dead) within ordered confines in space and time.
But symmetry in a scientific sense is any kind of transformation that leaves a system in the same state as before. A circle can be rotated without changing anything, and the conservation of angular momentum—what makes a figure skater spin faster when they pull their arms in—is a continuous symmetry. A fractal can be zoomed in on itself and remain unchanged, forming a kind of self-symmetry.
Many of the laws of physics are a result of symmetries, but others depend on symmetry being broken. The one-way arrow of time, illustrated by the progressive increase in entropy, shows that time is not symmetrical – we cannot run the Universe backward and have the same thing happen.
One of the most compelling submissions in the collection came from physicist Alan Barr, who talked about light and darkness. Darkness, it turns out, can be an absence of light, or it can be much more. It can mean that a black crow has absorbed visible light—only to emit it at an invisible frequency—or that there is matter present that is entirely transparent to light. That matter could be a neutrino or dark matter—or light itself. In not interacting with another light beam, he suggests, light itself has the properties of darkness.