Today the Nobel Prize for Chemistry was awarded to Daniel Shechtman for the discovery of quasicrystals – a material whose components are arranged in a seemingly ordered pattern, but one that never repeats itself.
Earlier this year I interviewed mathematician Edmund Harriss for an unrelated feature about design and science, and he told me a wonderful anecdote about these curious materials:
I work on aperiodic tiling, sets of shapes that fit together but never becomes periodic – there’s never one single unit that repeats again and again. The initial example by Robert Berger had 10,000 different shapes, very much an abstract theoretical object, but that was brought down, to Penrose tiling, which has just two different shapes. Even today we don’t understand a lot about how this process works.
Most people regarded it as recreational mathematics, just an interesting problem. Then in the 1980s, Dan Shechtman managed to get a crystal structure in an x-ray diffraction pattern that had a five-fold symmetry. In three dimensional space, you can’t have a periodic structure with five-fold rotational symmetry. This showed that the structure of this crystal couldn’t be periodic. This ran against the central beliefs that chemists had about how crystals form. The discovery of these non-periodic crystals disappeared without a trace, and one of the arguments was that it was mathematically impossible. The mathematicians then refined what was mathematically possible, so when quasicrystals were observed again you had models for what was happening.
Alongside the transcript I’d jotted the note: “So we ignored the existence of quasicrystals until someone figured out their underlying design?”.
Sometimes, even in science, things need to be believed in to be seen.