The Second Kind of Impossible: The Extraordinary Quest for a New Form of Matter

"It’s a window on the process of discovery, a blow-by-blow account of a long wrangle with theory and evidence. Paul Steinhardt — a cosmologist fascinated by novel forms of matter — relates his indefatigable decades-long quest for an ‘impossible’ material, the quasicrystal, with Holmesian intensity. And yet the journey is never less than engaging. Steinhardt immerses us in the human stories as well as the maths and physics. This is a book offering a real sense of the collaborative, generous-minded aspect of doing science. As for the thing discovered, Steinhardt delivers an excellent primer on his quarry. Quasicrystals are a form of matter upending the rules on crystalline structure. Crystals are periodic, or repeating, arrangements of atomic clusters forming regular shapes such as tetrahedrons. These shapes fit together neatly no matter how you rotate them — a phenomenon known as rotational symmetry. According to the laws, only one-, two-, three-, four- and six-fold symmetries are possible. That is, until the 1980s, when the work of Steinhardt, his collaborators and others began to reveal the possibility of other symmetries — and of quasicrystals. I loved how Steinhardt and then PhD student Dov Levine approached their theoretical experimentation on atomic arrangements — with paper, magnets, Styrofoam and pipe cleaners. Soon it resembled “an arts-and-crafts project gone berserk”. The two then discovered Penrose tiling – geometric patterns discovered by mathematical physicist Roger Penrose that had the necessary symmetry. It was the push they needed to give their work legs. “This is a book offering a real sense of the collaborative, generous-minded aspect of doing science” A thrilleresque edge emerges with a startling coincidence. In the early 1980s, materials scientist and Nobelist-to-be Daniel Shechtman had stumbled upon an ‘impossible’ 10-fold symmetry in grains of an aluminium-manganese alloy. When Steinhardt discovered Shechtman’s work in 1984, he was – briefly – the only person who’d seen both that experimental pattern, and the theoretical one he and Levine had worked on. It’s a riveting moment in the book. Two teams, working 150 miles apart, had made wholly complementary breakthroughs unbeknownst to each other. There are more scientific epiphanies, mixed in with hard knocks: Steinhardt is a master at conveying the emotional seesaw of lab life. But he takes it further: all the way to Siberia. Amid cooling interest in the scientific community, finding a quasicrystal in nature becomes an imperative. The narrative enters geological and ultimately expeditionary realms. Steinhardt and a by-now substantial team go quasicrystal-panning in Russia’s far east, dodging mosquitoes, freezing rain and gargantuan Kamchatka bears. It’s to Steinhardt’s credit that this mud-drenched phase of the adventure does not eclipse, in terms of thrills and spills, the long slog of labwork. By the time he and the many scientists he’s worked with triumph, you’re cheering with them. I emerged feeling as if I too have traversed a tumbled landscape of diffraction patterns and tundra into a new understanding of the world."

"Classic crystals are solid materials in which the atoms are arranged in definite repeating patterns. The patterns are clusters of atoms that repeat over and over in any direction with equal spacing—periodically. Quasicrystals are different. Like crystals, quasicrystals contain an ordered structure, but the patterns are more subtle. They do not recur at precisely regular intervals. Paul Steinhardt, a world-renowned physicist, takes us on a journey through the history of our understanding of crystals. He explains how scientific orthodoxy came to a firm view as to the sorts of structures nature would generate. These were periodic, repeating patterns of a particular geometric structure. Steinhardt’s own work was initially theoretical and inspired by, amongst others, Roger Penrose. This showed how non-periodic structures could be generated that packed all the space available using for example two different structures. Get the weekly Five Books newsletter If such structures existed, then they would produce very distinct crystallographic diffraction patterns—these are the images that result when X-Rays are passed through crystals and hit the atoms in their particular arrangements. No one had ever seen these patterns, and they were thought to be impossible. The ‘second kind of impossible’ references Steinhardt’s teacher Richard Feynman who used ‘impossible’ to sometimes allude to “something amazing that contradicts what we know to be true”. Feynman saw the diffraction patterns of a kind of matter that had not been encountered yet and deemed it in this sense ‘impossible’. The book recounts how this type of matter was first produced synthetically in the laboratory. In the second part of the book we go on a globe-hopping journey from Princeton to Italy to the remote mountains of Russia’s Kamchatka Peninsula in pursuit of tiny fragments of a meteorite forged at the birth of the solar system which contained the first confirmed examples of naturally occurring quasicrystals. Steinhardt himself led the expedition. This is a book full of great science and human adventure written from the perspective of someone at the heart of that story."