This week saw the publication date of a little book that, I confess, I am very excited about. I have always enjoyed and admired the Very Short Introduction series from Oxford University Press, and learned a great deal from the 30 000 word lay guides to topics from Abolitionism to Zionism, and everything (in several hundred titles) in between.
So I was thrilled to be asked by OUP to write Soft Matter – A Very Short Introduction, about three years ago. The final little volume was published on Thursday. This is the delightful field of interdisciplinary science in which I have worked as a theoretical physicist since the mid-1980s, a generation and more that has seen its birth and transformation into a global and mature field. One of the satisfying characteristics of soft matter is that its subject connects materials we meet with in daily life with deep scientific ideas. Rubber, creams, foams, inks, and even food – all these provide windows onto the molecular and microstructure worlds beneath their familiar properties.
scale, and (right) under the microscope
Soft matter reminds us of one of the most beautiful functions of science – that it reminds us of the difference between the ‘familiar’ and the ‘understood.’ Just because we are familiar with the experience of sitting on chairs and not falling through them does not mean that we understand the ability of atomic structures, themselves composed almost entirely of empty space, to support us. Just because we are familiar with the huge extensibility and resilience of rubber does not mean that we understand how a solid could be deformed by 500% without breaking. Rather than titling the chapters, therefore, under their scientific structural categories of ‘colloids’, ‘polymers’, ‘foams’ etc., they became, ‘milkiness,’ ‘stickiness,’ ‘foaminess,’ and so on.
Soft Matter is also satisfying because it brings communities and ideas from physics, chemistry, materials science, engineering and more. It embodies the interdisciplinary that requires team-building, an appreciation and understanding of each others’ methods, experiments and models. The polymer (plastic) research that I spent 25 years pursuing required chemistry to make the molecularly-tailored materials, materials scientists to measure their special flow-properties, experimental physicists to explore their molecular-scale deformation with neutron-scattering, chemical engineers to design carefully-interrogated process-geometries for them, theoretical physicists to create mathematical models for the way that elastic flow emerges from their entangled molecular chains, and computer scientists to develop and apply novel simulations of the flow. Furthermore, this broad academic community needed to talk continuously to a ‘mirror-team’ in a consortium of industrial laboratories, with whom we exchanged data and ideas.
It was therefore interesting that when the Principal of Oxford’s theological seminary Wycliffe Hall, Michael Lloyd, asked me as speaker for the college’s weekly ‘Principal’s Hour’, he suggested that I talk on ‘Soft Matter’ rather than the science-theology or even medieval science work that I also work on. Bravo Wycliffe Hall for an interest in science itself! There were great questions on the science of Brownian Motion, the fascinating dynamical source of softness itself, for example. But the hour also gave me a chance to contemplate the human and theological implications of the unexpected ability to do science in the first place.
The students did not, of course, entirely escape a visit to the Faith and Wisdom in Science core-text: the biblical Book of Job, shot-through as it is with reflection on the natural world. Even Job himself chooses soft matter properties at one point to complain at the chaotic decay of the material world outside, and even within him:
You molded me like clay, do you remember? Now you turn me to mire again. Did you not pour me out like milk? Did you not curdle me like cheese? With skin and flesh you clothed me, with bone and sinews knit me together. (Ch 10)
We were able to look at great Hymn to Wisdom of Job chapter 28, and its musing, through the experience of miners under the ground, on the unique way that human eyes perceive, as those of its Creator do, the hidden inner structure of the Earth. It bore close comparison to the description of the scientific imagination that appears in many later ages. The words of the 13th century polymath Robert Grosseteste, for example, knows what it is to imagine the inner structures of materials that give rise to their observed and felt properties:
“… the penetrating power in virtue of which the mind’s eye does not rest on the outer surface of an object, but penetrates to something below the visual image. For instance, when the mind’s eye falls on a coloured surface, it does not rest there, but descends to the physical structure of which the colour is an effect. It then penetrates this structure until it detects the elemental qualities of which the structure is itself an effect.”
Soft Matter illustrates this extraordinary human gift perfectly. When we look at milk, we may ‘see’ myriads of tiny fat particles suspended by continual thermal jostling from water molecules. When we notice the stringy way that melted plastic flows, we may ‘see’ a molecular jungle of entangled molecular chains.
The delicate interplay of order and chaos within the forms of soft matter are themselves a metaphor for the tension of order and chaos necessary for life to flourish, as Job found. Soft matter science is also, as the final chapter of Soft Matter – A Very Short Introduction explains, itself helping us to understand how living tissue works. One day it may point to the way life itself originates.
Faith and Wisdom in Science 