Me and My Breakfast Cereal
- A Different Universe: Reinventing Physics from the Bottom Down by Robert Laughlin
Basic Books, 254 pp, £15.50, September 2005, ISBN 0 04 650382 X
‘There is nothing new to be discovered in physics now,’ William Thomson, Lord Kelvin asserted at the British Association meeting in 1900. ‘All that remains is more and more precise measurement.’ Not to be outdone, the American scientist Albert Michelson said: ‘The grand underlying principles have been firmly established; further truths of physics are to be looked for in the sixth place of decimals.’
Nature repeatedly reveals the limits of our collective imagination. The discovery of the nuclear atom, and the rise of quantum mechanics and relativity, showed how naive Thomson and Michelson had been. Yet, undeterred by the lessons of history, many modern theorists and popular science magazines now tout the current candidate for a Theory of Everything: superstring theory. This posits that all physical forces are gravity acting in a Universe with ten dimensions, whose matter is made up of strings on a scale so small that a billion billion of them could fit into the nucleus of a hydrogen atom. Even without the intervention of experiments that might show such a theory to be highly presumptuous, Robert Laughlin cautions against searching ‘on smaller and smaller scales for meaning that is not there’.
Laughlin’s central argument is that instead of becoming obsessed with ultimate theories we would do better to focus on those properties of matter that ‘emerge’ from the organisation of large numbers of atoms. Examples of emergence include the hardness of crystals, the self-organisation of vast numbers of atoms that we know as life, and even the most fundamental laws of physics, such as Newton’s laws of motion.
Emergence is said to occur when a physical phenomenon arises as a result of organisation among any component pieces, whereas the same phenomenon is not produced by the individual pieces alone. Thus in art, the individual brush strokes in a canvas by Renoir are randomly shaped and coloured seen from close up, yet when viewed from a distance the whole becomes the image of a field of flowers. It is the very inadequacy of the brush strokes themselves that shows the emergence of the painting to be a result of their organisation. Analogously, individual atoms can form an organised whole which can do things that individual atoms, or even small groups of atoms, cannot. Thus one proton or electron is identical to another. All they can do individually is ensnare one another by their electrical attraction, thereby forming atoms. The electricity within atoms enables groups of them to join up, making molecules. Put enough molecules together and they can become self-aware, in the form of human beings.
Certain metals can expel magnetic fields when they are cooled to ultra-low temperatures, producing what is known as superconductivity, yet the individual atoms that make up the metal cannot do this. A more everyday example is the emergence of solids, liquids and gases from a large collection of molecules: we take it for granted that the floor of a plane flying at 40,000 feet will not suddenly lose its rigidity and release us into the clouds below, just as Eskimos trust the rigidity of the ice pack beneath them, even though a small rise in temperature could cause it to melt, leaving them stranded in the sea.
In a crystalline solid, the orderly arrangement of individual molecules into a lattice ensures the crystal’s solidity and also its beauty: carbon atoms may organise themselves into diamond, or into soot. In a solid, the individual atoms are locked in place relative to one another, but a rise in temperature causes them to jiggle a bit so that each is slightly displaced. The positional ‘errors’ do not accumulate, however, and the whole can retain its apparent solidity. In the liquid phase, the jiggling becomes so agitated that the atoms break ranks and flow.