More is Different is the title of a famous article (pdf) by Philip W Anderson in Science in 1972. In it he argues that when you go from say one electron or one atom or one molecule etc, to many electrons, many atoms or many molecules, then completely new behaviour governed by new laws of physics arise. Many molecules are different from one. A classic example of this new behaviour is the colour of gold, one gold atom is not gold coloured, only a crystal of many thousands or more gold atom is. Anderson argues for the importance and interest in studying behaviour like this that only happens due to having many atoms or molecules. He was pushing against particle physicists claiming that what was important was discovering the most fundamental particles, and that once they were known, then everything else (e.g., working out why gold is gold coloured) was just routine*.
I was particularly struck by the part where Anderson says: “The behaviour of large and complex aggregates of elementary particles, it turns out, is not to be understood in terms of a simple extrapolation of the properties of a few particles. Instead at each level of complexity entirely new properties appear, and the understanding of the new behaviors requires research which I think is as fundamental in its nature as any other.” I am writing a talk for a workshop on the behaviour of large and complex aggregates of proteins, which, it turns out, is not to be understood in terms of a simple extrapolation of the properties of a few protein molecules. Instead, in cells it seems likely that at each level of complexity entirely new properties appear, and the understanding of the new behaviours requires research which maybe as fundamental in its nature as any other. The workshop is at Princeton where Anderson is an emeritus professor.
I am really looking forward to the workshop. There is increasing evidence that in all our cells, proteins and other molecules are coming together into structures of thousands or more molecules, that are the analogs of liquid droplets. Just as the colour of gold is a collective property of many many gold atoms, some of the functions of our cells are a collective property of many many proteins, and I hope to learn more about that this week in Princeton.
* Perhaps a bit ironically for someone who pushed against some of the more arrogant particle physicists, the celebrated Higgs boson (aka God Particle) is associated with the Higgs mechanism, also known as the Anderson, Brout, Englert, Guralnik, Hagen, Higgs, Kibble and ‘t Hooft mechanism.
Chance & Necessity 