From Guy Inchbald, Upton-upon-Severn, Worcestershire, UK
Causal emergence – the idea that the cause of some events can’t be found at the microscopic level – is revolutionary in more ways than one (28 May, p 44). The concept seeks to explain physical phenomena that can’t be reduced to the current pillars of physics: relativity, quantum physics and thermodynamics. This idea must include new physical laws, independent of the established set, and would give a significant role to macroscopic information.
Communications engineering has a sophisticated information theory of its own, which includes the idea of information entropy, a measure of how deterministic a system is. Might incorporating this concept into classical thermodynamics prove sufficient to explain causal emergence? Might it offer up the missing physical principle, or will we need to create a new theory as a fourth, independent pillar of physics? Wherever this leads, information will take centre stage.
