A great introduction and overview of complex systems.

The definition of complex system is itself … well, not obvious. Sometimes complex feels like a synonym for not understood, but actually it’s more precise than that, referring to systems whose processes can exhibit macro-scale behaviour that isn’t simply the aggregation of the micro-scale behaviours of its components: the canonical example is that water freezes, but a single water molecule doesn’t. Another approach is to use the term to describe systems where chains of cause and effect are difficult to disentangle.

Whichever definition you prefer, this is a gentle but still very scientific introduction. There’s enough maths for it not to feel shallow, but little enough for it to be widely accessible even when dealing with concepts like entropy that are often a challenge to explain clearly. There’s a really good discussion of criticality and universality, as well as the irreversibility of phase transitions such as sand pile transitions. It’d be a good introduction for students.

4/5. Finished Sunday 5 February, 2023.

(Originally published on Goodreads.)