Per Bak is a critical (pun not intended) researcher in this field, having been one of the first to devise the famous sandpile experiments in which grains of sand are dropped one by one onto a pile of sand and the size of the subsequent avalanches recorded. From here to theoretical models of ridiculous simplicity modelled on desk top computers which provide results which closely match phenomena as diverse as:
- The distribution of earthquake size
- The distributions of extinctions within the fossil record
- Learning
- Economics
- Traffic jams
The suggestion is that many systems evolve into a position of 'Self Organized Criticality'. At this point small external events will trigger adjustments of the system, some of which will be unnoticeably small and some of which will be enormous. Key insights are:
- That you do not need to postulate an external trigger for a catastrophe, systems such as the world's ecosystem or a the world's stock markets are always on the edge of catastrophe anyway so that a very small trigger can create a massive landslide (but normally doesn't, of course)
- That these systems are very large so that you need to consider the entire ecosystem of the world (which might include the atmosphere - life creates oxygen - and the oceans and the landscape) or the entire geological system of the world (earthquakes and plate tectonics etc) or the economics systems of the world or an entire brain etc
- That these systems may be hierarchical such that complex astrophysical systems give rise to complex geological systems which give rise to complex biological systems (eg life) which give rise to complex ecological systems etc etc.
This was a fascinating book, mostly very readable, which gives insight into this fascinating new science. A slight criticism is that the bibliography appears quite selective and some of the researchers mentioned in the text do not appear, making it difficult to access their original work.
July 2015; 198 pages
Other books covering this interesting topic include:
- Deep Simplicity by John Gribbin which is an immensely readable and interesting overview of this area and similar non-equilibrium systems and 100% recommended
- Emergence: from chaos to order and Complexity: a very short introduction, both by John Holland, one of the leading experts in the field
- Ubiquity by Mark Buchanan
- At Home in the Universe by Stuart Kauffman, the inventor of the NK landscape model
- Six degrees about small world networks by Duncan Watts
- sync by Steven Strogatz
- Smart swarm by Peter Miller
- The Information by James Gleick although his Chaos (not reviewed on this blog) is perhaps better
Other books not reviewed on this blog on this topic include:
- The Wisdom of Crowds
- Tipping Point by Malcolm Gladwell about fads
- Ubiquity which is brilliant about fractals and power laws
- Critical mass by Philip Ball which is a brilliant explanation about phase changes
No comments:
Post a Comment