5.2 Complexity

A couple of years ago I read Mark Riddley's Mendel's Demon by which he received great accolades for explaining the rise in complexity in the biosphere. In the introduction he says the following..
“Complexity is an ill-defined term, and I have been tempted to avoid it completely. I do not think it is meaningless to say that some forms of life are more complex than others, but I am as puzzled as anyone by what exactly I mean when I say it. There is no biologically agreed definition of complexity, but I suspect most people would agree on what should contribute to it. Structural complexity is one factor.”
Bit of problem I would have thought, not knowing what it is you are trying to explain? He ends up choosing the number of genes in an organism as his measure of complexity, 'the number of the beast'! Convenienly avoiding the origin of the gene itself and life in the bargain. Well he is only a biologist.. if we want a definition which covers the whole spectrum of nature both non living and living then our definition must work in both. It must be a measurable quantity which in theory may be calculated for any state of matter. Sounds like a real toughie.. but is it?

Recall 'entropy' from 4.5 above.. we said it was a measure of the 'disorder' or how close a signal is to a random jumble from Shannon's 'inverse' information theory. Well, according to something Ludwig Boltzmann discovered (about 1904) this same measure also applies to any state of matter! Just what we are looking for. The term entropy was first coined by Rudolf Clausius around 1857 based on the observation that heat energy always moves by conduction through matter from hot to cold. He does not 'prove' this but uses it to establish a law of thermodynamics called the Second Law. Now laws are laws because they are inviolable.. its known so well we can say with confidence it will never be violated.

It says that in a 100% sealed system containing both mass and energy if they are not evenly distributed then after a period of time they will be. As it becomes more 'disorderly' the entropy will increase and cannot by itself decrease. This law is about as close as we will come to having an 'absolute' truth in science..

Have a nice day..