Tuesday, 27 May 2014

Lovelock and Reynolds

I was listening to James Lovelock talking the other day and something he said struck a chord. Although he's something like Moses to the ecological pantheon, his own views towards the environment and especially global warming are somewhat ambivalent. He lamented that an ecologist used to be someone who enjoyed walking in the country, but has become an angry protester.

Although the reaction of many to the amount of energy we are using is one of horror, he viewed the whole system in terms of the Reynolds number, and the increase in turbulence with more energy. Reynolds studied non-laminar flow, and you can see the effect of his eponymous number as you turn on a tap, first in a steady trickle, then with ripples and curves as the flow increases, and finally with splashes and crashes as it turns to chaos. In the same way, as we use more energy human output becomes much more interesting, and Lovelock suggested a threshold of one kilowatt per square metre for this to happen.

You probably don't need me to tell you this, but that's the amount of energy that comes from the sun. There are two implications, one dreadful, and the other divine.

The divine implications is that all of the stuff that's happening can be attributed to a concept from physics, and what appears to be chaotic and out of control is just business as usual for the universe. It's tempting to think of the world like a top that has been spinning merrily and steadily for a long time, and is now wobbling erratically before falling over at the end of its turn. Looking at the Reynolds number, rather than about to fall over, we are just starting to taking off.

The dreadful implication is that if we are going to continue to be "interesting" we need to continue using a kilowatt of energy per square metre, and this is not sustainable if we're using primary solar energy in the form of photovoltaics, secondary solar in the form of wind and waves, or historical solar in its various fossil forms.