Something in the water

The astronomer Arthur Eddington once pointed out that where most people see a coffee table, physicists see an area of empty space criss-crossed by ghostly subatomic particles whose electrical and magnetic fields keep books and magazines from falling to the floor.

Climate scientists are similar. They know that Russia's burning peatlands, the floods in China and Pakistan and the fatal cloudburst in the Himalayan desert in early August are the consequence of billions of molecules criss-crossing the planet. You know these molecules as water. Scientists have so far recorded 67-odd properties of water. Among these are that it alone expands upon freezing, and that turning it from liquid to gas requires a huge amount of energy.

These things matter. If water didn't expand upon freezing (due to an electrical interplay between its hydrogen and oxygen atoms), life would never have begun on earth. Ice wouldn't float on water and the oceans would have frozen solid from the bottom upwards. Perhaps a thin layer of liquid water would skim the planet's surface, but not enough to allow the development of complex life.

That it takes a great deal of heat to change water to a gas slowed the problem with the Russian peatlands; they ignited only after the peculiarly hot sun had evaporated all the moisture in the surrounding earth. The downside of water's high "heat capacity" is that water vapour and clouds in the atmosphere trap a lot of heat, and thus play a role in global warming. Water molecules are absorbers of the infrared radiation reflected off the earth's surface - bigger absorbers than carbon dioxide, in fact. The only reprieve comes from the fact that water vapour and clouds are quickly condensed to rain, and thus have a transient blanketing effect.

Not that anyone in Pakistan is grateful for the sudden precipitation of water molecules from the atmosphere. Aside from the destruction, the spread of cholera relies on water. How ironic, then, that the cholera bacterium kills human beings through dehydration.

The machinery inside biological cells works only in the presence of water. Copying DNA and making proteins, for instance, relies on the guidance of the electrical charges in nearby water molecules. Take away the water, and we die. Water and life are therefore inextricably connected - and largely through the water molecule's extremely sensitive relationship with heat energy.

Researchers studying the Pacific Ocean reported in mid-August that even a cloud of phytoplankton, tiny ocean-borne plants, can warm the surface water enough to make it more easily whipped into tropical storms and cyclones. On the fifth anniversary of Hurricane Katrina's destruction of New Orleans, it is worth noting how even a little change in temperature can make all the difference.

Michael Brooks holds a PhD in quantum physics. He writes a weekly science column for the New Statesman, and his most recent book is At the Edge of Uncertainty: 11 Discoveries Taking Science by Surprise.

This article first appeared in the 30 August 2010 issue of the New Statesman, Face off