Imagine Niagara Falls. Now multiply it, again and again and again.
Every day the sun beats down on the Earth, its energy literally making life possible. How much energy? A flow of 120,000 terawatts, which is, as science writer Oliver Morton puts it, "10,000 times the amount that flows through our industrial civilisation - all the world's reactors, turbines, cars, furnaces, boilers, generators and so on put together." Still can't quite picture what that amounts to? Morton has written a stunning little thought experiment to help. Here's how it goes:
Picture Horseshoe Falls, the most familiar, forceful and dramatic cataract in Niagara Falls, in full spate.
Now increase the height of the falls by a factor of 20; a kilometre of falling water, a cascade higher even than Angel Falls in Venezuela.
Now increase the flow by a factor of 10. Instead of 30 tonnes of water falling over each metre of the lip of the falls every second, allow 300 tonnes of water per metre.
Finally, widen the falls. Stretch them until they span a continent, with billions of tonnes of water falling over them every second. And don't stop there. Go on widening them until they stretch all around the equator: a kilometre-high wall of water thundering down incessantly, cutting the world in half, deafening leviathan in the abyss.
That is what 120,000 terawatts looks like. That is what drives the world in which you live.
So awesome. It's little wonder that Wikipedia's list of solar deities runs so long.
This article available online at: