The scientist Jeffrey Dukes was driving through the deserts of Utah on his way to a research station a few years ago. As his car ate up the miles, he began thinking about the fuel in the tank, and the plants that it had come from. How many ancient plants, he wondered, had it taken to power him across the desert? He asked around, but couldn't find out. “The more I searched, the more frustrated I got. No one knew the answer” (quoted in Willis, 2011). So he did the sums himself. He worked out that a staggering 25 tonnes of plant matter go into every single litre of petrol. Imagine that: if you drive an average car, you would need 25 tonnes of plants every ten miles or so. That's six times the weight of your car.

The fossil fuels that power our cars, and that still provide 70 per cent of the energy we use worldwide (International Energy Agency, 2018a), are the remains of plants that grew millions of years ago. Those plants used photosynthesis to turn sunlight into carbon; over millions of years, this was condensed into coal, oil or gas, below the earth's surface. We started to dig it up in any serious quantities around 500 years ago – and we’ve been using it at quite a rate. According to Dukes’ sums, the amount of fossil fuel we use per day is roughly equal to all the plant matter that grows on land and in the oceans over a whole year.

Dukes’ maths had a profound effect on him. “I realized,” he told me, “that nearly everything I do depends upon plants that grew millions of years ago; and that without them, my life would be completely different.” The modern world that we take for granted is shaped by what Dukes memorably calls “buried sunshine” (quoted in Willis, 2011).

As Dukes shows, contemporary life in industrialized countries depends on a constant flow of fossil energy. In the UK, we each use, on average, fifteen times more energy than we did before the Industrial Revolution. My favourite illustration of our energy use is the most eccentric of all.