“Only a tiny proportion of the sun’s energy reaches us, yet it amounts to 3,766,800 exajoules of energy each year (a joule is a unit of energy in the metric system, about the amount you expend to lift a small apple one yard straight up; an exajoule is a billion billion joules – that’s a lot of apples). All the world’s plants capture only about 3,000 of those solar exajoules through the process of photosynthesis. All human activities and industries put together consume about 500 exajoules annually, equivalent to the amount of energy earth receives from the sun in just ninety minutes. And that’s only solar energy.”