The 2017 solar eclipse will help scientists figure out just how much energy we get from the sun


Every living thing on Earth (except for a handful of exotic exceptions) gets its energy, directly or not, from the sun. If it’s green, or eats something green, or eats something that eats something green, you can bet it’s solar powered.

But although all that solar energy runs the planet, it also heats the planet, and in an age of climate change, it would be awfully helpful to know precisely how much energy the sun is sending our way.

But it turns out that’s pretty hard to calculate, since there’s usually a shifting screen of clouds between the sun and the Earth, which reflects energy back into space. While we see clouds often, scientists haven’t cracked how to accurately calculate how much energy they block. They’ve developed a mathematical model, but aren’t sure if it matches how energy dynamics work.

That’s in part because clouds have such irregular surfaces — they aren’t a smooth mirror, they reflect energy in lots of different directions at once. And clouds are always growing, shrinking, and moving.

The moon is much less troublesome — we know the details of its shape and composition. And on Aug. 21, it will be acting, in some ways, like a giant cloud as it casts a shadow on Earth.

So scientists can use it to work on the math behind their energy calculations. They’re planning to take measurements from two spots along the path of totality, in Wyoming and Missouri. At the same time, they’re enlisting instruments on satellites orbiting Earth: The Earth Polychromatic Imaging Camera has been taking stunning portraits of Earth since 2015 and the twin Moderate Resolution Imaging Spectroradiometer instruments specialize in climate data.

Pulling all those measurements together will let the scientists check a prediction they make in advance of the eclipse with their mathematical model. How closely the two numbers match will tell them how close they are to cracking the puzzle of how to model the impact of clouds on climate.