It was the middle of the 19th century when a mathematician realized that industrial growth was outstripping the production of coal, and we'd need to consider harnessing the sun.
That was far from the first time someone thought of the sun as a power source. Houses have been oriented to the sun for thousands of years, and people in China used mirrors to start fires from the sun three millennia ago.
Physics researcher John Perlin, who wants to cover the world with forests and rooftops with solar panels, has studied the long history of our use of the sun's rays.
His 2013 book Let It Shine: The 6000-Year Story of Solar Energy has been reissued in paperback, with new material.
We bring in John Perlin—a second time—to look back and forward to our ability to channel the sun's power for our needs.