Many people believe that solar energy is a twentieth century phenomenon, untried and untested. But I discovered through writing my new book Let It Shine: The 6000-Year Story of Solar Energy that houses have been designed since Neolithic times to scoop up sunlight in winter; that over the last three thousand years people have used solar concentrators to focus sunlight to light fires, during the Renaissance, to solder metal, and by the nineteenth century, to run steam engines; that since the end of the nineteenth century a solar water heater industry has developed and spread throughout the world; and that as far back as the 1870s, scientists and technologists have discovered and used certain solid state materials to convert sunlight directly into electricity. (See related quiz: “What You