Was There a Civilization On Earth Before Humans?
It only took five minutes for Gavin Schmidt to out-speculate me. Schmidt is the director of nasa’s Goddard Institute for Space Studies (a.k.a. GISS) a world-class climate-science facility. One day last year, I came to GISS with a far-out proposal. In my work as an astrophysicist, I’d begun researching global warming from an “astrobiological perspective.” That meant asking whether any industrial civilization that rises on any planet will, through their own activity...