One big debate in science is whether the impacts of human actions on earth are now so large that we have entered a new geological time. Called the Anthropocene, its formal designation would mean the old forces of nature that transformed our planet many millions of years ago, including meteorites and mega-volcanoes, are joined by another: us. What geologists call the Holocene Epoch would be over. The exact date would be up for debate, but it would probably be within …