As an astronomer, I have both feet firmly in the pro–space exploration camp—but when did we become so intent on wringing the resources out of our planet that relocating to the breathless, freezing deserts of Mars seems like a viable option? Am I the only one who saw Total Recall? While “Leave No Trace” is the mantra of any outdoor enthusiast, modern life is unfortunately built on human detritus. We can’t even go to the moon without leaving a flag and some golf balls lying around. However, thanks in part to Al Gore passing the environmental smelling salts, everyone is thinking of ways to lighten humanity’s tread on the planet. In A World Without Us, author Alan Weisman goes one step further: what would become of all our traces if humans disappeared, and nature was allowed to take over? From Korea’s DMZ to Chernobyl, Weisman explores nature’s reclamation of our mistakes.