We're going to deviate briefly from the physics of strange stunts on YouTube, and look instead at the new movie I Am Legend. Yes, there's a virus-based cure turned scourge that infects the vast majority of humanity, and plenty to think about along those lines, but we're going to stick to what happens to New York City.
In the beginning of the movie, the main character, Robert Neville, played by Will Smith, hunts deer in an almost entirely empty Manhattan. (Well, it's devoid of humans, anyway.) The filmmakers clearly put some thought into what the crowded metropolis would look like if people disappeared and the infrastructure shut down—they brought in at least one scientist for advice. Large weeds spring up everywhere from cracks in the sidewalk. But they're not too large, since Neville's only been alone on the island for about three years. There's at least one herd of deer, too, which isn't all that odd. They could have swam over to the island, or crossed one of the remaining bridges. Still, this version of people-free New York isn't as dramatic as the one imagined in Alan Weisman's bestseller The World Without Us. In the book, which reveals what would happen to Earth if humans simply disappeared, Weisman details the long-term changes to the city. He reminds us, first of all, that it wasn't always a concrete jungle: "Once, Manhattan was 27 square miles of porous ground interlaced with living roots that siphoned 47.2 inches of average annual rainfall up trees and into meadow grasses, which drank their fill and exhaled the rest back into the atmosphere." We don't want to give away the ending to I Am Legend, but as for The World Without Us, it's pretty predictable: Nature wins.—Gregory Mone