Modern Marvels: Doomsday threats range from very real (nuclear arsenals) to controversial (global warming) to futuristic (nanotechnology, cyborgs, and robots). Despite the Cold War's end, we live under the shadow of nuclear weapons, arms races, and accidental launches. Next, we stir up a hotter topic--the connection between global warming and fossil fuels--and ask if they're cooking up a sudden, new Ice Age. And we examine 21st-century technologies that typify the dual-edged sword of Doomsday Tech with massive potential for both creation and destruction--nanotechnology (engineering on a tiny scale), robotics, and cybernetics. We witness amazing applications in the works, wonder at the limitless promise, and hear warnings of a possible nano-doomsday, with tiny, out-of-control machines devouring everything around them.