Chapter 2
Doomsday DIY » Make Your Best Shot

ow do you turn molten metal into perfect spheres? Just pour it off the roof. About 230 years ago, molten lead that rained from the sky-historically something to avoid at all costs-became a clever new way to manufacture an important commodity: shotgun ammo.

Precisely round pellets fly straighter, but casting each in its own 1/8-inch mold isn't exactly mass production. In space, making them would be easy. In zero gravity, surface tension pulls any liquid into a sphere, the shape with the least surface area for a given volume. This is as true for molten metal as it is for drops of water floating inside the space shuttle. On Earth, the closest thing to zero gravity is freefall- falling objects experience weightlessness right up until they hit the ground.