It's been two generations since "your number is up" meant anything but relief at the DMV or a one-way ticket to the pearly gates.

But for any man older than 65, it once meant something entirely different. It was your draft number, whether it be your birthday (Vietnam) or your district number (WWII). The information was pushed into a capsule no bigger than a cyanide pill, which was tossed into a fishbowl filled with hundreds or thousands of other tiny blue orbs. On "lottery day," one capsule was plucked from the others. When a man's number was "up," he reported to the draft board and, if deemed fit for duty, was thrown into war.

Those were all the able-bodied men in a certain age range. Now imagine young women sitting in front of their televisions, or glued to their mobile devices, waiting to see if their numbers are up. It seems fantastical, 40 years after the draft was ended and with an all-volunteer force now filling the ranks for war. But the issue of whether to open the Selective Service to women—all men 18-25 are still required to register—is very much a debate on Capitol Hill today.