The aliens, if they're watching, probably have some questions for humanity. You might, too, so here's a closer look at what's happening.

The Joke

There's not much to it: In late June, Matty Roberts, a college student, created an event on Facebook called "Storm Area 51, They Can't Stop All of Us."

The event, scheduled for Sept. 20, was meant as a joke about making a run on the mysterious and well-protected military test site in southern Nevada, fabled to be dedicated to the research of real, honest-to-goodness alien spacecraft.

The joke caught fire.

Within three weeks, more than a million people marked themselves down as planning to attend. (By mid-September, the number had reached 2.1 million.) Even the Air Force noticed and, in July, a spokeswoman told The New York Times that "any attempt to illegally access military installations or military training areas is dangerous."