What if?

Randall Munroe (creator of XKCD) has another web-site called "What if..."which " Answers your hypothetical questions with physics, every Tuesday"

Everybody Out

Is there enough energy to move the entire current human population off-planet?

—Adam

There are a bunch of science fiction movies where, because of pollution, overpopulation, or nuclear war, humanity abandons Earth.
But lifting people into space is hard. Barring a massive reduction in the population, is launching the whole human race into space physically possible? Let’s not even worry about where we’re headed—we’ll assume we don’t have to find a new home, but we can’t stay here.

Recommended...!