When Stephen Hawking says it’s time to get out, you know it’s time to cut our losses and move to Mars—or whatever planet will have us. According to Hawking, if we don’t leave the Earth within the next 100 years, we will become extinct. “Our population and our use of the finite resources of planet Earth are growing exponentially, along with our technical ability to change the environment for good or ill,” he says. Obviously, we’re doing ill on a massive scale—which leads us to an important question.

Though it’s time to leave the planet, should we? We’ve already exploited the resources here so vastly and so wildly, we cannot prove that we won’t do it again on another planet. Indeed, we would likely just do it all over again—Wall-E notwithstanding.

There is definitely a mass extinction taking place right now. Corals, tropical species, and large mammals are disappearing the fastest, and scientists agree that the cause of this period of extinction is none other than us. John Alroy of the Department of Biological Sciences at Macquarie University says, “We’re 100 percent responsible for it. There is no precedent at all for what we’re doing.”

People need to remember this when they scoff, “Species have gone extinct plenty of times before! Just look at the dinosaurs. It’s natural.” Actually, what’s happening is the opposite of natural—it all boils down to activities carried out by mankind, not by events of nature or space.  Alroy explains this simply, saying that all of the extinctions the planet has previously experienced boil down to environmental shifts, not by an individual species.

So what do we do about it? Do we explore space, make a giant ark or space craft, or simply prepare for the worst? I don’t think any amount of recycling or solar paneling is going to undo what we’ve done already—though we should certainly keep trying to at least buy our children some time. Even so, as humans, you have to admit that we’ve had a good run, and that many of us have had exceptional lives. Maybe if we all look at this world as if there are only 100 years left on it for us, we would treat it—and each other—a little bit better.

Then again, as my husband says, it’s only a theory—an educated one that I happen to subscribe to, but still, not completely proven, and that things can still happen. Either way, it’s something to think about—and to perhaps keep in mind when we shop and continue to exploit the resources of this planet.