We may have just 100 to 200 years to figure out how to get off this rock and give our species a cosmic insurance policy, physicist Stephen Hawking says in a fresh interview with BigThink. Hawking has said this sort of thing several times before - but every time he mentions the time frame, it adds an extra bit of urgency to the warning.

This time, Hawking's views are given a stark spin: "Abandon Earth - or Face Extinction." But Hawking isn't really suggesting we should just give up on our planet. It's just that right now we have all our eggs in one planetary basket. Here's the key passage:

"If we are the only intelligent beings in the galaxy, we should make sure we survive and continue. But we are entering an increasingly dangerous period of our history. 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. But our genetic code still carries the selfish and aggressive instincts that were of survival advantage in the past. It will be difficult enough to avoid disaster in the next hundred years, let alone the next thousand or million. Our only chance of long-term survival is not to remain inward-looking on planet Earth, but to spread out into space. We have made remarkable progress in the last hundred years, but if we want to continue beyond the next hundred years, our future is in space. That is why I'm in favor of manned, or should I say, 'personed' spaceflight."

Hawking said that "if we can avoid disaster for the next two centuries, our species should be safe as we spread into space."

The threats that Hawking is worried about break down into two categories: First, there are the doomsdays we could bring down upon ourselves - such as biological or nuclear attacks, or human-caused climate change that has such sudden effects that we can't adjust. The other category would be catastrophes that we don't cause: for example, a direct hit by a huge space rock or a supernova blast; or a bizarre, world-changing eruption of super-volcanoes; or the emergence of a novel pathogen that our species can't fight.

The first category encompasses issues that we can do something about, and Hawking of course favors taking whatever action is necessary to save the environment and human society. The second category, however, takes in plausible extinction scenarios that humans couldn't do much about. Either category of catastrophe would require the human species to have an off-planet Plan B.

I've said for years that extinction avoidance is one of the five E's that explain why we have to spend our time and effort on space science and exploration. And I'm not by any means the first person to figure that out:

"The earth is the cradle of humankind, but one cannot live in the cradle forever" - Russian rocket pioneer Konstantin Tsiolkovsky, 1895

"Earth is too small a basket for mankind to keep all its eggs in." - science-fiction writer Robert Heinlein

"Since, in the long run, every planetary civilization will be endangered by impacts from space, every surviving civilization is obliged to become spacefaring - not because of exploratory or romantic zeal, but for the most practical reason imaginable: staying alive." - astronomer-author Carl Sagan, 1994

"The dinosaurs became extinct because they didn't have a space program. And if we become extinct because we don't have a space program, it'll serve us right!" - science-fiction writer Larry Niven, as quoted by Arthur C. Clarke in 2001

Mars would offer the best nearby second home for humanity and our allied species - and on that score, Hawking's view has been echoed by SpaceX founder Elon Musk, who says his ultimate aim is to make Homo sapiens a multiplanet species. In the longer term, our distant descendants will have to leave Earth entirely before the sun goes all red-giant on us. Humans would have to move outward to the solar system's rim - or perhaps eventually to other star systems, on a voyage that would most likely take many generations.

How can humans do that? Hawking doesn't put forward any detailed answers, but in recent months he has outlined three way-out ideas for time travel, including wormholes, black-hole encounters and super-fast acceleration. In the "Star Trek: First Contact" time line, humans came up with warp drive - and were visited by friendly Vulcans - in the year 2063. Will humans get that lucky in real life? Maybe there's an astronomically remote chance. But Hawking has another warning about that: We'd better be careful about the aliens we come across.

So what do you think? Considering all the trouble that NASA has been having with human spaceflight lately, how much do you think we can get done by 2110? Will it make a difference for our species' survival? Weigh in with your thoughts in the comment space below.

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