In an interview with Big Think
Stephen Hawking suggests that if mankind is to survive, it must leave this planet. "We are entering an increasingly dangerous period in our history," Hawking says. "There have been a number of times in the past when survival has been a question of touch and go," like the Cuban Missile Crisis of 1963, and the frequency of such occasions "is likely to increase in the future."
According to Big Think, Hawking’s view is that:
“One way or another, Earth will likely become uninhabitable for mankind in the future. We need to start seriously thinking about how we will free ourselves from the constraints of this dying planet.”
Although Stephen Hawking describes himself as an optimist, his feeling
“Because we are rapidly depleting the finite natural resources that Earth provides, and because our genetic code carries selfish and aggressive instincts our only chance for long term survival may be to spread out into space."
University of Sussex astrophysicist Dr. Robert Smith
seems to concur with Hawking that humankind’s future is this planet is rather bleak. He says that eventually our Sun will accelerate global warming to a point where all of Earth's water will simply evaporate
"Life on Earth will have disappeared long before 7.6 billion years," says Smith,
"Scientists have shown that the Sun's slow expansion will cause the temperature at the surface of the Earth to rise. Oceans will evaporate, and the atmosphere will become laden with water vapour, which (like carbon dioxide) is a very effective greenhouse gas. Eventually, the oceans will boil dry and the water vapour will escape into space. In a billion years from now the Earth will be a very hot, dry and uninhabitable ball."Katie Freese
, a professor of physics at the University of Michigan, and Associate Director of the Michigan Center for Theoretical Physics doesn’t argue much about her colleagues predictions, however, her view is that there is not a lot we can do about it. She believes that based on our current capabilities for space travel, we are basically stuck here and should make the best of it. "The nearest star [to Earth] is Proxima Centauri which is 4.2 light years away," says Freese, "That means that, if you were traveling at the speed of light the whole time, it would take 4.2 years to get there."
Unfortunately, at the moment, by using chemical fuel rockets similar to those used during the Apollo mission to the moon, we can only travel at about ten thousandth of the speed of light. Thus, the journey to the nearest star, and a potentially habitable Earth-like planet, would take about 50,000 years. Without the use of science-fiction-like tools or cryogenic freezing technology, no human would live long enough to reach that far. In addition, "the radiation you would encounter alone would kill you, even if you could get a rocket to go anywhere near that fast," says Freese.