He argued that we should prepare for a cosmic exodus to take place in the next 200 to 500 years.
“We are running out of space, and the only place we can go to are other worlds. It is time to explore other solar systems,” he said via video link to the audience gathered in Trondheim, Norway. “Spreading out may be the only thing that saves us from ourselves. I am convinced that humans need to leave Earth.”
.. “The Earth is becoming too small for us,” he said. Global warming is a threat, too, a view he knows is not shared by President Trump, “who may just have taken the most serious and wrong decision on climate change this world has seen.
.. In theory, an array of powerful lasers, blasting up to 100 gigawatts of power combined into space, could propel nanocraft like sailboats caught in a mighty wind. The probes would fly by Mars in an hour, Pluto in days and Alpha Centauri in 20 years, Hawking said. (He does not envision such a system being useful for human interstellar travel, though, in part because light-propelled craft have no brakes to pump.)