Is Stephen hawking a problem or a product?

Stephen Hawking said in Hong Kong last week that life on earth is at risk of being wiped out by a disaster. And, in order to survive it, we will have to spread out into space, travelling to the Moon and Mars. Was the eminent scientist, a professor of mathematics at the University of Cambridge serious—or was he just selling his new book, the children's book he wants to write with his daughter?

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And while we are at it, do you seriously think the world will end one day, some day? What might be the likely cause? Or are all these doomsday theories just hogwash?