It is a mathematical possibility (as Hawking states) and also simple reasoning might incline your mind to believe so.
Tangentially, two points
1) I am starting to believe that our Gods (any religion and particularly Hindu Gods) are actually aliens with superior powers who visited (or keep visiting) Earth. References in epics of sophisticated weapons and air travel might just allude to this thought. Also, imagine this scenario: a group of small insects living in a hill in a very remote forest. Lets assume that they are intelligent to communicate among themselves and have been living there for generations. One day, a vehicle (say a bull dozer) goes two miles far, mowing down. The vehicle does not return till another 5 years (by which generations of insects would have come and gone). Now, what will be the insects' knowledge passed through generations on that unidentified object? What would be the present generation's thought?
2) Stephen's last point (read last para in that link) actually is a very very likely scenario to happen to Earth itself. Knowing his intelligence, he may have been giving a cryptic clue to us. ha ha ha!
PS : I personally think the article is a marketing strategy (and those visuals they have described..he he)
