The universe is huge! I mean everybody knows that for a fact and it's not realistic to think we, humans, are the only intelligent beings that exist in this vast empty space. There have been many theories but like we said, they're just theories. There's more to know and understand than we could ever handle. But there are a few people whose ideas are more important than others on this subject and Stephen Hawking is definitely one of them. Today we'll tell you what he thinks about aliens not visiting us.