Life isnt just exist on earth. In universe, how many galaxies are they? Its almost impossible for earth only that got life. I believe there are billions of living thing that come from different galaxies in our universe. And the alien that we debated might be 1 of the 'billions living thing' out there. My theory is just my opinion. It might be faked or so. But the fact that i hope everyone to agree is, 'we are not alone'. 

Alien does not recognises us. They may think we are dangerous to them, imagine if those US millitary or other spot the ufo, they would probably fire a missile and do research on the UFO. And i do think that they are spying us right now. But again, nobody knows what is their motive. But hopefully not the real 'War of the World'