Maybe there's no aliens at all but if there is....people say that if they come it would be the end of humanity.Maybe one day the whole planet can get attacked and people will have to fight back.But think: Look and all the missiles..weapons...aircraft....ships and vehicules the US has, maybe if aliens come they can get pwned in a week.Look on google images for: ac 130-U, f 22 raptors, F-16,apache helicopters, tomahawk missiles,b-2 bombers, f-119 nighthawk and you will see what i'm talking about. But guys don't make illusions maybe aliens are immune to all of our weapons and they might own us in 3 days...no1 ever knows