Do extra-terrestrials exist? Surely,If they had the technology to fly from one planet, or even galaxy, to the other, I think it's safe to assume that we'd notice them by now and they'd likely conquer our civilization rather quickly to seize the planet for its resources.
Maybe they don't require our resources to live and that's why they haven't invaded us,don't assume that they need our simple resources. And we have noticed them by now,some people are just too ignorant to believe... Why don't they allow us to go into area 51? What are they trying to hide? Why is there a 6 mile runway? Maybe to test alien spacecraft and what not. How do you explain roswell new mexico and the government lying and changing the story of what they found about 3 times already?
I agree about the resources 100% if a civilization has advanced to the point of even interstellar travel, they can manage to turn an asteroid into steak or water or what ever they desire.
Area 51 might have alien tech, but I doubt it to be honest. It's just too visible, any testing of alien tech would be completely underground so as to avoid the Chinese or Russian's from using spy sats to grab pictures or possibly readings. The 6 mile long run way is needed for Aurora to land and take off from.... thats the replacement plane for the SR-71.
http://en.wikipedia....urora_(aircraft)