Perhaps we've never been visited by aliens because they have looked upon Earth and decided there's no sign of intelligent life.
Sentiment: NEGATIVE
Sometimes I think the surest sign that intelligent life exists elsewhere in the universe is that none of it has tried to contact us.
Perhaps, as some wit remarked, the best proof that there is Intelligent Life in Outer Space is the fact it hasn't come here. Well, it can't hide forever - one day we will overhear it.
We only have to look at ourselves to see how intelligent life might develop into something we wouldn't want to meet.
If an alien visited Earth, they would take some note of humans, but probably spend most of their time trying to understand the dominant form of life on our planet - microorganisms like bacteria and viruses.
I think anybody would have to be with out common sense to think there weren't aliens. There are billions of planets, and I am convinced Earth is not the only one that's inhabited. It would be quite an ego trip to think that. I think about it all the time.
If we find life out there, and it's not us, we will deem it not intelligent. But what may be equally as likely is that we find life that's vastly more intelligent than we are. If that's the case, we are putty in their hands.
Aliens didn't come down to Earth and give us technology. We invented it ourselves. Therefore it can never be alienating; it can only be an expression of our humanity.
The human race may be the only intelligent beings in the galaxy.
If this is the only planet on which not only life, but intelligent life, has arisen, that would be very unusual.
The surest sign that intelligent life exists elsewhere in the universe is that it has never tried to contact us.