Re: Aliens 
The voyager 1 footage of earth when it passed Neptune showed our planet as a kind of dot/ as a dot. 

If truly aliens exist, I believe they exist outside our solar system. 
And if for some reason, they decide to go on a space adventure, what motive would they have to come to earth. 

Think of it this way, when you pass Neptune, Saturn, Jupiter, extremely massive giants and they find no signs of civilization, why would they continue their voyage down to earth, closer to the Sun, and just a dot on the grand scheme of things.