The Drake Equation makes me a believer of other life outside of our planet. Not sure if they are visiting us, but I can't see Earth being the only planet with life.
The Hubble Deep Field Images should remove any doubt to the real possibilities of other life.
http://www.deepastronomy.com/hubble-deep-field.html <---- Click for image details.
Hubble Deep Field Image
Equates to the amount of space blocked by the end of a needle if you held it up to the night sky.
Then factor in how big the sky is,.....................
Then factor in how big our galaxy is,..................
Then factor in how many galaxies are in our universe,...................
Then factor in the Drake Equation,.................
Sorry for the size of this image, but this view shows just how many galaxies were visible in that little spec of darkness in the night sky. Every spec of light is not a star, but galaxies full of stars, just like our Milky Way. Estimations point to there being over ten thousand galaxies in this photo alone.
Here's another great picture.
Hubble Ultra Deep Field:
http://upload.wikimedia.org/wikipedi..._rez_edit1.jpg <---- Click the image for a full size view.
