Do aliens and ufo's exist? If they do, do they visiit earth?

Question

The word "alien" means foreigner or someone different. In that sense, there are many aliens.

Are there intelligent beings on other planets? We don't know. We have no scientific evidence of life on other planets or ufos.

This article discusses unidentified flying objects.

http://en.wikipedia.org/wiki/Unidentified_flying_object

See also here:

http://en.wikipedia.org/wiki/Fermi_paradox

what is a grid?