I can't tell you for certain that aliens do exist. But when one considers the vastness of our universe and the universes beyond our own, it seems to me that there must be other lifeforms. Now if you asked the question, have these other lifeforms visited our planet? My answer again would be, I don't know. I have seen things in the sky that I can't explain but I couldn't tell you if it was alien in nature or some secret testing plane that our military were testing. There are some people who believe that those who have reportedly visited earth are not really aliens but humans from the future. Some will tell you they have perfected time travel and come here to visit the past. I don't know what is true and there is no way of proving any of these speculations.

As for ghosts, I believe they are real. Having seen them myself since I was six years old.
But I, like everyone else that investigates hauntings are not able to prove this for a fact. 
I know we are all spiritual beings within a physical form - and I believe the spirit lives on after death. As a result I believe that some spirits find it hard to leave this plane of existence. Whether it be the results of unfinished business, sudden death or simply too many ties to this earthly plane. There are, in my belief, many levels on which we live. If you stop and think about it, you can live within your thoughts, you can live physically, and you live within a dream state while asleep and yet you also live within the physical form at the same time you can live within the dream state. Because this is possible one must consider the same possibility in the spiritual form.