You live on planet Earth. This whole planet is your world, your universe. You know there is more out there, beyond the soft blue of the sky, but you have only ever seen it from pictures, haven't you? Yet you believe - you know.
Who are you to say that there isn't life on Mars? That there is no such thing as haunted houses?
If reality is defined by what you see and don't see, you yourself are not real to those who haven't seen you. A ghost tied to this earth, wandering the empty streets.
What, then, is real?