Yea aliens exist I am sure in that but we are not interensted for them so they dont want visit us or they are in so big distance from us.Maybe they even dont know for us so they dont visit us.Also maybe is universe created like example humans have own universe and there is no tehnology which can help us to visit aliens which are in too big distance and aliens cant make tehnology which can bring them to us what means that every universe is created for other kind of life and it is not created to be connected with other because that can be dangerous because they can start war...or everybody must create own destiny.