@sidhu

yes u r right NathanUT, i also believe in the hypothesis u made from some time..........the visibility of vapors, i think can also depend on the size of vapours......bt i dont know that what size or in what range the size of water vapors or other liquid vapors have?.......could u plz post some data regarding the size of common liquid vapours......so that we can just see that they can be seen by naked eye?...................i think that the size will be far away from the range of our eyes ability to see them.......in my opinion.......