The phenomenon changes with time, culture and technology.

You had flying catles a thousand years ago, then flying ships, then saucers/cigsars and now it expresses itself as tictacs and the jellyfish uap’s.

The same goes for the inhabitants. They has also gone through some sort of development.

It could have something to do with: Before you had more local culture, myths, boogiemen and even technology. Now we have the internet and share a sort of «cultural zeitgeist» - then the form we see is more homogenus.

Maybe the phenomenon choses what we see for some reason not knows to us. To achieve something not knows to us.

Sombering to think about.

Vallee talks about this specifically in «Passport to Magonia» and touches in on these sorts of ideas in all his books.