Good logic, I think, Technosoul. They can only be called ART in some of their manifestations. See the thread I quoted for a few images.
The logic thing brings us to approximately three theories:
- A hoax by those who enjoy that type of thing.
- Advanced human technology, possibly military.
- Extraterrestrial technology, to an unknown purpose.
Some are hoaxes, no doubt. Not all. But there is no proof of aliens whatsoever. That leaves the remainder to secret advanced human tech.