They've been around for a long, long time. There is an interesting site that shows ufo's in ancient artwork.
http://www.dudeman.net/siriusly/ufo/art.shtml
I printed photos from it last year but I can't pull it up now, however when you search for it, it will take you to similar sites. Many of these were shown on a television program too. It's very interesting.
Yes, I guess the question sort of ignores the von Daniken type stuff.....but if there were extraterrestrials here way back then (and I certainly believe they might have been), any nuclear detonations would not have been produced by earthlings. Nonetheless, the detonations above groubd during WWII and later would surely be a signal to anyone out there capable of noticing it that we had discovered certain elements and some processes of interest to them as well as us.It seems reasonably notable that all the UFO fuss in the modern world began after our first detonations.
Thanks, very interesting site. I’d seen a couple of them but so many of them really makes one think.
I had to go to the main page and then link to this -
http://www.dudeman.net/siriusly/ufo/art.html