If there is anything more to UFOs than just mass hysteria and wishful thinking, then I've always thought it much more likely that they are from a previous indus

If there is anything more to UFOs than just mass hysteria and wishful thinking, then I've always thought it much more likely that they are from a previous industrial civilization here on earth than being extraterrestrial - the PETM from 56 million years ago would be a good candidate for their home time.