Searching for Alien Artifacts

If aliens have visited the earth, they surely would have left artifacts behind. If they have, what sort of articfacts would they have left, and how do we find them?

For many people, the very idea of needing to search for alien artifacts is ludicrous. After all, alien spacecraft can be seen in the skies of Earth every day of the week, and virtually every archaeological specimen older that three thousand years was fabricated, if not by extraterrestrials, then by dim-witted humans under the guidance of extraterrestrials. So for people who think along those lines, there's nothing to search for: the Earth is already overflowing with alien artifacts. But scientists (who are part of the Conspiracy) aren't allowed to admit that -- they have to look further afield. I've just been reading three fascinating articles on the subject at arXiv.org: Read more