Man, there are too many mysteries on earth to pick just one. How about the bermuda triangle; the idea that fluctuations in the inner molten and metal core create anomoles that we see on the surface of the earth. Lights, sounds, the disappearence of air and sea crafts, all due to something that we know nothing about and we cant see.... As far as non-scientific kind stuff, yea that crystal skill stuff is weird... I think it wasnt done justice being made the center plot of an indiana jones movie. But the strange things that occur with the skulls under certain external stimuli.... yea. That cant be human. OR the mayan idea that the earth has gone through cycles of time, and that even before now, we had a more advanced civilization that was simply wiped out by... well, something. Those crystal skulls, the ruins of atlantis, and a bunch of other things might be able to be attributed to an advanced civilization that lived before out time (be it aliens or humans, or some combination of the two????) When you really think about it, there are so many things that the human race doesnt know, as well as things we havent discovered that we dont know.. On a personal note, I find that idea alone makes me want live as long as possible, just to KNOW about some of these mysteries. We get closer and closer everyday to figuring out the mysteries of the earth or the universe, i find that keeps me going through anything. To just find out if we're alone in the universe, to find out if there was advanced life on earth before humans, to find out if the great pyramids and stonehenge were built with alien assistance. The list goes on... and we're in an age where these questions are being answered at a faster rate than we can imagine. Just check out Michio Kakus book, " physics of the impossible" Invisibilty, time travel, hyper space, all possible to some extent just at varying levels. LOL, just thinking about it makes me smile . I cant wait for the next great discovery in science or physics! Definately something that keeps me going