Submitted by SubcutaneousMilk t3_z6mclo in askscience
I hear it thrown around frequently that Uranium (also sometimes Plutonium) is the heaviest element which occurs naturally. I have recently learned, however, that the Oklo natural fission reactor is known to have at one time produced elements as heavy as Fermium. When the phrase "heaviest natural element" is used, how exact is that statement? Is there an atomic weight where it is theoretically impossible for a single atom to have once existed? For example, is there no possible scenario in which a single atom of Rutherfordium once existed without human intervention? If this is the case, what is the limiting factor? If not, is it simply the fact that increasing weights after uranium are EXTREMELY unlikely to form, but it is possible that trace amounts have come into existence in the last 14 billion years?