where did the uranium on earth come from
Uranium Along with all elements having atomic weights higher than that of iron, uranium is only naturally formed in supernovae.[52] Primordial thorium and uranium are only produced in the r-process (rapid neutron capture), because the s-process (slow neutron capture) is too slow and cannot pass the gap of instability after bismuth.[53][54] Besides the two extant primordial uranium isotopes, 235U and 238U, the r-process also produced significant quantities of 236U, which has a shorter half-life and has long since decayed completely to 232Th, which was itself enriched by the decay of 244Pu, accounting for the observed higher-than-expected abundance of thorium and lower-than-expected abundance of uranium.[55] While the natural abundance of uranium has been supplemented by the decay of extinct 242Pu (half-life 0.375 million years) and 247Cm (half-life 16 million years), producing 238U and 235U respectively, this occurred to an almost negligible extent due to the shorter half-lives of these parents and their lower production than 236U and 244Pu, the parents of thorium: the 247Cm:235U ratio at the formation of the Solar System was (7.0 ± 1.6) × 10−5.[56]
Fresh water The majority of fresh water on Earth is in ice caps.
New France Thus, it extended from Newfoundland to the Canadian prairies and from Hudson Bay to the Gulf of Mexico, including all the Great Lakes of North America.
Standard deviation Let X be a random variable with mean value Î¼:
Cotton Cotton remains a major export of the southern United States, and a majority of the world's annual cotton crop is of the long-staple American variety.[43]
Bull riding The flank strap