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quote:Originally posted by ampwelderHeavy elements, heavyer than iron, are ALL created in super nova explosions. Uranium (very heavy) has a half life of 760 million years (.76 billion years). We know that the sun formed some 5 billion years ago so the gas that the sun and planets were made from must have been expelled long befor that. If I remeber right uranium decays into lead, so shouldn't all the uranium that was formed from the explosion that made the gasses that the solar system was made from all be lead by now? Is this a question in physics or is there a logical answer?
quote:Code: [Select]Summary of Uranium Isotopes Isotope Percent in No. of No. of Half-Life natural uranium Protons Neutrons (in years) Uranium-238 99.284 92 146 4.46 billionUranium-235 0.711 92 143 704 millionUranium-234 0.0055 92 142 245,000
Summary of Uranium Isotopes Isotope Percent in No. of No. of Half-Life natural uranium Protons Neutrons (in years) Uranium-238 99.284 92 146 4.46 billionUranium-235 0.711 92 143 704 millionUranium-234 0.0055 92 142 245,000
quote:Originally posted by daveshortsHowever most of the carbon removed by photosynthesis is quite rapidly recycled in the carbon cycle - since some of the carbon cycle is as CO2 gas, more carbon in the cycle probably means more CO2 in the atmosphere. If this wasn't the case there would be no problem with burning coal.Essentially without the plate tectonics all the fossilised carbon (in the form of fossil fuels and limestone) wouldn't get released => not enough CO2 => the world would get too cold.There are in fact 'snowball earth' theories that say this has happened in the past when green plants were a new idea.