Carbon 14 with a half life of 5,700 years can only be used to date fossils of approximately 50,000 years. If 50% of pure uranium' is left in a sample the sample is assumed to be 4.5 billion years old.( This is assuming that the original sample was 100% uranium and no Uranium 238 has been eroded or lost in 4.5 billion years old.Most fossils are thought to be much older than 50,000 years. The fossilized remains have been mineralized where the original organic material has been replaced and turned into stones containing no carbon. If a fossil has only 25 % of the Uranium 238 the sample has an estimated age of 3.2 Billion years.Because the ratio of carbon 12 to carbon 14 present in all living organisms is the same, and because the decay rate of carbon 14 is constant, the length of time that has passed since an organism has died can be calculated by comparing the ratio of carbon 12 to carbon 14 in its remains to the known ratio in living organisms. Our Living Language : In the late 1940s, American chemist Willard Libby developed a method for determining when the death of an organism had occurred.He first noted that the cells of all living things contain atoms taken in from the organism's environment, including carbon; all organic compounds contain carbon.This procedure of radiocarbon dating has been widely adopted and is considered accurate enough for practical use to study remains up to 50,000 years old.If you're seeing this message, it means we're having trouble loading external resources on our website.
After two half lives, a quarter is left; after three half lives, only an eighth; after 10 half lives, less than a thousandth is left.Diamond is the hardest substance known, so its interior should be very resistant to contamination.Diamond requires very high pressure to form—pressure found naturally on earth only deep below the surface.This would be the estimated age of the earliest life or fossils. Uranium 238 is only found igneous or volcanic rocks. Because of the huge differences in the half lives of Carbon 14 and Uranium238 that cannot be used together.Carbon 14 can only be used to date fossils of a very recent age.