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blakedallenBest ResponseYou've already chosen the best response.1
Carbon 14 has a half life of 5,730 ± 40 years, and its amounts can be compared with general amounts in the atmosphere up to 60,000 years ago. By seeing the amount of carbon 14 in a fossil, it is possible to estimate the age of the fossil.
 2 years ago

abhirichsterBest ResponseYou've already chosen the best response.2
Dating a Fossil As soon as a living organism dies, it stops taking in new carbon. The ratio of carbon12 to carbon14 at the moment of death is the same as every other living thing, but the carbon14 decays and is not replaced. The carbon14 decays with its halflife of 5,700 years, while the amount of carbon12 remains constant in the sample. By looking at the ratio of carbon12 to carbon14 in the sample and comparing it to the ratio in a living organism, it is possible to determine the age of a formerly living thing fairly precisely. A formula to calculate how old a sample is by carbon14 dating is: t = [ ln (Nf/No) / (0.693) ] x t1/2 where ln is the natural logarithm, Nf/No is the percent of carbon14 in the sample compared to the amount in living tissue, and t1/2 is the halflife of carbon14 (5,700 years). So, if you had a fossil that had 10 percent carbon14 compared to a living sample, then that fossil would be: t = [ ln (0.10) / (0.693) ] x 5,700 years t = [ (2.303) / (0.693) ] x 5,700 years t = [ 3.323 ] x 5,700 years t = 18,940 years old Because the halflife of carbon14 is 5,700 years, it is only reliable for dating objects up to about 60,000 years old. However, the principle of carbon14 dating applies to other isotopes as well. Potassium40 is another radioactive element naturally found in your body and has a halflife of 1.3 billion years. Other useful radioisotopes for radioactive dating include Uranium 235 (halflife = 704 million years), Uranium 238 (halflife = 4.5 billion years), Thorium232 (halflife = 14 billion years) and Rubidium87 (halflife = 49 billion years). The use of various radioisotopes allows the dating of biological and geological samples with a high degree of accuracy. However, radioisotope dating may not work so well in the future. Anything that dies after the 1940s, when Nuclear bombs, nuclear reactors and openair nuclear tests started changing things, will be harder to date precisely.
 2 years ago

acesBest ResponseYou've already chosen the best response.0
carbon 14 has half life of.... what does half life mean here?
 2 years ago

reddfroggBest ResponseYou've already chosen the best response.1
Half life means the time it takes for half the sample to decay. For example, a half life of 20 years means that in 20 years half the sample will be gone. In another 20 years, half of that half will be gone, and so on, until there is nothing left. Also, Carbon 14 isn't usually used for dating fossils. It's half life is much too short for that. Other radiometric techniques are used, that have much longer half lives.
 2 years ago
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