The amount of carbon-14 gradually decreases through radioactive beta decay with a half-life of 5,730 years.
So, scientists can estimate the age of the fossil by looking at the level of decay in its radioactive carbon.
If you wait another 4.5 × 10 years and measure the mass of uranium-238 in that rock you will find there will be only ½ × 50 = 25 g left.
We could tabulate the mass of uranium-238 remaining after an interval of time measured in numbers of half-lives as shown below: years, we can read it straight of the graph as a mass of approximately 21.5 grams.
Cosmic rays enter the earth's atmosphere in large numbers every day.
For example, every person is hit by about half a million cosmic rays every hour.
Carbon-14 is radioactive, with a half-life of about 5,700 years.
For more information on cosmic rays and half-life, as well as the process of radioactive decay, see How Nuclear Radiation Works.
At time 0, the mass of strontium-90 in the bone is 36.00 mg.The ratio of normal carbon (carbon-12) to carbon-14 in the air and in all living things at any given time is nearly constant.Maybe one in a trillion carbon atoms are carbon-14.American physical chemist Willard Libby led a team of scientists in the post World War II era to develop a method that measures radiocarbon activity.He is credited to be the first scientist to suggest that the unstable carbon isotope called radiocarbon or carbon 14 might exist in living matter. Libby and his team of scientists were able to publish a paper summarizing the first detection of radiocarbon in an organic sample. Libby who first measured radiocarbon’s rate of decay and established 5568 years ± 30 years as the half-life. Libby was awarded the Nobel Prize in Chemistry in recognition of his efforts to develop radiocarbon dating.The half-life of some radioisotopes is given in the table below: years.