What kind of rock can radioactive dating be used on

For example, by using a laser, researchers can measure parent and daughter atoms in extremely small amounts of matter, making it possible to determine the age of very small samples [source: New Scientist].

As shown in the diagram above, the radioactive isotope carbon-14 originates in the Earth's atmosphere, is distributed among the living organisms on the surface, and ceases to replenish itself within an organism after that organism is dead.

This means that lifeless organic matter is effectively a closed system, since no carbon-14 enters the organism after death, an occurrence that would affect accurate measurements.

If there is too much daughter product(in this case nitrogen-14), age is hard to determine since the half-life does not make up a significant percentage of the material's age.

Dinosaur bones, on the other hand, are millions of years old -- some fossils are billions of years old.

To determine the ages of these specimens, scientists need an isotope with a very long half-life.

Since the half-life of carbon-14 is 5730 years, scientists can measure the age of a sample by determining how many times its original carbon-14 amount has been cut in half since the death of the organism.

For example, an object with a quarter of its original amount (2x1/2) should be roughly 11,460 years old.

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