How did scientists use radioactive decay to determine the absolute age of the rock?

Answer 1

Scientists use the half life of carbon-14 as a parameter to measure the age of an object. Based on the amount of molecular decay, because it happens at a constant rate, scientists are able to assume the age of said object.

Answer 2

Radioactive decay of an element can be used because we know how long it takes to decay and so therefore, from what's left, how long it's been around. For example, Argon takes about 1.3 Billion to decay to half of it's once mass (a half-life).

So after each half-life, the amount of the parent element (older element) halves what it was. So, if we saw that there is a rock where the ratio between the Potassium and Argon respectively is 1:3, we know that there has been two half lives and must be at least 2.6 Billion years old (not exactly common).

If you have noticed, I said (wrote) that it was AT LEAST 2.6 Billion years old. This is because, during metamorphism or melting, the radiometric age resets. So therefore, we can't be sure if a rock is 2.6 Billion years old 3.9 Billion years. That is how geologists figure at the absolute age (minimum).

Answer 3

Fossils are collected along with rocks that occur from the same strata. These samples are carefully cataloged and analyzed with a mass spectrometer. The mass spectrometer is able to give information about the type and amount of isotopes found in the rock. Scientists find the ratio of parent isotope to daughter isotope. By comparing this ratio to the half-life logarithmic scale of the parent isotope, they are able to find the age of the rock or fossil in question.

Answer 4

Scientist's calculate the age of a sample by measuring the amount of the radioactive material in the sample. Scientist use the half-life of the radioactive material to date the measurement.

Answer 5

In radioactive dating, scientists calculate the age of a sample based on the amount of remaining radioactive isotopes it contains.

Answer 6

We use that to compare among other orgnisms.

Answer 7

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