Radioactive dating animation
The release of radiation is also a random event and overtime the activity of the radioactive material decreases.
It is not possible to predict when an individual nucleus in a radioactive material will decay.
Measuring the uranium-to-lead ratios in the oldest rocks on Earth gave scientists an estimated age of the planet of 4.6 billion years.
Segment from A Science Odyssey: "Origins."Geologists have calculated the age of Earth at 4.6 billion years.
Using fossils as guides, they began to piece together a crude history of Earth, but it was an imperfect history.