Absolute dating definition
This information has also helped determine the age of the Earth itself.
While the oldest known rocks on Earth are about 3.5 billion years old, researchers have found zircon crystals that are 4.3 billion years old [source: USGS].
The most widely known form of radiometric dating is carbon-14 dating.
Using fossils as guides, they began to piece together a crude history of Earth, but it was an imperfect history.
After all, the ever-changing Earth rarely left a complete geological record.
Based on the analysis of these samples, scientists estimate that the Earth itself is about 4.5 billion years old.
In addition, the oldest known moon rocks are 4.5 billion years old.