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.
In addition, the oldest known moon rocks are 4.5 billion years old.Since the moon and the Earth probably formed at the same time, this supports the current idea of the Earth's age.Using the basic ideas of bracketing and radiometric dating, researchers have determined the age of rock layers all over the world.This information has also helped determine the age of the Earth itself.It's this resetting process that gives us the ability to date rocks that formed at different times in earth history.
A commonly used radiometric dating technique relies on the breakdown of potassium (Ar in an igneous rock can tell us the amount of time that has passed since the rock crystallized.
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].
Based on the analysis of these samples, scientists estimate that the Earth itself is about 4.5 billion years old.
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].
Radioactive elements were incorporated into the Earth when the Solar System formed.
The extreme temperatures of the magma would just destroy the bones.