How has the Earths age been determined?
The Earths age has been measured by using atomic clocks contained in the solar systems most primitive materials to which we have access, such as: a) The Earths oldest rocks; b) Lunar rocks retrieved by Americans and Russians, and c) Meteorites intercepted by Earth in its rotation around the sun. Two types of clocks have been used: some that wound down and stopped during the transition interval, and others that are still wound and ticking today. The prototypes of these clocks are as follows: The iodine-129 clock that, impelled by this radionuclide, decays with a period of 17 Ma to xenon-129 (stable) and that is used to measure time intervals of the order of millions of years. Readings of this clock can be taken in meteorites that, because they are very small celestial bodies, cool off immediately after formation. In this way, it has been observed on the basis of accumulated xenon-129 that all meteorites were formed during the transition interval: some, such as meteorite Allede, at the v
