The age of the solar system has been estimated to be about 5000 million years with the help of radiometric dating in investigations. The method of radiometric dating is based on the phenomenon of radioactivity. We know that certain unstable nuclei break-up spontaneously into smaller and more stable nuclei.
The atoms which undergo disintegration are called parent atoms and the smaller atoms formed as a result of disintegration are called daughter atoms. The rate at which parent atoms of a particular disintegrate into daughter atoms is known to be constant and can be determined by careful experiments.
For example, uranium is a radioactive element. It disintegrates spontaneously through a number of steps into lead. The rate at which uranium disintegrates into lead has been determined by carrying out careful experiments. It has been found that roughly one-third of atoms present in a mass of uranium decay into lead every 4.5 billions years 94.58 109 years. Thus, by determining the relative amounts of uranium and lead in given piece of rock (containing uranium), it is possible to estimate the age of the rock. However, this method makes one important assumption that all the lead in the rock is formed by radioactive decay of uranium.
BY determining the age of the rocks obtained as meteorites by radiometric methods it is possible t estimate the age of the solar system. Many meteorites, which have fallen to the earth from space, have been found to be 4.5 billion years old by radiometric techniques. Form the radiometric analysis of meteorites, the age of the solar system can be estimated to be about 4.5 billon years (4500 million years). Similarly, the radiometric analysis of the rock samples on the earth can give us idea about the age of the earth. The oldest known rock on the earth has a radiometric age of only 3700 million years. This rock is found in Greenland. Thus, the age of the earth is about 3700 million years (3.7 * 109 years).