A History of Agriculture in India v1.c13.5

v1.c13.5

Here it would be relevant to explain the technique for estimating the age of rocks and prehistoric objects. The so-called radioactivity method has been applied to the study of rocks. It is based on the fact that the emanations of radioactive bodies, such as radium, uranium, and so on, are transformed first into helium and then into lead. The amount of helium that issues, for example, from a given quantity of uranium during a fixed period has been calculated. Since the rate of disintegration of the uranium atom is known, the evaluation of the respective proportions of uranium, helium and lead in a mineral whose age it is desired to find gives some idea of the time that has passed since its formation.