Austin 1996 radiometric

It is nevertheless true that many of the measurements on rocks do lead to calculations of very long ages. It is assumed that the melting process eliminates all radioactive elements so that the process of radioactive decay starts at the point of solidifying.

Sedimentary rocks are not dated in this way but just rocks which were once melted.

It is up to us to figure out the significance of the values obtained from any given measurement. What the machines do tell us is a ratio of parent radioactive element to stable daughter element.

How can we argue with numbers? We must remember however that the rocks do not come with labels informing us of their ages. Many people find it hard to understand how we can be critical of actual observations made on once molten rock.