When Physics Met Geology
C14 dating, as mentioned in my last blog , is based on carbon. Which means, as we learnt at school, it can only be used for dating organic materials. How then are does one find the age of inorganic (non-Carbon) materials? Like the age of the earth, for example? That makes for an interesting tale. One always associates radioactivity with terrible things like cancer, nuclear bombs and Chernobyl. And yet, it was the principle of radioactivity that helped figure out the age of the earth! Radioactivity is the decay of one element into another, along with the emission of the catastrophic radiation. The rate of decay for different radioactive materials is fixed. That property means radioactive materials can be used like clocks. The idea was simple: uranium decays into lead. So if you found the ratio of uranium to lead in really, really old rocks, you could derive the age of the earth. The devil lay in the execution of the idea. How do you find uncontaminated really, really old ...