ABSTRACT
The absolute age of an event in Earth history can be measured with one or more of the Earth’s clocks. In most cases this is very difficult, either because the clocks are inaccurate (often the case in radiometric dating) or are difficult to read (almost always true for Milankovitch climate cycles); indeed, in many cases we can’t be certain that the event in question occurred at the same time as the clock we are using was set.
