Print this out on a piece of A4 paper and lay it on a table. Then imagine that the ruler-ends shown on the page belong to the same ruler, which leaves your table, circles the whole way around the Earth, and ends (by careful planning) back on your table.

This ruler is big enough that if we use it to represent Earth’s history since its formation, we can mark off individual years on it.


Our uncertainty about the age of the earth is a similar time period to the entire time life has existed on Earth’s landforms.