1 {scene: Edinburgh}
1 Isaac Newton: James Hutton, you're needed to help us save the universe.
2 James Hutton: But I've just discovered the Earth is vastly old, with no vestige of a beginning, no prospect of an end!
3 James Hutton: I have so much more to study and learn about Earth's history and future by painstakingly teasing skerricks of data out of the cryptic records left in the rocks!
4 Isaac Newton: I have a time machine.
4 James Hutton: I'm in.

James Hutton was a Scottish scientist of the mid to late 18th century. He developed an interest in landforms and the structure of rocks, travelling Britain to find examples of formations that revealed the structure of the exposed layers of the Earth.

He collated and used these data to arrive at a principle of uniformitarianism, which essentially says that the forces which act on the universe - and the Earth - now are generally the same as the forces which acted in the past, and will act in the future. This was significant, as it was at odds with the then generally accepted story of the Earth's creation by God only a few thousand years ago, followed by a history of wildly varying catastrophe - in particular the great flood of the story of Noah and the Ark.

With only a few thousand years to work, you need such globe-spanning catastrophic events to account for the accumulation of layers of rock strata and the subsequent lifting, buckling, and erosion of the layers of rocks that can be seen around the globe. What Hutton realised was that forces still at work today can also account for all the varied rock formations and strata that we find, if only given long enough to work. A very slow and gradual accumulation of sediments can build vast layers of rock, given enough time. A very slow uplifting of the land can raise kilometres of rock from flat plains into vast mountain ranges, given enough time. The slow erosion of rocks can wear down even the largest mountains into deep valleys and loose sediment to start the process all over again, given enough time.

How much time? Millions of years. Many millions of years. Hundreds and thousands of millions of years.

This was the first indication that the Earth was incredibly old, and it was gathered from scientific evidence uncovered by observing the natural world around us and thinking about what it meant. This discovery was somewhat shocking in its time. Even Hutton himself expressed wonder at what he had deduced, stating in a 1788 paper presented to the Royal Society of Edinburgh, that "we find no vestige of a beginning, no prospect of an end."