Thanks for downloading the NRTIME podcast. For more details about NRTIME and for our terms of use, please go to bbc.co.uk forward slash radio for. I hope you enjoy the program.

Hello, we used to be very clear about the origin of the earth. Bishop Usher in 1654 arrived at an exact figure and specified it in his work analysis of Etrus at Novi Testamenti.

He deduced that the work on planet earth began at exactly 9 a.m. on Monday the 23rd of October, 4,04 b.c.

The date was then printed in the margin of the Bible and preached from the pulpit right up to the 19th century to the left of, in the beginning, was specified before Christ, 4,04.

Christian believers thought the decoration story was solid as a rock, until the geologists arrived in how solid our rocks these days.

First Hutton, Nensmith, and then Lyle smashing away at Orthodox belief in a way that made poor Ruskin quail, but in doing so, they created a science.

With me to discuss the development of geology and our changing understanding of the structure of the earth is Simon Winchester, author of the map that changed the world, the tale of William Smith and the birth of a science.

Also with this is Cherry Lewis, geologist and author of the dating game, One Man Search for the Age of the Earth, and John Cosgrove, structural geologist from the Royal School of Minds at Imperial College London.

Cherry Lewis, can you give us some idea of where geology was up to the 18th century?

Yes, I think what you've just said about Archbishop Usher is really important because it puts in context the religious climate that was prevailing

through certainly the 17th and 18th centuries, that really dominated the understanding of geology.

I think perhaps if we start with somebody like James Hutton, who was beginning to get an understanding of what the rocks really meant, he trained as a doctor in fact, but went on to become a farmer.

It was while he was doing his farming that he started to look at landforms and he started to get a feel for the fact that weathering processes were extremely important, and he noticed that the sediments produced by weathering were then being taken down by the rivers and deposited in the oceans.

And he built up this picture of an evolving cycle of rocks, and gradually the rocks would be taken down to deposit it in the sea, and then over at long periods of time the sea would be uplifted to form the rocks that we're standing on today.

And he developed this theory of the earth, which really the main, I think, premise of it was that it involved enormous timescales, and he was probably the first person to really appreciate the enormity of geological time.

But of course this went very much against all the religious teaching of the time, which was very much dominated by archbishop's understanding that the earth had been created 4,000 and 4 BC.

And therefore it couldn't be much more than 6,000 years old.

But he was adamant in nature, he said there is no deficiency in time, and he looked at the rocks and saw that it was really required the most enormous amounts of time.

We were talking here about the 18th century, actually, and up in Edinburgh, up and up.

Simon Winchester, you were written about William Smith, most engagingly in his geological map of the British hours, which was published in 1815.

Did he was a sort of apostolic succession from, from James Hunt in Edinburgh to William Smith?

Not at all.

...