Where do we begin to think about time without humans to count it? Chris Gasson spends every spare moment on his local beach, Seatown on the Jurassic coast of Dorset, looking out for fossils and stones that speak of a past and future too vast for us to easily imagine.

On his walks, Chris has found countless time capsules - including a mammoth tooth, plesiosaur vertebrae and the remains of an ichthyosaur 190 million years old, now under research by Craig Chivers.

'It's a fantastic find,' says Craig. 'Fossils are a snapshot in time a bit like paintings and writings. Trace fossils that show where a dinosaur once stepped and left a footprint behind, or an ammonite has rolled along the sea floor and left an impression in the sediment, really stir the imagination.'

Our walk along Seatown beach is accompanied by readings by geologist and writer, Marcia Bjornerud, Walter Schober Professor of Environmental Studies and Professor of Geosciences at Lawrence University, Wisconsin. Her essay Wrinked Time imagines humans as wandering in a vast, labyrinthine library of time.

'We are like squatters living amid the remains of earlier empires, worlds defined by different geographies,' she writes in a work that first appeared in Emergence Magazine. Marcia shows us how fragments from that library still exist in the most synthetic, human-made products like phones and computers if only we have eyes to see them.

Produced by Jon Nicholls and Monica Whitlock

A Storyscape production for BBC Radio 4

For many more creative and surprising one-off documentaries like this, just search for Illuminated on BBC Sounds.