The team watch time tick away, as they look at the science behind the atomic clock.
BBC Radio 5 live
Y diweddaraf o'r byd ffermio gyda Dei Tomos.
BBC Radio Cymru
Helen Mark joins Sir Antony Gormley to explore his latest sculpture in rural Warwickshire. (R)
BBC Radio 4
Charlotte Smith explores the flower growing industry in the UK.
Rhai o'r pynciau - Gwyl TH, Twyni Niwbwrch a'r ddraig goch yn cyhwfan ar ben ein copaon.
Mark Stephen and Euan McIlwraith with outdoor activities from Shetland to the Borders.
BBC Radio Scotland
Food, countryside and agricultural issues, focusing on business, industry and technology.
BBC Radio Foyle
BBC Radio Ulster
The voices of Lisa Fischer and Kanika Kapoor help the stars of stage and screen to shine
BBC World Service
The world gets a leap second but how will it affect our IT networks?
GM wheat trial has been ineffective at repelling aphids in the outdoor trial
Listen live (BBC World Service homepage)
An examination of whether it is better to cut or spend your way out of an economic crisis