In this edition: the next big mission to Neptune or Uranus, a diplomat's response to COP21 and the unsteady history of the Earth's magnetic field.

The podcast is presented by Gareth Mitchell, a lecturer on Imperial's Science Communication MSc course and the presenter of Click Radio on the BBC World Service, with contributions from our roaming reporters.

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News: Festival preview and a marathon for a neglected disease – We look forward to getting hands on with everything from robots to DNA at the Imperial Festival 7-8 May, and we talk to Dr Mike French who ran the London marathon, raising £52,000 for schistosomiasis treatment and research.

Mission to the ice giants – Dr Adam Masters had an unusual Easter, helping to define the next big planetary mission to Neptune or Uranus, planets no missions have visited for more than 25 years.

Climate diplomacy – Christiana Figueres, the Executive Secretary of the UN Framework Convention on Climate Change, delivered the 2016 Grantham Institute annual lecture. In a chat with the Grantham’s co-director Jo Haigh and two PhD students, she talks about the impact of the COP21 agreement and her hopes for the future.

Flipping magnetic fields – By studying the properties of tiny magnetic minerals billions of years old, Dr Adrian Muxworthy can tell when the Earth’s magnetic field has flipped – north becoming south and vice versa.