Why is everything in space round? Drs Rutherford and Fry embark on a quest to find the perfect sphere.
Today the team study the heavens, thanks to listener Brian Passineau who wonders 'why everything in space tends to be circular or spherical?'
Hannah gazes at Jupiter at The Royal Observatory, Greenwich with Public Astronomer, Dr Marek Kukula.
Science writer, Philip Ball, explains how the astronomical obsession with celestial spheres came to an untidy end.
And physicist Dr Helen Czerski helps Adam on his quest to find the perfect natural sphere.
If you have a scientific mystery for the team to investigate, please email: firstname.lastname@example.org
Presenters: Hannah Fry, Adam Rutherford
Producer: Michelle Martin.