How to explain infinity to a 4-year-old
\u2018What\u2019s the number before infinity?\u2019 asks Claudia, aged 4. We challenge Johnny Ball, legendary British TV presenter, to explain. And in celebration of the voice of Sesame Street\u2019s Count von Count, Jerry Nelson, who\u2019s died aged 78, there\u2019s another chance to hear our 2009 interview with the Count, in which he revealed his favourite number: 34,969. Presented by Ruth Alexander, this programme was first broadcast on the BBC World Service.