Regular listener, Mike, asked: "When tennis players are about to serve, they get a selection of balls. They seem to look at them and then select two to serve with. Now these are all new and good quality balls, how do they select the ones they like to use? Do they recognise them? Do they have favourites?" Very topical, Mike. Rhys James travelled to meet the tennis coach, James Hoad in Bury St Edmunds: Like this podcast? Please help us by supporting the Naked Scientists