Radio astronomer Robert Wilson recalls a pair of pigeons who almost thwarted the discovery of cosmic background radiation. Wilson’s discovery of cosmic background radiation, ‘the echo of the big bang’, earned him a share of the 1978 Nobel Prize in physics. This is the fourth and final episode of the “Nature Video Lindau Collection 2015”. In this series of animated films, Nobel prize-winning scientists talk about work, life and discoveries that changed the world. The the films have been produced by our media partner Nature at the 65th Lindau Nobel Laureate Meeting with support from Mars, Incorporated. The whole series of films can be watched here at Nature’s website.