25 years studying the Big Bang’s afterglow

This week marks the 25th anniversary of a Nobel Prize winning discovery: the first image of the cosmic microwave background. This image showed the world what the universe looked like shortly after the big bang, and transformed cosmology. Reporter Davide Castelvecchi asks Nobel Laureate John Mather how the iconic image was taken, and investigates what the cosmic microwave background still has to teach us today.