Elements

The “element of life” also makes the air that we breathe a perilous and costly atmosphere in which to operate. Prof Andrea Sella of University College London provides presenter Justin Rowlatt with a characteristically striking argument for why oxygen is so “incredibly dangerous”, and how its advent turned Planet Earth into a snowball. Pawanexh Kohli, in charge of India’s national cold chain strategy, explains over a cup of chai why the oxygen needs of fresh vegetables and fresh meat are very different. Physics polymath Baldev Raj unpicks the mystery of Delhi’s 1,600-year-old iron pillar, and explains just how damaging rust and corrosion can be. And former “smoke-jumper” Frankie Romero explains the mesmerising attraction of wildfires, and why stamping them out isn’t always a good idea. (Photo: Wildfire in Los Alerces National Park, Argentina; Credit: Emiliano La Salvia/AFP/Getty Images)