Dr Helen Czerski examines the hottest natural phenomenon on the planet - lightning. Bolts of lightning five times hotter than the surface of the sun strike our planet over three million times every day - and yet we still know little about this deadly force of nature. Now, specialist photography is revealing how lightning travels through the air, high-speed cameras are unlocking the secrets of upward lightning that's triggered by our urban landscapes, and scientific expeditions are capturing rare images of intense electrical discharges over 80 kilometres wide. Show less