Dr Chris, Dr Dave and Dr Phil answer all your questions on science, technology and medicine, including why spiders do not run out of silk, what the universe is expanding into, what a flame looks like in space, and what happens when the brain is cut off from a supply of oxygen. We also talk to Dr Mark Peplow about polonium 210, how much was needed to kill former Russian spy Alexander Litvinenko, and where the perpetrators could have acquired it. Sticking with nasty substances, Derk and Dave make a mess with milk and vinegar in Kitchen Science. Like this podcast? Please help us by supporting the Naked Scientists)