Why do Bubbles go Down in Guinness?

What does the genetic fingerprint of Ozti, the 5300-year-old Alpine iceman, reveal? Why do the bubbles in a glass of Guinness appear to be defying the laws of physics? Could we replace food with pills? Why did a dead bee still sting me? Is there any evidence that Voodoo does do anything? Why do balloons go bang? How do ducklings recognise their mothers? And why are planets round? Join Dr Chris for this week's crop of top science questions from South Africa... Like this podcast? Please help us by supporting the Naked Scientists