Why do my wife's eyes light up when she sees me?

In this episode of Ask, if the universe is expanding, what's it expanding into? What's the relationship between descended testes and the chance of having children? Why does more urine come out when I stand rather than sit on the loo? How do surgeons join the cut ends of a colon together? At what age is it suitable to start taking creatine supplements? Why do I wake up in the middle of the night? Like this podcast? Please help us by supporting the Naked Scientists