Why does the Earth hum?

What is the Earth made from? Has the Voyager 1 spacecraft reached the edge of our solar sytem? Why do you lose your appetite when you feel unwell? How does lemon juice affect urine? Does the day on which you are born make a difference? How do we communicate in space? What are the origins of sceintific morality? How does castor oil affect your digestive system? Plus, the mass of the smallest exoplanet measured. Like this podcast? Please help us by supporting the Naked Scientists