Astronomer Philip Plait — who fell in love with Saturn after first viewing the gas giant, with its mesmerizing rings and moons, through a telescope as a child — shares some of the amazing discoveries we've made about the planet in recent years. Then actor Martin Sheen describes how his travels in the developing world have opened his eyes, and his heart, to the needs of others. And a Florence-based tour guide and culinary expert lets us in on where to find the best food in her adopted home.