I love the annual Royal Institution Christmas Lectures ever since I first saw them as a 16 year old. No one else in my community here in Singapore seems to know about it, so I'm glad Cosmos has mentioned them. Maybe now I can influence some of my nieces and nephews to watch it with me this year. These days, its as easy as visiting the RI's christmas lectures website where you can even watch Carl Sagan's lecture from 1977. I think its a good thing not to give all the answers. Doing it this way encourages young minds to discover the answers on their own. At any rate, the answers to these questions are something any competent science teacher will be able to impart.