What if you put all 7 billion humans into one city, a city as dense as New York, with its towers and skyscrapers? How big would that 7 billion-sized city be? As big as New Jersey? Texas? Bigger? Are cities protecting wild spaces on the planet? We try a little experiment to find out.

Roger Ebert wrote simply, abundantly, gorgeously — and on deadline for 46 years at the Chicago Sun-Times. Over the years, his work reminded us that empathy is the grace note of a good life, not just great art.

Host Michel Martin and editor Ammad Omar crack open the listener inbox for backtalk. This week, listeners weigh in on whether toddlers should be using tablet computers and other digital gadgets.

Roger Ebert, who died Thursday, was not only a writer but a social media master, a romantic and a guy who deeply believed in rice cookers. He was also one of the most influential critics of his generation.

Ruben Aguilar, 85, was forcibly deported with his family from the U.S. to Mexico at six. While his parents were not American citizens, he was, and at 18, he was drafted by the U.S. Army. Aguilar is a man who "got hurt by his country, came back to this country and is going to die in his country."

Rutgers University fired basketball coach Mike Rice Wednesday after a video showing Rice physically and verbally abusing players became public. Lionel Tiger, professor emeritus at Rutgers University, argues that Rice should have been fired when the school first learned of the tapes months ago.

Lexicographers know they're in the hot seat as they confront the changing use of the word "marriage." Linguist Geoff Nunberg says the key to getting the new definition right is to crisply describe everything that's in the category and nothing that isn't.