For years the Empire State Building topped the world. Then came the Sears Tower, and now the Petronas Towers in Malaysia eclipse them all. A lot of the world may be downsizing, but colossal engineering projects are back -- skyscrapers, dams, and suspension bridges. In this hour of To the Best of Our Knowledge, engineering marvels. Debating China's Three Gorges Dam. And, treehouses for adults.

David Lampton directs China Studies at John Hopkins' School for Advanced International Studies. He tells Jim Fleming about the Three Gorges Dam - a monumental effort to tame the Yangtze River. Westerners fear the environmental and archaeological damage the project will cause. Also, civil engineer and historian Henry Petroski talks with Judith Strasser about engineering science and the people who become engineers. Petroski teaches at Duke and is the author of "Remaking the World: Adventures in Engineering."

Peter Nelson builds spectacular treehouses for grown-ups and has written a book on how to build your own: "Home Tree Home: Principles of Treehouse Construction and Other Tall Tales." He tells Steve Paulson about some of his favorites and suggests reasons why people want to take to the trees.

Distribution dates:

• week of 02/08/98 - hour 2
• week of 01/03/99 - hour 2