Extreme Engineering Discovery, 8pm Engineering projects around the globe keep getting bigger and more ambitious. This new series looks at some impressive recent constructions including Hong Kong's airport, and future projects ranging from a transatlantic tunnel, a bridge over the Bering Strait (above) and the widening of the Panama Canal. The Living Nightmare Pearl, 9.30pm Scientists have discovered the causes of narcolepsy and in so doing have revealed a whole new system of the brain that may give clues to a host of other afflictions. This research could lead to a new era of drugs to deal with problems as diverse as dementia, obesity and even ageing. But above all, it has provided our first glimpse into one of nature's greatest mysteries - why we sleep.