For the last few hundred years, humans have tried to scale ever more dangerous peaks. But why do they do it? Mike Williams travels to the Alps to find out. He speaks to skilled climbers including the son of American mountaineer John Harlin II, who died trying to scale the north face of the savage Eiger in Switzerland. Why do they take such risks and what do they get out of it?(Image: North Face of the Eiger Mountain in the Swiss Alps. BBC Copyright)