What came first? Photos from the Valley of the Shadow of Death

This article from the New York Times is an elaborate attempt to determine which of two historic photographs was taken first. The article follows attempts to research the photographs, the photographer, the context of the Crimean War, and the scientific analyization of shadows. This is one of the best recent articles I've seen that gives people an idea of what historians and curators do to determine the "facts" of a story or event. Through some very circular, and often inconclusive, arguments the photographs are studied, researched, torn apart, recreated, and put back together again. This is the type of detective work historians and curators love to get involve with--a real puzzle.