Surprise: empty box does not detect explosives
Dowsing is an interesting phenomenon. I have seen a water dowser at work, and it really was impressive. It was a grizzled old man, something of a local legend, who had been dowsing for decades. A neighbor hired him to find a place where they could drill for a new well, because their old well had gone dry. The old man located the spot, they drilled, and presto: water.