A crater is a typically bowl-shaped depression in the ground caused by a sudden, violent release of energy. And the result of that sudden energetic event is often the loss of lives in the immediate area. More rarely, a crater saves a life. One such crater, in Quang Tri Province, Vietnam, US Army Corps of Engineers grid coordinates 317448, saved five young American soldiers. It also helped advance my understanding and appreciation of physics

It was last light, and my front scout, Gair Anderson, my assistant team leader, Bruce Cain, and I were each placing a claymore mine facing an enemy trail. It was a well-used trail, four miles west-southwest of Quang Tri City, and only the night before we had heard enemy troops casually talking as they walked along. We were confident that more enemy troops would return. Then, just as we slipped in the detonators, a dark figure suddenly appeared on another trail, a hundred feet away.