Old article: http://www.wired.com/wiredscience/2010/07/muon-detector/ Status update: http://www.economist.com/node/21552169 Basically, the idea is to use various particle physics detectors to actually plot the tracks of cosmic muons, and see if they scatter off of anything inside a cargo. Nuclear materials scatter incoming cosmics in a specific way. These are the same types of detectors we invented for use at the LHC 25 years ago. People often ask "what's the practical purpose of the research you did" and I respond "practical spinoffs often do not become clear until after the technology has existed for a while." This is a good example.