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GPS is great, unless you’re in a blind spot, inside a building, or under water. Professor Hiroyuki Tanaka at the University of Tokyo has developed a system that’s more reliable and precise. It uses muons, particles that are a natural form of radiation, which constantly bombard the Earth’s surface and are absorbed by the land or water they fall on. Tanaka’s muon positioning system tracks the level of radiation that reaches a receiver and computes how much has been absorbed along the way. This allows systems to map walls and floors or detect the presence of people. “The current positioning accuracy is 3.5 centimeters indoors,” says Tanaka. In March, the tech was used to uncover a hidden room within a 4,500-year-old Egyptian pyramid.

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