Tel Aviv University researchers say they have demonstrated a new way to chart underground voids at archaeological sites, using compact detectors that track cosmic-ray muons. “From the pyramids in Egypt, through the Maya cities in South America, to ancient sites in Israel, archaeologists struggle to discover underground spaces,” says Prof. Lipschits. “Therefore, by placing muon detectors underground and monitoring the environment, we can identify empty cavities where energy loss is minimal,” explains Prof. Etzion. “This is not our invention,” Prof. Etzion notes. “Our innovation lies in developing small and mobile detectors and learning how to operate them at archaeological sites.”