The group found this “void” through the use of muon particles, which work kind of like an X-ray, according to Mehdi Tayoubi, co-director of ScanPyramids. Tayoubi told Discovery News last year: "Just like X-rays pass through our bodies allowing us to visualize our skeleton, these elementary particles, weighing around 200 times more than electrons, can very easily pass through any structure, even large and thick rocks, such as mountains."
That being said, researchers aren’t quite sure if these newly discovered cavities will necessarily lead to anything, or if they even exist. Scan Pyramids notes in its report, “the precise shape, size, and exact position of this void is now under further investigation,” and that researchers should have more intel by the end of October.
In the meantime, marinate on the Scan Pyramid team’s launch video from October of last year. It should get you pumped on archaeology: