The Quick Study by Giulio Saracino and Cristina Cârloganu (Physics Today, December 2012, page 60) correctly identifies Luis Alvarez and collaborators as the first to use cosmic-ray muons to explore terrestrial structures by constructing a muon telescope in the Chephren pyramid’s Belzoni chamber to search for undiscovered chambers. However, the authors’ statement that Alvarez and coworkers “found nothing” is incorrect. What the Alvarez team found was that there were no undiscovered chambers. That is a distinction with a difference.