Uranium cubes reveal why the German nuclear project failed

During World War II, physicists on the Manhattan Project were concerned that Nazi Germany might develop the first nuclear bomb before the US and its allies. Although this did not happen, historians have long debated the extent of Germany's progress in building a nuclear reactor, specifically their final attempt known as the B8 pile.

Werner Heisenberg, who oversaw the project, believed they were close to achieving criticality but only needed an additional amount of uranium. However, a recent study published in the Proceedings of the National Academy of Sciences suggests otherwise. According to the research, Germany lacked sufficient uranium and heavy water to construct a functional bomb due to the design they employed.

This investigation began in 2013 when physicist Timothy Koeth, a co-author of the new paper, received a mysterious heavy metal cube from a friend. Recognizing the cube as one of the uranium cubes utilized by German scientists, Koeth embarked on a quest to uncover its origins and the story behind the other similar cubes scattered across the United States.

As of 2019, Koeth and his partner, Miriam "Mimi" Hiebert, had managed to trace down ten of these cubes. Some of these cubes have found their way into major institutions like the Smithsonian Institute and Harvard University, where they were used as curiosities in introductory physics classes.