Uranium cubes reveal why the German nuclear project failed

In the late 1940s, German physicists working on a secret nuclear project were unable to build a working bomb, despite claims that they were close to achieving criticality. This revelation comes from a recent study published in the Proceedings of the National Academy of Sciences Nexus. The project, led by physicist Werner Heisenberg, utilized uranium cubes in their attempts to create a nuclear reactor.

However, the study found that the German program lacked sufficient uranium and heavy water to successfully construct a nuclear weapon. Only 14 of these cubes remain known to exist today. Researchers Timothy Koeth and Miriam Hiebert embarked on a quest to uncover the origins of these cubes, tracking down ten of them in the United States.

The Smithsonian Institute holds one of these cubes, while Harvard University has another that is frequently used in introductory physics classes.