Researchers are piecing together what exactly happened to hundreds of cubes of uranium from a secretive and ultimately failed effort to build a working nuclear reactor in Nazi Germany during World War II.

Inside he found a heavy metal cube and a crumpled message, a provocative note wrapped around a stone that came crashing through the window of history. It read, «Taken from Germany, from the nuclear reactor Hitler tried to build. Gift of Ninninger.»

Koeth’s friend grinned, picked up the 5-pound block of uranium metal and handed it to him. Though modest in size, the cube was heavy, dense and steeped in lost history. Koeth accepted the cube and its note as an invitation to the adventure of a lifetime.

In the May 2019 issue of Physics Today, Koeth and Miriam Hiebert, a doctoral candidate working with him on this project at UMD’s A. James Clark School of Engineering, describe what they’ve discovered while exploring the German quest and failure to build a working nuclear reactor during World War II.

Uranium is weakly radioactive, and this particular cube measures about 2 inches on each side. «It’s surprisingly heavy, given its size, and it’s always a lot of fun to watch people’s reaction when they pick it up for the first time,» said Hiebert.

A Chandelier of Nuclear Elements

This cube represents one of 664 uranium metal components that were strung together in a form reminiscent of a chandelier to comprise the core of a nuclear reactor experiment that a team of German scientists attempted to build toward the end of the World War II, including Werner Heisenberg — a theoretical physicist and one of the key visionaries of quantum mechanics. The chandelier was submerged in heavy water to regulate the rate of fission.

Story Source: Materials provided by American Institute of Physics. Note: Content may be edited for style and length.