In 2013, a university radiation safety officer handed materials scientist Timothy Koeth a lunch bag. Inside was a heavy grey cube of uranium and a note saying it came from the reactor Nazi Germany tried to build.
We follow that cube back to 1945: the Uranium Club, the heavy water from occupied Norway, Werner Heisenberg’s B8 reactor experiment of 664 uranium cubes hanging in a cave beneath a church in Haigerloch, the Alsos mission that dug the cubes out of a plowed field, and the secretly recorded German scientists at Farm Hall. Then the 2026 nuclear archaeology study in PNAS Nexus that measured surviving cubes, rebuilt B8 in a computer, and found it was nowhere near working: about twice the uranium and more than twice the heavy water would have been needed, more than Germany had.
Featured print: Geiger Metronome, a vintage engraving-style radiation print for a classroom or study (PaperLedgerScience): https://www.etsy.com/listing/4569822739 (digital download $2.49).
Chapters:
00:00 A Cube in a Lunch Bag
00:58 The Uranium Club
01:59 The Heavy Water Problem
03:03 The Cave Under the Church
04:01 Alsos Arrives
05:22 Farm Hall
06:23 Ledger Note
07:17 Nuclear Archaeology
09:02 Back to the Cube
Sources:
– Park, Robertson, Hiebert, Zhao, Sivels and Koeth, “Nuclear archaeology reassesses Heisenberg’s last reactor experiment,” PNAS Nexus (2026): https://doi.org/10.1093/pnasnexus/pgag282
– Science (AAAS), “Nazi Germany had no hope of making an atomic bomb, uranium cubes reveal” (1 Oct 2026): https://www.science.org/content/article/nazi-germany-had-no-hope-making-atomic-bomb-uranium-cubes-reveal
– Live Science, “Uranium from World War II reveals how close the Nazis were to an atomic bomb” (21 Oct 2026): https://www.livescience.com/physics-mathematics/uranium-from-world-war-ii-reveals-how-close-the-nazis-were-to-an-atomic-bomb
– Koeth and Hiebert, “Tracking the journey of a uranium cube,” Physics Today (2019): https://doi.org/10.1063/pt.3.4202
– Physics Today, “Where in the world are Nazi Germany’s uranium cubes?”: https://physicstoday.aip.org/news/where-in-the-world-are-nazi-germanys-uranium-cubes
– Physics Today letter, Thorwart and Fechter, “Haigerloch Cave Survived the War”: https://physicstoday.aip.org/letters/haigerloch-cave-survived-the-war-1760119213642
– Atomic Heritage Foundation, “Alsos Mission”: https://ahf.nuclearmuseum.org/ahf/history/alsos-mission/
– German History in Documents and Images, Farm Hall transcripts (6-7 Aug 1945): https://ghdi.ghi-dc.org/sub_document.cfm?document_id=2320&language=english
– AIP Heisenberg exhibit, Farm Hall transcripts: https://history.aip.org/history/exhibits/heisenberg/farm-hall.html
Made with: Script researched and written by Paper Ledger; visuals created with AI image tools in our cut-paper style; voice: AI TTS (Kokoro).
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