The race to build the bomb On August 6, 1945, a single American aircraft dropped an atom bomb on the Japanese city of Hiroshima. Three days later Nagasaki met the same fate. Japan surrendered within a week, ending World War Two. More than 120,000 of the 450,000 people in the two cities were killed – a further 100,000 died from radiation-related illnesses Emperor Hirohito (right). Believed to have opposed Japan’s drift to war THE RISING SUN 1937, Jul 7: Japan invades China. Ultra-nationalist military leaders justify plan to occupy China, Manchuria and Korea under pretext of Hakko Ichiu – ancient Shinto concept of “all the world under one roof”, ruled by Japan’s divine Emperor. Invasion sets Japan on course for World War Two 1938: German scientists Otto Hahn and Fritz Strassman demonstrate nuclear fission – splitting the nucleus of a uranium atom and converting some of its mass to energy. Japanese atom bomb project begins under direction of physicist Yoshio Nishina (right). Japan purchases cyclotron – to enrich uranium – from University of California 1939: Germany starts project to build atom bomb. Rival teams led by physicists Kurt Diebner and Werner Heisenberg (left) explore uranium and plutonium devices Aug: Scientists led by Albert Einstein (left) write to U.S. President Franklin D. Roosevelt (right), warning of Nazi Germany’s A-bomb project. Letter recommends that U.S. develops its own atom bomb – Manhattan Project is born BLITZKRIEG Sep: Adolf Hitler invades Poland. Britain and France declare war on Germany. Britain begins GEN75 project to build atom bomb 1940: Heisenberg’s protégé Carl Friedrich Freiherr von Weizsäcke proposes use of eka-rhenium as nuclear explosive. Eka-rhenium – now called neptunium – decays into plutonium 1941: Heisenberg’s team files patent for plutonium bomb in Germany Dec 7: Japan attacks Pearl Harbour, bringing U.S. into war 1942: Soviet leader Joseph Stalin (above left) learns of U.S. and German A-bomb projects. Soviet atomic weapons programme begins under leadership of physicist Igor Kurchatov (right) 1944: In U.S., Manhattan Project employs almost 129,000 people – including British and Canadian atom scientists – under leadership of Robert Oppenheimer RAIN OF STEEL 1945, Apr 1: U.S. invades Okinawa – last stepping stone on road to Japan – 81-day battle claims more than 110,000 Japanese and 14,000 American lives. U.S. firebombing of Japanese cities forces Tokyo’s A-bomb project to be moved to Hungnam, in what is now North Korea Apr 12: Roosevelt dies, Harry S. Truman becomes U.S. president. Briefed on Manhattan Project, Truman sees bomb as way to end war quickly and save American lives May 7: Allied Armies accept unconditional surrender of Nazi Germany – Pacific war continues Jun 18, 1945: Truman approves plan to invade and occupy Japan. Invasion will employ 2.7 million U.S. troops Jul: Two atomic bombs – uranium-fuelled Little Boy and plutonium-fuelled Fat Man – are transported to Tinian in U.S.-occupied Marianas Jul 16, Trinity Test: After $2 billion of research ($23bn in current value), prototype plutonium device is detonated in New Mexico desert. It yields four times more energy than scientists had thought possible. Oppenheimer quotes Hindu Bhagavad Gita: “I am become Death, the destroyer of worlds” Jul 26, Potsdam Declaration: U.S., Britain and China demand Japanese surrender or face “prompt and utter destruction”. Japan ignores declaration Aug 6, 8:15am: B-29 bomber Enola Gay, flying at 9,150 metres, drops atomic bomb on Hiroshima, killing almost everyone within 1,000m of ground zero Aug 9, 11:02am: U.S. drops plutonium bomb on Nagasaki, killing 40,000 people instantly Aug 14: Japan surrenders ---------------- CHAIN REACTION: The power of an atom bomb comes from the release of energy holding together each individual atom of uranium. When sufficient fuel is brought together a chain reaction occurs – energy released is a hundred million times greater than that from a chemical reaction Neutron U-235 (stable) End products (barium and krypton) 1 Chain reaction starts when single neutron strikes nucleus of uranium-235 atom 2 Uranium atom changes to highly unstable uranium-236 3 Uranium-236 immediately splits into barium and krypton, releasing high-energy radiation and more neutrons 4 These neutrons strike other∂ uranium-235 atoms, which split, releasing more energy and neutrons FISSION ---------------- Extent of Japanese Empire June 1945, modern borders shown USSR Manchuria Kyushu Hungnam KOREA Honshu Okinawa New Guinea CHINA AUSTRALIA INDONESIA JAPAN PHILIPPINES INDO- CHINA (Vietnam, Laos, Cambodia) Tokyo Nagasaki Hiroshima Peking (Beijing) FORMOSA (Taiwan) Singapore SIAM (Thailand) BURMA Hokkaido Tinian Mariana Islands Guam ---------------- WORLD’S FIRST A-BOMB Little Boy uranium bomb Length: 3 metres Weight: 4,400kg Yield: 15 kilotons 1. Barometric safety switch operates when bomb is just 1,500m above target 2. Proximity fuze fires explosive charge 3. Wedge of uranium-235 is fired at large target of U-235 4. Force of impact welds two pieces together, creating super-critical mass of uranium drenched in neutrons. Chain reaction accelerates and atomic blast follows Sources: Physics World, Hitler’s Bomb by Rainer Karlsch and Mark Walker, Japan’s Secret War by Robert Wilcox, Ruin from the Air by Gordon Thomas & Max Morgan Witts, FAS, GlobalSecurity.org Pictures: Associated Press