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German scientists split the atom.
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World War II in Europe starts when Germany invades Poland.
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German scientists learn that uranium research has started in England and the United States.
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Alexander Sachs, a friend of both President Franklin D. Roosevelt and Albert Einstein, delivers a letter from Einstein to Roosevelt explaining that a chain reaction could lead to the construction of an extremely powerful bomb.
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More discoveries made in atomic energy
February — In Minneapolis, scientist Al Nier first separates a small amount of uranium-235 necessary to build the uranium bomb.
March — Scientist John Dunning, working with Niels Bohr, shows fission is more easily produced in the rare uranium-235 than in the more plentiful uranium-238.
April — Japanese studies into atomic energy begin with the military. -
Roosevelt is elected to third term as U.S. president
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February — Scientists in Berkeley, Calif., produce a new element, eventually to be named plutonium.
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Period: to
The world continues in crisis as the war expands.
June — Germany invades the Soviet Union.
September — A committee of elite British scientists determines an atomic bomb is possible and should be built.
December — President Roosevelt appoints a committee to determine if the United States should build the bomb and what it will cost. -
Japan attacks at Pearl Harbor
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The United States enters the war
January — Roosevelt urges develop ment of an atomic bomb.
May — U.S. scientists move ahead on five different methods to produce fissionable material. -
German armament minister Albert Speer discusses an atomic weapon with Hitler.
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Gen. Leslie Groves assumes control of the Manhattan Project. He selects Oak Ridge, Tenn., as the site for the uranium production plant.
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Oppenheimer recruited
Groves meets with J. Robert Oppenheimer to discuss the physicist’s interest in managing the Manhattan Project. A week later, Oppenheimer’s acceptance is final. -
Period: to
Critical mass achieved
October — Groves meets with J. Robert Oppenheimer to discuss the physicist’s interest in managing the Manhattan Project. A week later, Oppenheimer’s acceptance is final.
December — U.S. scientists led by Enrico Fermi working at the University of Chicago achieve critical mass for the first time in history.
December — U.S. government takes over the Los Alamos Ranch School for military purposes. The ranch, founded in 1917, and 54,000 acres around it is designated Site Y. -
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Scientists begin arriving in New Mexico
January — Groves selects Hanford, Wash., as the site for plutonium production reactors.
April — The new laboratory at Los Alamos officially opens. The technical areas had no power, telephones or equipment.
April — Nearly 100 scientists are in Los Alamos and ready to start work. Their average age is 25. -
Oppenheimer arrives in Santa Fe
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Implosion theory moves forward
February — Physician Louis Hempelmann reports on hazards of exposure to radiation.
June — Oppenheimer announces the existence of spontaneous fission in plutonium-240, making possible a gun-assembled weapon using plutonium.
July — Explosions are heard in the canyons around Los Alamos as scientists test the theory of implosion. Fuchs arrives in Los Alsmos. -
B-29 raid on Tokyo kills 83,793 people and destroys more than a million buildings.
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President Roosevelt dies. Harry Truman is sworn in and told about the atomic bomb.
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Period: to
Plans are made to invade Japan
April 27 — GIs at Los Alamos and Trinity hear that all furloughs are canceled until after July.
May 25 — Joint Chiefs of Staff sets November as date for invasion of Japan.
May 31 — At a congressional meeting to discuss the use of the bomb, Oppenheimer estimates 20,000 people will die in an atomic bomb explosion.
June 2 — Fuchs meets his contact Harry Gold in Santa Fe and reveals scientists at Los Alamos are making tremendous progress and plan a test in July. -
VE Day Germany surrenders
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At the bottom of Los Alamos Canyon, scientist Louis Slotin assembles, for the first time, two full-scale plutonium hemispheres in a test for criticality.
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Period: to
Intrigue grows as the Gadget nears completion
June 16 — The Interim Committee scientific panel says it sees no alternative to direct military use of the bomb.
June 19 — In Flushing, N.Y., Harry Gold meets with his Soviet superior and turns over information about the implosion lens and other matters given to him by Fuchs and Greenglass.
June 24 — Scientists establish the size of the Trinity bomb. -
Leo Szilard circulates a petition intended for Truman, asking that atomic bombs not be used.
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Truman leaves Washington for the Potsdam Conference near Berlin.
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“The Gadget” is assembled at Trinity Site.
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The Gadget is hoisted atop 100-foot tower.
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TRINITY
Video of the blastThe first atomic bomb is exploded at precisely 5:29:45, sending a fireball eight miles into the sky. After watching his handiwork, Oppenheimer recalls the Hindu epic Bhagavad Gita and a quotation about Lord Krishna: “I am become death, destroyer of worlds.” Another scientist says: “Oppie, now we’re all sons of bitches.”
