The following is a timeline of the Manhattan Project, the effort by the United States, United Kingdom, and Canada to develop the first nuclear weapons for use during World War II. The following includes a number of events prior to the official formation of the Manhattan Project as the Manhattan Engineering District (MED) in August 1945 and a number of events after the atomic bombings of Hiroshima and Nagasaki, until the MED was formally replaced by the United States Atomic Energy Commission in 1947. For the novel by Michael Crichton, see Timeline (novel). ... This article is about the World War II nuclear project. ... The mushroom cloud of the atomic bombing of Nagasaki, Japan, 1945, rose some 18 kilometers (11 mi) above the hypocenter A nuclear weapon derives its destructive force from nuclear reactions of fusion or fission. ... Combatants Allied powers: China France Great Britain Soviet Union United States and others Axis powers: Germany Italy Japan and others Commanders Chiang Kai-shek Charles de Gaulle Winston Churchill Joseph Stalin Franklin Roosevelt Adolf Hitler Benito Mussolini Hideki Tōjō Casualties Military dead: 17,000,000 Civilian dead: 33,000... The mushroom cloud over Hiroshima after the dropping of Little Boy. ... Shield of the U.S. Atomic Energy Commission. ...

1939

• August 2 — Albert Einstein signs a letter authored by physicist Leo Szilard addressed to President Franklin D. Roosevelt, advising him to fund research into the possibility of using nuclear fission as a weapon in the event that Nazi Germany may also be conducting such research. He later regretted signing the letter.
• September 1 — Nazi Germany invades Poland, beginning World War II.
• October 11 — Economist Alexander Sachs meets with President Roosevelt and delivers the Einstein-Szilard letter. Roosevelt authorizes the creation of the Advisory Committee on Uranium.
• October 21 — First meeting of the Uranium Committee, headed by Lyman Briggs of the National Bureau of Standards. $6,000 is budgeted for neutron experiments.

is the 214th day of the year (215th in leap years) in the Gregorian calendar. ... “Einstein” redirects here. ... Many years later, Albert Einstein and Leó Szilárd re-enact the signing of the Einstein-Szilárd letter to Roosevelt. ... Leó Szilárd (right) working with Albert Einstein. ... FDR redirects here. ... For the generation of electrical power by fission, see Nuclear power plant. ... Nazi Germany, or the Third Reich, commonly refers to Germany in the years 1933–1945, when it was under the firm control of the totalitarian and fascist ideology of the Nazi Party, with the Führer Adolf Hitler as dictator. ... is the 244th day of the year (245th in leap years) in the Gregorian calendar. ... Nazi Germany, or the Third Reich, commonly refers to Germany in the years 1933–1945, when it was under the firm control of the totalitarian and fascist ideology of the Nazi Party, with the Führer Adolf Hitler as dictator. ... Combatants Allied powers: China France Great Britain Soviet Union United States and others Axis powers: Germany Italy Japan and others Commanders Chiang Kai-shek Charles de Gaulle Winston Churchill Joseph Stalin Franklin Roosevelt Adolf Hitler Benito Mussolini Hideki Tōjō Casualties Military dead: 17,000,000 Civilian dead: 33,000... is the 284th day of the year (285th in leap years) in the Gregorian calendar. ... Alexander Sachs (August 1, 1893 - June 23, 1973) was an American economist and banker. ... Many years later, Albert Einstein and Leó Szilárd re-enact the signing of the Einstein-Szilárd letter to Roosevelt. ... is the 294th day of the year (295th in leap years) in the Gregorian calendar. ... The S-1 Uranium Committee was a Committee of the National Defense Research Committee (NDRC) that superceded the Briggs Advisory Committee on Uranium and later grew into the Manhattan Project. ... Lyman James Briggs (7 May 1874 - April 1963) was a scientist and administrator, who is now chiefly known for delaying the start of the American atomic bomb program, and for the School of Science at Michigan State University named after him. ... As a non-regulatory agency of the United States Department of Commerce’s Technology Administration, the National Institute of Standards (NIST) develops and promotes measurement, standards, and technology to enhance productivity, facilitate trade, and improve the quality of life. ...

1940

• March — Otto Frisch and Rudolph Peierls author the Frisch-Peierls memorandum, calculating that an atomic bomb might need as little as 1 lb of enriched uranium to work.
• April 10 — MAUD Committee established by Henry Tizard to investigate feasibility of an atomic bomb
• July 1 — Responsibility for fission research is taken over by Vannevar Bush's National Defense Research Committee.
• December — Franz Simon reports to MAUD that uranium-235 can be separated using gaseous diffusion. Gives cost estimates and technical specifications. James Chadwick realizes "a nuclear bomb...is inevitable"

Sir Rudolf Ernst Peierls, (June 5, 1907, Berlin – September 19, 1995, Oxford), was a German-Born British physicist. ... The Frisch-Peierls memorandum was written by Otto Frisch and Rudolf Peierls while they were both working at Birmingham University, England. ... is the 100th day of the year (101st in leap years) in the Gregorian calendar. ... The Maud Committee was the beginning of the British atomic bomb project, before the United Kingdom joined forces with the United States in the Manhattan Project. ... Sir Henry Thomas Tizard (1885 - 1959) was a British scientist and inventor. ... is the 182nd day of the year (183rd in leap years) in the Gregorian calendar. ... Vannevar Bush (March 11, 1890 – June 30, 1974) was an American engineer and science administrator, known for his political role in the development of the atomic bomb, and the idea of the memex—seen as a pioneering concept for the World Wide Web. ... In June of 1940, U.S. President Franklin D. Roosevelt established the National Defense Research Committee (NDRC) to coordinate, supervise, and conduct scientific research on the problems underlying the development, production, and use of mechanisms and devices of warfare. ... Sir Francis Simon was a British scientist and a Fellow of the Royal Society. ... -1... Sir James Chadwick, CH (20 October 1891 – 24 July 1974) was an English physicist and Nobel laureate who is best known for discovering the neutron. ...

1941

• February 26 — Conclusive discovery of plutonium by Glenn Seaborg and Arthur Wahl.
• March — MAUD Committee prepares interim report urging immediate action and sends it to USA. Lyman Briggs locks it in his safe and fails to tell Uranium Committee. [1]
• May 17 — A report by Arthur Compton and the National Academy of Sciences is issued which finds favorable the prospects of developing nuclear power production for military use. Vannevar Bush creates the Office of Scientific Research and Development (OSRD)
• July 15 — The MAUD Committee issues final detailed technical report on design and costs to develop a bomb. Advance copy sent to Vannevar Bush who decides to wait for official version before taking any action
• August — Mark Oliphant travels to USA to urge development of a bomb rather than power production [2]
• October 3 — Official copy of MAUD Report reaches Bush
• October 9 — Bush takes MAUD Report to Roosevelt who approves project to confirm MAUD's findings
• December 6 — Vannevar Bush holds a meeting to organize an accelerated research project, still managed by Arthur Compton. Harold Urey is assigned to develop research into gaseous diffusion as a uranium enrichment method, while Ernest O. Lawrence is assigned to investigate electromagnetic separation methods.
• December 7 — The Japanese attack Pearl Harbor. The United States issues a formal declaration of war against Japan the next day. Four days later, Nazi Germany declares war on the United States.
• December 18 — First meeting of the OSRD sponsored S-1 project, dedicated to developing fission weapons.

is the 57th day of the year in the Gregorian calendar. ... This article is about the radioactive element. ... Glenn Theodore Seaborg (April 19, 1912 – February 25, 1999) was an American atomic scientist. ... Arthur Wahl (September 8, 1917 – April, 2006) was an American physicist who, as a graduate student in February 1941, was the first to isolate plutonium in a laboratory. ... Lyman James Briggs (7 May 1874 - April 1963) was a scientist and administrator, who is now chiefly known for delaying the start of the American atomic bomb program, and for the School of Science at Michigan State University named after him. ... is the 137th day of the year (138th in leap years) in the Gregorian calendar. ... Arthur Holly Compton (September 10, 1892 – March 15, 1962) won the Nobel Prize in Physics (1927) for discovery of the Compton effect named in his honor. ... President Harding and the National Academy of Sciences at the White House, Washington, DC, April 1921 The National Academy of Sciences (NAS) is a corporation in the United States whose members serve pro bono as advisers to the nation on science, engineering, and medicine. ... Vannevar Bush (March 11, 1890 – June 30, 1974) was an American engineer and science administrator, known for his political role in the development of the atomic bomb, and the idea of the memex—seen as a pioneering concept for the World Wide Web. ... In June of 1941, the Office of Scientific Research and Development (OSRD) superseded the committee structure [of the National Defense Research Committee (NDRC)]. The OSRD projects gave the United States and Allied troops more powerful and more accurate bombs, more reliable detonators, lighter and more accurate weapons, safer and more... is the 196th day of the year (197th in leap years) in the Gregorian calendar. ... Vannevar Bush (March 11, 1890 – June 30, 1974) was an American engineer and science administrator, known for his political role in the development of the atomic bomb, and the idea of the memex—seen as a pioneering concept for the World Wide Web. ... Mark Oliphant Sir Marcus Mark Laurence Elwin Oliphant (October 8, 1901 - July 14, 2000) was an Australian physicist and humanitarian. ... is the 276th day of the year (277th in leap years) in the Gregorian calendar. ... is the 282nd day of the year (283rd in leap years) in the Gregorian calendar. ... is the 340th day of the year (341st in leap years) in the Gregorian calendar. ... Research is often described as an active, diligent, and systematic process of inquiry aimed at discovering, interpreting, and revising facts. ... Arthur Holly Compton (September 10, 1892 – March 15, 1962) won the Nobel Prize in Physics (1927) for discovery of the Compton effect named in his honor. ... Harold Urey, circa 1963. ... Ernest Orlando Lawrence (August 8, 1901 - August 27, 1958) was an American physicist and Nobel laureate best known for his invention of the cyclotron. ... is the 341st day of the year (342nd in leap years) in the Gregorian calendar. ... This article is about the actual attack. ... Nazi Germany, or the Third Reich, commonly refers to Germany in the years 1933–1945, when it was under the firm control of the totalitarian and fascist ideology of the Nazi Party, with the Führer Adolf Hitler as dictator. ... is the 352nd day of the year (353rd in leap years) in the Gregorian calendar. ... The S-1 Uranium Committee was a Committee of the National Defense Research Committee (NDRC) that superceded the Briggs Advisory Committee on Uranium and later grew into the Manhattan Project. ...

1942

Gen. Leslie Groves and physicist Robert Oppenheimer became the military and scientific heads of the Manhattan Project.

• July-September — Physicist Robert Oppenheimer convenes a summer conference at the University of California, Berkeley to discuss the design of a fission bomb. Edward Teller brings up the possibility of a hydrogen bomb as a major point of discussion.
• August — Creation of the Manhattan Engineering District by the Army Corps of Engineers.
• September 13 — At a meeting of the S-1 Executive Committee, it is decided that a centralized laboratory should be established to study fast neutrons, code-named "Project Y".
• September 17 — Col. Leslie Groves is assigned command of the Manhattan Engineering District. Six days later he is appointed to Brigadier General.
• September 24 — After a visit to Tennessee, Groves purchases 52,000 acres (210 km²) of land in Tennessee for "Site X", which will become the Oak Ridge, Tennessee laboratory and production site.
• September 26 — The Manhattan Project is given permission to use the highest wartime priority rating by the War Production Board.
• October 15 — Groves appoints Robert Oppenheimer to coordinate the scientific research of the project at the "Site Y" laboratory.
• November 16 — Groves and Oppenheimer visit Los Alamos, New Mexico and designate it as the location for "Site Y".
• December 2 — Chicago Pile-1, the first nuclear reactor goes critical at the University of Chicago under the leadership and design of Enrico Fermi.

Image File history File links Download high resolution version (526x689, 283 KB) General Leslie Groves (left), military head of the Manhattan Project, with Prof. ... Image File history File links Download high resolution version (526x689, 283 KB) General Leslie Groves (left), military head of the Manhattan Project, with Prof. ... Leslie Groves Leslie Richard Groves (August 17, 1896 – July 13, 1970) was a United States Army officer who oversaw the construction of the Pentagon and was the primary military leader in charge of the Manhattan Project to develop the atomic bomb during World War II. Descended from French Huguenots who... J. Robert Oppenheimer[1] (April 22, 1904 – February 18, 1967) was an American theoretical physicist, best known for his role as the director of the Manhattan Project, the World War II effort to develop the first nuclear weapons, at the secret Los Alamos laboratory in New Mexico. ... J. Robert Oppenheimer[1] (April 22, 1904 – February 18, 1967) was an American theoretical physicist, best known for his role as the director of the Manhattan Project, the World War II effort to develop the first nuclear weapons, at the secret Los Alamos laboratory in New Mexico. ... Sather Tower (the Campanile) looking out over the San Francisco Bay and Mount Tamalpais. ... Edward Teller (original Hungarian name Teller Ede) (January 15, 1908 – September 9, 2003) was a Hungarian-born American theoretical physicist, known colloquially as the father of the hydrogen bomb, even though he did not care for the title. ... The mushroom cloud of the atomic bombing of Nagasaki, Japan, in 1945 lifted nuclear fallout some 18 km (60,000 feet) above the epicenter. ... United States Army Corps of Engineers logo The United States Army Corps of Engineers, or USACE, is made up of some 34,600 military men and women. ... is the 256th day of the year (257th in leap years) in the Gregorian calendar. ... is the 260th day of the year (261st in leap years) in the Gregorian calendar. ... Leslie Groves Leslie Richard Groves (August 17, 1896 – July 13, 1970) was a United States Army officer who oversaw the construction of the Pentagon and was the primary military leader in charge of the Manhattan Project to develop the atomic bomb during World War II. Descended from French Huguenots who... is the 267th day of the year (268th in leap years) in the Gregorian calendar. ... This article is about the U.S. state of Tennessee. ... Oak Ridge National Laboratory (ORNL) is a multiprogram science and technology national laboratory managed for the United States Department of Energy by UT-Battelle, LLC. ORNL is located in Oak Ridge, Tennessee, near Knoxville. ... Oak Ridge is an incorporated city in Anderson and Roane Counties in East Tennessee, about 25 miles northwest of Knoxville. ... is the 269th day of the year (270th in leap years) in the Gregorian calendar. ... The War Production Board (WPB) was established in 1942 by executive order of Franklin D. Roosevelt. ... is the 288th day of the year (289th in leap years) in the Gregorian calendar. ... J. Robert Oppenheimer[1] (April 22, 1904 – February 18, 1967) was an American theoretical physicist, best known for his role as the director of the Manhattan Project, the World War II effort to develop the first nuclear weapons, at the secret Los Alamos laboratory in New Mexico. ... is the 320th day of the year (321st in leap years) in the Gregorian calendar. ... Los Alamos is an unincorporated townsite in Los Alamos County, New Mexico. ... Los Alamos National Laboratory, aerial view from 1995. ... is the 336th day of the year (337th in leap years) in the Gregorian calendar. ... On December 2, 1942, the worlds first self-sustaining nuclear chain reaction, Chicago Pile-1, took place on a squash court beneath Stagg Field on the University of Chicago campus. ... Core of a small nuclear reactor used for research. ... For other uses, see University of Chicago (disambiguation). ... Fermi redirects here. ...

1943

Massive calutrons at Oak Ridge, Tennessee, worked around the clock to enrich uranium for a bomb.

• February 18 — Construction begins for Y-12 at Oak Ridge, Tennessee, a massive electromagnetic separation plant for enriching uranium.
• April 5-14 — Introductory lectures began at Los Alamos, later are compiled into The Los Alamos Primer.
• April 20 — The University of California becomes the formal business manager of the Los Alamos laboratory.
• August 19 — Roosevelt and Winston Churchill sign Quebec Agreement. Team of British scientists join project as a result, including Klaus Fuchs
• October 4 — Construction begins for the first reactor at Hanford Site.
• October — Project W-47, later called Project Alberta set up to plan delivery of the bomb

Download high resolution version (640x684, 72 KB)Control panels and operators for calutrons at Oak Ridge National Laboratory. ... Download high resolution version (640x684, 72 KB)Control panels and operators for calutrons at Oak Ridge National Laboratory. ... A Calutron was a mass spectrometer used for separating the isotopes of uranium developed by Ernest O. Lawrence during the Manhattan Project. ... is the 49th day of the year in the Gregorian calendar. ... Oak Ridge National Laboratory (ORNL) is a multiprogram science and technology national laboratory managed for the United States Department of Energy by UT-Battelle, LLC. ORNL is located in Oak Ridge, Tennessee, near Knoxville. ... Oak Ridge is an incorporated city in Anderson and Roane Counties in East Tennessee, about 25 miles northwest of Knoxville. ... A number of the different fission bomb assembly methods explored during the summer 1942 conference, later reproduced as drawings in The Los Alamos Primer. ... is the 110th day of the year (111th in leap years) in the Gregorian calendar. ... Berkeley Davis Irvine Los Angeles Merced Riverside San Diego Santa Barbara Santa Cruz UC Office of the President in Oakland The University of California (UC) is a public university system in the state of California. ... Los Alamos National Laboratory, aerial view from 1995. ... is the 231st day of the year (232nd in leap years) in the Gregorian calendar. ... Churchill redirects here. ... The Quebec Agreement was an Anglo-Canadian-American document which outlined the terms of nuclear nonproliferation between the United Kingdom and the United States. ... Klaus Fuchs ID badge at Los Alamos. ... is the 277th day of the year (278th in leap years) in the Gregorian calendar. ... Hanford Site plutonium production reactors along the Columbia River during the Manhattan Project. ... Project Alberta was a section of the U.S. Army Air Force and Manhattan Project which developed the actual combat delivery of the first atomic bombs onto the Empire of Japan during World War II. Much of its work consisted in training a crew for preparation of the atomic bombing...

1944

The two types of fission weapon designs pursued during the Manhattan Project.

• April 5 — At Los Alamos, Emilio Segrè receives the first sample of reactor-bred plutonium from Oak Ridge, and within ten days discovers that the spontaneous fission rate is too high for use in a gun-type fission weapon.
• May — Fermi at Los Alamos tests the world's third reactor, LOPO, the first aqueous homogeneous reactor, and the first fueled by enriched uranium.
• July 4 — Oppenheimer reveals Segrè's final measurements to the Los Alamos staff, and the development of the gun-type plutonium weapon "Thin Man" is abandoned. Designing a workable "implosion" design becomes top priority of the laboratory.
• July 20 — The Los Alamos organizational structure is completely changed to reflect the new priority of "implosion".
• September 2 — chemists Peter N. Bragg, Jr. [3] and Douglas P. Meigs [4] are killed, and Arnold Kramish almost killed, while attempting to unclog a uranium enrichment device which is part of the pilot thermal diffusion plant at the Philadelphia Navy Yard. Two soldiers, George LeFevre and John Tompkins, also receive extensive injuries. An explosion of liquid uranium hexafluoride burst nearby steam pipes, and steam combined with the uranium hexafluoride to spray them with highly corrosive hydrofluoric acid. See also [5] [6] and [7]
• December 9 — 509th Composite Group of USAAF constituted to deliver the bomb
• Mid-December — Successful test of explosive lens for Fat Man.

Image File history File links Fission_bomb_assembly_methods. ... Image File history File links Fission_bomb_assembly_methods. ... is the 95th day of the year (96th in leap years) in the Gregorian calendar. ... Portrait of Dr. Emilio Segre Emilio Gino Segrè (February 1, 1905 - April 22, 1989) was an Italian American physicist who, with Owen Chamberlain, won the 1959 Nobel Prize in Physics for their discovery of the antiproton. ... Gun-type fission weapons are fission-based nuclear weapons whose design assembles their fissile material into a supercritical mass by the use of the gun method: shooting one piece of sub-critical material into another. ... Aqueous homogeneous reactors (AHR) are a type of nuclear reactor in which soluble nuclear salts (usually uranium sulfate or uranium nitrate) have been dissolved in water. ... These pie-graphs showing the relative proportions of uranium-238 (blue) and uranium-235 (red) at different levels of enrichment. ... is the 185th day of the year (186th in leap years) in the Gregorian calendar. ... is the 201st day of the year (202nd in leap years) in the Gregorian calendar. ... is the 245th day of the year (246th in leap years) in the Gregorian calendar. ... Arnold Kramish was a physicist and author associated with the Manhattan Project. ... The Philadelphia Naval Shipyard, formerly Navy Yard, was the first naval shipyard of the United States. ... R-phrases , S-phrases , , , , Flash point nonflammable Related Compounds Other anions Hydrochloric acid Hydrobromic acid Hydroiodic acid Related compounds Hydrogen fluoride fluorosilicic acid Supplementary data page Structure and properties n, εr, etc. ... is the 343rd day of the year (344th in leap years) in the Gregorian calendar. ... The 509th Bomb Wing is a component of the US Air Force of the United States of America. ... Modern high explosive lenses. ... This article is about the nuclear weapon used in World War II. For other uses, see Fat Man (disambiguation). ...

1945

The atomic bombings of Hiroshima and Nagasaki were the culmination of the wartime effort.

• January — Gen. Thomas Farrell named Gen. Groves' deputy.
• May 7 — Nazi Germany formally surrenders to Allied powers, marking the end of World War II in Europe.
• May 10-11 — second meeting of the Target Committee, at Los Alamos, which works to finalize the list of cities on which atomic bombs may be dropped.[8]
• June 11 — Metallurgical Laboratory scientists under James Franck issue the Franck Report arguing for a demonstration of the bomb before using it against civilian targets.
• July 16 — the first nuclear explosion, the "Trinity" test of an implosion-style plutonium-based nuclear weapon known as "the gadget", near Alamogordo, New Mexico.
• July 24 — President Harry S. Truman discloses to Soviet leader Joseph Stalin that the United States has atomic weapons. Stalin feigns little surprise; he already knows this through espionage.
• July 25 — General Carl Spaatz is ordered to bomb one of the targets: Hiroshima, Kokura, Niigata, or Nagasaki as soon after August 3.[9] [10]
• August 6 — "Little Boy", a gun-type uranium-235 weapon, is used against the city of Hiroshima, Japan.
• August 9 — "Fat Man", an implosion-type plutonium-239 weapon, is used against the city of Nagasaki, Japan.
• August 12 — The Smyth Report is released to the public, giving the first technical history of the development of the first atomic bombs.
• August 15 — Surrender of Japan to the Allied powers.
• August 21 — Harry K. Daghlian, Jr., a physicist, receives a fatal dose (510 rems) of radiation from a criticality accident when he accidentally dropped a tungsten carbide brick onto a plutonium bomb core. He dies on September 15.
• October 16 — Oppenheimer resigns as director of Los Alamos, and is succeeded by Norris Bradbury the next day.

Image File history File linksMetadata Download high-resolution version (1246x1468, 760 KB) if you look closely, you can see a japanese person in the bottom right corner TITLE: Mushroom cloud CALL NUMBER: POS 6 - U.S., no. ... Image File history File linksMetadata Download high-resolution version (1246x1468, 760 KB) if you look closely, you can see a japanese person in the bottom right corner TITLE: Mushroom cloud CALL NUMBER: POS 6 - U.S., no. ... The mushroom cloud over Hiroshima after the dropping of Little Boy. ... General Thomas Francis Farrell (December 3, 1891 –April 1967) was the Deputy Commanding General and Chief of Field Operations of the Manhattan Engineer District, acting as executive officer to General Leslie Groves. ... is the 127th day of the year (128th in leap years) in the Gregorian calendar. ... During the Battle for Berlin, the Red Flag was raised over the Reichstag, May 1945. ... is the 162nd day of the year (163rd in leap years) in the Gregorian calendar. ... James Franck (August 26, 1882 - May 21, 1964) was a German-born physicist and Nobel laureate. ... The Franck Report of June 1945, named for James Franck, recommended that the US either a) keep its atomic discoveries secret for an indefinite time, or b) develop nuclear armaments at such a pace that no other nation would think of attacking first from fear of overwhelming retaliation. ... is the 197th day of the year (198th in leap years) in the Gregorian calendar. ... It has been suggested that Nuclear explosive be merged into this article or section. ... The Trinity test was the first test of a nuclear weapon, conducted by the United States on July 16, 1945 at , thirty miles (48 km) southeast of Socorro on what is now White Sands Missile Range, headquartered near Alamogordo, New Mexico. ... The mushroom cloud of the atomic bombing of Nagasaki, Japan, 1945, rose some 18 kilometers (11 mi) above the hypocenter A nuclear weapon derives its destructive force from nuclear reactions of fusion or fission. ... The gadget, partially assembled on the shot tower for the Trinity test. ... Alamogordo is a city in Otero County, New Mexico, United States of America. ... is the 205th day of the year (206th in leap years) in the Gregorian calendar. ... For other persons named Harry Truman, see Harry Truman (disambiguation). ... Josef Vissarionovich Dzhugashvili (Georgian: , Ioseb Besarionis Dze Jughashvili; Russian: , Iosif Vissarionovich Dzhugashvili) (December 18 [O.S. December 6] 1878[1] – March 5, 1953), better known by his adopted name, Joseph Stalin (alternatively transliterated Josef Stalin), was General Secretary of the Communist Party of the Soviet Unions Central Committee from... is the 206th day of the year (207th in leap years) in the Gregorian calendar. ... Carl Tooey Spaatz (June 28, 1891 – July 14, 1974) was an American general in World War II. Carl Andrew Spatz (Spaatz added the second a in 1937 at the request of his wife and daughters to clarify the pronunciation of the name) was born on June 28, 1891, in Boyertown... is the 218th day of the year (219th in leap years) in the Gregorian calendar. ... Little Boy was the codename of the atomic bomb which was dropped on Hiroshima, on August 6, 1945 by the 12-man crew of the B-29 Superfortress Enola Gay, piloted by Colonel Paul Tibbets (Tibbets, age 92, died Nov. ... The mushroom cloud over Hiroshima after the dropping of Little Boy. ... Main keep of Hiroshima Castle The city of Hiroshima (広島市; -shi) is the capital of Hiroshima Prefecture, and the largest city in the Chugoku region of western Honshu, the largest of Japans islands. ... is the 221st day of the year (222nd in leap years) in the Gregorian calendar. ... This article is about the nuclear weapon used in World War II. For other uses, see Fat Man (disambiguation). ... The mushroom cloud over Hiroshima after the dropping of Little Boy. ... Megane-bashi (Spectacles Bridge) Nagasaki   listen? (長崎市; -shi, literally long peninsula) is the capital and the largest city of Nagasaki Prefecture located at the south-western coast of Kyushu, Japan. ... is the 224th day of the year (225th in leap years) in the Gregorian calendar. ... The Smyth Report was the common name given to an administrative history written by physicist Henry DeWolf Smyth about the Allied World War II effort to develop the atomic bomb, the Manhattan Project. ... is the 227th day of the year (228th in leap years) in the Gregorian calendar. ... The Japanese representatives, Mamoru Shigemitsu and Yoshijiro Umezu, on board USS Missouri during the surrender ceremonies on 2 September 1945. ... is the 233rd day of the year (234th in leap years) in the Gregorian calendar. ... Harry K. Daghlian, Jr. ... A criticality accident (also sometimes referred to as an excursion or power excursion) occurs when a nuclear chain reaction is accidentally allowed to occur in fissile material, such as enriched uranium or plutonium. ... is the 289th day of the year (290th in leap years) in the Gregorian calendar. ... Norris Bradbury in his later years. ...

1946

• May 21 — Louis Slotin, a physicist, received a fatal dose of radiation (2100 rems) when the screwdriver he was using to keep two beryllium hemispheres apart slipped; they were placed around the same plutonium core that had irradiated Daghilan. The upper hemisphere fell, causing a "prompt critical" reaction with a burst of hard radiation. Slotin lifted the upper hemisphere with his left hand and dropped it on the floor, so preventing a more serious accident. He was rushed to hospital, and died nine days later on May 30. Slotin had spent many hours with the dying Daghlian in 1945.

is the 141st day of the year (142nd in leap years) in the Gregorian calendar. ... A sketch used by doctors to determine the amount of radiation to which each person in the room had been exposed during the excursion. ... In nuclear engineering, an assembly is prompt critical if for each nuclear fission event, one or more of the immediate or prompt neutrons released causes an additional fission event. ... Hard radiation is a term used to describe high-energy electromagnetic radiation, typically high energy X-rays or gamma rays. ...

1947

• January 1 — the Atomic Energy Act of 1946 (known as the McMahon Act) takes effect, and the Manhattan Project is officially turned over to the United States Atomic Energy Commission.

is the 1st day of the year in the Gregorian calendar. ... Truman signs the Atomic Energy Act on August 1, 1946. ... Shield of the U.S. Atomic Energy Commission. ...

References

• Richard Rhodes, The Making of the Atomic Bomb (Simon and Schuster: New York, 1986).

Richard Rhodes (born July 4, 1937) is an American author of fiction and verity, including the Pulitzer Prize-winning The Making of the Atomic Bomb in 1986, and most recently, John James Audubon: the Making of an American in 2004. ...

External links

• Chronology for the origin of atomic weapons from Carey Sublette's NuclearWeaponArchive.org
• Manhattan Project Chronology from Department of Energy's The Manhattan Project: Making the Atomic Bomb

v • d • e Manhattan Project
Project Sites	Hanford Engineer Works · Oak Ridge, Tennessee · Los Alamos, New Mexico · Berkeley Radiation Laboratory · Chicago Metallurgical Laboratory · Trinity Test Site · Project Alberta · Project Ames · Dayton Project
People	Robert Oppenheimer · Leslie Groves · Enrico Fermi · David Bohm · Emilio Segrè · Edward Teller
Related Articles	Timeline of the Manhattan Project · History of nuclear weapons · Nuclear weapons and the United States · S-1 Uranium Committee · Chicago Pile-1 · X-10 Graphite Reactor · Y-12 National Security Complex · Operation Alsos · Smyth Report · 509th Operations Group · Fat Man · Little Boy · Atomic bombings of Hiroshima and Nagasaki (debate)