Nuclei of atoms split into smaller parts, producing free neutrons, and releasing a lot of energy in the form of kinetic energy and electromagnetic radiation.

Spontaneous fission happens very slowly in nature.

Induced fission happens in nuclear reactors and bombs. Heavy elements are bombarded with neutrons that split their nucleaus.

Uranium 235—very fissile form of uranium

Uranium 238—not so fissile form, used in reactors to make plutonium

Plutonium 239—very fissile form of plutonium

Atom bomb—a portable atomic reactor designed to release as much energy as possible as fast as possible before the reactor explodes.

The massive explosion causes hot, low density air to rise so rapidly that it curls back on itself and forms a mushroom cloud in the air.

32 detonators, whose charged point inward and squeezedThe plutonium core, initiating nuclear reaction.

The theoretical possibility of developing an atomic bomb was not a secret. Fission had been discovered in Berlin, and word of the breakthrough had spread quickly around the world. The scientific basis for a sustained, or even explosive, chain reaction was now clear to any well-versed research physicist. Most physicists initially may have thought an explosive chain reaction unlikely, but the possibility could not be entirely discounted.

A Hungarian-American physicist who worked on the Manhattan Project he was probably the first scientist to think seriously of building real atomic bombs. Was a great political thinker also. He worked with Enrico Fermi at Columbia and then at University of Chicago on developing the bomb. If anyone truly saw the bomb from start to finish, it was Szilard.

He also was the co-holder, with Enrico Fermi, of the patent on the nuclear reactor.

Conducted the first nuclear fission experiment at Columbia University, developed the first nuclear reactor, and demonstrated the existence of new radioactive elements produced by neutron irradiation. Worked in the Chicago on the Manhattan Project.

Won the Nobel Prize in 1938.

Danish physicist, developer of quantum theory.

Gained crucial insights on the nature of uranium and plutonium isotopes. Worked at Los Alamos during the Manhattan Project.

Physicist E=MC2, relativity in early 1900s.

Co-authored, with Szilard, to President Roosevelt, which warned him of the possibilities of nuclear weapons, delivered in October 1939.

British scientist who studied under Ernst Rutherford.

In 1932, he proved the existence of neutrons. Neutrons, since they are not electrically charged, need not overcome any electric barrier and are capable of penetrating and splitting the nuclei of even the heaviest elements. Paved the way towards the fission of uranium 235 and towards the creation of the atomic bomb.

He was awarded the Nobel Prize for Physics in 1935.

In 1929 he invented the cyclotron, a device for accelerating nuclear particles to very high velocities without the use of high voltages. He was involved with the Manhattan Project from nearly the beginning. He was in charge of the electromagnetic separation work at Oak Ridge, Tennessee.

He won the Nobel Prize in Physics in 1939.

Founder of the American school for theoretical physics, Berkeley.

Scientific director of the Manhattan Project, based in Los Alamos, New Mexico. “The Father of the Atomic Bomb.”

After the war, he was chief advisor to the US Atomic Energy Commission to control the use of nuclear weapons.

World War II erupted at a moment when the promise of atomic energy had progressed from being possibile to being probable. It was not clear whether this energy could be released explosively however.

Many magazines and newspapers in the late 1940s were filled with stories touting the benefits of virtually free and unlimited energy, and predictions of everything from "atomic cars" to "atomic medicines." The belief that nuclear energy would ultimately prove more beneficial than harmful was strongest among those who had the most education.

1941 Szilard had recently succeeded in the enrichment of uranium convincing scientists in the still-neutral United States to keep secret the results of their atomic research, and, as a result, the Germans could not learn of their own mistakes from the open scientific literature.

Anything related to the topic of fission disappeared from scientific publications in the US and Britain.

German physicists heard rumors and suspected an atomic bomb project was underway in Britain, the United States, or both, but that was all.

On October 15, 1942 Groves asks Dr. J. Robert Oppenheimer to head Project Y, the new planned central laboratory for weapon physics research and design at Los Alamos, New Mexico.

Fermi built CP-1 in Chicago. Groves took the fissile material programs out of

the hands of the scientists and placed them under the management of industrial corporations like DuPont and the Kellog Corporation.

Plutonium Production Reactors

Headquarters:Plutonium Processing TestingAssembly Buildings

Thermal Diffusion PlantGraphite ReactorElectromagnetic Plant

CP-1 (Chicago Pile #1)CP-2 and CP-3 Nuclear Reactors

On December 2, 1942, physicists working under top-secret conditions at the University of Chicago, created the world’s first controlled, self-sustaining nuclear chain reaction. Nobel prize-winning physicist Enrico Fermi directed the experiment. “We’re cooking!” was the exuberant reaction recorded when the experiment succeeded. (The data shown on these notebook pages is the record of the nuclear reactor’s response to the movement of the control rods.)

The Second World War and the Manhattan Project transformed a small number of specialized researchers into the largest and one of the most secretive research projects ever undertaken, bringing them to one of four locations in the US to work on the Manhattan Project.

Scientists who had once raced to publish their results learned to speak in codes accessible only to those with a "need to know." Indeed, during the war the very existence of the man-made element plutonium was a national secret.

All the scientists knew is that they were gathered to build atomic weapons before the Germans could develop them. In 1943, measured spontaneous fission rates were so high that gun assembly was abandoned and bomb-making was undertaken.

This discovery was a turning point for Los Alamos, the Manhattan Project, Oppenheimer was forced to make implosion research a top priority, using all available resources to attack it. A complete reorganization of Los Alamos Laboratory was required.

August 6, 1945: Little Boy bomb, dropped by the U.S. B-29 Enola Gay, explodes with the force of 15 kilotons of explosive. (The U-235 weapon was considered very inefficient, with only 1.38% of its material fissioning.)

August 9, 1945: Fatman bomb dropped by the U.S. B-29 Bock's Car, explodes with the force of 22 kilotons of explosive.

The United States expected to have another atomic bomb ready for use in the third week of August, with three more in September and a further three in October.

Hiroshima--Americans estimated that 4.7 square miles of the city were destroyed. 69% of Hiroshima's buildings were destroyed and another 6–7% damaged. 70,000–80,000 people, or some 30% of the population of Hiroshima were killed immediately, and another 70,000 injured.

Nagasaki--Because of Nagasaki's hilly terrain, the damage was somewhat less extensive than that in relatively flat Hiroshima. An estimated 39,000 people were killed outright by the bombing at Nagasaki; a further 25,000 were injured.

15m radius fireball, shock wave

Thermal burns—infrared heat whatever was facing the blast.

Radioactive debris deposited by ‘black rain.’

Uniform radiation burn—electromagnetic waves (like the sun’s rays but really high energy) detach electrons from atoms in your skin cells, degrading tissues all over your body.

white fabric reflects more infra-red light than dark fabric

Sixteen hours after the bombing, the White House released a statement by President Harry S. Truman, who was en route from the Potsdam Conference aboard the U.S.S. Augusta. "It is an atomic bomb," Truman announced, "harnessing . . . the basic power of the universe. The force from which the sun draws its power has been loosed against those who brought war to the Far East."

In early 1944 officials began a carefully designed public relations program in to both allay public inquisitiveness and satisfy the legitimate public need to know. They perceived that, from the standpoint of security, the release of some selected information would make it easier to maintain the secrecy of the highly classified aspects of the project.

The public relations program had 2 parts: preparation of a series of public releases and preparation of an administrative and scientific history of the project.

The well-known science reporter for the New York Times, wrote all the press releases for the Manhattan Project, was the only journalist allowed access to it. Witnessed the Trinity test and flew in the plane that dropped the atomic bomb on Nagasaki. During this time, he was on the payroll of the US War Department.

And he became a staunch advocate of the atomic bomb long before the atomic bomb was ever dropped. Throughout the 1930's he was advocating for research into the use of atomic power, such that he earned a nickname, "Atomic Bill.”

His ten-part series profiling the bomb, would win him and the Times a Pulitzer Prize in 1946.

He withheld what he knew about radioactive fallout across the southwestern desert that poisoned local residents and livestock. He kept mum about the spiking Geiger counters all around the test site.

After the first bomb was dropped on Hiroshima, the government handed The Times the records and on Aug. 7, 1945, Laurence’s secrets were finally revealed on the front page.

The Smyth Report—a document released not long after the bombing, descibing the Manhattan Project and the atomic bomb. “The Smyth Report was intended to control the amount and nature of information on the bomb released to the public.”

Dictated to the science public what was now considered ‘declassified.’

Despite undergoing extensive security review before release, the Smyth Report was criticized by politicians as having "given away the secret of the A-bomb."

The Smyth Report did mention fission of uranium and the kinds of facilities used, but did not contain any details on creating a functional weapon, nor any illustrations. It did not outline how one would actually construct an atomic bomb.

It was made clear that persons either disclosing or securing additional information without authorization, Groves declared, would be "subject to severe penalties under the Espionage Act."

No journalist was on the ground to see the effect of the Hiroshima and Nagasaki bombs. The world's media crowded onto the USS Missouri off the coast of Japan to cover the surrender of the Japanese.

Australian war correspondent Wilfred Burchett – who had eluded the censors – had been the first reporter to cover the A-bomb aftermath. NAGASAKI, Sept.9 (cdn) — The atomic bomb’s peculiar "disease," uncured because it is untreated

and untreated because it is not diagnosed, is still snatching away lives here. London Daily Examiner article

In response, the US government flatly denied reports of deadly radiation and its lingering effects, and accused Burchett of falling for Japanese propaganda. The Times headlined Laurence’s story on September 12: "US Atom Bomb Site Belies Tokyo Tales: Tests on New Mexico Range Confirm that Blast and Not Radiation Took Toll.

Chicago Daily News reporter George Weller, a Pulitzer Prize-winning journalist dispatches were stopped in 1945 by US military censors, were just recently discovered by his son in 2005. Both Weller and another reporter had documented the atrocities in post-bombing Japan, but only one successfully made it to press.

The Los Angeles Times on September 16 1945 published a front page article "By George Weller Chicago Daily News Foreign Service Nagasaki. (Delayed) U.S. Prisoner Sees A-Bomb Rip Nagasaki.

Wilfred Burchett George Weller

The immediate public response to news of the Manhattan Project and the atomic bombings of Japan, as filtered through the project's public relations efforts, was overwhelmingly favorable. When asked simply "do you approve of the use of the atomic bomb?", 85 percent of Americans in one August 1945 poll replied "yes."

Over time, other reactions to the abrupt beginning of the atomic age began to emerge. These ran the spectrum from dark pessimism about the future of the human race to an unbounded utopian optimism.

A certain sense of remorse also slowly began to build among the public, especially as details became known of the destruction at Hiroshima and Nagasaki

August 21, 1946, issue of The New Yorker magazine was devoted to stories of the devastation of Hiroshima.

Szilard Petition, first version, July 3, 1945 - called atomic bombs "a means for the ruthless annihilation of cities." It asked the President "to rule that the United States shall not, in the present phase of the war, resort to the use of atomic bombs.” 155 scientists at Los Alamos signed.

many signers urged the A-bomb be demonstrated to force Japan's surrender, and then be locked under new international controls to forestall a post-war nuclear arms race.

Oak Ridge petition, July 13, 1945 - Szilard's petition inspired a similar petition at Oak Ridge.

Oak Ridge petition, late-July 1945 - Another petition at Oak Ridge called for the power of the bomb to be "adequately described and demonstrated" before use.

Director J. Robert Oppenheimer forbade the petition's circulation.

On July 17th, 1945, the day after the first A-bomb was tested, Szilard bundled his signed petition sheets into a manila envelope, addressed it to the President, and passed it up the Army's chain-of-command. But, alerted by Oppenheimer, General Groves had his subordinates delay the petition until he received word from Tinian Island in the Pacific that the bombs were ready to be dropped.

Groves kept Szilard from publishing the petition in Science magazine by having it declared "Secret”.

Copyright, August 15, 1960, U.S. News & World Report.

President Truman Did Not Understand

NEW YORK

Q Dr. Szilard, what was your attitude in 1945 toward the question of dropping the atomic bomb on Japan?

A I opposed it with all my power, but I'm afraid not as effectively as I should have wished.

Q Did any other scientists feel the same way you did?

A Very many other scientists felt this way. This is particularly true of Oak Ridge and the Metallurgical Laboratory of the University of Chicago. I don't know how the scientists felt at Los Alamos.

Q At the Oak Ridge and Chicago branches of the A-bomb project, was there any division of opinion?

A I'll say this: Almost without exception, all the creative physicists had misgivings about the use of the bomb. I would not say the same about the chemists. The biologists felt very much as the physicists did.

“Their petition highlights a cruel duality shared by all scientists: eager to reveal nature's secrets, they are then often powerless to influence how their discoveries are used.”

William Lanouette, 2009

September 1945 Y-12 shutdown begins.

August 15, 1947 The Manhattan Engineer District is abolished.

Los Alamos persisted, developing further atomic weapons such as fission/fussion hydrogen bombs.