Chicago Pile-1 in the context of "Free neutron"

The neutron is a subatomic particle, symbol n or n
, that has no electric charge, and a mass slightly greater than that of a proton. The neutron was discovered by James Chadwick in 1932, leading to the discovery of nuclear fission in 1938, the first self-sustaining nuclear reactor (Chicago Pile-1, 1942), and the first nuclear weapon (Trinity, 1945).

Neutrons are found, together with a similar number of protons in the nuclei of atoms. Atoms of a chemical element that differ only in neutron number are called isotopes. Free neutrons are produced copiously in nuclear fission and fusion. They are a primary contributor to the nucleosynthesis of chemical elements within stars through fission, fusion, and neutron capture processes. Neutron stars, formed from massive collapsing stars, consist of neutrons at the density of atomic nuclei but a total mass more than the Sun.

The Atomic Age, also known as the Atomic Era, is the period of history following the detonation of the first nuclear weapon, The Gadget at the Trinity test in New Mexico on 16 July 1945 during World War II. Although nuclear chain reactions had been hypothesized in 1933 and the first artificial self-sustaining nuclear chain reaction (Chicago Pile-1) had taken place in December 1942, the Trinity test and the ensuing bombings of Hiroshima and Nagasaki that ended World War II represented the first large-scale use of nuclear technology and ushered in profound changes in sociopolitical thinking and the course of technological development.

While atomic power was promoted for a time as the epitome of progress and modernity, entering into the nuclear power era also entailed frightful implications of nuclear warfare, the Cold War, mutual assured destruction, nuclear proliferation, the risk of nuclear disaster (potentially as extreme as anthropogenic global nuclear winter), as well as beneficial civilian applications in nuclear medicine. It is no easy matter to fully segregate peaceful uses of nuclear technology from military or terrorist uses (such as the fabrication of dirty bombs from radioactive waste), which complicated the development of a global nuclear-power export industry right from the outset.

Hyde Park is a community area on the South Side of Chicago, Illinois, located on and near the shore of Lake Michigan 7 miles (11 km) south of the Loop. It is one of the city's 77 community areas.

Hyde Park is home to the University of Chicago and several seminaries and graduate schools of theology: Catholic Theological Union, the Lutheran School of Theology at Chicago, the Chicago Theological Seminary, and McCormick Theological Seminary (in addition to, UChicago's own Divinity School). The Griffin Museum of Science and Industry and two of Chicago's four historic sites listed in the original 1966 National Register of Historic Places—Chicago Pile-1, the world's first artificial nuclear reactor, and Robie House—are also in the neighborhood. In the early 21st century, Hyde Park received national attention for its association with U.S. president Barack Obama, who, before running for president, was a Senior Lecturer for twelve years at the University of Chicago Law School, an Illinois state senator representing the area, and U.S. senator from Illinois. The Barack Obama Presidential Center is currently under construction in Jackson Park, on its border with Hyde Park.

Enrico Fermi (Italian: [enˈriːko ˈfermi]; 29 September 1901 – 28 November 1954) was an Italian and naturalized American physicist, renowned for being the creator of the world's first artificial nuclear reactor, the Chicago Pile-1, and a member of the Manhattan Project. He has been called the "architect of the nuclear age" and the "architect of the atomic bomb". He was one of very few physicists to excel in both theoretical and experimental physics. Fermi was awarded the 1938 Nobel Prize in Physics for his work on induced radioactivity by neutron bombardment and for the discovery of transuranium elements. With his colleagues, Fermi filed several patents related to the use of nuclear power, all of which were taken over by the US government. He made significant contributions to the development of statistical mechanics, quantum theory, and nuclear and particle physics.

Fermi's first major contribution involved the field of statistical mechanics. After Wolfgang Pauli formulated his exclusion principle in 1925, Fermi followed with a paper in which he applied the principle to an ideal gas, employing a statistical formulation now known as Fermi–Dirac statistics. Today, particles that obey the exclusion principle are called "fermions". Pauli later postulated the existence of an uncharged invisible particle emitted along with an electron during beta decay, to satisfy the law of conservation of energy. Fermi took up this idea, developing a model that incorporated the postulated particle, which he named the "neutrino". His theory, later referred to as Fermi's interaction and now called weak interaction, described one of the four fundamental interactions in nature. Through experiments inducing radioactivity with the recently discovered neutron, Fermi discovered that slow neutrons were more easily captured by atomic nuclei than fast ones, and he developed the Fermi age equation to describe this. After bombarding thorium and uranium with slow neutrons, he concluded that he had created new elements. Although he was awarded the Nobel Prize for this discovery, the new elements were later revealed to be nuclear fission products.

The Metallurgical Laboratory (or Met Lab) was a scientific laboratory from 1942 to 1946 at the University of Chicago. It was established in February 1942 and became the Argonne National Laboratory in July 1946.

The laboratory was established in February 1942 to study and use the newly discovered chemical element plutonium. It researched plutonium's chemistry and metallurgy, designed the world's first nuclear reactors to produce it, and developed chemical processes to separate it from other elements. In August 1942 the lab's chemical section was the first to chemically separate a weighable sample of plutonium, and on 2 December 1942, the Met Lab produced the first controlled nuclear chain reaction, in the reactor Chicago Pile-1, which was constructed under the stands of the university's old football stadium, Stagg Field.

Amos Alonzo Stagg Field is the name of two successive football fields for the University of Chicago. Beyond sports, the first Stagg Field (1893–1957), named for famed coach Alonzo Stagg, is remembered for its role in a landmark scientific achievement of Enrico Fermi and the Metallurgical Laboratory during the Manhattan Project. The site of the first artificial nuclear chain reaction, which occurred within the field's west viewing-stands structure, received designation as a National Historic Landmark on February 18, 1965. On October 15, 1966, which is the day that the National Historic Preservation Act of 1966 was enacted creating the National Register of Historic Places, it was added to that as well. The site was named a Chicago Landmark on October 27, 1971.

A Henry Moore sculpture, Nuclear Energy, in a small quadrangle commemorates the location of the nuclear experiment. The University's current Stagg Field a football, soccer, and track field is located a few blocks away and reuses one of the original gates.