Frisch-Peierls memorandum
Encyclopedia
The Frisch–Peierls memorandum was written by Otto Frisch and Rudolf Peierls
while they were both working at the University of Birmingham
, England. The memorandum contained new calculations about the size of the critical mass
needed for an atomic bomb, and helped accelerate British and U.S. efforts towards bomb development during World War II
.
Given to Marcus Oliphant, Oliphant passed the document on to Henry Tizard
, chairman of the Committee on the Scientific Survey of Air Defence who, as a result, requested the setting-up of what was to become the secret MAUD Committee
. The memorandum (a copy of which is held in the Public Record Office
at Kew) is dated March 1940.
The two men were the first to calculate that an atomic bomb would require about 1 lb of the isotope
uranium-235
. (The estimate of 1 lb turned out to be too low; see Critical mass
.) Before it had been assumed that the bomb itself would require many tons of uranium, implying that it was theoretically possible, but not a practical military device. An earlier letter to President Franklin D. Roosevelt
, signed by Albert Einstein
(but written by Leó Szilárd
), had suggested it may need to be delivered by ship but could not be small enough to drop from the air.
The memo was written in two parts. The second was an explanation of the science supporting their conclusions. The first was an elegant and comprehensive outline of the implications of their calculations. It included a proposal that the best defence against such a weapon would be to develop one before Germany did so. In a few short pages these two scientists had anticipated the policies of deterrence
which would later shape Cold War
geopolitics
.
The memorandum opens with:
The memorandum helped galvanize both Britain and America down a path which led to a report by the British MAUD Committee
, the Tube Alloys
project, the Manhattan Project
, and ultimately the atomic bombings of Hiroshima and Nagasaki
.
Rudolf Peierls
Sir Rudolf Ernst Peierls, CBE was a German-born British physicist. Rudolf Peierls had a major role in Britain's nuclear program, but he also had a role in many modern sciences...
while they were both working at the University of Birmingham
University of Birmingham
The University of Birmingham is a British Redbrick university located in the city of Birmingham, England. It received its royal charter in 1900 as a successor to Birmingham Medical School and Mason Science College . Birmingham was the first Redbrick university to gain a charter and thus...
, England. The memorandum contained new calculations about the size of the critical mass
Critical mass
A critical mass is the smallest amount of fissile material needed for a sustained nuclear chain reaction. The critical mass of a fissionable material depends upon its nuclear properties A critical mass is the smallest amount of fissile material needed for a sustained nuclear chain reaction. The...
needed for an atomic bomb, and helped accelerate British and U.S. efforts towards bomb development during World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
.
Given to Marcus Oliphant, Oliphant passed the document on to Henry Tizard
Henry Tizard
Sir Henry Thomas Tizard FRS was an English chemist and inventor and past Rector of Imperial College....
, chairman of the Committee on the Scientific Survey of Air Defence who, as a result, requested the setting-up of what was to become the secret MAUD Committee
MAUD Committee
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.-Frisch & Peierls:...
. The memorandum (a copy of which is held in the Public Record Office
Public Record Office
The Public Record Office of the United Kingdom is one of the three organisations that make up the National Archives...
at Kew) is dated March 1940.
The two men were the first to calculate that an atomic bomb would require about 1 lb of the isotope
Isotope
Isotopes are variants of atoms of a particular chemical element, which have differing numbers of neutrons. Atoms of a particular element by definition must contain the same number of protons but may have a distinct number of neutrons which differs from atom to atom, without changing the designation...
uranium-235
Uranium-235
- References :* .* DOE Fundamentals handbook: Nuclear Physics and Reactor theory , .* A piece of U-235 the size of a grain of rice can produce energy equal to that contained in three tons of coal or fourteen barrels of oil. -External links:* * * one of the earliest articles on U-235 for the...
. (The estimate of 1 lb turned out to be too low; see Critical mass
Critical mass
A critical mass is the smallest amount of fissile material needed for a sustained nuclear chain reaction. The critical mass of a fissionable material depends upon its nuclear properties A critical mass is the smallest amount of fissile material needed for a sustained nuclear chain reaction. The...
.) Before it had been assumed that the bomb itself would require many tons of uranium, implying that it was theoretically possible, but not a practical military device. An earlier letter to President Franklin D. Roosevelt
Franklin D. Roosevelt
Franklin Delano Roosevelt , also known by his initials, FDR, was the 32nd President of the United States and a central figure in world events during the mid-20th century, leading the United States during a time of worldwide economic crisis and world war...
, signed by Albert Einstein
Albert Einstein
Albert Einstein was a German-born theoretical physicist who developed the theory of general relativity, effecting a revolution in physics. For this achievement, Einstein is often regarded as the father of modern physics and one of the most prolific intellects in human history...
(but written by Leó Szilárd
Leó Szilárd
Leó Szilárd was an Austro-Hungarian physicist and inventor who conceived the nuclear chain reaction in 1933, patented the idea of a nuclear reactor with Enrico Fermi, and in late 1939 wrote the letter for Albert Einstein's signature that resulted in the Manhattan Project that built the atomic bomb...
), had suggested it may need to be delivered by ship but could not be small enough to drop from the air.
The memo was written in two parts. The second was an explanation of the science supporting their conclusions. The first was an elegant and comprehensive outline of the implications of their calculations. It included a proposal that the best defence against such a weapon would be to develop one before Germany did so. In a few short pages these two scientists had anticipated the policies of deterrence
Deterrence theory
Deterrence theory gained increased prominence as a military strategy during the Cold War with regard to the use of nuclear weapons, and features prominently in current United States foreign policy regarding the development of nuclear technology in North Korea and Iran. Deterrence theory however was...
which would later shape Cold War
Cold War
The Cold War was the continuing state from roughly 1946 to 1991 of political conflict, military tension, proxy wars, and economic competition between the Communist World—primarily the Soviet Union and its satellite states and allies—and the powers of the Western world, primarily the United States...
geopolitics
Geopolitics
Geopolitics, from Greek Γη and Πολιτική in broad terms, is a theory that describes the relation between politics and territory whether on local or international scale....
.
The memorandum opens with:
Strictly Confidential
Memorandum on the properties of a radioactive “super-bomb”
The attached detailed report concerns the possibility of constructing a “super-bomb” which utilizes the energy stored in atomic nuclei as a source of energy. The energy liberated in the explosion of such a super-bomb is about the same as that produced by the explosion of 1000 tons of dynamite. This energy is liberated in a small volume, in which it will, for an instant, produce a temperature comparable to that in the interior of the sun. The blast from such an explosion would destroy life in a wide area. The size of this area is difficult to estimate, but it will probably cover the centre of a big city.
In addition, some part of the energy set free by the bomb goes to produce radioactive substances, and these will emit very powerful and dangerous radiations. The effect of these radiations is greatest immediately after the explosion, but it decays only gradually and even for days after the explosion any person entering the affected area will be killed.
Some of this radioactivity will be carried along with the wind and will spread the contamination; several miles downwind this may kill people.
The memorandum helped galvanize both Britain and America down a path which led to a report by the British MAUD Committee
MAUD Committee
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.-Frisch & Peierls:...
, the Tube Alloys
Tube Alloys
Tube Alloys was the code-name for the British nuclear weapon directorate during World War II, when the development of nuclear weapons was kept at such a high level of secrecy that it had to be referred to by code even in the highest circles of government...
project, the Manhattan Project
Manhattan Project
The Manhattan Project was a research and development program, led by the United States with participation from the United Kingdom and Canada, that produced the first atomic bomb during World War II. From 1942 to 1946, the project was under the direction of Major General Leslie Groves of the US Army...
, and ultimately the atomic bombings of Hiroshima and Nagasaki
Atomic bombings of Hiroshima and Nagasaki
During the final stages of World War II in 1945, the United States conducted two atomic bombings against the cities of Hiroshima and Nagasaki in Japan, the first on August 6, 1945, and the second on August 9, 1945. These two events are the only use of nuclear weapons in war to date.For six months...
.
See also
- Einstein–Szilárd letter
- Timeline of the Manhattan ProjectTimeline of the Manhattan ProjectThe 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...
- Allied technological cooperation during World War IIAllied technological cooperation during World War IIThe Second World War was not won by one nation; the Allies had to cooperate while fighting on the ground, as well as by sharing technological resources and innovations...
External links
- Stanford UniversityStanford UniversityThe Leland Stanford Junior University, commonly referred to as Stanford University or Stanford, is a private research university on an campus located near Palo Alto, California. It is situated in the northwestern Santa Clara Valley on the San Francisco Peninsula, approximately northwest of San...
—The Frisch–Peierls memorandum (PDF) - Frisch and Peierls's second memorandum