193-637: The Pacific Proving Grounds was the name given by the United States government to a number of sites in the Marshall Islands and a few other sites in the Pacific Ocean at which it conducted nuclear testing between 1946 and 1962. The U.S. tested a nuclear weapon (codenamed Able ) on Bikini Atoll on June 30, 1946. This was followed by Baker on July 24, 1946 (dates are Universal Time , local dates were July 1 and 25, respectively). On July 18, 1947,
386-546: A circular bifrustum . All parts of the tamper were similarly locked together to provide structural support and rigidity to the secondary assembly. Surrounding the fusion-fuel–spark-plug assembly was the uranium tamper with a standoff air-gap about 0.9 cm wide that was to increase the tamper's momentum, a levitation technique used as early as Operation Sandstone and described by physicist Ted Taylor as hammer-on-the-nail-impact . Since there were also technical concerns that high- Z tamper material would mix rapidly with
579-414: A neutron from the fissioning plutonium and emit an alpha particle and tritium in the process, of which the latter would then fuse with the deuterium and increase the yield in a predicted manner. Lithium-6 indeed reacted in this manner. It was assumed that the lithium-7 would absorb one neutron, producing lithium-8, which decays (through beta decay into beryllium-8 ) to a pair of alpha particles on
772-562: A " Special Relationship " with the United Kingdom and strong ties with Canada , Australia , New Zealand , the Philippines , Japan , South Korea , Israel , and several European Union countries ( France , Italy , Germany , Spain , and Poland ). The U.S. works closely with its NATO allies on military and national security issues, and with countries in the Americas through
965-516: A 28% to 69% uncertainty range) among 82 persons exposed in 1954 on Rongelap Atoll and Ailinginae Atoll , 10% (2.4% to 22%) for 157 persons exposed on Utirik Atoll , and 2.2% (0.5% to 4.8%) and 0.8% (0.2% to 1.8%), respectively, for the much larger populations exposed in mid-latitude locations including Kwajalein and in southern locations including Majuro . Since 1956, the U.S. has paid at least $ 759 million to Marshall Islanders as compensation for their exposure to U.S. nuclear testing. Following
1158-533: A coordinated, continent-wide military effort. Finally, deteriorating relations between the British military establishment and the colonists, relations that were already less than positive, set the stage for further distrust and dislike of British troops. Following their victory in the French and Indian War, Britain began to assert greater control over local colonial affairs, resulting in colonial political resistance ; one of
1351-777: A cracked cylinder liner, slowed Patapsco to one-third of her full speed, and when the Castle Bravo detonation took place, she was still about 180 to 195 nautical miles east of Bikini. Patapsco was in the range of nuclear fallout, which began landing on the ship in the mid-afternoon of March 2. By this time Patapsco was 565 to 586 nautical miles from ground zero. The fallout was at first thought to be harmless and there were no radiation detectors aboard, so no decontamination measures were taken. Measurements taken after Patapsco had returned to Pearl Harbor suggested an exposure range of 0.18 to 0.62 R/hr . Total exposure estimates range from 3.3 R to 18 R of whole-body radiation, taking into account
1544-522: A decentralized government that operated until 1789. After the British surrender at the siege of Yorktown in 1781 American sovereignty was internationally recognized by the Treaty of Paris (1783), through which the U.S. gained territory stretching west to the Mississippi River, north to present-day Canada, and south to Spanish Florida . The Northwest Ordinance (1787) established the precedent by which
1737-691: A federal capital district, Washington, D.C. The 48 contiguous states border Canada to the north and Mexico to the south, with the states of Alaska to the northwest and the archipelagic Hawaii in the Pacific Ocean . The United States also asserts sovereignty over five major island territories and various uninhabited islands . The country has the world's third-largest land area , largest exclusive economic zone , and third-largest population , exceeding 334 million. Its three largest metropolitan areas are New York , Los Angeles , and Chicago , and its three most populous states are California , Texas , and Florida . Paleo-Indians migrated across
1930-407: A few prominent industrialists , largely by their formation of trusts and monopolies to prevent competition. Tycoons led the nation's expansion in the railroad , petroleum , and steel industries. The United States emerged as a pioneer of the automotive industry . These changes were accompanied by significant increases in economic inequality , slum conditions , and social unrest , creating
2123-409: A free path of uranium would be needlessly heavy and costly. At the same time, the angular anisotropy increases as the atomic number of the scatterer material is reduced. Therefore, hohlraum liners require the use of copper (or, as in other devices, gold or aluminium ), as the absorption probability increases with the value of Z eff of the scatterer. There are two sources of X-rays in the hohlraum:
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#17328446852032316-644: A global reach. The U.S. is a founding member of the World Bank , Organization of American States , NATO , and the United Nations , as well as a permanent member of the UN Security Council . The first documented use of the phrase "United States of America" is a letter from January 2, 1776. Stephen Moylan , a Continental Army aide to General George Washington , wrote to Joseph Reed , Washington's aide-de-camp , seeking to go "with full and ample powers from
2509-432: A height of 47,000 feet (14,000 m) and a diameter of 7 miles (11 km) in about a minute, a height of 130,000 feet (40 km) and 62 mi (100 km) in diameter in less than 10 minutes and was expanding at more than 160 meters per second (580 km/h; 360 mph). As a result of the blast, the cloud contaminated more than 7,000 square miles (18,000 km ) of the surrounding Pacific Ocean, including some of
2702-651: A live warhead ever undertaken by the USA). The signing of the Partial Test Ban Treaty in 1963 forbade atmospheric and underwater nuclear weapons, and so no further U.S. tests were conducted at the Pacific Proving Grounds, with all but ten occurring at the Nevada Test Site until the end of testing in 1992. The Bikini and Enewetak Atolls are each a collection of islands. Various names have been assigned to
2895-453: A low-molecular-weight hydrocarbon (possibly methane gas), which turned to a low- Z plasma from the X-rays, and along with channeling radiation it modulated the ablation front on the high-Z surfaces; it "tamped" the sputtering effect that would otherwise "choke" radiation from compressing the secondary. The reemitted X-rays from the radiation case must be deposited uniformly on the outer walls of
3088-583: A period of heightened, overt racism following Reconstruction, a time often called the nadir of American race relations . A series of Supreme Court decisions, including Plessy v. Ferguson , emptied the Fourteenth and Fifteenth Amendments of their force, allowing Jim Crow laws in the South to remain unchecked, sundown towns in the Midwest, and segregation in communities across the country , which would be reinforced by
3281-488: A prominent leader in the early 1960s. The Great Society plan of President Lyndon Johnson 's administration resulted in groundbreaking and broad-reaching laws, policies and a constitutional amendment to counteract some of the worst effects of lingering institutional racism . The counterculture movement in the U.S. brought significant social changes, including the liberalization of attitudes toward recreational drug use and sexuality . It also encouraged open defiance of
3474-406: A range of 0.2 to 2 keV) , corresponding to several million kelvins . Wall temperature depended on the temperature of the primary's core which peaked at about 5.4 keV during boosted-fission. The final wall-temperature, which corresponds to energy of the wall-reradiated X-rays to the secondary's pusher, also drops due to losses from the hohlraum material itself. Natural uranium nails, lined to
3667-503: A reflective cavity. The radiation from the exploding fission primary brought the fuel in the fusion secondary to critical density and pressure, setting off thermonuclear (fusion) chain reactions, which in turn set off a tertiary fissioning of the bomb's U fusion tamper and casing. Consequently, this type of bomb is also known as a "fission-fusion-fission" device. The Soviet researchers, led by Andrei Sakharov , developed and tested their first Teller–Ulam device in 1955. The publication of
3860-485: A secondary infection six months later after acute radiation exposure, and another had a child that was stillborn and deformed. This resulted in an international incident and reignited Japanese concerns about radiation, especially as Japanese citizens were once more adversely affected by US nuclear weapons. The official US position had been that the growth in the strength of atomic bombs was not accompanied by an equivalent growth in radioactivity released, and they denied that
4053-518: A sense of manifest destiny . The Missouri Compromise attempted to balance the desire of northern states to prevent the expansion of slavery into new territories with that of southern states to extend it, admitting Missouri as a slave state and Maine as a free state. It further prohibited slavery in all other lands of the Louisiana Purchase north of the 36°30′ parallel . As Americans expanded further into land inhabited by Native Americans,
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#17328446852034246-603: A sense of American identity as well. Men who otherwise never left their own colony now traveled across the continent to fight alongside men from decidedly different backgrounds but who were no less "American". British officers trained American officers for battle, most notably George Washington ; these officers would lend their skills and expertise to the colonists' cause during the American Revolutionary War to come. In addition, colonial legislatures and officials found it necessary to cooperate intensively in pursuit of
4439-497: A timescale of nearly a second, vastly longer than the timescale of nuclear detonation. However, when lithium-7 is bombarded with energetic neutrons with an energy greater than 2.47 MeV, rather than simply absorbing a neutron, it undergoes nuclear fission into an alpha particle, a tritium nucleus , and another neutron. As a result, much more tritium was produced than expected, the extra tritium fusing with deuterium and producing an extra neutron. The extra neutron produced by fusion and
4632-502: A true thermonuclear device. The Teller–Ulam-based "Ivy Mike" device had a much greater yield of 10.4 Mt , but most of this also came from fission: 77% of the total came from fast fission of its natural-uranium tamper. Castle Bravo had the greatest yield of any U.S. nuclear test, 15 Mt, though again, a substantial fraction came from fission. In the Teller–Ulam design, the fission and fusion stages were kept physically separate in
4825-476: A very compact MK 7 device. This boosted fission device had been tested in the Upshot-Knothole Climax event and yielded 61 kilotons of TNT [kt] (260 TJ) (out of 50–70 kt expected yield range). It was considered successful enough that the planned operation series Domino , designed to explore the same question about a suitable primary for thermonuclear bombs, could be canceled. The implosion system
5018-457: A year). Juvenile correctional facilities are operated by local or state governments and serve as longer-term placements for any minor adjudicated as delinquent and ordered by a judge to be confined. As of January 2023, the United States has the sixth-highest per capita incarceration rate in the world—531 people per 100,000 inhabitants—and the largest prison and jail population in
5211-403: Is a very important design parameter for any inertial-confinement configuration. A relatively high albedo permits higher interstage coupling due to the more favorable azimuthal and latitudinal angles of reflected radiation. The limiting value of the albedo for high- Z materials is reached when the thickness is 5–10 g/cm , or 0.5–1.0 free paths. Thus, a hohlraum made of uranium much thicker than
5404-571: Is believed to be the first widespread culture in the Americas. Over time, indigenous North American cultures grew increasingly sophisticated, and some, such as the Mississippian culture , developed agriculture , architecture , and complex societies . In the post-archaic period , the Mississippian cultures were located in the midwestern , eastern , and southern regions, and the Algonquian in
5597-498: Is indirectly driven, and the techniques used in the interstage to smooth the spatial profile (i.e. reduce coherence and nonuniformities) of the primary's irradiance are of utmost importance. This was done with the introduction of the channel filler —an optical element used as a refractive medium, also encountered as random-phase plate in the ICF laser assemblies. This medium was a polystyrene plastic foam filling, extruded or impregnated with
5790-492: Is known as the presidential system , in contrast to the parliamentary system , where the executive is part of the legislative body. Many countries around the world imitated this aspect of the 1789 Constitution of the United States , especially in the Americas. The Constitution is silent on political parties. However, they developed independently in the 18th century with the Federalist and Anti-Federalist parties. Since then,
5983-562: Is not surrounded by a reef. The island does not support the inhabitants' traditional way of life. Because of the large amount of atmospheric testing, and especially the Castle Bravo accident of 1954, many of the islands which were part of the Pacific Proving Grounds are still contaminated by nuclear fallout . Scientists calculated in 2010 that during the lifetimes of members of the Marshall Islands population, potentially exposed to ionizing radiation from weapons test fallout deposited during
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6176-438: Is now the United States experienced conflicts with Native Americans, they also engaged in trade, exchanging European tools for food and animal pelts. Relations ranged from close cooperation to warfare and massacres. The colonial authorities often pursued policies that forced Native Americans to adopt European lifestyles, including conversion to Christianity. Along the eastern seaboard, settlers trafficked African slaves through
6369-419: Is relatively poor in the aftermost sections of the secondary. This made the use of a higher mass of the then scarce fusion fuel in the rear end of the secondary assembly ineffective and the overall design wasteful. This was also the reason why the lower-enriched slugs of fusion fuel were placed far aft of the fuel capsule. Second, as the primary could not illuminate the whole surface of the hohlraum, in part due to
6562-542: Is the federal agency charged with addressing most environmental-related issues . The idea of wilderness has shaped the management of public lands since 1964, with the Wilderness Act . The Endangered Species Act of 1973 provides a way to protect threatened and endangered species and their habitats. The United States Fish and Wildlife Service implements and enforces the Act. In 2024, the U.S. ranked 34th among 180 countries in
6755-578: Is unable to implode the secondary's mass. Its plasma-pressure is confined in the boiled-off sections of the tamper and the radiation case so that material from neither of these two walls can enter the radiation channel that has to be open for the radiation transit. The device was mounted in a "shot cab" on an artificial island built on a reef off Namu Island, in Bikini Atoll . A sizable array of diagnostic instruments were trained on it, including high-speed cameras trained through an arc of mirror towers around
6948-584: The Allies of World War I , helping to turn the tide against the Central Powers . In 1920, a constitutional amendment granted nationwide women's suffrage . During the 1920s and '30s, radio for mass communication and the invention of early television transformed communications nationwide. The Wall Street Crash of 1929 triggered the Great Depression , which President Franklin D. Roosevelt responded to with
7141-548: The Atlantic slave trade . The original Thirteen Colonies that would later found the United States were administered as possessions of Great Britain , and had local governments with elections open to most white male property owners . The colonial population grew rapidly, eclipsing Native American populations; by the 1770s, the natural increase of the population was such that only a small minority of Americans had been born overseas. The colonies' distance from Britain allowed for
7334-773: The Bering land bridge more than 12,000 years ago, and formed various civilizations and societies . British colonization led to the first settlement of the Thirteen Colonies in Virginia in 1607. Clashes with the British Crown over taxation and political representation sparked the American Revolution , with the Second Continental Congress formally declaring independence on July 4, 1776. Following its victory in
7527-529: The Environmental Performance Index . The country joined the Paris Agreement on climate change in 2016 and has many other environmental commitments. The United States is a federal republic of 50 states and a separate federal capital district, Washington, D.C. It also asserts sovereignty over five unincorporated territories and several uninhabited island possessions . The U.S. is
7720-493: The Federal Bureau of Investigation (FBI) and the U.S. Marshals Service have national jurisdiction and specialized duties, such as protecting civil rights , national security and enforcing U.S. federal courts ' rulings and federal laws. State courts conduct most civil and criminal trials, and federal courts handle designated crimes and appeals of state court decisions . There is no unified "criminal justice system" in
7913-688: The Great Lakes , Mississippi River and Gulf of Mexico . British colonization of the East Coast began with the Virginia Colony (1607) and Plymouth Colony (1620). The Mayflower Compact and the Fundamental Orders of Connecticut established precedents for representative self-governance and constitutionalism that would develop throughout the American colonies. While European settlers in what
Pacific Proving Grounds - Misplaced Pages Continue
8106-701: The Great Lakes region and along the Eastern Seaboard , while the Hohokam culture and Ancestral Puebloans inhabited the southwest . Native population estimates of what is now the United States before the arrival of European immigrants range from around 500,000 to nearly 10 million. Christopher Columbus began exploring the Caribbean for Spain in 1492, leading to Spanish-speaking settlements and missions from Puerto Rico and Florida to New Mexico and California . France established its own settlements along
8299-516: The House of Representatives , a lower house based on population; and the Senate , an upper house based on equal representation for each state. Federalism provides substantial autonomy to the 50 states, while the country's political culture promotes liberty , equality , individualism , personal autonomy , and limited government . One of the world's most developed countries , the United States has had
8492-580: The Midwest . At the same time, about one million French Canadians migrated from Quebec to New England . During the Great Migration , millions of African Americans left the rural South for urban areas in the North. Alaska was purchased from Russia in 1867. The Compromise of 1877 effectively ended Reconstruction and white supremacists took local control of Southern politics . African Americans endured
8685-672: The National Park Service and other agencies. About 28% of the country's land is publicly owned and federally managed, primarily in the Western States . Most of this land is protected , though some is leased for commercial use, and less than one percent is used for military purposes. Environmental issues in the United States include debates on non-renewable resources and nuclear energy , air and water pollution , biodiversity , logging and deforestation , and climate change . The U.S. Environmental Protection Agency (EPA)
8878-634: The New Deal , a series of sweeping programs and public works projects combined with financial reforms and regulations . All were intended to protect against future economic depressions. Initially neutral during World War II , the U.S. began supplying war materiel to the Allies of World War II in March 1941 and entered the war in December after the Empire of Japan 's attack on Pearl Harbor . The U.S. developed
9071-701: The Organization of American States and the United States–Mexico–Canada Free Trade Agreement . In South America, Colombia is traditionally considered to be the closest ally of the United States. The U.S. exercises full international defense authority and responsibility for Micronesia , the Marshall Islands , and Palau through the Compact of Free Association . It has increasingly conducted strategic cooperation with India , but its ties with China have steadily deteriorated. Since 2014,
9264-638: The Pentium microprocessor in accordance with Moore's law , rechargeable lithium-ion batteries , the first gene therapy trial, and cloning either emerged in the U.S. or were improved upon there. The Human Genome Project was formally launched in 1990, while Nasdaq became the first stock market in the United States to trade online in 1998. In the Gulf War of 1991, an American-led international coalition of states expelled an Iraqi invasion force that had occupied neighboring Kuwait . The September 11 attacks on
9457-577: The Radiation Exposure Compensation Act of 1990, at least $ 759 million has been paid to Marshall Islanders as compensation for their exposure to U.S. nuclear testing. Following the Castle Bravo accident, the U.S. paid $ 15.3 million to Japan . Scientists have calculated that the residents of the Marshall Islands during their lifetimes will be diagnosed with an added 1.6% (with 90% uncertainty range 0.4% to 3.4%) cancers attributable to fallout-related radiation exposures. The cancers are
9650-632: The SHRIMP . The proposed weight reduction (from TX-17's 42,000 pounds (19,000 kg) to TX-21's 25,000 pounds (11,000 kg)) would provide the Air Force with a much more versatile deliverable gravity bomb . The final version tested in Castle used partially enriched lithium as its fusion fuel. Natural lithium is a mixture of lithium-6 and lithium-7 isotopes (with 7.5% of the former). The enriched lithium used in Bravo
9843-629: The Southwestern United States received the greatest total fallout, about five times that received in Japan. Stratospheric fallout particles of strontium-90 from the test were later captured with balloon-borne air filters used to sample the air at stratospheric altitudes; the research ( Project Ashcan ) was conducted to better understand the stratosphere and fallout times, and arrive at more accurate meteorological models after hindcasting . The fallout from Castle Bravo and other testing on
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#173284468520310036-523: The Soviet Union's collapse and the end of the Cold War in 1991, the U.S. emerged as the world's sole superpower , wielding significant geopolitical influence globally . The U.S. national government is a presidential constitutional federal republic and liberal democracy with three separate branches : legislative , executive , and judicial . It has a bicameral national legislature composed of
10229-576: The Spanish–American War . (The Philippines was granted full independence from the U.S. on July 4, 1946, following World War II. Puerto Rico and Guam have remained U.S. territories.) American Samoa was acquired by the United States in 1900 after the Second Samoan Civil War . The U.S. Virgin Islands were purchased from Denmark in 1917. The United States entered World War I alongside
10422-589: The United States at Bikini Atoll , Marshall Islands , as part of Operation Castle . Detonated on March 1, 1954, the device remains the most powerful nuclear device ever detonated by the United States and the first lithium deuteride -fueled thermonuclear weapon tested using the Teller-Ulam design . Castle Bravo's yield was 15 megatons of TNT [Mt] (63 PJ ), 2.5 times the predicted 6 Mt (25 PJ), due to unforeseen additional reactions involving lithium-7 , which led to radioactive contamination in
10615-631: The United States Atomic Energy Commission established the Pacific Proving Grounds. The United States conducted 105 atmospheric and underwater (i.e., not underground ) nuclear tests in the Pacific, many with extremely high yields. While the Marshall Islands testing composed 14% of all U.S. tests, it composed nearly 80% of the total yields of those detonated by the U.S., with an estimated total yield of around 210 megatons , with
10808-670: The cotton gin made the institution increasingly profitable for Southern elites . This sectional conflict regarding slavery culminated in the American Civil War (1861–1865). Eleven slave states seceded and formed the Confederate States of America , while the other states remained in the Union . War broke out in April 1861 after the Confederates bombarded Fort Sumter . After
11001-524: The fall of communism and the collapse of the Soviet Union , which marked the end of the Cold War and left the United States as the world's sole superpower . The 1990s saw the longest recorded economic expansion in American history , a dramatic decline in U.S. crime rates , and advances in technology . Throughout this decade, technological innovations such as the World Wide Web , the evolution of
11194-445: The largest nominal GDP since about 1890 and accounted for over 15% of the global economy in 2023. It possesses by far the largest amount of wealth of any country and has the highest disposable household income per capita among OECD countries. The U.S. ranks among the world's highest in economic competitiveness , productivity , innovation , human rights , and higher education . Its hard power and cultural influence have
11387-430: The lithium deuteride fusion fuel in a stainless-steel canister. Running down to the center of the secondary was a 1.3 cm thick hollow cylindrical rod of plutonium , nested in the steel canister. This was the spark plug , a tritium-boosted fission device. It was assembled by plutonium rings and had a hollow volume inside that measured about 0.5 cm in diameter. This central volume was lined with copper, which like
11580-695: The 1775 Battles of Lexington and Concord , igniting the American Revolutionary War . At the Second Continental Congress , the colonies appointed George Washington commander-in-chief of the Continental Army , and created a committee that named Thomas Jefferson to draft the Declaration of Independence . Two days after passing the Lee Resolution to create an independent nation the Declaration
11773-408: The 1775–1783 Revolutionary War , the country continued to expand westward across North America , resulting in the dispossession of native inhabitants . As more states were admitted , a North–South division over slavery led to the secession of the Confederate States of America , which fought states remaining in the Union in the 1861–1865 American Civil War . With the victory and preservation of
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#173284468520311966-466: The 2010s, political polarization in the country increased between liberal and conservative factions. This polarization was capitalized upon in the January 2021 Capitol attack , when a mob of insurrectionists entered the U.S. Capitol and sought to prevent the peaceful transfer of power in an attempted self-coup d'état . The United States is the world's third-largest country by total area behind Russia and Canada. The 48 contiguous states and
12159-426: The American West have an alpine climate . The climate is arid in the Southwest, Mediterranean in coastal California , and oceanic in coastal Oregon , Washington , and southern Alaska . Most of Alaska is subarctic or polar . Hawaii , the southern tip of Florida and U.S. territories in the Caribbean and Pacific are tropical . States bordering the Gulf of Mexico are prone to hurricanes, and most of
12352-425: The American military names used after occupation through the atomic testing period, and the Japanese names used while they occupied the islands during World War II, plus names gleaned from other sources. United States The United States of America ( USA ), commonly known as the United States ( U.S. ) or America , is a country primarily located in North America . It is a federal union of 50 states and
12545-403: The Bikini Atoll, Enewetak Atoll, and Johnston Island as part of Operation Hardtack I in 1958. Thirty-six weapons were detonated at sites in the Pacific Ocean in the vicinity of Christmas Island and Johnston Atoll as part of Operation Dominic I . Though these tests were not conducted in the Marshall Islands, they are officially considered part of the Pacific Proving Grounds. The portion of
12738-417: The Bravo fallout analysis was a militarily sensitive issue, with Joseph Rotblat possibly deducing the staging nature of the Castle Bravo device by studying the ratio and presence of tell-tale isotopes, namely uranium-237 , present in the fallout. This information could potentially reveal the means by which megaton-yield nuclear devices achieve their yield. Soviet scientist Andrei Sakharov hit upon what
12931-401: The Castle Bravo accident on March 1, 1954, the U.S. paid $ 15.3 million to Japan . In June 1983, the U.S. and the Marshall islanders signed the Compact of Free Association , which gave the Marshall Islands independence. The Compact became effective in 1986 and was subsequently modified by the Amended Compact that became effective in 2004. It also established the Nuclear Claims Tribunal , which
13124-461: The Castle Bravo causeway are at 11°42′6″N 165°17′7″E / 11.70167°N 165.28528°E / 11.70167; 165.28528 . The Castle Bravo device was housed in a cylinder that weighed 23,500 pounds (10,700 kg) and measured 179.5 inches (456 cm) in length and 53.9 inches (137 cm) in diameter. The primary device was a COBRA deuterium-tritium gas-boosted atomic bomb made by Los Alamos Scientific Laboratory ,
13317-643: The Castle Bravo test are the highest in history. Populations neighboring the test site were exposed to high levels of radiation resulting in mild radiation sickness of many (nausea, vomiting, diarrhea). The unexpected strength of the detonation, combined with shifting wind patterns, sent some of the radioactive fallout over the inhabited atolls of Rongelap and Utrik . Within 52 hours, the 86 people on Rongelap and 167 on Utrik were evacuated to Kwajalein for medical care. Several weeks later, many people began suffering from alopecia (hair loss) and skin lesions as well. The exposure to fallout has been linked to increase
13510-420: The Declaration of Independence on July 4, 1776. The term "United States" and the initialism "U.S.", used as nouns or as adjectives in English, are common short names for the country. The initialism "USA", a noun, is also common. "United States" and "U.S." are the established terms throughout the U.S. federal government , with prescribed rules. In English, the term "America" rarely refers to topics unrelated to
13703-404: The District of Columbia occupy a combined area of 3,119,885 square miles (8,080,470 km ). The coastal plain of the Atlantic seaboard gives way to inland forests and rolling hills in the Piedmont plateau region. The Appalachian Mountains and the Adirondack massif separate the East Coast from the Great Lakes and the grasslands of the Midwest . The Mississippi River System ,
13896-592: The Dominic series of tests that were high altitude nuclear explosions were known as Operation Fishbowl , though not all were successful (one detonated on launchpad and resulted in a substantial plutonium contamination). Two of the tests were of operational weapons systems—the ASROC anti-submarine rocket and the Polaris SLBM (the latter test, Frigate Bird, was the only operational submarine-launched ballistic missile test with
14089-562: The Elder concluded that major military resources needed to be devoted to North America to win the war against France. For the first time, the continent became one of the main theaters of what could be termed a " world war ". The British colonies' position as an integral part of the British Empire became more apparent during the war, with British military and civilian officials becoming a more significant presence in American life. The war increased
14282-485: The Enewetak Atoll as part of Operation Greenhouse in 1951. Two are of particular note: Greenhouse "Item" was the first use of a boosted fission weapon , and "George" was a thermonuclear experiment designed to prove the feasibility of the Teller-Ulam design for the possibility of developing hydrogen bombs . Two weapons were detonated at the Enewetak Atoll as part of Operation Ivy in 1952. One of them, Ivy King ,
14475-664: The January 1863 Emancipation Proclamation , many freed slaves joined the Union army . The war began to turn in the Union's favor following the 1863 Siege of Vicksburg and Battle of Gettysburg , and the Confederacy surrendered in 1865 after the Union's victory in the Battle of Appomattox Court House . The Reconstruction era followed the war. After the assassination of President Abraham Lincoln , Reconstruction Amendments were passed to protect
14668-662: The Japanese fishing vessel, the Daigo Fukuryu Maru , were additionally exposed and one man died soon after from complications of radiation sickness , resulting in considerable international controversy. Seventeen nuclear weapons were detonated on the Bikini and Enewetak Atolls as part of Operation Redwing in 1956. Many of them were designed to prove the feasibility of numerous thermonuclear weapon designs, with yields ranging from around 2 to 5 Mt. Thirty-five weapons were detonated at
14861-499: The Nuclear Claims Tribunal ruled against the United States for damages done to the islands and its people. The Nuclear Claims Tribunal awarded the islanders a total of $ 563,315,500 after deducting past awards. However, the U.S. Congress has failed to fund the settlement. The only recourse is for the Bikini people to petition the U.S. Congress to fund the payment and fulfill this award. The United States Supreme Court turned down
15054-595: The Rocky Mountains, the Yellowstone Caldera , is the continent's largest volcanic feature. In 2021, the United States had 8% of global permanent meadows and pastures and 10% of cropland. With its large size and geographic variety, the United States includes most climate types. East of the 100th meridian , the climate ranges from humid continental in the north to humid subtropical in the south. The western Great Plains are semi-arid . Many mountainous areas of
15247-544: The Soviet Union regarded as " Sakharov's third idea " during the month after the Castle Bravo test, the final piece of the puzzle being the idea that the compression of the secondary can be accomplished by the primary's X-rays before fusion began. The Shrimp device design later evolved into the Mark 21 nuclear bomb , of which 275 units were produced, weighing 17,600 pounds (8,000 kg) and measuring 12.5 feet (3.8 m) long and 58 inches (1.5 m) in diameter. This 18-megaton bomb
15440-625: The U.S. has become a key ally of Ukraine ; it has also provided the country with significant military equipment and other support in response to Russia's 2022 invasion . The president is the commander-in-chief of the United States Armed Forces and appoints its leaders, the secretary of defense and the Joint Chiefs of Staff . The Department of Defense , which is headquartered at the Pentagon near Washington, D.C., administers five of
15633-661: The U.S. territories." Despite disparate systems of confinement, four main institutions dominate: federal prisons , state prisons , local jails, and juvenile correctional facilities . Federal prisons are run by the Federal Bureau of Prisons and hold people who have been convicted of federal crimes, including pretrial detainees. State prisons, run by the official department of correction of each state, hold sentenced people serving prison time (usually longer than one year) for felony offenses. Local jails are county or municipal facilities that incarcerate defendants prior to trial; they also hold those serving short sentences (typically under
15826-461: The United States and the peaceful transfer of power , respectively. The Louisiana Purchase of 1803 from France nearly doubled the territory of the United States. Lingering issues with Britain remained , leading to the War of 1812 , which was fought to a draw. Spain ceded Florida and its Gulf Coast territory in 1819. In the late 18th century, American settlers began to expand westward , many with
16019-697: The United States entered the Cold War, where geopolitical tensions between the U.S. and the Soviet Union led the two countries to dominate world affairs . The U.S. utilized the policy of containment to limit the USSR's sphere of influence, and prevailed in the Space Race , which culminated with the first crewed Moon landing in 1969. Domestically, the U.S. experienced economic growth , urbanization , and population growth following World War II . The civil rights movement emerged, with Martin Luther King Jr. becoming
16212-649: The United States has operated as a de facto two-party system , though the parties in that system have been different at different times. The two main national parties are presently the Democratic and the Republican . The former is perceived as relatively liberal in its political platform while the latter is perceived as relatively conservative . In the American federal system , sovereign powers are shared between two levels of elected government: national and state. People in
16405-572: The United States in 2001 by the pan-Islamist militant organization al-Qaeda led to the war on terror , and subsequent military interventions in Afghanistan and Iraq . The cultural impact of the attacks was profound and long-lasting. The U.S. housing bubble culminated in 2007 with the Great Recession , the largest economic contraction since the Great Depression. Coming to a head in
16598-578: The United States of America to Spain" to seek assistance in the Revolutionary War effort. The first known public usage is an anonymous essay published in the Williamsburg newspaper, The Virginia Gazette , on April 6, 1776. By June 1776, the "United States of America" appeared in the Articles of Confederation and the Declaration of Independence . The Second Continental Congress adopted
16791-553: The United States of a practical deliverable fusion bomb , even though the TX-21 as proof-tested in the Bravo event was not weaponized. The successful test rendered obsolete the cryogenic design used by Ivy Mike and its weaponized derivative, the JUGHEAD , which was slated to be tested as the initial Castle Yankee . It also used a 3.7-inch-thick (9.5 cm) 7075 aluminum ballistic case. Aluminum
16984-662: The United States secured an agreement with the United Nations to govern the islands of Micronesia as the Trust Territory of the Pacific Islands , a strategic trusteeship territory . This is the only such trusteeship ever granted by the United Nations to the United States. The Trust Territory comprised about 2,000 islands spread over 3,000,000 square miles (7,800,000 km) of the North Pacific Ocean . Five days later,
17177-681: The United States should "promote the economic advancement and self-sufficiency of the inhabitants, and to this end shall... protect the inhabitants against the loss of their lands and resources..." The United States Navy controlled the Trust from a headquarters in Guam until 1951, when the United States Department of the Interior took over control, administering the territory from a base in Saipan . Despite
17370-591: The United States, slavery was abolished nationally . By 1900, the country had established itself as a great power , a status solidified after its involvement in World War I . After Japan 's attack on Pearl Harbor in December 1941, the U.S. entered World War II . Its aftermath left the U.S. and the Soviet Union as the world's two superpowers and led to the Cold War , during which both countries struggled for ideological dominance and international influence . Following
17563-532: The United States, despite the usage of "the Americas " as the totality of North and South America. "The States" is an established colloquial shortening of the name, used particularly from abroad; "stateside" is the corresponding adjective or adverb. The first inhabitants of North America migrated from Siberia across the Bering land bridge about 12,000 years ago; the Clovis culture , which appeared around 11,000 BC,
17756-605: The United States, except Iran , North Korea , and Bhutan . Though Taiwan does not have formal diplomatic relations with the U.S., it maintains close unofficial relations. The United States regularly supplies Taiwan with military equipment to deter potential Chinese aggression. Its geopolitical attention also turned to the Indo-Pacific when the United States joined the Quadrilateral Security Dialogue with Australia, India, and Japan. The United States has
17949-444: The United States. Its yield, at 15 Mt, was over twice as powerful as was predicted, and remains the largest weapon ever detonated by the United States. It spread nuclear fallout over a wide area, including the Enewetak Atoll, Rongerik Atoll , Ailinginae Atoll , and Rongelap Atoll . The U.S. Navy evacuated the islanders within the next few days, but many of the natives were exposed to radiation prior to evacuation. The fishermen aboard
18142-509: The United States. The American prison system is largely heterogenous, with thousands of relatively independent systems operating across federal, state, local, and tribal levels. In 2023, "these systems [held] almost 2 million people in 1,566 state prisons, 98 federal prisons, 3,116 local jails, 1,323 juvenile correctional facilities, 181 immigration detention facilities, and 80 Indian country jails, as well as in military prisons , civil commitment centers, state psychiatric hospitals, and prisons in
18335-458: The assembly by a small hole through the ≈28 cm thick U blast-heat shield. It was positioned in front of the secondary assembly facing the primary. Similar to the tamper-fusion capsule assembly, the shield was shaped as a circular frustum, with its small diameter facing the primary's side, and with its large diameter locked by a type of mortise and tenon joint to the rest of the secondary assembly. The shield-tamper ensemble can be visualized as
18528-446: The atoll a second time. The American magazine Consumer Reports warned of the contamination of milk with strontium-90. The Soviet Union had previously used lithium deuteride in its Sloika design (known as the " Joe-4 " in the U.S.), in 1953. It was not a true hydrogen bomb; fusion provided only 15–20% of its yield, most coming from boosted fission reactions. Its yield was 400 kilotons, and it could not be infinitely scaled, as with
18721-583: The atoll also affected islanders who had previously inhabited the atoll, and who returned there some time after the tests. This was due to the presence of radioactive caesium-137 in locally grown coconut milk. Plants and trees absorb potassium as part of the normal biological process, but will also readily absorb caesium if present, being of the same group on the periodic table , and therefore very similar chemically. Islanders consuming contaminated coconut milk were found to have abnormally high concentrations of caesium in their bodies and so had to be evacuated from
18914-468: The blast. In an additional unexpected event, albeit one of far less consequence, X-rays traveling through line-of-sight (LOS) pipes caused a small second fireball at Station 1200 with a yield of 1 kiloton of TNT (4.2 TJ). The fission reactions of the natural uranium tamper were quite dirty, producing a large amount of fallout . That, combined with the larger than expected yield and a major wind shift, produced some very serious consequences for those in
19107-420: The conditions needed to start the fusion reaction, and its other end was a cylinder , as also seen in Bravo's declassified film. The space between the uranium fusion tamper , and the case formed a radiation channel to conduct X-rays from the primary to the secondary assembly; the interstage. It is one of the most closely guarded secrets of a multistage thermonuclear weapon. Implosion of the secondary assembly
19300-491: The consequence of exposure to ionizing radiation from weapons test fallout deposited during the testing period (1948–1958) and from residual radioactive sources during the subsequent 12 years (1959–1970). On July 18, 1947, the United States convinced the United Nations to designate the islands of Micronesia as the Strategic Trust Territory . This was the only trust ever granted by the U.N. The directive stated that
19493-453: The contiguous United States are in the State of California, about 84 miles (135 km) apart. At an elevation of 20,310 feet (6,190.5 m), Alaska's Denali is the highest peak in the country and continent. Active volcanoes are common throughout Alaska's Alexander and Aleutian Islands , and Hawaii consists of volcanic islands. The supervolcano underlying Yellowstone National Park in
19686-411: The control panel scientist if the test can be aborted and is told "yes", but it would ruin all their preparations in setting up timed measuring instruments. In Mike, the fallout correctly landed north of the inhabited area but, in the 1954 Bravo test, there was a large amount of wind shear , and the wind that was blowing north the day before the test steadily veered towards the east. Radioactive fallout
19879-549: The country's GDP. The U.S. has 42% of the world's nuclear weapons —the second-largest share after Russia. The United States has the third-largest combined armed forces in the world, behind the Chinese People's Liberation Army and Indian Armed Forces . The military operates about 800 bases and facilities abroad, and maintains deployments greater than 100 active duty personnel in 25 foreign countries. State defense forces (SDFs) are military units that operate under
20072-464: The country's territory would expand with the admission of new states , rather than the expansion of existing states. The U.S. Constitution was drafted at the 1787 Constitutional Convention to overcome the limitations of the Articles. It went into effect in 1789, creating a federal republic governed by three separate branches that together ensured a system of checks and balances . George Washington
20265-485: The crew of the Lucky Dragon No. 5 , who did not anticipate the hazard and therefore did not take shelter in the hold of their ship, or refrain from inhaling the fallout dust, the firing crew that triggered the explosion safely sheltered in their firing station when they noticed the wind was carrying the fallout in the unanticipated direction towards the island of Enyu on the Bikini Atoll where they were located, with
20458-407: The crew was affected by radioactive fallout. Japanese scientists who had collected data from the fishing vessel disagreed with this. Sir Joseph Rotblat , working at St Bartholomew's Hospital , London, demonstrated that the contamination caused by the fallout from the test was far greater than that stated officially. Rotblat deduced that the bomb had three stages and showed that the fission phase at
20651-466: The cylindrical ballistic case was a natural-uranium liner, the radiation case, that was about 2.5 cm thick. Its internal surface was lined with copper that was about 240 μm thick, and made from 0.08-μm thick copper foil, to increase the overall albedo of the hohlraum . Copper possesses excellent reflecting properties, and its low cost, compared to other reflecting materials like gold, made it useful for mass-produced hydrogen weapons. Hohlraum albedo
20844-699: The development of self-governance, and the First Great Awakening , a series of Christian revivals , fueled colonial interest in religious liberty . For a century, the American colonists had been providing their own troops and materiel in conflicts with indigenous peoples allied with Britain's colonial rivals , especially France, and the Americans had begun to develop a sense of self-defense and self-reliance separate from Britain. The French and Indian War (1754–1763) took on new significance for all North American colonists after Parliament under William Pitt
21037-407: The device severely damaged many of the permanent buildings on the control site island on the far side of the atoll. Little of the desired diagnostic data on the shot was collected; many instruments designed to transmit their data back before being destroyed by the blast were instead vaporized instantly, while most of the instruments that were expected to be recovered for data retrieval were destroyed by
21230-454: The effects of natural washdown from rain, and variations between above- and below-deck exposure. The fallout spread traces of radioactive material as far as Australia, India and Japan, and even the United States and parts of Europe. Though organized as a secret test, Castle Bravo quickly became an international incident, prompting calls for a ban on the atmospheric testing of thermonuclear devices. A worldwide network of gummed film stations
21423-429: The end of the explosion increased the amount of radioactivity a thousand-fold. Rotblat's paper was taken up by the media, and the outcry in Japan reached such a level that diplomatic relations became strained and the incident was even dubbed by some as a "second Hiroshima". Nevertheless, the Japanese and US governments quickly reached a political settlement, with the transfer to Japan of $ 15.3 million as compensation, with
21616-478: The energy lost to fuel's vicinity (as radiation, particle losses). After all, for any hydrogen weapon system to work, this energy equilibrium must be maintained through the compression equilibrium between the fusion tamper and the spark plug (see below), hence their name equilibrium supers . Since the ablative process takes place on both walls of the radiation channel, a numerical estimate made with ISRINEX (a thermonuclear explosion simulation program) suggested that
21809-455: The entire Bikini population, while the remaining $ 2.6 million is paid into The Bikini Claims Trust Fund . This trust is intended to exist in perpetuity and to provide the islanders a 5% payment from the trust annually. The United States also passed the Radiation Exposure Compensation Act in 1990 to allow individuals to file claims for compensation in relation to testing as well as those employed at nuclear weapons facilities. On March 5, 2001,
22002-564: The environment for labor unions to begin to flourish . This period eventually ended with the advent of the Progressive Era , which was characterized by significant reforms. Pro-American elements in Hawaii overthrew the Hawaiian monarchy ; the islands were annexed in 1898. That same year, Puerto Rico , the Philippines , and Guam were ceded to the U.S. by Spain after the latter's defeat in
22195-412: The event. From those pipes, mirrors would reflect early bomb light from the bomb casing to a series of remote high-speed cameras, and so that Los Alamos could determine both the simultaneity of the design (i.e. the time interval between primary's firing and secondary's ignition) and the thermonuclear burn rate in these two crucial areas of the secondary device. This secondary assembly device contained
22388-470: The extra neutron released directly by lithium-7 decay produced a much larger neutron flux . The result was greatly increased fissioning of the uranium tamper and increased yield. Summarizing, the reactions involving lithium-6 result in some combination of the two following net reactions: But when lithium-7 is present, one also has some amounts of the following two net reactions: This resultant extra fuel (both lithium-6 and lithium-7) contributed greatly to
22581-496: The fallout range. In the declassified film Operation Castle , the task force commander Major General Percy Clarkson pointed to a diagram indicating that the wind shift was still in the range of "acceptable fallout", although just barely. The decision to carry out the Bravo test under the prevailing winds was made by Dr. Alvin C. Graves , the Scientific Director of Operation Castle. Graves had total authority over detonating
22774-527: The federal government often applied policies of Indian removal or assimilation . The Trail of Tears (1830–1850) was a U.S. government policy that forcibly removed and displaced most Native Americans living east of the Mississippi River to lands far to the west. These and earlier organized displacements prompted a long series of American Indian Wars west of the Mississippi. The Republic of Texas
22967-465: The fire crew sheltering in place ("buttoning up") for several hours until outside radiation decayed to safer levels. "25 roentgens per hour" was recorded above the bunker. The US Navy tanker USS Patapsco was at Enewetak Atoll in late February 1954. Patapsco lacked a decontamination washdown system, and was therefore ordered on February 27, to return to Pearl Harbor at the highest possible speed. A breakdown in her engine systems, namely
23160-399: The first nuclear testing done after the atomic bombing of Hiroshima and Nagasaki . Two fission bombs, both with a yield of 21 kilotons, were tested at Bikini Atoll . "Able" was detonated at an altitude of 520 ft (158 m) on July 1, 1946, and "Baker" was detonated at a depth of 90 ft (27 m) underwater on July 25. Both tests used a flotilla of obsolete vessels from World War II with
23353-539: The first nuclear weapons and used them against the Japanese cities of Hiroshima and Nagasaki in August 1945, ending the war. The United States was one of the " Four Policemen " who met to plan the post-war world , alongside the United Kingdom , Soviet Union , and China . The U.S. emerged relatively unscathed from the war, with even greater economic power and international political influence . After World War II,
23546-550: The first of the Alloy Development Plants (ADP) started production in late 1953. The volume of LiD fuel used was approximately 60% the volume of the fusion fuel filling used in the wet SAUSAGE and dry RUNT I and II devices, or about 500 liters (110 imp gal; 130 U.S. gal), corresponding to about 390 kg of lithium deuteride (as LiD has a density of 0.78201 g/cm ). The mixture cost about 4.54 USD /g at that time. The fusion burn efficiency
23739-504: The fission fuel in the primary) pulsations (generations) of high-energy neutrons with an average temperature of 14 MeV through Jetter's cycle. The Jetter cycle is a combination of reactions involving lithium , deuterium , and tritium . It consumes lithium-6 and deuterium, and in two reactions (with energies of 17.6 MeV and 4.8 MeV, mediated by a neutron and tritium) it produces two alpha particles . The reaction would produce high-energy neutrons with 14 MeV, and its neutronicity
23932-451: The fusion neutrons, contributing about 330 kilotonnes of TNT (1,400 TJ) to the total yield. The energy required by the spark plug to counteract the compression of the fusion fuel was lower than the primary's yield because coupling of the primary's energy in the hohlraum is accompanied by losses due to the difference between the X-ray fireball and the hohlraum temperatures. The neutrons entered
24125-428: The fusion reactions and neutron production and in this manner greatly increased the device's explosive output. The test used lithium with a high percentage of lithium-7 only because lithium-6 was then scarce and expensive; the later Castle Union test used almost pure lithium-6. Had sufficient lithium-6 been available, the usability of the common lithium-7 might not have been discovered. The unexpectedly high yield of
24318-400: The heavy fallout, experiencing acute radiation syndrome , including the death six months later of Kuboyama Aikichi, the boat's chief radioman. The blast incited a strong international reaction over atmospheric thermonuclear testing. The Bravo Crater is located at 11°41′50″N 165°16′19″E / 11.69722°N 165.27194°E / 11.69722; 165.27194 . The remains of
24511-463: The integration of Army National Guard units and personnel into the U.S. Army and (since 1947) the U.S. Air Force. There are about 18,000 U.S. police agencies from local to national level in the United States. Law in the United States is mainly enforced by local police departments and sheriff departments in their municipal or county jurisdictions. The state police departments have authority in their respective state , and federal agencies such as
24704-488: The intent of learning the effects of nuclear weapons on naval fleets. The "Baker" shot created a large condensation cloud and spread much more radioactive water onto the ships than was expected; many of the surviving ships became too "hot" to be used or decontaminated and eventually had to be sunk. Three weapons were detonated on the Enewetak Atoll as part of Operation Sandstone in 1948. Four weapons were detonated on
24897-402: The islanders' appeal of the United States courts of appeals decision that refused to compel the government to fund their claim. As of 2012, trusts remaining from the settlement produced about US$ 6 to $ 8 million annually in investment income, and the trusts paid out about US$ 15,000 per family each year in benefits. The first use of the Pacific Proving Grounds was during Operation Crossroads ,
25090-403: The islanders. Although the atmospheric fallout plume drifted eastward, once fallout landed in the water it was carried in several directions by ocean currents, including northwest and southwest. A Japanese fishing boat, Daigo Fukuryū Maru (Lucky Dragon No. 5), came in direct contact with the fallout, which caused many of the crew to grow ill due to radiation sickness. One member died of
25283-423: The islands over time, and the confusion over the names (and their alternate transliterations) have been the source of much confusion. In addition, some islands over time have appeared, disappeared, separated, joined, and been excavated by bombs. Here are the islands listed in clockwise fashion starting with left side of the major inlet into the lagoon in each atoll. The names include the official Marshall Island names,
25476-401: The large axial length of the secondary, relatively small solid angles would be effective to compress the secondary, leading to poor radiation focusing. By tapering the secondary, the hohlraum could be shaped as a cylinder in its aft section obviating the need to machine the radiation case to a parabola at both ends. This optimized radiation focusing and enabled a streamlined production line, as it
25669-469: The largest being the 15 Mt Castle Bravo shot of 1954 which spread considerable nuclear fallout on many of the islands, including several that were inhabited and some that had not been evacuated. Many of the islands which were part of the Pacific Proving Grounds are still contaminated from the nuclear fallout , and many of those who were living on the islands at the time of testing have suffered from an increased incidence of various health problems. Through
25862-482: The liner in the primary's fissile core prevented DT gas diffusion in plutonium. The spark plug's boosting charge contained about 4 grams of tritium and, imploding together with the secondary's compression, was timed to detonate by the first generations of neutrons that arrived from the primary. Timing was defined by the geometric characteristics of the sparkplug (its uncompressed annular radius), which detonated when its criticality, or k eff , transcended 1. Its purpose
26055-407: The middle and left section of the device. These pipe sections were 8 + 5 ⁄ 8 inches (220 mm) in diameter and 40 feet (12 m) long and were butt-welded end-to-end to the ballistic case leading out to the top of the shot cab. They would carry the initial reaction's light up to the array of 12 mirror towers built in an arc on the artificial 1-acre (0.40 ha) shot island created for
26248-477: The military draft (leading to the end of conscription in 1973) and wide opposition to U.S. intervention in Vietnam (with the U.S. totally withdrawing in 1975). A societal shift in the roles of women was significantly responsible for the large increase in female paid labor participation during the 1970s, and by 1985 the majority of American women aged 16 and older were employed. The late 1980s and early 1990s saw
26441-612: The most attractive to the population are the most vulnerable. The U.S. is one of 17 megadiverse countries containing large numbers of endemic species : about 17,000 species of vascular plants occur in the contiguous United States and Alaska, and over 1,800 species of flowering plants are found in Hawaii, few of which occur on the mainland. The United States is home to 428 mammal species, 784 birds, 311 reptiles, 295 amphibians , and around 91,000 insect species. There are 63 national parks , and hundreds of other federally managed parks, forests, and wilderness areas , managed by
26634-642: The most violent, the California genocide of thousands of Native inhabitants, lasted into the early 1870s, just as additional western territories and states were created. During the colonial period, slavery had been legal in the American colonies , though the practice began to be significantly questioned during the American Revolution. States in the North enacted abolition laws , though support for slavery strengthened in Southern states , as inventions such as
26827-470: The plutonium, a technique first tested in Greenhouse Item . The assembled module weighed 1,840 lb (830 kg), measuring 30.5 in (770 mm) across. It was located at the end of the device, which, as seen in the declassified film, shows a small cone projecting from the ballistic case. This cone is the part of the paraboloid that was used to focus the radiation emanating from the primary into
27020-408: The policy of redlining later adopted by the federal Home Owners' Loan Corporation . An explosion of technological advancement accompanied by the exploitation of cheap immigrant labor led to rapid economic expansion during the late 19th and early 20th centuries , allowing the United States to outpace the economies of England, France, and Germany combined. This fostered the amassing of power by
27213-553: The primary colonial grievances was a denial of their rights as Englishmen , particularly the right to representation in the British government that taxed them . To demonstrate their dissatisfaction and resolve, the First Continental Congress met in 1774 and passed the Continental Association , a colonial boycott of British goods that proved effective. The British attempt to then disarm the colonists resulted in
27406-464: The primary's irradiance, which is dominant at the beginning and during the pulse rise; and the wall, which is important during the required radiation temperature's ( T r ) plateau. The primary emits radiation in a manner similar to a flash bulb , and the secondary needs constant T r to properly implode. This constant wall temperature is dictated by the ablation pressure requirements to drive compression, which lie on average at about 0.4 keV (out of
27599-529: The promise to "protect the inhabitants", from July 1946 through July 1947, the residents of Bikini Atoll who had been relocated to Rongerik Atoll were starving for lack of food. A team of U.S. investigators concluded in late 1947 that the islanders must be moved immediately. Press from around the world harshly criticized the U.S. Navy for ignoring the people. Harold Ickes , a syndicated columnist, wrote "The natives are actually and literally starving to death." The islanders were later moved again to Kili Island , which
27792-464: The relatively low-density fusion fuel—leading to unacceptably large radiation losses—the stand-off gap also acted as a buffer to mitigate the unavoidable and undesirable Taylor mixing . Boron was used at many locations in this dry system; it has a high cross-section for the absorption of slow neutrons, which fission U and Pu, but a low cross-section for the absorption of fast neutrons, which fission U. Because of this characteristic, B deposited onto
27985-515: The rights of African Americans . National infrastructure, including transcontinental telegraph and railroads , spurred growth in the American frontier . From 1865 through 1917 an unprecedented stream of immigrants arrived in the United States, including 24.4 million from Europe. Most came through the port of New York City , and New York City and other large cities on the East Coast became home to large Jewish , Irish , and Italian populations, while many Germans and Central Europeans moved to
28178-596: The rocky Great Basin and Chihuahua , Sonoran , and Mojave deserts. In the northwest corner of Arizona , carved by the Colorado River over millions of years, is the Grand Canyon , a steep-sided canyon and popular tourist destination known for its overwhelming visual size and intricate, colorful landscape. The Sierra Nevada and Cascade mountain ranges run close to the Pacific coast . The lowest and highest points in
28371-443: The secondary and had better structural strength to support the secondary's assembly, which had most of the device's mass. A visualization to this is that the joint looked much like a cap (the secondary) fitted in a cone (the projection of the radiation case). Any other major supporting structure would interfere to radiation transfer from the primary to the secondary and complex vibrational behavior. With this form of joint bearing most of
28564-460: The secondary with the primary, as they diminished bending and torsional loads on the secondary, another technique adopted from the SAUSAGE . The secondary assembly was an elongated truncated cone. From its front part (excluding the blast-heat shield) to its aft section it was steeply tapered. Tapering was used for two reasons. First, radiation drops by the square of the distance, hence radiation coupling
28757-425: The secondary's tamper and ablate it externally, driving the thermonuclear fuel capsule (increasing the density and temperature of the fusion fuel) to the point needed to sustain a thermonuclear reaction. (see Nuclear weapon design ). This point is above the threshold where the fusion fuel would turn opaque to its emitting radiation, as determined from its Rosseland opacity , meaning that the generated energy balances
28950-451: The secondary. The device was called SHRIMP , and had the same basic configuration (radiation implosion) as the Ivy Mike wet device, except with a different type of fusion fuel. SHRIMP used lithium deuteride (LiD), which is solid at room temperature; Ivy Mike used cryogenic liquid deuterium (D 2 ), which required elaborate cooling equipment. Castle Bravo was the first test by
29143-476: The shot cab. The detonation took place at 06:45 on March 1, 1954, local time (18:45 on February 28 GMT ). When Bravo was detonated, within one second it formed a fireball almost 4.5 miles (7.2 km) across. This fireball was visible on Kwajalein Atoll over 250 miles (400 km) away. The explosion left a crater 6,500 feet (2,000 m) in diameter and 250 feet (76 m) in depth. The mushroom cloud reached
29336-563: The six service branches, which are made up of the U.S. Army , Marine Corps , Navy , Air Force , and Space Force . The Coast Guard is administered by the Department of Homeland Security in peacetime and can be transferred to the Department of the Navy in wartime. The United States spent $ 916 billion on its military in 2023, which is by far the largest amount of any country , making up 37% of global military spending and accounting for 3.4% of
29529-528: The sole authority of a state government. SDFs are authorized by state and federal law but are under the command of the state's governor . They are distinct from the state's National Guard units in that they cannot become federalized entities. A state's National Guard personnel, however, may be federalized under the National Defense Act Amendments of 1933 , which created the Guard and provides for
29722-471: The spark plug's plutonium rod. The ratio of deuterium (and tritium) atoms burned by 14 MeV neutrons spawned by the burning was expected to vary from 5:1 to 3:1, a standardization derived from Mike , while for these estimations, the ratio of 3:1 was predominantly used in ISRINEX. The neutronicity of the fusion reactions harnessed by the fusion tamper would dramatically increase the yield of the device. Attached to
29915-543: The states are also represented by local elected governments , which are administrative divisions of the states. States are subdivided into counties or county equivalents , and further divided into municipalities . The District of Columbia is a federal district containing the U.S. capital, Washington, D.C. . The federal district is an administrative division of the federal government. Federally recognized tribes govern 326 Indian reservations . The United States has an established structure of foreign relations, and it has
30108-473: The structural foam holding the secondary in place within the casing was doped with B, the secondary was compressed more highly, at a cost of some radiated neutrons. (The Castle Koon MORGENSTERN device did not use B in its design; as a result, the intense neutron flux from its RACER IV primary predetonated the spherical fission spark plug, which in turn "cooked" the fusion fuel, leading to an overall poor compression. ) The plastic's low molecular weight
30301-399: The structural loads of the secondary, the latter and the hohlraum-ballistic case ensemble behaved as a single mass sharing common eigenmodes. To reduce excessive loading of the joint, especially during deployment of the weapon, the forward section of the secondary (i.e. the thermal blast/heat shield) was anchored to the radiation case by a set of thin wires, which also aligned the center line of
30494-504: The structure and responsibilities of the national federal government and its relationship with the individual states. The U.S. Constitution is the world's oldest national constitution still in effect (from March 4, 1789). Composed of three branches, all headquartered in Washington, D.C., the federal government is the national government of the United States. It is regulated by a strong system of checks and balances . The three-branch system
30687-508: The suit was rejected by the Kochi District Court, who acknowledged the fishermen's radiation exposure but could not "conclude that the state persistently gave up providing support and conducting health surveys to hide the radiation exposure". Unanticipated fallout and the radiation emitted by it also affected many of the vessels and personnel involved in the test, in some cases forcing them into bunkers for several hours. In contrast to
30880-560: The surface of the hohlraum would force the radiation case to speed outwards. The ballistic case would confine the exploding radiation case for as long as necessary. The fact that the tamper material was uranium enriched in U is primarily based on the final fission reaction fragments detected in the radiochemical analysis, which conclusively showed the presence of U, found by the Japanese in the shot debris. The first-generation thermonuclear weapons (MK-14, 16, 17, 21, 22 and 24) all used uranium tampers enriched to 37.5% U. The exception to this
31073-403: The surface of the secondary stage would prevent pre-detonation of the spark plug by stray neutrons from the primary without interfering with the subsequent fissioning of the U of the fusion tamper wrapping the secondary. Boron also played a role in increasing the compressive plasma pressure around the secondary by blocking the sputtering effect, leading to higher thermonuclear efficiency. Because
31266-481: The surrounding area. Fallout , the heaviest of which was in the form of pulverized surface coral from the detonation, fell on residents of Rongelap and Utirik atolls, while the more particulate and gaseous fallout spread around the world. The inhabitants of the islands were evacuated only three days later and suffered radiation sickness . Twenty-three crew members of the Japanese fishing vessel Daigo Fukuryū Maru ("Lucky Dragon No. 5") were also contaminated by
31459-658: The surrounding small islands like Rongerik , Rongelap , and Utirik . In terms of energy released (usually measured in TNT equivalence ), Castle Bravo was about 1,000 times more powerful than the atomic bomb that was dropped on Hiroshima during World War II . Castle Bravo is the sixth largest nuclear explosion in history, exceeded by the Soviet tests of Tsar Bomba at approximately 50 Mt, Test 219 at 24.2 Mt, and three other ( Test 147 , Test 173 and Test 174 ) ≈20 Mt Soviet tests in 1962 at Novaya Zemlya . The yield of 15 (± 5) Mt
31652-449: The surviving victims receiving about ¥2 million each ($ 5,550 in 1954, or about $ 63,000 in 2024). It was also agreed that the victims would not be given Hibakusha status. In 2016, 45 Japanese fishermen from other ships sued their government for not disclosing records about their exposure to Operation Castle fallout. Records released in 2014 acknowledge that the crews of 10 ships were exposed but under health-damaging levels. In 2018
31845-408: The testing period (1948–1958) and from residual radioactive sources during the subsequent 12 years (1959–1970), perhaps 1.6% (with 90% uncertainty range 0.4% to 3.4%) of all cancers might be attributable to fallout-related radiation exposures. By sub-population, the projected proportion of cancers attributable to radiation from fallout from all nuclear tests conducted in the Marshall Islands is 55% (with
32038-478: The time of Bravo, and many birth defects were reported. The islanders received compensation from the U.S. government, relative to how much contamination they received, beginning in 1956; by 1995 the Nuclear Claims Tribunal reported that it had awarded $ 43.2 million, nearly its entire fund, to 1,196 claimants for 1,311 illnesses. A medical study, named Project 4.1 , studied the effects of the fallout on
32231-517: The top of their head with copper, attached the radiation case to the ballistic case. The nails were bolted in vertical arrays in a double-shear configuration to better distribute the shear loads. This method of attaching the radiation case to the ballistic case was first used successfully in the Ivy Mike device. The radiation case had a parabolic end, which housed the COBRA primary that was employed to create
32424-415: The uranium tamper also had a thickness of 2.5 cm, so that an equal pressure would be applied to both walls of the hohlraum . The rocket effect on the surface of tamper's wall created by the ablation of its several superficial layers would force an equal mass of uranium that rested in the remainder of the tamper to speed inwards, thus imploding the thermonuclear core. At the same time, the rocket effect on
32617-413: The weapon, above that of the military commander of Operation Castle. Graves appears in the widely available film of the earlier 1952 test "Ivy Mike", which examines the last-minute fallout decisions. The narrator, the western actor Reed Hadley , is filmed aboard the control ship in that film, showing the final conference. Hadley points out that 20,000 people live in the potential area of the fallout. He asks
32810-565: The world's fourth-longest river system , runs predominantly north–south through the heart of the country. The flat and fertile prairie of the Great Plains stretches to the west, interrupted by a highland region in the southeast. The Rocky Mountains , west of the Great Plains, extend north to south across the country, peaking at over 14,000 feet (4,300 m) in Colorado . Farther west are
33003-567: The world's second-largest diplomatic corps as of 2024 . It is a permanent member of the United Nations Security Council , and home to the United Nations headquarters . The United States is a member of the G7 , G20 , and OECD intergovernmental organizations. Almost all countries have embassies and many have consulates (official representatives) in the country. Likewise, nearly all countries host formal diplomatic missions with
33196-444: The world's oldest surviving federation, and its presidential system of national government has been adopted, in whole or in part, by many newly independent states worldwide following their decolonization . It is a liberal representative democracy "in which majority rule is tempered by minority rights protected by law ". The Constitution of the United States serves as the country's supreme legal document , also establishing
33389-538: The world's tornadoes occur in the country , mainly in Tornado Alley . Overall, the United States receives more high-impact extreme weather incidents than any other country. Extreme weather became more frequent in the U.S. in the 21st century, with three times the number of reported heat waves as in the 1960s. In the American Southwest , droughts became more persistent and more severe. The regions considered as
33582-407: The world, with almost 2 million people incarcerated . An analysis of the World Health Organization Mortality Database from 2010 showed U.S. homicide rates "were 7 times higher than in other high-income countries, driven by a gun homicide rate that was 25 times higher". Castle Bravo Castle Bravo was the first in a series of high-yield thermonuclear weapon design tests conducted by
33775-458: Was annexed in 1845, and the 1846 Oregon Treaty led to U.S. control of the present-day American Northwest . Victory in the Mexican–American War resulted in the 1848 Mexican Cession of California, Nevada, Utah, and much of present-day Colorado and the American Southwest . The California gold rush of 1848–1849 spurred a huge migration of white settlers to the Pacific coast, leading to even more confrontations with Native populations. One of
33968-405: Was a scaled-down version of these devices, and its origins can be traced back to 1953. The United States Air Force indicated the importance of lighter thermonuclear weapons for delivery by the B-47 Stratojet and B-58 Hustler . Los Alamos National Laboratory responded to this indication with a follow-up enriched version of the RUNT scaled down to a 3/4 scale radiation-implosion system called
34161-703: Was adopted on July 4, 1776. The political values of the American Revolution included liberty , inalienable individual rights ; and the sovereignty of the people ; supporting republicanism and rejecting monarchy , aristocracy , and all hereditary political power; civic virtue ; and vilification of political corruption . The Founding Fathers of the United States , who included Washington, Jefferson, John Adams , Benjamin Franklin , Alexander Hamilton , John Jay , James Madison , Thomas Paine , and many others, were inspired by Greco-Roman , Renaissance , and Enlightenment philosophies and ideas. The Articles of Confederation were ratified in 1781 and established
34354-439: Was cheaper, faster and easier to manufacture a radiation case with only one parabolic end. The tapering in this design was much steeper than its cousins, the RUNT , and the ALARM CLOCK devices. SHRIMP's tapering and its mounting to the hohlraum apparently made the whole secondary assembly resemble the body of a shrimp . The secondary's length is defined by the two pairs of dark-colored diagnostic hot spot pipes attached to
34547-514: Was close to 25.1%, the highest attained efficiency of the first thermonuclear weapon generation. This efficiency is well within the figures given in a November 1956 statement, when a DOD official disclosed that thermonuclear devices with efficiencies ranging from 15% to up about 40% had been tested. Hans Bethe reportedly stated independently that the first generation of thermonuclear weapons had (fusion) efficiencies varying from as low as 15% to up about 25%. The thermonuclear burn would produce (like
34740-461: Was denser than Composition B and thus could generate the same amount of explosive force in a smaller volume (it provided 13 percent more compressive energy than Comp B). The composite uranium-plutonium COBRA core was levitated in a type-D pit. COBRA was Los Alamos' most recent product of design work on the "new principles" of the hollow core. A copper pit liner encased within the weapon-grade plutonium inner capsule prevented DT gas diffusion into
34933-404: Was elected the country's first president under the Constitution, and the Bill of Rights was adopted in 1791 to allay skeptics' concerns about the power of the more centralized government. His resignation as commander-in-chief after the Revolutionary War and his later refusal to run for a third term as the country's first president established a precedent for the supremacy of civil authority in
35126-410: Was established to monitor fallout following Operation Castle. Although meteorological data was poor, a general connection of tropospheric flow patterns with observed fallout was evident. There was a tendency for fallout/debris to remain in tropical latitudes , with incursions into the temperate regions associated with meteorological disturbances of the predominantly zonal flow. Outside of the tropics ,
35319-416: Was estimated at ≈0.885 (for a Lawson criterion of ≈1.5). As SHRIMP , along with the RUNT I and ALARM CLOCK , were to be high-yield shots required to assure the thermonuclear " emergency capability ," their fusion fuel may have been spiked with additional tritium, in the form of LiT. All of the high-energy 14 MeV neutrons would cause fission in the uranium fusion tamper wrapped around the secondary and
35512-562: Was given the task of adjudicating compensation for victims and families affected by the nuclear testing program. Section 177 of the compact provided for reparations to the Bikini islanders and other northern atolls for damages. It included $ 150 million to be paid over a 15-year period ending in 2001. During that time, payments averaging about $ 18 million per year were made to the peoples of Bikini, Enewetak, Rongelap, and Utrik for medical and radiological monitoring, and in response to claims. The payments began in 1987 with $ 2.4 million paid annually to
35705-479: Was nominally 40% lithium-6 (the remainder was the much more common lithium-7, which was incorrectly assumed to be inert). The fuel slugs varied in enrichment from 37 to 40% in Li, and the slugs with lower enrichment were positioned at the end of the fusion-fuel chamber, away from the primary. The lower levels of lithium enrichment in the fuel slugs, compared with the ALARM CLOCK and many later hydrogen weapons, were due to shortages in enriched lithium at that time, as
35898-404: Was produced until July 1956. In 1957, it was converted into the Mark 36 nuclear bomb and entered into production again. Following the test, the United States Department of Energy estimated that 253 inhabitants of the Marshall Islands were impacted by the radioactive fallout. This single test exposed the surrounding populations to varying levels of radiation. The fallout levels attributed to
36091-424: Was quite lightweight at 900 lb (410 kg), because it eliminated the aluminum pusher shell around the tamper and used the more compact ring lenses, a design feature shared with the Mark 5, 12, 13 and 18 designs. The explosive material of the inner charges in the MK 7 was changed to the more powerful Cyclotol 75/25, instead of the Composition B used in most stockpiled bombs at that time, as Cyclotol 75/25
36284-623: Was spread eastward onto the inhabited Rongelap and Rongerik atolls, which were evacuated 48 hours after the detonation. In 1957, the Atomic Energy Commission deemed Rongelap safe to return, and allowed 82 inhabitants to move back to the island. Upon their return, they discovered that their previous staple foods , including arrowroot , makmok, and fish, had either disappeared or gave residents various illnesses, and they were again removed. Ultimately, 15 islands and atolls were contaminated, and by 1963 Marshall Islands natives began to suffer from thyroid tumors, including 20 of 29 Rongelap children at
36477-492: Was the MK-15 ZOMBIE that used a 93.5% enriched fission jacket. The secondary assembly was the actual SHRIMP component of the weapon. The weapon, like most contemporary thermonuclear weapons at that time, bore the same codename as the secondary component. The secondary was situated in the cylindrical end of the device, where its end was locked to the radiation case by a type of mortise and tenon joint. The hohlraum at its cylindrical end had an internal projection, which nested
36670-449: Was the largest pure-fission bomb ever detonated, with a yield of 500 kilotons , and the other, Ivy Mike , was the first hydrogen bomb device (it was too large to be an actual weapon), with a yield of 10.4 Mt . Six very large nuclear tests were conducted at the Bikini Atoll and the Enewetak Atoll as part of Operation Castle in 1954. The most notable was Castle Bravo , which was the first deployable (dry fuel) hydrogen bomb developed by
36863-468: Was to compress the fusion material around it from its inside, equally applying pressure with the tamper. The compression factor of the fusion fuel and its adiabatic compression energy determined the minimal energy required for the spark plug to counteract the compression of the fusion fuel and the tamper's momentum. The spark plug weighed about 18 kg, and its initial firing yielded 0.6 kilotonnes of TNT (2.5 TJ). Then it would be completely fissioned by
37056-413: Was triple that of the 5 Mt predicted by its designers. The cause of the higher yield was an error made by designers of the device at Los Alamos National Laboratory . They considered only the lithium-6 isotope in the lithium deuteride secondary to be reactive; the lithium-7 isotope, accounting for 60% of the lithium content, was assumed to be inert. It was expected that the lithium-6 isotope would absorb
37249-465: Was used to drastically reduce the bomb's weight and simultaneously provided sufficient radiation confinement time to raise yield, a departure from the heavy stainless steel casing (304L or MIM 316L) employed by other weapon-projects at the time. The SHRIMP was at least in theory and in many critical aspects identical in geometry to the RUNT and RUNT II devices later proof-fired in Castle Romeo and Castle Yankee respectively. On paper it
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