SUMMARY / RELATED TOPICS

Battle of Pusan Perimeter

The Battle of the Pusan Perimeter was a large-scale battle between United Nations Command and North Korean forces lasting from August 4 to September 18, 1950. It was one of the first major engagements of the Korean War. An army of 140,000 UN troops, having been pushed to the brink of defeat, were rallied to make a final stand against the invading Korean People's Army, 98,000 men strong. UN forces, having been defeated by the advancing KPA, were forced back to the "Pusan Perimeter", a 140-mile defensive line around an area on the southeastern tip of South Korea that included the port of Busan; the UN troops, consisting of forces from the Republic of Korea Army, United States, United Kingdom mounted a last stand around the perimeter, fighting off repeated KPA attacks for six weeks as they were engaged around the cities of Daegu and Pohang and the Nakdong River. The massive KPA assaults were unsuccessful in forcing the UN troops back further from the perimeter, despite two major pushes in August and September.

North Korean troops, hampered by supply shortages and massive losses, continually staged attacks on UN forces in an attempt to penetrate the perimeter and collapse the line. However, the UN used the port to amass an overwhelming advantage in troops and logistics, its navy and air forces remained unchallenged by the KPA during the fight. After six weeks, the KPA force collapsed and retreated in defeat after the UN force launched a counterattack at Inchon on September 15 and the UN forces in the perimeter broke out from the perimeter the following day; the battle would be the furthest the KPA would advance in the war, as subsequent fighting ground the war into a stalemate. Following the outbreak of the Korean War, the United Nations decided to commit troops in support of South Korea, invaded by the neighboring North Korea; the United States subsequently sent ground forces to the Korean Peninsula with the goal of fighting back the North Korean invasion and to prevent South Korea from collapsing.

However, US forces in the Far East had been decreasing since the end of World War II, five years earlier, at the time the closest forces were the 24th Infantry Division of the Eighth United States Army, headquartered in Japan. The division was understrength, most of its equipment was antiquated due to reductions in military spending. Regardless, the 24th Infantry Division was ordered into South Korea; the KPA, 89,000 men strong, had advanced into South Korea in six columns, catching the ROKA by surprise and routing it. The smaller ROK suffered from widespread lack of organization and equipment, was unprepared for war. Numerically superior, KPA forces destroyed isolated resistance from the 38,000 ROK soldiers on the front before moving south. Most of South Korea's forces retreated in the face of the advance. By June 28, the KPA had captured South Korea's capital Seoul, forcing the government and its shattered forces to retreat further south. Though it was pushed back, ROK forces increased their resistance further south, hoping to delay KPA units as much as possible.

North and South Korean units sparred for control of several cities, inflicting heavy casualties on one another. The ROK defended Yeongdeok fiercely before being forced back, managed to repel KPA forces in the Battle of Andong. Outnumbered and under-equipped US forces—committed in piecemeal fashion as as they could be deployed—were defeated and pushed south; the 24th Division, the first US division committed, took heavy losses in the Battle of Taejon in mid-July, which they were driven from after heavy fighting. Elements of the 3rd Battalion, 29th Infantry Regiment, newly arrived in the country, were wiped out at Hadong in a coordinated ambush by KPA forces on July 27, leaving open a pass to the Pusan area. Soon after, Chinju to the west was taken, pushing back the 19th Infantry Regiment and leaving open routes to Pusan. US units were subsequently able to defeat and push back the KPA on the flank in the Battle of the Notch on August 2. Suffering mounting losses, the KPA force on the west flank withdrew for several days to re-equip and receive reinforcements.

This granted both sides several days of reprieve to prepare for the attack on the Pusan Perimeter. The KPA was organized into a mechanized combined arms force of ten divisions numbering some 90,000 well-trained and well-equipped troops in July, with hundreds of T-34 tanks. However, defensive actions by US and ROK forces had delayed the KPA in their invasion of South Korea, costing them 58,000 of their troops and a large number of tanks. In order to recoup these losses, the KPA had to rely on less-experienced replacements and conscripts, many of whom had been taken from the conquered regions of South Korea. During the course of the battle, the KPA raised a total of 13 infantry divisions and one armored division to fight at the Pusan Perimeter; the UN forces were organized under the command of the Eighth United States Army, which served and was headquartered at Taegu. Under it were three weak US divisions; these forces occupied the western segment of the perimeter, along the Naktong River. The ROK, a force of 58,000, was organized into five divisions.

A reconstituted ROK 3rd Infantry Division was placed under direct ROK control. Morale among the UN units was low due to the large number of defeats incurred to that point in the war. US forces had suffered over 6,00

Age of the Earth

The age of the Earth is estimated to be 4.54 ± 0.05 billion years. This age may represent the age of the Earth's accretion, or core formation, or of the material from which the Earth formed; this dating is based on evidence from radiometric age-dating of meteorite material and is consistent with the radiometric ages of the oldest-known terrestrial and lunar samples. Following the development of radiometric age-dating in the early 20th century, measurements of lead in uranium-rich minerals showed that some were in excess of a billion years old; the oldest such minerals analyzed to date—small crystals of zircon from the Jack Hills of Western Australia—are at least 4.404 billion years old. Calcium–aluminium-rich inclusions—the oldest known solid constituents within meteorites that are formed within the Solar System—are 4.567 billion years old, giving a lower limit for the age of the Solar System. It is hypothesised that the accretion of Earth began soon after the formation of the calcium-aluminium-rich inclusions and the meteorites.

Because the time this accretion process took is not yet known, predictions from different accretion models range from a few million up to about 100 million years, the difference between the age of Earth and of the oldest rocks is difficult to determine. It is difficult to determine the exact age of the oldest rocks on Earth, exposed at the surface, as they are aggregates of minerals of different ages. Studies of strata - the layering of rocks and earth - gave naturalists an appreciation that Earth may have been through many changes during its existence; these layers contained fossilized remains of unknown creatures, leading some to interpret a progression of organisms from layer to layer. Nicolas Steno in the 17th century was one of the first naturalists to appreciate the connection between fossil remains and strata, his observations led him to formulate important stratigraphic concepts. In the 1790s, William Smith hypothesized that if two layers of rock at differing locations contained similar fossils it was plausible that the layers were the same age.

William Smith's nephew and student, John Phillips calculated by such means that Earth was about 96 million years old. In the mid-18th century, the naturalist Mikhail Lomonosov suggested that Earth had been created separately from, several hundred thousand years before, the rest of the universe. Lomonosov's ideas were speculative. In 1779 the Comte du Buffon tried to obtain a value for the age of Earth using an experiment: He created a small globe that resembled Earth in composition and measured its rate of cooling; this led him to estimate. Other naturalists used these hypotheses to construct a history of Earth, though their timelines were inexact as they did not know how long it took to lay down stratigraphic layers. In 1830, geologist Charles Lyell, developing ideas found in James Hutton's works, popularized the concept that the features of Earth were in perpetual change and reforming continuously, the rate of this change was constant; this was a challenge to the traditional view, which saw the history of Earth as dominated by intermittent catastrophes.

Many naturalists were influenced by Lyell to become "uniformitarians" who believed that changes were constant and uniform. In 1862, the physicist William Thomson, 1st Baron Kelvin published calculations that fixed the age of Earth at between 20 million and 400 million years, he assumed that Earth had formed as a molten object, determined the amount of time it would take for the near-surface temperature gradient to decrease to its present value. His calculations did not account for heat produced via radioactive decay or, more convection inside the Earth, which allows the temperature in the upper mantle to remain high much longer, maintaining a high thermal gradient in the crust much longer. More constraining were Kelvin's estimates of the age of the Sun, which were based on estimates of its thermal output and a theory that the Sun obtains its energy from gravitational collapse. Geologists such as Charles Lyell had trouble accepting such a short age for Earth. For biologists 100 million years seemed much too short to be plausible.

In Darwin's theory of evolution, the process of random heritable variation with cumulative selection requires great durations of time. According to modern biology, the total evolutionary history from the beginning of life to today has taken place since 3.5 to 3.8 billion years ago, the amount of time which passed since the last universal ancestor of all living organisms as shown by geological dating. In a lecture in 1869, Darwin's great advocate, Thomas H. Huxley, attacked Thomson's calculations, suggesting they appeared precise in themselves but were based on faulty assumptions; the physicist Hermann von Helmholtz and astronomer Simon Newcomb contributed their own calculations of 22 and 18 million years to the debate: they independently calculated the amount of time it would take for the Sun to condense down to its current diameter and brightness from the nebula of gas and dust from which it was born. Their values were consistent with Thomson's calculations. However, they assumed; the process of solar nuclear fusion was not yet known to science.

In 1895 John Perry challenged Kelvin's figure on the basis of his assumptions on conductivity, Oliver Heaviside entered the dialogue, considering it "a vehicle to display the ability of his operator method to solve problems of astonishi

Segovia (Congress of Deputies constituency)

Segovia is one of the 52 constituencies represented in the Congress of Deputies, the lower chamber of the Spanish parliament, the Cortes Generales. The constituency elects four deputies, its boundaries correspond to those of the Spanish province of Segovia. The electoral system uses the D'Hondt method and a closed-list proportional representation, with a minimum threshold of three percent; the constituency was created as per the Political Reform Act 1977 and was first contested in the 1977 general election. The Act provided for the provinces of Spain to be established as multi-member districts in the Congress of Deputies, with this regulation being maintained under the Spanish Constitution of 1978. Additionally, the Constitution requires for any modification of the provincial limits to be approved under an organic law, needing an absolute majority in the Cortes Generales. Voting is on the basis of universal suffrage, which comprises all nationals over eighteen and in full enjoyment of their political rights.

The only exception was in 1977, when this was limited to nationals over twenty-one and in full enjoyment of their political and civil rights. Amendments to the electoral law in 2011 required for Spaniards abroad to apply for voting before being permitted to vote, a system known as "begged" or expat vote. 348 seats are elected using the D'Hondt method and a closed list proportional representation, with a threshold of three percent of valid votes—which includes blank ballots—being applied in each constituency. Parties not reaching the threshold are not taken into consideration for seat distribution; each provincial constituency is entitled to an initial minimum of two seats, with the remaining 248 being distributed in proportion to their populations. Ceuta and Melilla are allocated the two remaining seats; the use of the D'Hondt method may result in a higher effective threshold, depending on the district magnitude. The electoral law allows for parties and federations registered in the interior ministry and groupings of electors to present lists of candidates.

Parties and federations intending to form a coalition ahead of an election are required to inform the relevant Electoral Commission within ten days of the election call—fifteen before 1985—whereas groupings of electors need to secure the signature of at least one percent of the electorate in the constituencies for which they seek election—one-thousandth of the electorate, with a compulsory minimum of 500 signatures, until 1985—disallowing electors from signing for more than one list of candidates. Since 2011, federations or coalitions that have not obtained a mandate in either chamber of the Cortes at the preceding election are required to secure the signature of at least 0.1 percent of electors in the aforementioned constituencies