The Boshin War (戊辰戦争, Boshin Sensō?, "War of the Year of the Dragon")[3] was a civil war in Japan, fought from 1868 to 1869 between forces of the ruling Tokugawa shogunate and those seeking to return political power to the imperial court. The war found its origins in dissatisfaction among many nobles and young samurai with the Shogunate's handling of foreigners following the opening of Japan the prior decade. An alliance of southern samurai and court officials secured the cooperation of the young Emperor Meiji, who declared the abolition of the two-hundred-year-old Shogunate. Military movements by imperial forces and partisan violence in Edo led Tokugawa Yoshinobu, the sitting shogun, to launch a military campaign to seize the emperor's court at Kyoto. The military tide rapidly turned in favor of the smaller but relatively modernized imperial faction, and after a series of battles culminating in the surrender of Edo, Yoshinobu personally surrendered. The Tokugawa remnant retreated to northern Honshū and later to Hokkaidō, where they founded the Ezo republic. Defeat at the Battle of Hakodate broke this last holdout and left the imperial rule supreme throughout the whole of Japan, completing the military phase of the Meiji Restoration.
Around 120,000 men were mobilized during the conflict, and of these about 3,500 were killed.[4] In the end, the victorious imperial faction abandoned its objective to expel foreigners from Japan and instead adopted a policy of continued modernization with an eye to eventual renegotiation of the Unequal Treaties with the Western powers. Due to the persistence of Saigō Takamori, a prominent leader of the imperial faction, the Tokugawa loyalists were shown clemency, and many former shogunate leaders were later given positions of responsibility under the new government.
The Boshin War testifies to the advanced state of modernization already achieved by Japan barely fourteen years after its opening to the West, the already high involvement of Western nations (especially United Kingdom and France) in the country's politics, and the rather turbulent installation of Imperial power. Over time, the war has been romanticized by Japanese and others who view the Meiji Restoration as a "bloodless revolution," despite the number of casualties. Various dramatizations of the war have been made in Japan, and elements of the conflict were incorporated into the 2003 American film The Last Samurai.
Thursday, January 10, 2008
Monday, January 7, 2008
Ulysses
"Ulysses" is a poem by the Victorian poet Alfred, Lord Tennyson (1809–1892), written in 1833 and published in 1842 in Tennyson's well-received second volume of poems. An oft-quoted poem, it is popularly used to illustrate the dramatic monologue poetic form. In the poem, Ulysses describes, to an unspecified audience, his discontent and restlessness upon returning to his kingdom, Ithaca, after his far-ranging travels. Facing old age, Ulysses yearns to explore again, despite his reunion with his wife Penelope and son Telemachus.
The character of Ulysses (Greek: Odysseus) has been explored widely in literature. The adventures of Odysseus were first recorded in Homer's Iliad and Odyssey (c. 800–600 BC), and Tennyson draws on Homer's narrative in the poem; most critics, however, find that Tennyson's Ulysses recalls the character Ulisse in Dante's Inferno (c. 1320). In Dante's re-telling, Ulisse is condemned to hell among the false counsellors, both for his pursuit of knowledge beyond human bounds and for his adventures in disregard of his family.
For most of this poem's history, readers viewed Ulysses as resolute and heroic, admiring him for his determination "To strive, to seek, to find, and not to yield".[1] The view that Tennyson intended a heroic character is supported by his statements about the poem, and by the events in his life—the death of his closest friend—that prompted him to write it. In the twentieth century, scholars began to offer interpretations of "Ulysses" that highlight potential ironies in the poem. They argue, for example, that Ulysses wishes to selfishly abandon his kingdom and family, and they question Ulysses' character by demonstrating how he resembles flawed protagonists in earlier literature.
The character of Ulysses (Greek: Odysseus) has been explored widely in literature. The adventures of Odysseus were first recorded in Homer's Iliad and Odyssey (c. 800–600 BC), and Tennyson draws on Homer's narrative in the poem; most critics, however, find that Tennyson's Ulysses recalls the character Ulisse in Dante's Inferno (c. 1320). In Dante's re-telling, Ulisse is condemned to hell among the false counsellors, both for his pursuit of knowledge beyond human bounds and for his adventures in disregard of his family.
For most of this poem's history, readers viewed Ulysses as resolute and heroic, admiring him for his determination "To strive, to seek, to find, and not to yield".[1] The view that Tennyson intended a heroic character is supported by his statements about the poem, and by the events in his life—the death of his closest friend—that prompted him to write it. In the twentieth century, scholars began to offer interpretations of "Ulysses" that highlight potential ironies in the poem. They argue, for example, that Ulysses wishes to selfishly abandon his kingdom and family, and they question Ulysses' character by demonstrating how he resembles flawed protagonists in earlier literature.
Chicxulub Crater
Chicxulub Crater is an ancient impact crater buried underneath the Yucatán Peninsula, with its center located near the town of Chicxulub, Yucatán, Mexico. The crater is over 180 kilometers (110 mi) in diameter, making the feature one of the largest confirmed impact structures in the world; the asteroid or comet whose impact formed the crater was at least 10 km (6 mi) in diameter. The crater was named for the nearby town, as well as for the literal Maya translation of the name: "tail of the devil."[1]
The crater was discovered by Glen Penfield, a geophysicist who had been working in the Yucatán while looking for oil during the late 1970s. The presence of tektites, shocked quartz and gravity anomalies, as well as the age of the rocks and isotope analysis, show that this impact structure dates from the late Cretaceous Period, roughly 65 million years ago. The impact associated with the crater is implicated in causing the extinction of the dinosaurs as suggested by the K–T boundary, although some critics disagree that the impact was the sole reason[2] and also debate whether there was a single impact or whether the Chicxulub impactor was one of several that may have struck the Earth at around the same time. Recent evidence suggests that the impactor was a piece of a much larger asteroid which broke up in a collision more than 160 million years ago.
Impact specifics
An animation showing the impact, and subsequent crater formation. (University of Arizona, Space Imagery Center)
An animation showing the impact, and subsequent crater formation. (University of Arizona, Space Imagery Center)
The impactor's estimated size was about 10 km (6 mi) in diameter and may have released an estimated 500 zettajoules (5×1023 joules) of energy, equivalent to 100 teratons of TNT (1014 tons),[4] on impact. By contrast, the most powerful man-made explosive device ever detonated, the Tsar Bomba or Emperor Bomb, had a yield of only 50 megatons,[5] making the Chicxulub impact 2 million times more powerful.[6] Even the largest known explosive volcanic eruption, which released approximately 10 zettajoules and created the La Garita Caldera,[7] was substantially less powerful than the Chicxulub impact.
The impact caused some of the largest megatsunamis in Earth's history. A cloud of dust, ash and steam would have spread from the crater, as the impactor burrowed underground in less than a second.[8] Pieces of the impactor, ejected out of the atmosphere by the blast, would have been heated to incandescence upon reentry, broiling the Earth's surface and igniting global wildfires; meanwhile, shock waves spawned global earthquakes and volcanic eruptions.[9] The emission of dust and particles could have covered the entire surface of the Earth for several years, possibly a decade, creating a harsh environment for living things to survive in. The shock production of carbon dioxide caused by the destruction of carbonate rocks would have led to a dramatic greenhouse effect,[10] and sunlight would have been filtered out by dust particles in the atmosphere. The photosynthesis of plants would be interrupted, subsequently affecting the entire food chain
Geology and morphology
In their 1991 paper, Hildebrand, Penfield, and company described the geology and composition of the impact feature.[13] The rocks above the impact feature are layers of marl and limestone reaching to almost 1,000 meters (3,300 ft) in depth. These rocks date back as far as the Paleocene.[14] Below these layers lie more than 500 m (1,600 ft) of andesite glass and breccia. These andesitic igneous rocks were found only within the supposed impact feature; similarly, quantities of feldspar and augite, normally only found in impact-melt rocks, are present,[15] as is shocked quartz.[14] The K–T boundary inside the feature is depressed between 600 and 1,100 m (2,000–3,600 ft) compared to the normal depth of about 500 m (1,600 ft) depth 5 km (3 mi) away from the impact feature.[16] Along the edge of the crater are clusters of cenotes or sinkholes, which suggest that there was a water basin inside the feature during the Tertiary period, after the impact.[16] Such a basin's groundwater dissolved the limestone and created the caves and cenotes beneath the surface.[17] The paper also noted that the crater seemed to be a good candidate source for the tektites reported at Haiti.[18]
[edit] Origin
On September 5, 2007 a report was issued in Nature that proposed an origin of the asteroid that created Chicxulub Crater.[11] The authors, William F. Bottke, David Vokrouhlický, and David Nesvorný, argue that a collision in the asteroid belt 160 million years ago resulted in the creation of the Baptistina family of asteroids, the largest surviving member of which is 298 Baptistina. They proposed that the "Chicxulub asteroid" was also a member of this group. The connection between Chicxulub and Baptistina is supported by the large amount of carbonaceous material present in microscopic fragments of the impactor, suggesting the impactor was a member of a rare class of asteroids called carbonaceous chondrites, like Baptistina.[3] According to Bottke, the Chicxulub impactor was a fragment of a much larger parent body about 170 km (105 mi) across, with the other impacting body being around 60 km (40 mi) in diameter.[19][3]
[edit] Chicxulub and dinosaur extinction
Main article: Cretaceous–Tertiary extinction event
Walter Alvarez holding the piece of clay which sparked research into the impact theory. The second green band from the bottom is extremely rich in iridium.
Walter Alvarez holding the piece of clay which sparked research into the impact theory. The second green band from the bottom is extremely rich in iridium.
The Chicxulub Crater lends support to the theory postulated by the late physicist Luis Alvarez and his son, geologist Walter Alvarez, for the extinction of the dinosaurs by an asteroid. The Alvarezes, at the time both faculty members at the University of California, Berkeley, postulated that the extinction of the dinosaurs, roughly contemporaneous with the K–T boundary, could have been caused by just such a large impact.[20] This theory is now widely, though not universally, accepted by the scientific community. Some critics, including paleontologist Robert Bakker, argue that such an impact would have killed frogs as well as dinosaurs, yet the frogs survived the extinction event.[21] Gerta Keller of Princeton University argues that recent core samples from Chicxulub prove the impact occurred about 300,000 years before the extinction of the dinosaurs, and thus could not have been the cause of their demise.[22]
The main evidence of such an impact, besides the crater itself, is a widespread, thin layer of clay present in the K–T boundary across the world. In the late 1970s, the Alvarezes and colleagues reported[23] that it contained an abnormally high concentration of iridium. In this layer, iridium levels reached 6 parts per billion by weight or more compared to 0.4[24] for the Earth's crust as a whole; in comparison, meteorites can contain around 470 parts per billion[25] of this element. It was hypothesised that the iridium was spread into the atmosphere when the impactor was vapourized and settled across the Earth's surface amongst other material thrown up by the impact, producing the relatively iridium-rich layer of clay.[26]
[edit] Multiple impact theory
See also: Roche limit
In recent years, several other craters of around the same age as Chicxulub have been discovered, all between latitudes 20°N and 70°N. Examples include the Silverpit crater in the North Sea,[27] and the Boltysh crater in Ukraine.[28] Both are much smaller than Chicxulub, but likely to have been caused by objects many tens of metres across striking the Earth.[29] This has led to the hypothesis that the Chicxulub impact may have been only one of several impacts that happened nearly at the same time.[30] Another possible crater thought to have been formed at the same time is the Shiva crater, though the structure's status as a crater is contested.[31]
The collision of Comet Shoemaker-Levy 9 with Jupiter in 1994 proved that gravitational interactions can fragment a comet, giving rise to many impacts over a period of a few days if the comet should collide with a planet. Comets frequently undergo gravitational interactions with the gas giants, and similar disruptions and collisions are very likely to have occurred in the past.[32] This scenario may have occurred on Earth 65 million years ago.[30]
In late 2006, Ken MacLeod, a geology professor from the University of Missouri–Columbia, completed an analysis of sediment below the ocean's surface bolstering the single-impact theory. MacLeod conducted his analysis approximately 4,500 kilometers (2,800 mi) from the Chicxulub Crater to control for possible changes in soil composition at the impact site while still close enough to be affected by the impact. The analysis revealed there was only one layer of impact debris in the sediment, which indicated there was only one impact.[33] Multiple-impact proponents such as Gerta Keller regard the results as "rather hyper-inflated" and do not agree with the conclusion of MacLeod's analysis.
The crater was discovered by Glen Penfield, a geophysicist who had been working in the Yucatán while looking for oil during the late 1970s. The presence of tektites, shocked quartz and gravity anomalies, as well as the age of the rocks and isotope analysis, show that this impact structure dates from the late Cretaceous Period, roughly 65 million years ago. The impact associated with the crater is implicated in causing the extinction of the dinosaurs as suggested by the K–T boundary, although some critics disagree that the impact was the sole reason[2] and also debate whether there was a single impact or whether the Chicxulub impactor was one of several that may have struck the Earth at around the same time. Recent evidence suggests that the impactor was a piece of a much larger asteroid which broke up in a collision more than 160 million years ago.
Impact specifics
An animation showing the impact, and subsequent crater formation. (University of Arizona, Space Imagery Center)
An animation showing the impact, and subsequent crater formation. (University of Arizona, Space Imagery Center)
The impactor's estimated size was about 10 km (6 mi) in diameter and may have released an estimated 500 zettajoules (5×1023 joules) of energy, equivalent to 100 teratons of TNT (1014 tons),[4] on impact. By contrast, the most powerful man-made explosive device ever detonated, the Tsar Bomba or Emperor Bomb, had a yield of only 50 megatons,[5] making the Chicxulub impact 2 million times more powerful.[6] Even the largest known explosive volcanic eruption, which released approximately 10 zettajoules and created the La Garita Caldera,[7] was substantially less powerful than the Chicxulub impact.
The impact caused some of the largest megatsunamis in Earth's history. A cloud of dust, ash and steam would have spread from the crater, as the impactor burrowed underground in less than a second.[8] Pieces of the impactor, ejected out of the atmosphere by the blast, would have been heated to incandescence upon reentry, broiling the Earth's surface and igniting global wildfires; meanwhile, shock waves spawned global earthquakes and volcanic eruptions.[9] The emission of dust and particles could have covered the entire surface of the Earth for several years, possibly a decade, creating a harsh environment for living things to survive in. The shock production of carbon dioxide caused by the destruction of carbonate rocks would have led to a dramatic greenhouse effect,[10] and sunlight would have been filtered out by dust particles in the atmosphere. The photosynthesis of plants would be interrupted, subsequently affecting the entire food chain
Geology and morphology
In their 1991 paper, Hildebrand, Penfield, and company described the geology and composition of the impact feature.[13] The rocks above the impact feature are layers of marl and limestone reaching to almost 1,000 meters (3,300 ft) in depth. These rocks date back as far as the Paleocene.[14] Below these layers lie more than 500 m (1,600 ft) of andesite glass and breccia. These andesitic igneous rocks were found only within the supposed impact feature; similarly, quantities of feldspar and augite, normally only found in impact-melt rocks, are present,[15] as is shocked quartz.[14] The K–T boundary inside the feature is depressed between 600 and 1,100 m (2,000–3,600 ft) compared to the normal depth of about 500 m (1,600 ft) depth 5 km (3 mi) away from the impact feature.[16] Along the edge of the crater are clusters of cenotes or sinkholes, which suggest that there was a water basin inside the feature during the Tertiary period, after the impact.[16] Such a basin's groundwater dissolved the limestone and created the caves and cenotes beneath the surface.[17] The paper also noted that the crater seemed to be a good candidate source for the tektites reported at Haiti.[18]
[edit] Origin
On September 5, 2007 a report was issued in Nature that proposed an origin of the asteroid that created Chicxulub Crater.[11] The authors, William F. Bottke, David Vokrouhlický, and David Nesvorný, argue that a collision in the asteroid belt 160 million years ago resulted in the creation of the Baptistina family of asteroids, the largest surviving member of which is 298 Baptistina. They proposed that the "Chicxulub asteroid" was also a member of this group. The connection between Chicxulub and Baptistina is supported by the large amount of carbonaceous material present in microscopic fragments of the impactor, suggesting the impactor was a member of a rare class of asteroids called carbonaceous chondrites, like Baptistina.[3] According to Bottke, the Chicxulub impactor was a fragment of a much larger parent body about 170 km (105 mi) across, with the other impacting body being around 60 km (40 mi) in diameter.[19][3]
[edit] Chicxulub and dinosaur extinction
Main article: Cretaceous–Tertiary extinction event
Walter Alvarez holding the piece of clay which sparked research into the impact theory. The second green band from the bottom is extremely rich in iridium.
Walter Alvarez holding the piece of clay which sparked research into the impact theory. The second green band from the bottom is extremely rich in iridium.
The Chicxulub Crater lends support to the theory postulated by the late physicist Luis Alvarez and his son, geologist Walter Alvarez, for the extinction of the dinosaurs by an asteroid. The Alvarezes, at the time both faculty members at the University of California, Berkeley, postulated that the extinction of the dinosaurs, roughly contemporaneous with the K–T boundary, could have been caused by just such a large impact.[20] This theory is now widely, though not universally, accepted by the scientific community. Some critics, including paleontologist Robert Bakker, argue that such an impact would have killed frogs as well as dinosaurs, yet the frogs survived the extinction event.[21] Gerta Keller of Princeton University argues that recent core samples from Chicxulub prove the impact occurred about 300,000 years before the extinction of the dinosaurs, and thus could not have been the cause of their demise.[22]
The main evidence of such an impact, besides the crater itself, is a widespread, thin layer of clay present in the K–T boundary across the world. In the late 1970s, the Alvarezes and colleagues reported[23] that it contained an abnormally high concentration of iridium. In this layer, iridium levels reached 6 parts per billion by weight or more compared to 0.4[24] for the Earth's crust as a whole; in comparison, meteorites can contain around 470 parts per billion[25] of this element. It was hypothesised that the iridium was spread into the atmosphere when the impactor was vapourized and settled across the Earth's surface amongst other material thrown up by the impact, producing the relatively iridium-rich layer of clay.[26]
[edit] Multiple impact theory
See also: Roche limit
In recent years, several other craters of around the same age as Chicxulub have been discovered, all between latitudes 20°N and 70°N. Examples include the Silverpit crater in the North Sea,[27] and the Boltysh crater in Ukraine.[28] Both are much smaller than Chicxulub, but likely to have been caused by objects many tens of metres across striking the Earth.[29] This has led to the hypothesis that the Chicxulub impact may have been only one of several impacts that happened nearly at the same time.[30] Another possible crater thought to have been formed at the same time is the Shiva crater, though the structure's status as a crater is contested.[31]
The collision of Comet Shoemaker-Levy 9 with Jupiter in 1994 proved that gravitational interactions can fragment a comet, giving rise to many impacts over a period of a few days if the comet should collide with a planet. Comets frequently undergo gravitational interactions with the gas giants, and similar disruptions and collisions are very likely to have occurred in the past.[32] This scenario may have occurred on Earth 65 million years ago.[30]
In late 2006, Ken MacLeod, a geology professor from the University of Missouri–Columbia, completed an analysis of sediment below the ocean's surface bolstering the single-impact theory. MacLeod conducted his analysis approximately 4,500 kilometers (2,800 mi) from the Chicxulub Crater to control for possible changes in soil composition at the impact site while still close enough to be affected by the impact. The analysis revealed there was only one layer of impact debris in the sediment, which indicated there was only one impact.[33] Multiple-impact proponents such as Gerta Keller regard the results as "rather hyper-inflated" and do not agree with the conclusion of MacLeod's analysis.
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