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Laschamp Excursion
The Laschamp or Laschamps event, also termed the Adams event, was a geomagnetic excursion (a short reversal of the Earth's magnetic field). It occurred between 42,200 and 41,500 years ago, during the Last Glacial Period. It was discovered from geomagnetic anomalies found in the Laschamps and Olby lava flows near Clermont-Ferrand, France in the 1960s. The Laschamp event was the first known geomagnetic excursion and remains the most thoroughly studied among the known geomagnetic excursions. It is named after the village of Laschamps, part of the commune of Saint-Genès-Champanelle in France. Background and effects Since its discovery, the magnetic excursion has been demonstrated in geological archives from many parts of the world. The transition from the normal field to the reversed field lasted approximately 250 years, while the magnetic field remained reversed for approximately 440 years. During the transition, Earth's magnetic field declined to a minimum of 5% of its ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Geomagnetic Excursion
A geomagnetic excursion, like a ''geomagnetic reversal'', is a significant change in the Earth's magnetic field. Unlike ''reversals'', an excursion is not a long-term re-orientation of the large-scale field, but rather represents a dramatic, typically a (geologically) short-lived change in field intensity, with a variation in pole orientation of up to 45° from the previous position. Excursion events typically only last a few thousand to a few tens of thousands of years, and often involve declines in field strength to between 0 and 20% of normal. Unlike full ''reversals'', ''excursions'' are generally not recorded around the entire globe. This is certainly due in part to them not registering well in the sedimentary record, but it also seems likely that excursions may not typically extend through the entire global geomagnetic field. There are significant exceptions, however. Occurrence Except for recent periods of the geologic past, it is not well known how frequently geomagnetic e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
The Guardian
''The Guardian'' is a British daily newspaper. It was founded in Manchester in 1821 as ''The Manchester Guardian'' and changed its name in 1959, followed by a move to London. Along with its sister paper, ''The Guardian Weekly'', ''The Guardian'' is part of the Guardian Media Group, owned by the Scott Trust Limited. The trust was created in 1936 to "secure the financial and editorial independence of ''The Guardian'' in perpetuity and to safeguard the journalistic freedom and liberal values of ''The Guardian'' free from commercial or political interference". The trust was converted into a limited company in 2008, with a constitution written so as to maintain for ''The Guardian'' the same protections as were built into the structure of the Scott Trust by its creators. Profits are reinvested in its journalism rather than distributed to owners or shareholders. It is considered a newspaper of record in the UK. The editor-in-chief Katharine Viner succeeded Alan Rusbridger in 2015. S ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Late Pleistocene Extinctions
The Late Pleistocene to the beginning of the Holocene saw the extinction of the majority of the world's megafauna, typically defined as animal species having body masses over , which resulted in a collapse in faunal density and diversity across the globe. The extinctions during the Late Pleistocene are differentiated from previous extinctions by their extreme size bias towards large animals (with small animals being largely unaffected), and widespread absence of ecological succession to replace these extinct megafaunal species, and the regime shift of previously established faunal relationships and habitats as a consequence. The timing and severity of the extinctions varied by region and are generally thought to have been driven by humans, climatic change, or a combination of both. Human impact on megafauna populations is thought to have been driven by hunting ("overkill"), as well as possibly environmental alteration. The relative importance of human vs climatic factors in the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Timeline Of Prehistory
This timeline of prehistory covers the time from the appearance of ''Homo sapiens'' approximately 315,000 years ago in Africa to the invention of writing, over 5,000 years ago, with the earliest records going back to 3,200 BC. Prehistory covers the time from the Paleolithic (Old Stone Age) to the beginning of ancient history. All dates are approximate and subject to revision based on new discoveries or analyses. Middle Paleolithic * 320 kya – 305 kya: Populations at Olorgesailie in Southern Kenya undergo technological improvements in tool making and engage in long-distance trade. * 315 kya: Approximate date of appearance of ''Homo sapiens'' (Jebel Irhoud, Morocco). * 270 kya: Age of Y-DNA haplogroup A00 ("Y-chromosomal Adam"). * 250 kya: First appearance of ''Homo neanderthalensis'' ( Saccopastore skulls). * 230 kya: Latest proposed date for the Terra Amata site, home of the first confirmed purpose-built structure and probably made by Homo heidelbergensis. * 230 ky ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Solar Cycle 1
Solar cycle 1 was the first solar cycle during which extensive recording of solar sunspot activity took place. The solar cycle lasted 11.3 years, beginning in February 1755 and ending in June 1766. The maximum smoothed sunspot number observed during the solar cycle was 144.1 (June 1761), and the starting minimum was 14.0. Solar cycle 1 was discovered by Johann Rudolph Wolf who, inspired by the discovery of the solar cycle by Heinrich Schwabe in 1843, collected all available sunspot observations going back to the first telescopic observations by Galileo. He was able to improve Schwabe's estimate of the mean length of the cycle from about a decade to 11.11 years. However, he could not find enough observations before 1755 to reliably identify cycles, hence the 1755–1766 cycle is conventionally numbered as cycle 1. Wolf published his results in 1852. See also *List of solar cycles Solar cycles are nearly periodic 11-year changes in the Sun's activity that are based on the nu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Solar Cycle
The Solar cycle, also known as the solar magnetic activity cycle, sunspot cycle, or Schwabe cycle, is a periodic 11-year change in the Sun's activity measured in terms of Modern Maximum, variations in the number of observed sunspots on the Sun's surface. Over the period of a solar cycle, levels of solar radiation and ejection of solar material, the number and size of sunspots, solar flares, and coronal loops all exhibit a synchronized fluctuation from a Solar minimum, period of minimum activity to a Solar maximum, period of a maximum activity back to a period of minimum activity. The magnetic field of the Sun flips during each solar cycle, with the flip occurring when the solar cycle is near its maximum. After two solar cycles, the Sun's magnetic field returns to its original state, completing what is known as a Hale cycle. This cycle has been observed for centuries by changes in the Sun's appearance and by terrestrial phenomena such as aurora but was not clearly identified un ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
National Public Radio
National Public Radio (NPR) is an American public broadcasting organization headquartered in Washington, D.C., with its NPR West headquarters in Culver City, California. It serves as a national Radio syndication, syndicator to a network of more than List of NPR stations, 1,000 public radio stations in the United States. Funding for NPR comes from dues and fees paid by member stations, Underwriting spot, underwriting from corporate sponsors, and annual grants from the publicly funded Corporation for Public Broadcasting. Most of its member stations are owned by non-profit organizations, including public school districts, colleges, and universities. NPR operates independently of any government or corporation, and has full control of its content. NPR produces and distributes both news and cultural programming. The organization's flagship shows are two drive time, drive-time news broadcasts: ''Morning Edition'' and the afternoon ''All Things Considered'', both carried by most NPR me ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Weekend Edition
''Weekend Edition'' is a set of American radio news magazine programs produced and distributed by National Public Radio ( NPR). It is the weekend counterpart to the NPR radio program ''Morning Edition''. It consists of ''Weekend Edition Saturday'' and ''Weekend Edition Sunday'', each of which airs for two hours, from 8:00a.m. to 10:00a.m. Eastern time, with refeeds until 2:00 p.m. ''Weekend Edition Saturday'' is hosted by Scott Simon. ''Weekend Edition Sunday'' is hosted by Ayesha Rascoe. The programs feature longer stories than most NPR news magazines, and more arts and culture stories. Format Weekday sibling ''Morning Edition'' breaks up each hour into five segments, none more than twelve minutes long; ''Weekend Edition'' uses only three segments per hour, accommodating longer stories than ''Morning Edition'' typically accommodates. ''Weekend Edition'' begins with a sixty-second billboard. Both Simon and Rascoe use the billboard as a general discussion about what's com ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radiocarbon Dating
Radiocarbon dating (also referred to as carbon dating or carbon-14 dating) is a method for Chronological dating, determining the age of an object containing organic material by using the properties of carbon-14, radiocarbon, a radioactive Isotopes of carbon, isotope of carbon. The method was developed in the late 1940s at the University of Chicago by Willard Libby. It is based on the fact that radiocarbon () is constantly being created in the Atmosphere of Earth, Earth's atmosphere by the interaction of cosmic rays with atmospheric nitrogen. The resulting combines with atmospheric oxygen to form radioactive carbon dioxide, which is incorporated into plants by photosynthesis; animals then acquire by eating the plants. When the animal or plant dies, it stops exchanging carbon with its environment, and thereafter the amount of it contains begins to decrease as the undergoes radioactive decay. Measuring the amount of in a sample from a dead plant or animal, such as a piece of w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kauri Tree
''Agathis'', commonly known as kauri or dammara, is a genus of evergreen coniferous trees, native to Australasia and Southeast Asia. It is one of three extant genera in the family Araucariaceae, alongside ''Wollemia'' and ''Araucaria'' (being more closely related to the former).de Laubenfels, David J. 1988. Coniferales. P. 337–453 in Flora Malesiana, Series I, Volume 10. Dordrecht: Kluwer Academic. Its leaves are much broader than most conifers. Kauri gum is commercially harvested from New Zealand kauri. Description Mature kauri trees have characteristically large trunks, with little or no branching below the crown. In contrast, young trees are normally conical in shape, forming a more rounded or irregularly shaped crown as they achieve maturity.Whitmore, T.C. 1977. ''A first look at Agathis''. Tropical Forestry Papers No. 11. University of Oxford Commonwealth Forestry Institute. The bark is smooth and light grey to grey-brown, usually peeling into irregular flakes that ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
The Hitchhiker's Guide To The Galaxy
''The Hitchhiker's Guide to the Galaxy'' is a Science fiction comedy, comedy science fiction franchise created by Douglas Adams. Originally a The Hitchhiker's Guide to the Galaxy (radio series), radio sitcom broadcast over two series on BBC Radio 4 between 1978 and 1980, it was soon adapted to other formats, including both novels and comic books; a The Hitchhiker's Guide to the Galaxy (TV series), 1981 BBC television series; a The Hitchhiker's Guide to the Galaxy (video game), 1984 text adventure game; stage shows; and a The Hitchhiker's Guide to the Galaxy (film), 2005 feature film. ''The Hitchhiker's Guide to the Galaxy'' is an international multimedia phenomenon; the novels are the most widely distributed, having been translated into more than 30 languages by 2005. The first novel, ''The Hitchhiker's Guide to the Galaxy (novel), The Hitchhiker's Guide to the Galaxy'' (1979), has been ranked fourth on the BBC's The Big Read poll. The sixth novel, ''And Another Thing... (no ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Douglas Adams
Douglas Noel Adams (11 March 1952 – 11 May 2001) was an English author, humorist, and screenwriter, best known as the creator of ''The Hitchhiker's Guide to the Galaxy''. Originally a 1978 BBC radio comedy, ''The Hitchhiker's Guide to the Galaxy'' evolved into a "trilogy" of six (or five, according to the author) books which sold more than 15 million copies in his life. It was made into a television series, several stage plays, comics, a video game, and a 2005 feature film. Adams's contribution to UK radio is commemorated in The Radio Academy's Hall of Fame. Adams wrote ''Dirk Gently's Holistic Detective Agency'' (1987) and '' The Long Dark Tea-Time of the Soul'' (1988), and co-wrote '' The Meaning of Liff'' (1983), '' The Deeper Meaning of Liff'' (1990) and '' Last Chance to See'' (1990). He wrote two stories for the television series ''Doctor Who'', including the unaired serial '' Shada'', co-wrote '' City of Death'' (1979), and served as script editor for its 1 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
