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Laschamp Event
The Laschamp or Laschamps 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 end of the Last Glacial Period. It was discovered from geomagnetic anomalies found in the Laschamps lava flows in 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. 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 current strength, and was at about 25% of its current strength when fully reversed. This reduction in geomagnetic field strength resu ... [...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 "permanent" 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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
The Guardian
''The Guardian'' is a British daily newspaper. It was founded in 1821 as ''The Manchester Guardian'', and changed its name in 1959. Along with its sister papers ''The Observer'' and ''The Guardian Weekly'', ''The Guardian'' is part of the Guardian Media Group, owned by the Scott Trust. 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 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. Since 2018, the paper's main news ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Solar Cycle 1
Solar cycle 1 was the first solar cycle since extensive recording of solar sunspot activity began. 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 number of sun ... [...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 nearly periodic 11-year change in the Sun's activity measured in terms of 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 period of minimum activity to a 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 until 1843. Solar activity, driven by ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
National Public Radio
National Public Radio (NPR, stylized in all lowercase) is an American privately and state funded nonprofit media organization headquartered in Washington, D.C., with its NPR West headquarters in Culver City, California. It differs from other non-profit membership media organizations such as the Associated Press, in that it was established by an act of Congress. Most of its member stations are owned by non-profit organizations, including public school districts, colleges, and universities. It serves as a national Radio syndication, syndicator to a network of over 1,000 public radio List of NPR stations, stations in the United States. , NPR employed 840 people. NPR produces and distributes 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 member stations, and among the List of most-listened-to radio programs, most popular radio p ... [...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, while ''Weekend Edition Sunday'' is hosted by Ayesha Rascoe, a White House correspondent for NPR, whose first broadcast as permanent host was March 27, 2022. Rascoe and other NPR correspondents alternated hosting ''Weekend Edition Sunday'', after previous host Lulu Garcia-Navarro departed in October 2021. 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 ... [...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 determining the age of an object containing organic material by using the properties of radiocarbon, a radioactive 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 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 wood or a fragment of bone, provides information that can be used to calc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kauri Tree
''Agathis'', commonly known as kauri or dammara, is a genus of 22 species of evergreen tree. The genus is part of the ancient conifer family Araucariaceae, a group once widespread during the Jurassic and Cretaceous periods, but now largely restricted to the Southern Hemisphere except for a number of extant Malesian ''Agathis''.de Laubenfels, David J. 1988. Coniferales. P. 337–453 in Flora Malesiana, Series I, Vol. 10. Dordrecht: Kluwer Academic. 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 become thicker on more mature trees. The branch structu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
The Hitchhiker's Guide To The Galaxy
''The Hitchhiker's Guide to the Galaxy'' (sometimes referred to as ''HG2G'', ''HHGTTG'', ''H2G2'', or ''tHGttG'') is a comic science fiction, comedy science fiction franchise created by Douglas Adams. Originally The Hitchhiker's Guide to the Galaxy (radio series), a 1978 radio comedy broadcast on BBC Radio 4, it was later adapted to other formats, including novels, stage shows, comic books, a The Hitchhiker's Guide to the Galaxy (TV series), 1981 TV series, a The Hitchhiker's Guide to the Galaxy (video game), 1984 text-based computer game, and The Hitchhiker's Guide to the Galaxy (film), 2005 feature film. ''The Hitchhiker's Guide to the Galaxy'' has become an international multi-media 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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Douglas Adams
Douglas Noel Adams (11 March 1952 – 11 May 2001) was an English author and screenwriter, best known for ''The Hitchhiker's Guide to the Galaxy''. Originally a 1978 BBC radio comedy, ''The Hitchhiker's Guide to the Galaxy'' developed into a "trilogy" of five books that sold more than 15 million copies in his lifetime. It was further developed 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 also 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'', co-wrote ''City of Death'' (1979), and served as script editor for its seventeenth season. He co-wrote the sketch "Patient Abuse" for the final episode of ' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Science Fiction
Science fiction (sometimes shortened to Sci-Fi or SF) is a genre of speculative fiction which typically deals with imaginative and futuristic concepts such as advanced science and technology, space exploration, time travel, parallel universes, extraterrestrial life, sentient artificial intelligence, cybernetics, certain forms of immortality (like mind uploading), and the singularity. Science fiction predicted several existing inventions, such as the atomic bomb, robots, and borazon, whose names entirely match their fictional predecessors. In addition, science fiction might serve as an outlet to facilitate future scientific and technological innovations. Science fiction can trace its roots to ancient mythology. It is also related to fantasy, horror, and superhero fiction and contains many subgenres. Its exact definition has long been disputed among authors, critics, scholars, and readers. Science fiction, in literature, film, television, and other media, has beco ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Population Bottleneck
A population bottleneck or genetic bottleneck is a sharp reduction in the size of a population due to environmental events such as famines, earthquakes, floods, fires, disease, and droughts; or human activities such as specicide, widespread violence or intentional culling, and human population planning. Such events can reduce the variation in the gene pool of a population; thereafter, a smaller population, with a smaller genetic diversity, remains to pass on genes to future generations of offspring through sexual reproduction. Genetic diversity remains lower, increasing only when gene flow from another population occurs or very slowly increasing with time as random mutations occur. This results in a reduction in the robustness of the population and in its ability to adapt to and survive natural selection, selecting environmental changes, such as Climate change (general concept), climate change or a shift in available resources. Alternatively, if survivors of the bottleneck are the i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
