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774–775 Carbon-14 Spike
The 774–775 carbon-14 spike is an observed increase of 1.2% in the concentration of carbon-14 isotope in tree rings dated to 774 or 775, which is about 20 times as high as the normal background rate of variation. It was discovered during a study of Japanese cedar trees, with the year of occurrence determined through dendrochronology. A surge in beryllium isotope , detected in Antarctic ice cores, has also been associated with the 774–775 event. It is known as the Miyake event or the Charlemagne event and it produced the largest and most rapid rise in carbon-14 ever recorded. The event appears to have been global, with the same carbon-14 signal found in tree rings from Germany, Russia, the United States, Finland and New Zealand. The signal exhibits a sharp increase of around 1.2% followed by a slow decline (see Figure 1), which is typical for an instant production of carbon-14 in the atmosphere, indicating that the event was short in duration. The globally averaged product ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carbon-14
Carbon-14, C-14, or radiocarbon, is a radioactive isotope of carbon with an atomic nucleus containing 6 protons and 8 neutrons. Its presence in organic materials is the basis of the radiocarbon dating method pioneered by Willard Libby and colleagues (1949) to date archaeological, geological and hydrogeological samples. Carbon-14 was discovered on February 27, 1940, by Martin Kamen and Sam Ruben at the University of California Radiation Laboratory in Berkeley, California. Its existence had been suggested by Franz Kurie in 1934. There are three naturally occurring isotopes of carbon on Earth: carbon-12 (), which makes up 99% of all carbon on Earth; carbon-13 (), which makes up 1%; and carbon-14 (), which occurs in trace amounts, making up about 1 or 1.5 atoms per 1012 atoms of carbon in the atmosphere. Carbon-12 and carbon-13 are both stable, while carbon-14 is unstable and has a half-life of 5,730 ± 40 years. Carbon-14 decays into nitrogen-14 () through beta decay. A gra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kingdom Of Kent
la, Regnum Cantuariorum , conventional_long_name = Kingdom of the Kentish , common_name = Kent , era = Heptarchy , status = vassal , status_text = , government_type = Monarchy , event_start = , date_start = , year_start = c. 455 , event_end = , date_end = , year_end = 871 , event1 = , date_event1 = , event2 = , date_event2 = , event3 = , date_event3 = , event4 = , date_event4 = , p1 = Sub-Roman Britain , flag_p1 = Vexilloid of the Roman Empire.svg , border_p1 = no , s1 = Kingdom of England , flag_s1 = Flag of Wessex.svg , border_s1 = no , image_coat = , symbol = , symbol_ty ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
993–994 Carbon-14 Spike
The 993–994 carbon-14 spike was a rapid 0.91% increase in carbon-14 isotope content from tree rings. This event was also confirmed with an associated increase of beryllium-10 in Antarctic ice core samples, supporting the hypothesis that this event was of solar origin. There were several astronomical observations during this time that correspond with the 14C and 10Be spikes, but these texts are few and far between. In 2021, a scientific paper used the 993–994 carbon-14 spike as a benchmark in dendrochronology (tree-ring studies) to precisely determine that Vikings were present in L’Anse aux Meadows in Newfoundland exactly 1000 years prior, in 1021 AD. Historical observations The solar storm hypothesis is heavily supported by several observations of aurora events from late 992 in Korea, Germany and Ireland, usually describing a red sky, presumably due to major auroras. These historical observations don't completely prove the cause of the 993-994 14C spike, but show evidence ... [...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] |
Wood
Wood is a porous and fibrous structural tissue found in the stems and roots of trees and other woody plants. It is an organic materiala natural composite of cellulose fibers that are strong in tension and embedded in a matrix of lignin that resists compression. Wood is sometimes defined as only the secondary xylem in the stems of trees, or it is defined more broadly to include the same type of tissue elsewhere such as in the roots of trees or shrubs. In a living tree it performs a support function, enabling woody plants to grow large or to stand up by themselves. It also conveys water and nutrients between the leaves, other growing tissues, and the roots. Wood may also refer to other plant materials with comparable properties, and to material engineered from wood, or woodchips or fiber. Wood has been used for thousands of years for fuel, as a construction material, for making tools and weapons, furniture and paper. More recently it emerged as a feedstock for the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Before Present
Before Present (BP) years, or "years before present", is a time scale used mainly in archaeology, geology and other scientific disciplines to specify when events occurred relative to the origin of practical radiocarbon dating in the 1950s. Because the "present" time changes, standard practice is to use 1 January 1950 as the commencement date (epoch) of the age scale. The abbreviation "BP" has been interpreted retrospectively as "Before Physics", which refers to the time before nuclear weapons testing artificially altered the proportion of the carbon isotopes in the atmosphere, which scientists must now account for. In a convention that is not always observed, many sources restrict the use of BP dates to those produced with radiocarbon dating; the alternative notation RCYBP stands for the explicit "radio carbon years before present". Usage The BP scale is sometimes used for dates established by means other than radiocarbon dating, such as stratigraphy. This usage differs from ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gamma-ray Burst
In gamma-ray astronomy, gamma-ray bursts (GRBs) are immensely energetic explosions that have been observed in distant galaxies. They are the most energetic and luminous electromagnetic events since the Big Bang. Bursts can last from ten milliseconds to several hours. After an initial flash of gamma rays, a longer-lived "afterglow" is usually emitted at longer wavelengths (X-ray, ultraviolet, optical, infrared, microwave and radio). The intense radiation of most observed GRBs is thought to be released during a supernova or superluminous supernova as a high-mass star implodes to form a neutron star or a black hole. A subclass of GRBs appear to originate from the merger of binary neutron stars. The sources of most GRBs are billions of light years away from Earth, implying that the explosions are both extremely energetic (a typical burst releases as much energy in a few seconds as the Sun will in its entire 10-billion-year lifetime) and extremely rare (a few per galaxy per mill ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Solar Flare
A solar flare is an intense localized eruption of electromagnetic radiation in the Sun's atmosphere. Flares occur in active regions and are often, but not always, accompanied by coronal mass ejections, solar particle events, and other solar phenomena. The occurrence of solar flares varies with the 11-year solar cycle. Solar flares are thought to occur when stored magnetic energy in the Sun's atmosphere accelerates charged particles in the surrounding plasma. This results in the emission of electromagnetic radiation across the electromagnetic spectrum. High-energy electromagnetic radiation from solar flares is absorbed by the daylight side of Earth's upper atmosphere, in particular the ionosphere, and does not reach the surface. This absorption can temporarily increase the ionization of the ionosphere which may interfere with short-wave radio communication. The prediction of solar flares is an active area of research. Flares also occur on other stars, where the term ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Solar Particle Event
In solar physics, a solar particle event (SPE), also known as a solar energetic particle (SEP) event or solar radiation storm, is a solar phenomenon which occurs when particles emitted by the Sun, mostly protons, become accelerated either in the Sun's atmosphere during a solar flare or in interplanetary space by a coronal mass ejection shock. Other nuclei such as helium and HZE ions may also be accelerated during the event. These particles can penetrate the Earth's magnetic field and cause partial ionization of the ionosphere. Energetic protons are a significant radiation hazard to spacecraft and astronauts. Description SPEs occur when charged particles in the Sun's atmosphere are accelerated to extremely high velocities. These charged particles, referred to as solar energetic particles, can escape into interplanetary space where they follow the interplanetary magnetic field. When solar energetic particles interact with the Earth's magnetosphere, they are guided by the Eart ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aurora Borealis
An aurora (plural: auroras or aurorae), also commonly known as the polar lights, is a natural light display in Earth's sky, predominantly seen in high-latitude regions (around the Arctic and Antarctic). Auroras display dynamic patterns of brilliant lights that appear as curtains, rays, spirals, or dynamic flickers covering the entire sky. Auroras are the result of disturbances in the magnetosphere caused by the solar wind. Major disturbances result from enhancements in the speed of the solar wind from coronal holes and coronal mass ejections. These disturbances alter the trajectories of charged particles in the magnetospheric plasma. These particles, mainly electrons and protons, precipitate into the upper atmosphere (thermosphere/exosphere). The resulting ionization and excitation of atmospheric constituents emit light of varying colour and complexity. The form of the aurora, occurring within bands around both polar regions, is also dependent on the amount of acceleration im ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Supernova
A supernova is a powerful and luminous explosion of a star. It has the plural form supernovae or supernovas, and is abbreviated SN or SNe. This transient astronomical event occurs during the last evolutionary stages of a massive star or when a white dwarf is triggered into runaway nuclear fusion. The original object, called the ''progenitor'', either collapses to a neutron star or black hole, or is completely destroyed. The peak optical luminosity of a supernova can be comparable to that of an entire galaxy before fading over several weeks or months. Supernovae are more energetic than novae. In Latin, ''nova'' means "new", referring astronomically to what appears to be a temporary new bright star. Adding the prefix "super-" distinguishes supernovae from ordinary novae, which are far less luminous. The word ''supernova'' was coined by Walter Baade and Fritz Zwicky in 1929. The last supernova to be directly observed in the Milky Way was Kepler's Supernova in 1604, ap ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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