Earth

Question

This piglix contains articles or sub-piglix about Earth

Answer 1

Jaramillo reversal

The Jaramillo reversal was a reversal and excursion of the Earth's magnetic field that occurred approximately one million years ago. In the geological time scale it was a "short-term" positive reversal in the then-dominant Matuyama reversed magnetic chronozone; its beginning is widely dated to 990,000 years before the present (BP), and its end to 950,000 BP (though an alternative date of 1.07 million years ago to 990,000 is also found in the scientific literature).

The causes and mechanisms of short-term reversals and excursions like the Jaramillo, as well as the major field reversals like the Brunhes–Matuyama reversal, are subjects of study and dispute among researchers. One theory associates the Jaramillo with the Bosumtwi impact event, as evidenced by a tektite strewnfield in the Ivory Coast, though this hypothesis has been claimed as "highly speculative" and "refuted".

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Answer 2

List of artificial radiation belts

Artificial radiation belts are radiation belts that have been created by high altitude nuclear explosions.

The table above only lists those high-altitude nuclear explosions for which a reference exists in the open (unclassified) English-language scientific literature to persistent artificial radiation belts resulting from the explosion.

The Starfish Prime radiation belt had, by far, the greatest intensity and duration of any of the artificial radiation belts.

The Starfish Prime radiation belt damaged the United Kingdom Satellite Ariel 1 and the United States satellites, Traac, Transit 4B, Injun I and Telstar I.  It also damaged the Soviet satellite Cosmos V.  All of these satellites failed completely within several months of the Starfish detonation.

Telstar I lasted the longest of the satellites damaged by the Starfish Prime radiation, with its complete failure occurring on February 21, 1963.

In Los Alamos Scientific Laboratory report LA-6405, Herman Hoerlin gave the following explanation of the history of the original Argus experiment and of how the nuclear detonations lead to the development of artificial radiation belts.

Before the discovery of the natural Van Allen belts in 1958, N. C. Christofilos had suggested in October 1957 that many observable geophysical effects could be produced by a nuclear explosion at high altitude in the upper atmosphere. This suggestion was reduced to practice with the sponsorship of the Advanced Research Project Agency (ARPA) of the Department of Defense and under the overall direction of Herbert York, who was then Chief Scientist of ARPA. It required only four months from the time it was decided to proceed with the tests until the first bomb was exploded. The code name of the project was Argus. Three events took place in the South Atlantic. ... Following these events, artificial belts of trapped radiation were observed.

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Answer 3

List of Earth flybys

List of Earth flybys is a list of cases where spacecraft incidentally performed Earth flybys, typically for a gravity assist to another body.

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Answer 4

Earth%27s location in the Universe

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Answer 5

Magmatic water

Magmatic water or juvenile water is water that exists within, and in equilibrium with, a magma or water-rich volatile fluids that are derived from a magma. This magmatic water is released to the atmosphere during a volcanic eruption. Magmatic water may also be released as hydrothermal fluids during the late stages of magmatic crystallization or solidification within the Earth's crust. The crystallization of hydroxyl bearing amphibole and mica minerals acts to contain part of the magmatic water within a solidified igneous rock. Ultimate sources of this magmatic water includes water and hydrous minerals in rocks melted during subduction as well as primordial water brought up from the deep mantle.

Water has limited solubility in silicate melts ranging from essentially zero at surface pressure to up to as much as 10% at 1100 °C and 5 kbar of pressure for a granitic melt. Solubility is lower for more mafic magmas. As the temperature and pressure drop during emplacement and cooling of the magma a separate aqueous phase will exsolve. This aqueous phase will be enriched in other volatile and silicate incompatible species such as the metals: copper, lead, zinc, silver and gold; alkalis and alkaline earths and others, including: lithium, beryllium, boron, rubidium; and volatiles: fluorine, chlorine and carbon dioxide.

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Answer 6

Earth mass

Earth mass (M_⊕, where ⊕ is the standard astronomical symbol for planet Earth) is the unit of mass equal to that of Earth. This value includes the atmosphere but excludes the moon. The current best estimate for Earth mass is M_⊕ = 7024597220000000000â™ (5.9722±0.0006)×10²⁴ kg Earth mass is a standard unit of mass in astronomy that is used to indicate the masses of other planets, including rocky terrestrial planets and exoplanets.

The mass of Earth is estimated to be:

which can be expressed in terms of solar mass as:

The ratio of Earth mass to lunar mass has been measured to great accuracy. The current best estimate is:

The mass of Earth is measured indirectly by determining other quantities such as Earth's density, gravity, or gravitational constant.

Modern methods of determining the mass of Earth involve calculating the gravitational coefficient of the Earth and dividing by the Newtonian constant of gravitation,

The GM_⊕ product is determined using laser ranging data from Earth-orbiting satellites. The GM_⊕ product can also be calculated by observing the motion of the Moon or the period of a pendulum at various elevations. These methods are less precise than observations of artificial satellites.

Earlier efforts (after 1798) to determine Earth's mass involved measuring G directly as in the Cavendish experiment. Earth's mass could be then found by combining two equations; Newton's second law, and Newton's law of universal gravitation:

Substituting earth's gravity, g for the acceleration term, and combining the two equations gives

The equation can then be solved for M_⊕

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Answer 7

Mediocrity principle

The mediocrity principle is the philosophical notion that "if an item is drawn at random from one of several sets or categories, it's likelier to come from the most numerous category than from any one of the less numerous categories". The principle has been taken to suggest that there is nothing very unusual about the evolution of the Solar System, Earth's history, the evolution of biological complexity, human evolution, or any one nation. It is a heuristic in the vein of the Copernican principle, and is sometimes used as a philosophical statement about the place of humanity. The idea is to assume mediocrity, rather than starting with the assumption that a phenomenon is special, privileged, exceptional, or even superior.

The mediocrity principle suggests, given the existence of life on Earth, that life typically exists on Earth-like planets throughout the universe.

David Deutsch argues that the mediocrity principle is not actually correct from a physical point of view, either in reference to our part of the universe or to our species. Deutsch refers to Stephen Hawking's quote that "The human race is just a chemical scum on a moderate-sized planet, orbiting around a very average star in the outer suburb of one among a hundred billion galaxies", writing that our neighborhood in the universe is not typical (80% of the universe's matter is dark matter) and that a concentration of mass such as the Solar System is an "isolated, uncommon phenomenon". He also argues with Richard Dawkins' opinion that humans, as result of natural evolution, are limited to the capabilities of our species — Deutsch responds that even though evolution did not give humans the ability to detect neutrinos, scientists can currently detect them, significantly expanding their capabilities beyond what is available as a result of evolution.

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Answer 8

Earth%27s orbit

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Answer 9

Origin of water on Earth

The origin of water on Earth, or the reason that there is clearly more liquid water on Earth than on the other rocky planets of the Solar System, is not completely understood. There exist numerous more or less mutually compatible hypotheses as to how water may have accumulated on Earth's surface over the past 4.5 billion years in sufficient quantity to form oceans.

Comets, trans-Neptunian objects or water-rich meteoroids (protoplanets) from the outer reaches of the asteroid belt colliding with Earth may have brought water to the world's oceans. Measurements of the ratio of the hydrogen isotopes deuterium and protium point to asteroids, since similar percentage impurities in carbon-rich chondrites were found in oceanic water, whereas previous measurement of the isotopes' concentrations in comets and trans-Neptunian objects correspond only slightly to water on Earth.

Large enough Planetesimals were heated by the decay of aluminium isotope. This could cause water to rise to the surface. Recent studies suggest that water with similar deuterium-to-hydrogen ratio was already available at the time of Earth's formation, as evidenced in ancient "eucrites" meteorites originating from the asteroid Vesta.

That Earth's water originated purely from comets is implausible, since a result of measurements of the isotope ratios of deuterium to protium (D/H ratio) in the four comets Halley, Hyakutake, Hale-Bopp, and 67P/Churyumov–Gerasimenko, by researchers such as David Jewitt, is approximately double that of oceanic water. What is however unclear is whether these comets are representative of those from the Kuiper Belt. According to Alessandro Morbidelli, the largest part of today's water comes from protoplanets formed in the outer asteroid belt that plunged towards Earth, as indicated by the D/H proportions in carbon-rich chondrites. The water in carbon-rich chondrites point to a similar D/H ratio as oceanic water. Nevertheless, mechanisms have been proposed to suggest that the D/H-ratio of oceanic water may have increased significantly throughout Earth's history. Such a proposal is consistent with the possibility that a significant amount of the water on Earth was already present during the planet's early evolution.

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Answer 10

Circle of Poison

The Circle of Poison (COP) refers to the export of domestically banned pesticides for use on foods elsewhere, some of which returns by way of import. The "circle" is complete when the toxic chemicals that were exported are then used to grow fruit, meat, and produce that are imported and available for domestic consumption. This circle was first identified relative to the United States but the relationship also exists between other nations of the Global North and South.

In the book, Circle of Poison: Pesticides and People in a Hungry World, David Weir (journalist) and Mark Schapiro of the Oakland-based Center for Investigative Reporting present an investigative study of how certain dangerous chemicals, which are banned in the U.S., still enter back into the United States and the American diet through food imports. Many restricted chemicals, especially pesticides, are produced in the U.S. and exported to the global south. The banned chemicals are then used on 'cash crops', which are subsequently exported to the U.S. and other industrialized countries for high profit.

The investigative study done by Wier and Schapiro showed that the highly potent and dangerous chemicals used in domestic agriculture led to a public clamor for strict regulations, and that pesticides contribute to the expansion of an export-oriented agriculture at the expense of food production for local needs. Even where they are applied to food crops, pesticide are often linked to the Green Revolution, which can mean more hunger even while it raises production. Pesticides, they aregue, are no solution to hunger-they bypass the needs of the poor who 'have neither money to buy food nor the land to grow it on'. Moreover, they claim because agrochemical companies are profit driven, they have tailored the regulations to permit unrestricted export of dangerous chemicals. Wier and Schapiro argue that this loophole has been a disaster.

In April 1991, the "Circle of Poison prevention Act" was introduced by Senator Patrick Leahy (D-VT) in the U.S. Senate and by Representatives Mike Synar (D-OK) and Leon Panetta (D-CA) in the House. This bill would have placed strict controls on exports of hazardous chemicals. Similar legislation passed both houses of Congress but died in conference committee.

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