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Antarctic Circle
The Antarctic Circle is the most southerly of the five major circles of latitude that mark maps of Earth. The region south of this circle is known as the Antarctic, and the zone immediately to the north is called the Southern Temperate Zone. South of the Antarctic Circle, the Sun is above the horizon for 24 continuous hours at least once per year (and therefore visible at solar midnight) and the centre of the Sun (ignoring refraction) is below the horizon for 24 continuous hours at least once per year (and therefore not visible at solar noon); this is also true within the Arctic Circle, the Antarctic Circle’s counterpart in the Northern Hemisphere. The position of the Antarctic Circle is not fixed and, not taking account of the nutation, currently runs south of the Equator. This figure may be slightly inaccurate because it does not allow for the effects of astronomical nutation, which can be up to 10″. Its latitude depends on the Earth's axial tilt, which fluctuates within ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
December Solstice
The December solstice, also known as the southern solstice, is the solstice that occurs each December – typically on 21 December, but may vary by one day in either direction according to the Gregorian calendar. In the Northern Hemisphere, the December solstice is the winter solstice (the day with the shortest period of daylight), whilst in the Southern Hemisphere it is the summer solstice (the day with the longest period of daylight). During December solstice, the Sun is directly over the Tropic of Capricorn, located in the Southern Hemisphere. The December solstice is often seen as the middle of winter in the Northern Hemisphere and the middle of summer in the Southern Hemisphere. Solar year The December-solstice solar year is the solar year based on the December solstice. It is thus the length of time between adjacent December solstices. The length of the December-solstice year has been relatively stable between 6000 BC and AD 2000, in the range of 49 minutes 30 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Antarctica
Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean (also known as the Antarctic Ocean), it contains the geographic South Pole. Antarctica is the fifth-largest continent, being about 40% larger than Europe, and has an area of . Most of Antarctica is covered by the Antarctic ice sheet, with an average thickness of . Antarctica is, on average, the coldest, driest, and windiest of the continents, and it has the highest average elevation. It is mainly a polar desert, with annual Climate of Antarctica#Precipitation, precipitation of over along the coast and far less inland. About 70% of the world's freshwater reserves are frozen in Antarctica, which, if melted, would raise global sea levels by almost . Antarctica holds the record for the Lowest temperature recorded on Earth, lowest measured temperature on Earth, . The coastal regions can reach temperatures over in the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Continent
A continent is any of several large geographical regions. Continents are generally identified by convention (norm), convention rather than any strict criteria. A continent could be a single large landmass, a part of a very large landmass, as in the case of Asia or Europe within Eurasia, or a landmass and nearby islands within its continental shelf. Due to these varying definitions, the number of continents varies; up to seven or as few as four geographical regions are commonly regarded as continents. Most English-speaking world, English-speaking countries recognize seven regions as continents. In order from largest to smallest in area, these seven regions are Asia, Africa, North America, South America, Antarctica, Europe, and Australia (continent), Australia (sometimes called Oceania or Australasia). Different variations with fewer continents merge some of these regions; examples of this are merging Asia and Europe into Eurasia, "Most people recognize seven continents—Asia, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Whaling
Whaling is the hunting of whales for their products such as meat and blubber, which can be turned into a type of oil that was important in the Industrial Revolution. Whaling was practiced as an organized industry as early as 875 AD. By the 16th century, it had become the principal industry in the Basque coastal regions of Spain and France. The whaling industry spread throughout the world and became very profitable in terms of trade and resources. Some regions of the world's oceans, along the animals' migration routes, had a particularly dense whale population and became targets for large concentrations of whaling ships, and the industry continued to grow well into the 20th century. The depletion of some whale species to near extinction led to the banning of whaling in many countries by 1969 and to an international cessation of whaling as an industry in the late 1980s. Archaeological evidence suggests the earliest known forms of whaling date to at least 3000 BC, practiced by the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Research Stations In Antarctica
Multiple governments have set up permanent research stations in Antarctica and these bases are widely distributed. Unlike the drifting ice stations set up in the Arctic, the current research stations of the Antarctic are constructed either on rocks or on ice that are (for practical purposes) fixed in place. Many of these stations are demographics of Antarctica, staffed throughout the year. Of the 56 signatories to the Antarctic Treaty System, Antarctic Treaty, a total of 55 countries (as of 2023) operate seasonal (summer) and year-round research stations on the continent. The number of people performing and supporting scientific research on the continent and nearby islands varies from approximately 4,800 during the summer to around 1,200 during the winter (June). In addition to these permanent stations, approximately Antarctic field camps, 30 field camps are established each summer to support specific projects. History First bases During the Heroic Age of Antarctic Explo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Antarctic Circle Icberg
The Antarctic (, ; commonly ) is the polar region of Earth that surrounds the South Pole, lying within the Antarctic Circle. It is diametrically opposite of the Arctic region around the North Pole. The Antarctic comprises the continent of Antarctica, the Kerguelen Plateau, and other island territories located on the Antarctic Plate or south of the Antarctic Convergence. The Antarctic region includes the ice shelves, waters, and all the island territories in the Southern Ocean situated south of the Antarctic Convergence, a zone approximately wide and varying in latitude seasonally. The region covers some 20 percent of the Southern Hemisphere, of which 5.5 percent (14 million km2) is the surface area of the Antarctica continent itself. All of the land and ice shelves south of 60°S latitude are administered under the Antarctic Treaty System. Biogeographically, the Antarctic realm is one of eight biogeographic realms on Earth's land surface. Climate change in Antarcti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mirage
A mirage is a naturally-occurring optical phenomenon in which light rays bend via refraction to produce a displaced image of distant objects or the sky. The word comes to English via the French ''(se) mirer'', from the Latin ''mirari'', meaning "to look at, to wonder at". Mirages can be categorized as "inferior" (meaning lower), "superior" (meaning higher) and " Fata Morgana", one kind of superior mirage consisting of a series of unusually elaborate, vertically stacked images, which form one rapidly-changing mirage. In contrast to a hallucination, a mirage is a real optical phenomenon that can be captured on camera, since light rays are actually refracted to form the false image at the observer's location. What the image appears to represent, however, is determined by the interpretive faculties of the human mind. For example, inferior images on land are very easily mistaken for the reflections from a small body of water. Inferior mirage In an inferior mirage, the mirage im ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Winter Solstice
The winter solstice, or hibernal solstice, occurs when either of Earth's geographical pole, poles reaches its maximum axial tilt, tilt away from the Sun. This happens twice yearly, once in each hemisphere (Northern Hemisphere, Northern and Southern Hemisphere, Southern). For that hemisphere, the winter solstice is the day with the shortest daytime, period of daylight and longest night of the year, and when the Sun is at its lowest culmination, daily maximum elevation in the sky. Each Polar Circle, polar region experiences polar night, continuous darkness or twilight around its winter solstice. The opposite event is the summer solstice. The winter solstice occurs during the hemisphere's winter. In the Northern Hemisphere, this is the December solstice (December 21 or 22) and in the Southern Hemisphere, this is the June solstice (June 20 or 21). Although the winter solstice itself lasts only a moment, the term also refers to the day on which it occurs. Traditionally, in many Tem ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Minute And Second Of Arc
A minute of arc, arcminute (abbreviated as arcmin), arc minute, or minute arc, denoted by the symbol , is a unit of Angular unit, angular measurement equal to of a Degree (angle), degree. Since one degree is of a turn (geometry), turn, or complete rotation, one arcminute is of a turn. The nautical miles, nautical mile (nmi) was originally defined as the meridian arc, arc length of a minute of latitude on a spherical Earth, so the actual Earth's circumference is very near . A minute of arc is of a radian. A second of arc, arcsecond (abbreviated as arcsec), or arc second, denoted by the symbol , is a unit of Angular unit, angular measurement equal to of a minute of arc, of a degree, of a turn, and (about ) of a radian. These units originated in Babylonian astronomy as sexagesimal (base 60) subdivisions of the degree; they are used in fields that involve very small angles, such as astronomy, optometry, ophthalmology, optics, navigation, land surveying, and marksmanship. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Summer Solstice
The summer solstice or estival solstice occurs when one of Earth's poles has its maximum tilt toward the Sun. It happens twice yearly, once in each hemisphere ( Northern and Southern). The summer solstice is the day with the longest period of daylight and shortest night of the year in that hemisphere, when the sun is at its highest position in the sky. At either pole there is continuous daylight at the time of its summer solstice. The opposite event is the winter solstice. The summer solstice occurs during the hemisphere's summer. In the Northern Hemisphere, this is the June solstice (20, 21 or 22 June) and in the Southern Hemisphere, this is the December solstice (20, 21, 22 or 23 of December). Since prehistory, the summer solstice has been a significant time of year in many cultures, and has been marked by festivals and rituals. Traditionally, in temperate regions (especially Europe), the summer solstice is seen as the middle of summer and referred to as midsum ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mirage
A mirage is a naturally-occurring optical phenomenon in which light rays bend via refraction to produce a displaced image of distant objects or the sky. The word comes to English via the French ''(se) mirer'', from the Latin ''mirari'', meaning "to look at, to wonder at". Mirages can be categorized as "inferior" (meaning lower), "superior" (meaning higher) and " Fata Morgana", one kind of superior mirage consisting of a series of unusually elaborate, vertically stacked images, which form one rapidly-changing mirage. In contrast to a hallucination, a mirage is a real optical phenomenon that can be captured on camera, since light rays are actually refracted to form the false image at the observer's location. What the image appears to represent, however, is determined by the interpretive faculties of the human mind. For example, inferior images on land are very easily mistaken for the reflections from a small body of water. Inferior mirage In an inferior mirage, the mirage im ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
