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43-615: The Xingu corydoras ( Corydoras xinguensis ) is a tropical freshwater fish belonging to the subfamily Corydoradinae of the family Callichthyidae . It originates in inland waters in South America , and is found in the upper Xingu River basin in Brazil . It is named for the river in which it is found. In the system of "C-Numbers" developed by the German fishkeeping magazine DATZ to identify undescribed species of Corydoras in

86-511: A break in rainfall during mid-season when the Intertropical Convergence Zone or monsoon trough moves poleward of their location during the middle of the warm season; Typical vegetation in these areas ranges from moist seasonal tropical forests to savannahs . When the wet season occurs during the warm season, or summer , precipitation falls mainly during the late afternoon and early evening hours. The wet season

129-652: A mean value, with a period of 672 years, an idea known as trepidation of the equinoxes. Perhaps the first to realize this was incorrect (during historic time) was Ibn al-Shatir in the fourteenth century and the first to realize that the obliquity is decreasing at a relatively constant rate was Fracastoro in 1538. The first accurate, modern, western observations of the obliquity were probably those of Tycho Brahe from Denmark , about 1584, although observations by several others, including al-Ma'mun , al-Tusi , Purbach , Regiomontanus , and Walther , could have provided similar information. Earth 's axis remains tilted in

172-453: A period of several million years, long-term changes in Earth's orbit , and hence its obliquity, have been investigated. For the past 5 million years, Earth's obliquity has varied between 22°2′33″ and 24°30′16″ , with a mean period of 41,040 years. This cycle is a combination of precession and the largest term in the motion of the ecliptic . For the next 1 million years, the cycle will carry

215-500: Is a time when air quality improves, freshwater quality improves and vegetation grows significantly due to the wet season supplementing flora, leading to crop yields late in the season. Floods and rains cause rivers to overflow their banks, and some animals to retreat to higher ground. Soil nutrients are washed away and erosion increases. The incidence of malaria increases in areas where the rainy season coincides with high temperatures. Animals have adaptation and survival strategies for

258-415: Is quite variable over millions of years and may be in a chaotic state; it varies as much as 0° to 60° over some millions of years, depending on perturbations of the planets. Some authors dispute that Mars's obliquity is chaotic, and show that tidal dissipation and viscous core-mantle coupling are adequate for it to have reached a fully damped state, similar to Mercury and Venus. The occasional shifts in

301-585: Is that the tropics represent a ' Garden of Eden ', a heaven on Earth, a land of rich biodiversity or a tropical paradise. The alternative is that the tropics consist of wild, unconquerable nature. The latter view was often discussed in old Western literature more so than the first. Evidence suggests over time that the view of the tropics as such in popular literature has been supplanted by more well-rounded and sophisticated interpretations. Western scholars tried to theorise why tropical areas were relatively more inhospitable to human civilisations than colder regions of

344-445: Is the angle between an object's rotational axis and its orbital axis, which is the line perpendicular to its orbital plane ; equivalently, it is the angle between its equatorial plane and orbital plane. It differs from orbital inclination . At an obliquity of 0 degrees, the two axes point in the same direction; that is, the rotational axis is perpendicular to the orbital plane. The rotational axis of Earth , for example,

387-507: Is the imaginary line that passes through both the North Pole and South Pole , whereas the Earth's orbital axis is the line perpendicular to the imaginary plane through which the Earth moves as it revolves around the Sun ; the Earth's obliquity or axial tilt is the angle between these two lines. Over the course of an orbital period , the obliquity usually does not change considerably, and

430-680: Is the obliquity and T is tropical centuries from B1900.0 to the date in question. From 1984, the Jet Propulsion Laboratory's DE series of computer-generated ephemerides took over as the fundamental ephemeris of the Astronomical Almanac . Obliquity based on DE200, which analyzed observations from 1911 to 1979, was calculated: where hereafter T is Julian centuries from J2000.0 . JPL's fundamental ephemerides have been continually updated. For instance, according to IAU resolution in 2006 in favor of

473-605: The Andes as far south as the northernmost parts of Chile and Perú . The climate is changing in the tropics, as it is in the rest of the world. The effects of steadily rising concentrations of greenhouse gases on the climate may be less obvious to tropical residents, however, because they are overlain by considerable natural variability. Much of this variability is driven by the El Niño-Southern Oscillation (ENSO) . The Tropics has warmed by 0.7–0.8 °C over

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516-547: The Northern hemisphere when the north pole is directed toward the Sun. Variations in Earth's axial tilt can influence the seasons and is likely a factor in long-term climatic change (also see Milankovitch cycles ) . The exact angular value of the obliquity is found by observation of the motions of Earth and planets over many years. Astronomers produce new fundamental ephemerides as the accuracy of observation improves and as

559-732: The Pantropic . The system of biogeographic realms differs somewhat; the Neotropical realm includes both the Neotropics and temperate South America, and the Paleotropics correspond to the Afrotropical , Indomalayan , Oceanian , and tropical Australasian realms . Flora are plants found in a specific region at a specific time. Some well-known plants that are exclusively found in, originate from, or are often associated with

602-579: The Waterberg Biosphere of South Africa , and eastern Madagascar rainforests. Often the soils of tropical forests are low in nutrient content, making them quite vulnerable to slash-and-burn deforestation techniques, which are sometimes an element of shifting cultivation agricultural systems. In biogeography , the tropics are divided into Paleotropics (Africa, Asia and Australia) and Neotropics (Caribbean, Central America, and South America). Together, they are sometimes referred to as

645-619: The axial tilt of the Earth . The Tropic of Cancer is the Northernmost latitude from which the Sun can ever be seen directly overhead , and the Tropic of Capricorn is the Southernmost. This means that the tropical zone includes everywhere on Earth which is a subsolar point at least once during the solar year . Thus the maximum latitudes of the tropics have equal distances from the equator on either side. Likewise, they approximate

688-426: The orientation of the axis remains the same relative to the background of stars . This causes one pole to be pointed more toward the Sun on one side of the orbit, and more away from the Sun on the other side—the cause of the seasons on Earth. There are two standard methods of specifying a planet's tilt. One way is based on the planet's north pole , defined in relation to the direction of Earth's north pole, and

731-576: The Northern Hemisphere. A popular explanation focused on the differences in climate. Tropical jungles and rainforests have much more humid and hotter weather than colder and drier temperaments of the Northern Hemisphere, giving to a more diverse biosphere. This theme led some scholars to suggest that humid hot climates correlate to human populations lacking control over nature e.g. 'the wild Amazonian rainforests'. Axial tilt#Earth In astronomy , axial tilt , also known as obliquity ,

774-493: The P03 astronomical model, the Astronomical Almanac for 2010 specifies: These expressions for the obliquity are intended for high precision over a relatively short time span, perhaps ± several centuries. Jacques Laskar computed an expression to order T good to 0.02″ over 1000 years and several arcseconds over 10,000 years. where here t is multiples of 10,000 Julian years from J2000.0 . These expressions are for

817-456: The Sun on a planet's equatorial bulge. Like Earth, all of the rocky planets show axial precession. If the precession rate were very fast the obliquity would actually remain fairly constant even as the orbital plane changes. The rate varies due to tidal dissipation and core - mantle interaction, among other things. When a planet's precession rate approaches certain values, orbital resonances may cause large changes in obliquity. The amplitude of

860-545: The absence of the Moon, Earth's obliquity might not be quite so unstable; varying only by about 20–25°. To resolve this contradiction, diffusion rate of obliquity has been calculated, and it was found that it takes more than billions of years for Earth's obliquity to reach near 90°. The Moon's stabilizing effect will continue for less than two billion years. As the Moon continues to recede from Earth due to tidal acceleration , resonances may occur which will cause large oscillations of

903-399: The angle of the Earth's axial tilt. This angle is not perfectly fixed, mainly due to the influence of the moon, but the limits of the tropics are a geographic convention, and their variance from the true latitudes is very small. Many tropical areas have both a dry and a wet season. The wet season , rainy season or green season is the time of year, ranging from one or more months when most of

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946-493: The aquarium hobby, this fish had been assigned numbers "C55", "C105", "C106", "C107", and "C108" until these were correctly identified. The fish will grow in length up to 1.5 inches (3.7 centimeters). It lives in a tropical climate in water with a 6.0–8.0 pH , a water hardness of 2–25 dGH , and a temperature range of 72–79 °F (22–26 °C). It feeds on worms , benthic crustaceans , insects , and plant matter. It lays eggs in dense vegetation and adults do not guard

989-459: The average annual rainfall in a region falls. Areas with wet seasons are disseminated across portions of the tropics and subtropics , some even in temperate regions. Under the Köppen climate classification , for tropical climates , a wet-season month is defined as one or more months where average precipitation is 60 mm (2.4 in) or more. Some areas with pronounced rainy seasons see

1032-433: The axial tilt of Mars have been suggested as an explanation for the appearance and disappearance of rivers and lakes over the course of the existence of Mars. A shift could cause a burst of methane into the atmosphere, causing warming, but then the methane would be destroyed and the climate would become arid again. The obliquities of the outer planets are considered relatively stable. The stellar obliquity ψ s , i.e.

1075-520: The axial tilt of a star with respect to the orbital plane of one of its planets, has been determined for only a few systems. By 2012, 49 stars have had sky-projected spin-orbit misalignment λ has been observed, which serves as a lower limit to ψ s . Most of these measurements rely on the Rossiter–McLaughlin effect . Since the launch of space-based telescopes such as Kepler space telescope , it has been made possible to determine and estimate

1118-431: The contribution having one of the resonant rates is divided by the difference between the resonant rate and the precession rate, so it becomes large when the two are similar. Mercury and Venus have most likely been stabilized by the tidal dissipation of the Sun. Earth was stabilized by the Moon, as mentioned above, but before its formation , Earth, too, could have passed through times of instability. Mars 's obliquity

1161-652: The course of the year, and consequently have the highest temperatures on the planet. Even when not directly overhead, the sun is still close to overhead throughout the year, therefore the tropics also have the lowest seasonal variation on the planet; "winter" and "summer" lose their contrast. Instead, seasons are more commonly divided by precipitation variations than by temperature variations. The tropics maintain wide diversity of local climates, such as rain forests , monsoons , savannahs , deserts , and high altitude snow-capped mountains . The word "tropical" can specifically refer to certain kinds of weather , rather than to

1204-399: The eggs. The Xingu corydoras is of commercial importance in the aquarium trade industry. As they mature they develop a pinkish tinge to their main body colouration which is broken by brown speckles. This Callichthyidae -related article is a stub . You can help Misplaced Pages by expanding it . Tropical Due to the overhead sun, the tropics receive the most solar energy over

1247-460: The geographic region; these usages ought not be confused. The Earth's axial tilt is currently around 23.4° , and therefore so are the latitudes of the tropical circles , marking the boundary of the tropics: specifically, ±23°26′09.8″ (or 23.43605°). The northern one is called the Tropic of Cancer , and the southern is the Tropic of Capricorn . As the Earth's axial tilt changes, so too do

1290-961: The last century—only slightly less than the global average—but a strong El Niño made 1998 the warmest year in most areas, with no significant warming since. Climate models predict a further 1–2 °C warming by 2050 and 1–4 °C by 2100. Tropical plants and animals are those species native to the tropics. Tropical ecosystems may consist of tropical rainforests , seasonal tropical forests , dry (often deciduous) forests , spiny forests, deserts , savannahs, grasslands and other habitat types. There are often wide areas of biodiversity , and species endemism present, particularly in rainforests and seasonal forests. Some examples of important biodiversity and high-endemism ecosystems are El Yunque National Forest in Puerto Rico , Costa Rican and Nicaraguan rainforests, Amazon Rainforest territories of several South American countries, Madagascar dry deciduous forests ,

1333-540: The obliquity between 22°13′44″ and 24°20′50″ . The Moon has a stabilizing effect on Earth's obliquity. Frequency map analysis conducted in 1993 suggested that, in the absence of the Moon, the obliquity could change rapidly due to orbital resonances and chaotic behavior of the Solar System , reaching as high as 90° in as little as a few million years ( also see Orbit of the Moon ). However, more recent numerical simulations made in 2011 indicated that even in

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1376-450: The obliquity of an extrasolar planet. The rotational flattening of the planet and the entourage of moons and/or rings, which are traceable with high-precision photometry provide access to planetary obliquity, ψ p . Many extrasolar planets have since had their obliquity determined, such as Kepler-186f and Kepler-413b . Astrophysicists have applied tidal theories to predict the obliquity of extrasolar planets . It has been shown that

1419-479: The obliquity. All four of the innermost, rocky planets of the Solar System may have had large variations of their obliquity in the past. Since obliquity is the angle between the axis of rotation and the direction perpendicular to the orbital plane, it changes as the orbital plane changes due to the influence of other planets. But the axis of rotation can also move ( axial precession ), due to torque exerted by

1462-504: The other way is based on the planet's positive pole , defined by the right-hand rule : Earth 's orbital plane is known as the ecliptic plane, and Earth's tilt is known to astronomers as the obliquity of the ecliptic , being the angle between the ecliptic and the celestial equator on the celestial sphere . It is denoted by the Greek letter Epsilon ε . Earth currently has an axial tilt of about 23.44°. This value remains about

1505-425: The same direction with reference to the background stars throughout a year (regardless of where it is in its orbit ) due to the gyroscope effect . This means that one pole (and the associated hemisphere of Earth ) will be directed away from the Sun at one side of the orbit, and half an orbit later (half a year later) this pole will be directed towards the Sun. This is the cause of Earth's seasons . Summer occurs in

1548-511: The same relative to a stationary orbital plane throughout the cycles of axial precession . But the ecliptic (i.e., Earth's orbit) moves due to planetary perturbations , and the obliquity of the ecliptic is not a fixed quantity. At present, it is decreasing at a rate of about 46.8″ per century (see details in Short term below) . The ancient Greeks had good measurements of the obliquity since about 350 BCE, when Pytheas of Marseilles measured

1591-574: The shadow of a gnomon at the summer solstice. About 830 CE, the Caliph Al-Mamun of Baghdad directed his astronomers to measure the obliquity, and the result was used in the Arab world for many years. In 1437, Ulugh Beg determined the Earth's axial tilt as 23°30′17″ (23.5047°). During the Middle Ages , it was widely believed that both precession and Earth's obliquity oscillated around

1634-464: The so-called mean obliquity, that is, the obliquity free from short-term variations. Periodic motions of the Moon and of Earth in its orbit cause much smaller (9.2 arcseconds ) short-period (about 18.6 years) oscillations of the rotation axis of Earth, known as nutation , which add a periodic component to Earth's obliquity. The true or instantaneous obliquity includes this nutation. Using numerical methods to simulate Solar System behavior over

1677-516: The tropical and polar circles . The tropics constitute 39.8% of Earth's surface area and contain 36% of Earth's landmass . As of 2014 , the region was home also to 40% of the world's population , and this figure was then projected to reach 50% by 2050. Because of global warming , the weather conditions of the tropics are expanding with areas in the subtropics , having more extreme weather events such as heatwaves and more intense storms. These changes in weather conditions may make certain parts of

1720-469: The tropics include: Tropicality refers to the image of the tropics that people from outside the tropics have of the region, ranging from critical to verging on fetishism. Tropicality gained renewed interest in geographical discourse when French geographer Pierre Gourou published Les pays tropicaux ( The Tropical World in English), in the late 1940s. Tropicality encompassed two major images. One,

1763-568: The tropics uninhabitable. The word "tropic" comes via Latin from Ancient Greek τροπή ( tropē ), meaning "to turn" or "change direction". The tropics are defined as the region between the Tropic of Cancer in the Northern Hemisphere at 23°26′09.8″ (or 23.43605°) N and the Tropic of Capricorn in the Southern Hemisphere at 23°26′09.8″ (or 23.43605°) S; these latitudes correspond to

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1806-426: The understanding of the dynamics increases, and from these ephemerides various astronomical values, including the obliquity, are derived. Annual almanacs are published listing the derived values and methods of use. Until 1983, the Astronomical Almanac 's angular value of the mean obliquity for any date was calculated based on the work of Newcomb , who analyzed positions of the planets until about 1895: where ε

1849-726: The wetter regime. The previous dry season leads to food shortages into the wet season, as the crops have yet to mature. However, regions within the tropics may well not have a tropical climate. Under the Köppen climate classification, much of the area within the geographical tropics is classed not as "tropical" but as "dry" ( arid or semi-arid ), including the Sahara Desert , the Atacama Desert and Australian Outback . Also, there are alpine tundra and snow-capped peaks, including Mauna Kea , Mount Kilimanjaro , Puncak Jaya and

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