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119-522: Visual perception is the ability to interpret the surrounding environment through photopic vision (daytime vision), color vision , scotopic vision (night vision), and mesopic vision (twilight vision), using light in the visible spectrum reflected by objects in the environment. This is different from visual acuity , which refers to how clearly a person sees (for example "20/20 vision"). A person can have problems with visual perceptual processing even if they have 20/20 vision. The resulting perception

238-477: A corruption of Greek mathematical terms. Euclid is best known for his thirteen-book treatise, the Elements ( Ancient Greek : Στοιχεῖα ; Stoicheia ), considered his magnum opus . Much of its content originates from earlier mathematicians, including Eudoxus , Hippocrates of Chios , Thales and Theaetetus , while other theorems are mentioned by Plato and Aristotle. It is difficult to differentiate

357-430: A two-dimensional visual array (on the retina) to a three-dimensional description of the world as output. His stages of vision include: Marr's 2 1 ⁄ 2 D sketch assumes that a depth map is constructed, and that this map is the basis of 3D shape perception. However, both stereoscopic and pictorial perception, as well as monocular viewing, make clear that the perception of 3D shape precedes, and does not rely on,

476-441: A capacity to grow , respond to stimuli , reproduce and, through natural selection , adapt to their environment in successive generations. More complex living organisms can communicate through various means. An ecosystem (also called an environment) is a natural unit consisting of all plants, animals, and micro-organisms ( biotic factors) in an area functioning together with all of the non-living physical ( abiotic ) factors of

595-458: A certain way. But I found it to be completely different." His main experimental finding was that there is only a distinct and clear vision at the line of sight—the optical line that ends at the fovea . Although he did not use these words literally he actually is the father of the modern distinction between foveal and peripheral vision . Isaac Newton (1642–1726/27) was the first to discover through experimentation, by isolating individual colors of

714-502: A continuum, from 100% natural in one extreme to 0% natural in the other. The massive environmental changes of humanity in the Anthropocene have fundamentally effected all natural environments including: climate change , biodiversity loss and pollution from plastic and other chemicals in the air and water . More precisely, we can consider the different aspects or components of an environment, and see that their degree of naturalness

833-637: A decreased food supply for the wildlife in an area. The atmosphere of the Earth serves as a key factor in sustaining the planetary ecosystem. The thin layer of gases that envelops the Earth is held in place by the planet's gravity. Dry air consists of 78% nitrogen , 21% oxygen , 1% argon , inert gases and carbon dioxide . The remaining gases are often referred to as trace gases. The atmosphere includes greenhouse gases such as carbon dioxide, methane, nitrous oxide and ozone. Filtered air includes trace amounts of many other chemical compounds . Air also contains

952-449: A genetic anomaly, a color vision deficiency , sometimes called color blindness will occur. Transduction involves chemical messages sent from the photoreceptors to the bipolar cells to the ganglion cells. Several photoreceptors may send their information to one ganglion cell. There are two types of ganglion cells: red/green and yellow/blue. These neurons constantly fire—even when not stimulated. The brain interprets different colors (and with

1071-413: A lot of information, an image) when the rate of firing of these neurons alters. Red light stimulates the red cone, which in turn stimulates the red/green ganglion cell. Likewise, green light stimulates the green cone, which stimulates the green/red ganglion cell and blue light stimulates the blue cone which stimulates the blue/yellow ganglion cell. The rate of firing of the ganglion cells is increased when it

1190-501: A mechanism for face recognition in macaque monkeys. The inferotemporal cortex has a key role in the task of recognition and differentiation of different objects. A study by MIT shows that subset regions of the IT cortex are in charge of different objects. By selectively shutting off neural activity of many small areas of the cortex, the animal gets alternately unable to distinguish between certain particular pairments of objects. This shows that

1309-596: A mere conjecture. In any event, the contents of Euclid's work demonstrate familiarity with the Platonic geometry tradition. In his Collection , Pappus mentions that Apollonius studied with Euclid's students in Alexandria , and this has been taken to imply that Euclid worked and founded a mathematical tradition there. The city was founded by Alexander the Great in 331 BC, and the rule of Ptolemy I from 306 BC onwards gave it

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1428-500: A more detailed discussion, see Pizlo (2008). A more recent, alternative framework proposes that vision is composed instead of the following three stages: encoding, selection, and decoding. Encoding is to sample and represent visual inputs (e.g., to represent visual inputs as neural activities in the retina). Selection, or attentional selection , is to select a tiny fraction of input information for further processing, e.g., by shifting gaze to an object or visual location to better process

1547-486: A number of other mammals, light enters the eye through the cornea and is focused by the lens onto the retina , a light-sensitive membrane at the back of the eye. The retina serves as a transducer for the conversion of light into neuronal signals. This transduction is achieved by specialized photoreceptive cells of the retina, also known as the rods and cones, which detect the photons of light and respond by producing neural impulses . These signals are transmitted by

1666-454: A pond from many other aquatic terrain features, such as stream pools and tide pools . Humans impact the water in different ways such as modifying rivers (through dams and stream channelization ), urbanization and deforestation . These impact lake levels, groundwater conditions, water pollution, thermal pollution, and marine pollution . Humans modify rivers by using direct channel manipulation. We build dams and reservoirs and manipulate

1785-400: A qualitative and quantitative understanding of the principal areas or spheres of Earth. The Earth's crust or lithosphere , is the outermost solid surface of the planet and is chemically, physically and mechanically different from underlying mantle . It has been generated greatly by igneous processes in which magma cools and solidifies to form solid rock. Beneath the lithosphere lies

1904-430: A river is usually in a channel , made up of a stream bed between banks . In larger rivers there is often also a wider floodplain shaped by waters over-topping the channel. Flood plains may be very wide in relation to the size of the river channel. Rivers are a part of the hydrological cycle . Water within a river is generally collected from precipitation through surface runoff , groundwater recharge , springs and

2023-402: A speculation lacking any experimental foundation. (In eighteenth-century England, Isaac Newton , John Locke , and others, carried the intromission theory of vision forward by insisting that vision involved a process in which rays—composed of actual corporeal matter—emanated from seen objects and entered the seer's mind/sensorium through the eye's aperture.) Both schools of thought relied upon

2142-494: A stability which was relatively unique amid the chaotic wars over dividing Alexander's empire . Ptolemy began a process of hellenization and commissioned numerous constructions, building the massive Musaeum institution, which was a leading center of education. Euclid is speculated to have been among the Musaeum's first scholars. Euclid's date of death is unknown; it has been speculated that he died c.  270 BC . Euclid

2261-507: A variable amount of water vapor and suspensions of water droplets and ice crystals seen as clouds . Many natural substances may be present in tiny amounts in an unfiltered air sample, including dust , pollen and spores , sea spray , volcanic ash and meteoroids . Various industrial pollutants also may be present, such as chlorine (elementary or in compounds), fluorine compounds, elemental mercury , and sulphur compounds such as sulphur dioxide (SO 2 ). The ozone layer of

2380-436: Is a terrain feature , a body of water that is localized to the bottom of basin . A body of water is considered a lake when it is inland, is not part of an ocean and is larger and deeper than a pond . Natural lakes on Earth are generally found in mountainous areas, rift zones and areas with ongoing or recent glaciation . Other lakes are found in endorheic basins or along the courses of mature rivers. In some parts of

2499-439: Is a set of cortical structures, that receive information from striate cortex, as well as each other. Recent descriptions of visual association cortex describe a division into two functional pathways, a ventral and a dorsal pathway. This conjecture is known as the two streams hypothesis . The human visual system is generally believed to be sensitive to visible light in the range of wavelengths between 370 and 730 nanometers of

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2618-411: Is also known as vision , sight , or eyesight (adjectives visual , optical , and ocular , respectively). The various physiological components involved in vision are referred to collectively as the visual system , and are the focus of much research in linguistics , psychology , cognitive science , neuroscience , and molecular biology , collectively referred to as vision science . In humans and

2737-516: Is around 35 parts per thousand (ppt) (3.5%), and nearly all seawater has a salinity in the range of 30 to 38 ppt. Though generally recognized as several separate oceans, these waters comprise one global, interconnected body of salt water often referred to as the World Ocean or global ocean. The deep seabeds are more than half the Earth's surface, and are among the least-modified natural environments. The major oceanic divisions are defined in part by

2856-455: Is found in various kinds of natural body of water . An ocean is a major body of saline water and a component of the hydrosphere. Approximately 71% of the surface of the Earth (an area of some 362 million square kilometers) is covered by ocean, a continuous body of water that is customarily divided into several principal oceans and smaller seas . More than half of this area is over 3,000 meters (9,800 ft) deep. Average oceanic salinity

2975-785: Is from the Old English wildeornes , which in turn derives from wildeor meaning wild beast (wild + deor = beast, deer). From this point of view, it is the wildness of a place that makes it a wilderness. The mere presence or activity of people does not disqualify an area from being "wilderness". Many ecosystems that are, or have been, inhabited or influenced by activities of people may still be considered "wild". This way of looking at wilderness includes areas within which natural processes operate without very noticeable human interference. Wildlife includes all non- domesticated plants, animals and other organisms. Domesticating wild plant and animal species for human benefit has occurred many times all over

3094-420: Is generally considered among the greatest mathematicians of antiquity, and one of the most influential in the history of mathematics . Very little is known of Euclid's life, and most information comes from the scholars Proclus and Pappus of Alexandria many centuries later. Medieval Islamic mathematicians invented a fanciful biography, and medieval Byzantine and early Renaissance scholars mistook him for

3213-500: Is greatly changed into a simplified human environment. Even acts which seem less extreme, such as building a mud hut or a photovoltaic system in the desert , the modified environment becomes an artificial one. Though many animals build things to provide a better environment for themselves, they are not human, hence beaver dams and the works of mound-building termites are thought of as natural. People cannot find absolutely natural environments on Earth,naturalness usually varies in

3332-614: Is in Apollonius' prefatory letter to the Conics (early 2nd century BC): "The third book of the Conics contains many astonishing theorems that are useful for both the syntheses and the determinations of number of solutions of solid loci . Most of these, and the finest of them, are novel. And when we discovered them we realized that Euclid had not made the synthesis of the locus on three and four lines but only an accidental fragment of it, and even that

3451-416: Is increased, the brain would know that the light was red, if the rate was decreased, the brain would know that the color of the light was green. Theories and observations of visual perception have been the main source of inspiration for computer vision (also called machine vision , or computational vision). Special hardware structures and software algorithms provide machines with the capability to interpret

3570-440: Is increasingly rare, wild nature (e.g., unmanaged forests , uncultivated grasslands , wildlife , wildflowers ) can be found in many locations previously inhabited by humans. Goals for the benefit of people and natural systems, commonly expressed by environmental scientists and environmentalists include: In some cultures the term environment is meaningless because there is no separation between people and what they view as

3689-465: Is no royal road to geometry". This anecdote is questionable since a very similar interaction between Menaechmus and Alexander the Great is recorded from Stobaeus . Both accounts were written in the 5th century AD, neither indicates its source, and neither appears in ancient Greek literature. Any firm dating of Euclid's activity c.  300 BC is called into question by a lack of contemporary references. The earliest original reference to Euclid

Visual perception - Misplaced Pages Continue

3808-568: Is not clear how proponents of this view derive, in principle, the relevant probabilities required by the Bayesian equation. Models based on this idea have been used to describe various visual perceptual functions, such as the perception of motion , the perception of depth , and figure-ground perception . The "wholly empirical theory of perception" is a related and newer approach that rationalizes visual perception without explicitly invoking Bayesian formalisms. Gestalt psychologists working primarily in

3927-443: Is not uniform. If, for instance, in an agricultural field, the mineralogic composition and the structure of its soil are similar to those of an undisturbed forest soil, but the structure is quite different. Earth science generally recognizes four spheres, the lithosphere , the hydrosphere , the atmosphere and the biosphere as correspondent to rocks , water , air and life respectively. Some scientists include as part of

4046-418: Is often referred to as 'Euclid of Alexandria' to differentiate him from the earlier philosopher Euclid of Megara , a pupil of Socrates included in dialogues of Plato with whom he was historically conflated. Valerius Maximus , the 1st century AD Roman compiler of anecdotes, mistakenly substituted Euclid's name for Eudoxus (4th century BC) as the mathematician to whom Plato sent those asking how to double

4165-690: Is presumed that he was of Greek descent, but his birthplace is unknown. Proclus held that Euclid followed the Platonic tradition , but there is no definitive confirmation for this. It is unlikely he was a contemporary of Plato, so it is often presumed that he was educated by Plato's disciples at the Platonic Academy in Athens. Historian Thomas Heath supported this theory, noting that most capable geometers lived in Athens, including many of those whose work Euclid built on; historian Michalis Sialaros considers this

4284-414: Is signaled by one cone and decreased (inhibited) when it is signaled by the other cone. The first color in the name of the ganglion cell is the color that excites it and the second is the color that inhibits it. i.e.: A red cone would excite the red/green ganglion cell and the green cone would inhibit the red/green ganglion cell. This is an opponent process . If the rate of firing of a red/green ganglion cell

4403-671: Is the application of science and technology to predict the state of the atmosphere for a future time and a given location. The atmosphere is a chaotic system , and small changes to one part of the system can grow to have large effects on the system as a whole. Human attempts to control the weather have occurred throughout human history, and there is evidence that civilized human activity such as agriculture and industry has inadvertently modified weather patterns. Evidence suggests that life on Earth has existed for about 3.7 billion years. All known life forms share fundamental molecular mechanisms, and based on these observations, theories on

4522-430: Is the one originally developed by Wladimir Köppen . The Thornthwaite system , in use since 1948, uses evapotranspiration as well as temperature and precipitation information to study animal species diversity and the potential impacts of climate changes . Weather is a set of all the phenomena occurring in a given atmospheric area at a given time . Most weather phenomena occur in the troposphere , just below

4641-501: Is the process through which energy from environmental stimuli is converted to neural activity. The retina contains three different cell layers: photoreceptor layer, bipolar cell layer and ganglion cell layer. The photoreceptor layer where transduction occurs is farthest from the lens. It contains photoreceptors with different sensitivities called rods and cones. The cones are responsible for color perception and are of three distinct types labelled red, green and blue. Rods are responsible for

4760-525: Is thought to have written many lost works . The English name 'Euclid' is the anglicized version of the Ancient Greek name Eukleídes ( Εὐκλείδης ). It is derived from ' eu- ' ( εὖ ; 'well') and 'klês' ( -κλῆς ; 'fame'), meaning "renowned, glorious". In English, by metonymy , 'Euclid' can mean his most well-known work, Euclid's Elements , or a copy thereof, and is sometimes synonymous with 'geometry'. As with many ancient Greek mathematicians ,

4879-540: Is unknown if Euclid intended the Elements as a textbook, but its method of presentation makes it a natural fit. As a whole, the authorial voice remains general and impersonal. Book 1 of the Elements is foundational for the entire text. It begins with a series of 20 definitions for basic geometric concepts such as lines , angles and various regular polygons . Euclid then presents 10 assumptions (see table, right), grouped into five postulates (axioms) and five common notions. These assumptions are intended to provide

Visual perception - Misplaced Pages Continue

4998-569: Is used to rapidly scan a particular scene/image. Lastly, pursuit movement is smooth eye movement and is used to follow objects in motion. There is considerable evidence that face and object recognition are accomplished by distinct systems. For example, prosopagnosic patients show deficits in face, but not object processing, while object agnosic patients (most notably, patient C.K. ) show deficits in object processing with spared face processing. Behaviorally, it has been shown that faces, but not objects, are subject to inversion effects, leading to

5117-477: The Elements in works whose dates are firmly known are not until the 2nd century AD, by Galen and Alexander of Aphrodisias ; by this time it was a standard school text. Some ancient Greek mathematicians mention Euclid by name, but he is usually referred to as "ὁ στοιχειώτης" ("the author of Elements "). In the Middle Ages, some scholars contended Euclid was not a historical personage and that his name arose from

5236-416: The Elements reveals authorial control beyond the limits of a mere editor". The Elements does not exclusively discuss geometry as is sometimes believed. It is traditionally divided into three topics: plane geometry (books 1–6), basic number theory (books 7–10) and solid geometry (books 11–13)—though book 5 (on proportions) and 10 (on irrational lines) do not exactly fit this scheme. The heart of

5355-600: The Elements was published in 1570 by Henry Billingsley and John Dee . The mathematician Oliver Byrne published a well-known version of the Elements in 1847 entitled The First Six Books of the Elements of Euclid in Which Coloured Diagrams and Symbols Are Used Instead of Letters for the Greater Ease of Learners , which included colored diagrams intended to increase its pedagogical effect. David Hilbert authored

5474-447: The Elements , Euclid deduced the theorems from a small set of axioms . He also wrote works on perspective , conic sections , spherical geometry , number theory , and mathematical rigour . In addition to the Elements , Euclid wrote a central early text in the optics field, Optics , and lesser-known works including Data and Phaenomena . Euclid's authorship of On Divisions of Figures and Catoptrics has been questioned. He

5593-412: The Elements , at least five works of Euclid have survived to the present day. They follow the same logical structure as Elements , with definitions and proved propositions. Four other works are credibly attributed to Euclid, but have been lost. Euclid is generally considered with Archimedes and Apollonius of Perga as among the greatest mathematicians of antiquity. Many commentators cite him as one of

5712-544: The Elements , book 10 is by far the largest and most complex, dealing with irrational numbers in the context of magnitudes. The final three books (11–13) primarily discuss solid geometry . By introducing a list of 37 definitions, Book 11 contextualizes the next two. Although its foundational character resembles Book 1, unlike the latter it features no axiomatic system or postulates. The three sections of Book 11 include content on solid geometry (1–19), solid angles (20–23) and parallelepipedal solids (24–37). In addition to

5831-540: The area of triangles and parallelograms (35–45); and the Pythagorean theorem (46–48). The last of these includes the earliest surviving proof of the Pythagorean theorem, described by Sialaros as "remarkably delicate". Book 2 is traditionally understood as concerning " geometric algebra ", though this interpretation has been heavily debated since the 1970s; critics describe the characterization as anachronistic, since

5950-742: The continents , various archipelagos and other criteria, these divisions are : (in descending order of size) the Pacific Ocean , the Atlantic Ocean , the Indian Ocean , the Southern Ocean and the Arctic Ocean . A river is a natural watercourse , usually freshwater , flowing toward an ocean , a lake , a sea or another river. A few rivers simply flow into the ground and dry up completely without reaching another body of water. The water in

6069-400: The electromagnetic spectrum . However, some research suggests that humans can perceive light in wavelengths down to 340 nanometers (UV-A), especially the young. Under optimal conditions these limits of human perception can extend to 310 nm ( UV ) to 1100 nm ( NIR ). The major problem in visual perception is that what people see is not simply a translation of retinal stimuli (i.e., the image on

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6188-408: The mitigation of greenhouse gases that are causing climatic changes, on developing adaptative strategies to global warming, to assist humans, other animal, and plant species, ecosystems, regions and nations in adjusting to the effects of global warming . Some examples of recent collaboration to address climate change and global warming include: A significantly profound challenge is to identify

6307-430: The optic nerve , from the retina upstream to central ganglia in the brain . The lateral geniculate nucleus , which transmits the information to the visual cortex . Signals from the retina also travel directly from the retina to the superior colliculus . The lateral geniculate nucleus sends signals to the primary visual cortex , also called striate cortex. Extrastriate cortex , also called visual association cortex

6426-501: The pentagon . Book 5 is among the work's most important sections and presents what is usually termed as the "general theory of proportion". Book 6 utilizes the "theory of ratios " in the context of plane geometry. It is built almost entirely of its first proposition: "Triangles and parallelograms which are under the same height are to one another as their bases". From Book 7 onwards, the mathematician Benno Artmann  [ de ] notes that "Euclid starts afresh. Nothing from

6545-421: The stratosphere . Weather refers, generally, to day-to-day temperature and precipitation activity, whereas climate is the term for the average atmospheric conditions over longer periods of time. When used without qualification, "weather" is understood to be the weather of Earth. Weather occurs due to density (temperature and moisture) differences between one place and another. These differences can occur due to

6664-524: The "father of geometry", he is chiefly known for the Elements treatise, which established the foundations of geometry that largely dominated the field until the early 19th century. His system, now referred to as Euclidean geometry , involved innovations in combination with a synthesis of theories from earlier Greek mathematicians, including Eudoxus of Cnidus , Hippocrates of Chios , Thales and Theaetetus . With Archimedes and Apollonius of Perga , Euclid

6783-465: The 1930s and 1940s raised many of the research questions that are studied by vision scientists today. The Gestalt Laws of Organization have guided the study of how people perceive visual components as organized patterns or wholes, instead of many different parts. "Gestalt" is a German word that partially translates to "configuration or pattern" along with "whole or emergent structure". According to this theory, there are eight main factors that determine how

6902-518: The Earth's atmosphere plays an important role in reducing the amount of ultraviolet (UV) radiation that reaches the surface. As DNA is readily damaged by UV light, this serves to protect life at the surface. The atmosphere also retains heat during the night, thereby reducing the daily temperature extremes. Earth's atmosphere can be divided into five main layers. These layers are mainly determined by whether temperature increases or decreases with altitude. From highest to lowest, these layers are: Within

7021-457: The IT cortex is divided into regions that respond to different and particular visual features. In a similar way, certain particular patches and regions of the cortex are more involved in face recognition than other object recognition. Some studies tend to show that rather than the uniform global image, some particular features and regions of interest of the objects are key elements when the brain needs to recognise an object in an image. In this way,

7140-415: The abiotic constituents of their biotope . A more significant number or variety of species or biological diversity of an ecosystem may contribute to greater resilience of an ecosystem because there are more species present at a location to respond to change and thus "absorb" or reduce its effects. This reduces the effect before the ecosystem's structure changes to a different state. This is not universally

7259-425: The biological manifestation of life is characterized by organization , metabolism , growth , adaptation , response to stimuli and reproduction . Life may also be said to be simply the characteristic state of organisms . In biology , the science of living organisms, "life" is the condition which distinguishes active organisms from inorganic matter , including the capacity for growth, functional activity and

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7378-562: The brain. The following fixations jump from face to face. They might even permit comparisons between faces. It may be concluded that the icon face is a very attractive search icon within the peripheral field of vision. The foveal vision adds detailed information to the peripheral first impression . It can also be noted that there are different types of eye movements: fixational eye movements ( microsaccades , ocular drift, and tremor), vergence movements, saccadic movements and pursuit movements. Fixations are comparably static points where

7497-407: The case and there is no proven relationship between the species diversity of an ecosystem and its ability to provide goods and services on a sustainable level. The term ecosystem can also pertain to human-made environments, such as human ecosystems and human-influenced ecosystems. It can describe any situation where there is relationship between living organisms and their environment. Fewer areas on

7616-495: The claim that faces are "special". Further, face and object processing recruit distinct neural systems. Notably, some have argued that the apparent specialization of the human brain for face processing does not reflect true domain specificity, but rather a more general process of expert-level discrimination within a given class of stimulus, though this latter claim is the subject of substantial debate . Using fMRI and electrophysiology Doris Tsao and colleagues described brain regions and

7735-425: The continual change preceding death. A diverse variety of living organisms (life forms) can be found in the biosphere on Earth, and properties common to these organisms—plants, animals , fungi , protists , archaea , and bacteria —are a carbon - and water-based cellular form with complex organization and heritable genetic information. Living organisms undergo metabolism , maintain homeostasis , possess

7854-441: The cube . Perhaps on the basis of this mention of a mathematical Euclid roughly a century early, Euclid became mixed up with Euclid of Megara in medieval Byzantine sources (now lost), eventually leading Euclid the mathematician to be ascribed details of both men's biographies and described as Megarensis ( lit.   ' of Megara ' ). The Byzantine scholar Theodore Metochites ( c.  1300 ) explicitly conflated

7973-478: The details of Euclid's life are mostly unknown. He is accepted as the author of four mostly extant treatises—the Elements , Optics , Data , Phaenomena —but besides this, there is nothing known for certain of him. The traditional narrative mainly follows the 5th century AD account by Proclus in his Commentary on the First Book of Euclid's Elements , as well as a few anecdotes from Pappus of Alexandria in

8092-624: The direction of the rivers and water path. Dams can usefully create reservoirs and hydroelectric power. However, reservoirs and dams may negatively impact the environment and wildlife. Dams stop fish migration and the movement of organisms downstream. Urbanization affects the environment because of deforestation and changing lake levels, groundwater conditions, etc. Deforestation and urbanization go hand in hand. Deforestation may cause flooding, declining stream flow and changes in riverside vegetation. The changing vegetation occurs because when trees cannot get adequate water they start to deteriorate, leading to

8211-505: The earlier philosopher Euclid of Megara . It is now generally accepted that he spent his career in Alexandria and lived around 300 BC, after Plato 's students and before Archimedes. There is some speculation that Euclid studied at the Platonic Academy and later taught at the Musaeum ; he is regarded as bridging the earlier Platonic tradition in Athens with the later tradition of Alexandria. In

8330-442: The early 4th century. According to Proclus, Euclid lived shortly after several of Plato 's ( d.  347 BC) followers and before the mathematician Archimedes ( c.  287  – c.  212 BC); specifically, Proclus placed Euclid during the rule of Ptolemy I ( r.  305/304–282 BC). Euclid's birthdate is unknown; some scholars estimate around 330 or 325 BC, but others refrain from speculating. It

8449-409: The environment. Central to the ecosystem concept is the idea that living organisms are continually engaged in a highly interrelated set of relationships with every other element constituting the environment in which they exist. Eugene Odum , one of the founders of the science of ecology , stated: "Any unit that includes all of the organisms (i.e.: the "community") in a given area interacting with

8568-472: The extinction of natural habitats, which in turn leads to a reduction in wildlife population. The most recent report from the Intergovernmental Panel on Climate Change (the group of the leading climate scientists in the world) concluded that the earth will warm anywhere from 2.7 to almost 11 degrees Fahrenheit (1.5 to 6 degrees Celsius) between 1990 and 2100. Efforts have been increasingly focused on

8687-450: The eye rests. However, the eye is never completely still, and gaze position will drift. These drifts are in turn corrected by microsaccades, very small fixational eye movements. Vergence movements involve the cooperation of both eyes to allow for an image to fall on the same area of both retinas. This results in a single focused image. Saccadic movements is the type of eye movement that makes jumps from one position to another position and

8806-415: The eyes and are intercepted by visual objects. If an object was seen directly it was by 'means of rays' coming out of the eyes and again falling on the object. A refracted image was, however, seen by 'means of rays' as well, which came out of the eyes, traversed through the air, and after refraction, fell on the visible object which was sighted as the result of the movement of the rays from the eye. This theory

8925-486: The fictionalization was done to strengthen the connection between a revered mathematician and the Arab world. There are also numerous anecdotal stories concerning to Euclid, all of uncertain historicity, which "picture him as a kindly and gentle old man". The best known of these is Proclus' story about Ptolemy asking Euclid if there was a quicker path to learning geometry than reading his Elements , which Euclid replied with "there

9044-586: The five principal layers determined by temperature there are several layers determined by other properties. The dangers of global warming are being increasingly studied by a wide global consortium of scientists. These scientists are increasingly concerned about the potential long-term effects of global warming on our natural environment and on the planet. Of particular concern is how climate change and global warming caused by anthropogenic , or human-made releases of greenhouse gases , most notably carbon dioxide , can act interactively and have adverse effects upon

9163-411: The foundations of even nascent algebra occurred many centuries later. The second book has a more focused scope and mostly provides algebraic theorems to accompany various geometric shapes. It focuses on the area of rectangles and squares (see Quadrature ), and leads up to a geometric precursor of the law of cosines . Book 3 focuses on circles, while the 4th discusses regular polygons , especially

9282-463: The human vision is vulnerable to small particular changes to the image, such as disrupting the edges of the object, modifying texture or any small change in a crucial region of the image. Studies of people whose sight has been restored after a long blindness reveal that they cannot necessarily recognize objects and faces (as opposed to color, motion, and simple geometric shapes). Some hypothesize that being blind during childhood prevents some part of

9401-469: The images coming from a camera or a sensor. For instance, the 2022 Toyota 86 uses the Subaru EyeSight system for driver-assist technology . Biophysical environment In contrast to the natural environment is the built environment . Built environments are where humans have fundamentally transformed landscapes such as urban settings and agricultural land conversion , the natural environment

9520-426: The inference process goes wrong) has yielded much insight into what sort of assumptions the visual system makes. Another type of unconscious inference hypothesis (based on probabilities) has recently been revived in so-called Bayesian studies of visual perception. Proponents of this approach consider that the visual system performs some form of Bayesian inference to derive a perception from sensory data. However, it

9639-492: The logical basis for every subsequent theorem, i.e. serve as an axiomatic system . The common notions exclusively concern the comparison of magnitudes . While postulates 1 through 4 are relatively straightforward, the 5th is known as the parallel postulate and particularly famous. Book 1 also includes 48 propositions, which can be loosely divided into those concerning basic theorems and constructions of plane geometry and triangle congruence (1–26); parallel lines (27–34);

9758-593: The lunar crater Euclides , and the minor planet 4354 Euclides . The Elements is often considered after the Bible as the most frequently translated, published, and studied book in the Western World 's history. With Aristotle's Metaphysics , the Elements is perhaps the most successful ancient Greek text, and was the dominant mathematical textbook in the Medieval Arab and Latin worlds. The first English edition of

9877-415: The mantle which is heated by the decay of radioactive elements . The mantle though solid is in a state of rheic convection . This convection process causes the lithospheric plates to move, albeit slowly. The resulting process is known as plate tectonics . Volcanoes result primarily from the melting of subducted crust material or of rising mantle at mid-ocean ridges and mantle plumes . Most water

9996-466: The most influential figures in the history of mathematics . The geometrical system established by the Elements long dominated the field; however, today that system is often referred to as ' Euclidean geometry ' to distinguish it from other non-Euclidean geometries discovered in the early 19th century. Among Euclid's many namesakes are the European Space Agency 's (ESA) Euclid spacecraft,

10115-410: The natural environmental dynamics in contrast to environmental changes not within natural variances. A common solution is to adapt a static view neglecting natural variances to exist. Methodologically, this view could be defended when looking at processes which change slowly and short time series, while the problem arrives when fast processes turns essential in the object of the study. Climate looks at

10234-459: The natural world, or their surroundings. Specifically in the United States and Arabian countries many native cultures do not recognize the "environment", or see themselves as environmentalists. Euclid Euclid ( / ˈ j uː k l ɪ d / ; Ancient Greek : Εὐκλείδης ; fl.  300 BC) was an ancient Greek mathematician active as a geometer and logician . Considered

10353-409: The origin of life attempt to find a mechanism explaining the formation of a primordial single cell organism from which all life originates. There are many different hypotheses regarding the path that might have been taken from simple organic molecules via pre-cellular life to protocells and metabolism. Although there is no universal agreement on the definition of life, scientists generally accept that

10472-426: The perception of objects in low light. Photoreceptors contain within them a special chemical called a photopigment, which is embedded in the membrane of the lamellae; a single human rod contains approximately 10 million of them. The photopigment molecules consist of two parts: an opsin (a protein) and retinal (a lipid). There are 3 specific photopigments (each with their own wavelength sensitivity) that respond across

10591-420: The perception of the depth of points. It is not clear how a preliminary depth map could, in principle, be constructed, nor how this would address the question of figure-ground organization, or grouping. The role of perceptual organizing constraints, overlooked by Marr, in the production of 3D shape percepts from binocularly-viewed 3D objects has been demonstrated empirically for the case of 3D wire objects, e.g. For

10710-438: The physical environment so that a flow of energy leads to clearly defined trophic structure, biotic diversity, and material cycles (i.e.: exchange of materials between living and nonliving parts) within the system is an ecosystem." The human ecosystem concept is then grounded in the deconstruction of the human/nature dichotomy , and the emergent premise that all species are ecologically integrated with each other, as well as with

10829-400: The planet, and has a major impact on the environment, both positive and negative. Wildlife can be found in all ecosystems. Deserts, rain forests, plains, and other areas—including the most developed urban sites—all have distinct forms of wildlife. While the term in popular culture usually refers to animals that are untouched by civilized human factors, most scientists agree that wildlife around

10948-415: The planet, its natural environment and humans' existence. It is clear the planet is warming, and warming rapidly. This is due to the greenhouse effect , which is caused by greenhouse gases, which trap heat inside the Earth's atmosphere because of their more complex molecular structure which allows them to vibrate and in turn trap heat and release it back towards the Earth. This warming is also responsible for

11067-528: The preceding books is used". Number theory is covered by books 7 to 10, the former beginning with a set of 22 definitions for parity , prime numbers and other arithmetic-related concepts. Book 7 includes the Euclidean algorithm , a method for finding the greatest common divisor of two numbers. The 8th book discusses geometric progressions , while book 9 includes the proposition, now called Euclid's theorem , that there are infinitely many prime numbers . Of

11186-475: The principle that "like is only known by like", and thus upon the notion that the eye was composed of some "internal fire" that interacted with the "external fire" of visible light and made vision possible. Plato makes this assertion in his dialogue Timaeus (45b and 46b), as does Empedocles (as reported by Aristotle in his De Sensu , DK frag. B17). Alhazen (965 – c. 1040) carried out many investigations and experiments on visual perception, extended

11305-412: The problems that the visual system must overcome. The algorithmic level attempts to identify the strategy that may be used to solve these problems. Finally, the implementational level attempts to explain how solutions to these problems are realized in neural circuitry. Marr suggested that it is possible to investigate vision at any of these levels independently. Marr described vision as proceeding from

11424-443: The release of water stored in glaciers and snowpacks. Small rivers may also be called by several other names, including stream , creek and brook. Their current is confined within a bed and stream banks . Streams play an important corridor role in connecting fragmented habitats and thus in conserving biodiversity . The study of streams and waterways in general is known as surface hydrology . A lake (from Latin lacus )

11543-411: The retina), with the brain altering the basic information taken in. Thus people interested in perception have long struggled to explain what visual processing does to create what is actually seen. There were two major ancient Greek schools, providing a primitive explanation of how vision works. The first was the " emission theory " of vision which maintained that vision occurs when rays emanate from

11662-434: The right shows what may happen during the first two seconds of visual inspection. While the background is out of focus, representing the peripheral vision , the first eye movement goes to the boots of the man (just because they are very near the starting fixation and have a reasonable contrast). Eye movements serve the function of attentional selection , i.e., to select a fraction of all visual inputs for deeper processing by

11781-434: The spectrum of light passing through a prism , that the visually perceived color of objects appeared due to the character of light the objects reflected, and that these divided colors could not be changed into any other color, which was contrary to scientific expectation of the day. Hermann von Helmholtz is often credited with the first modern study of visual perception. Helmholtz examined the human eye and concluded that it

11900-417: The spectrum of visible light. When the appropriate wavelengths (those that the specific photopigment is sensitive to) hit the photoreceptor, the photopigment splits into two, which sends a signal to the bipolar cell layer, which in turn sends a signal to the ganglion cells, the axons of which form the optic nerve and transmit the information to the brain. If a particular cone type is missing or abnormal, due to

12019-627: The spheres of the Earth, the cryosphere (corresponding to ice ) as a distinct portion of the hydrosphere, as well as the pedosphere (to soil ) as an active and intermixed sphere. Earth science (also known as geoscience, the geographical sciences or the Earth Sciences), is an all-embracing term for the sciences related to the planet Earth . There are four major disciplines in earth sciences, namely geography , geology , geophysics and geodesy . These major disciplines use physics , chemistry , biology , chronology and mathematics to build

12138-495: The statistics of temperature , humidity , atmospheric pressure , wind , rainfall , atmospheric particle count and other meteorological elements in a given region over long periods of time. Weather , on the other hand, is the present condition of these same elements over periods up to two weeks. Climates can be classified according to the average and typical ranges of different variables, most commonly temperature and precipitation. The most commonly used classification scheme

12257-434: The sun angle at any particular spot, which varies by latitude from the tropics. The strong temperature contrast between polar and tropical air gives rise to the jet stream . Weather systems in the mid-latitudes , such as extratropical cyclones , are caused by instabilities of the jet stream flow. Because the Earth's axis is tilted relative to its orbital plane, sunlight is incident at different angles at different times of

12376-775: The surface of the earth today exist free from human contact, although some genuine wilderness areas continue to exist without any forms of human intervention. Global biogeochemical cycles are critical to life, most notably those of water , oxygen , carbon , nitrogen and phosphorus . Wilderness is generally defined as a natural environment on Earth that has not been significantly modified by human activity. The WILD Foundation goes into more detail, defining wilderness as: "The most intact, undisturbed wild natural areas left on our planet – those last truly wild places that humans do not control and have not developed with roads, pipelines or other industrial infrastructure." Wilderness areas and protected parks are considered important for

12495-420: The survival of certain species , ecological studies, conservation , solitude, and recreation . Wilderness is deeply valued for cultural, spiritual, moral , and aesthetic reasons. Some nature writers believe wilderness areas are vital for the human spirit and creativity. The word, "wilderness", derives from the notion of wildness ; in other words that which is not controllable by humans. The word etymology

12614-538: The text is the theorems scattered throughout. Using Aristotle's terminology, these may be generally separated into two categories: "first principles" and "second principles". The first group includes statements labeled as a "definition" ( Ancient Greek : ὅρος or ὁρισμός ), "postulate" ( αἴτημα ), or a "common notion" ( κοινὴ ἔννοια ); only the first book includes postulates—later known as axioms —and common notions. The second group consists of propositions, presented alongside mathematical proofs and diagrams. It

12733-769: The two Euclids, as did printer Erhard Ratdolt 's 1482 editio princeps of Campanus of Novara 's Latin translation of the Elements . After the mathematician Bartolomeo Zamberti  [ fr ; de ] appended most of the extant biographical fragments about either Euclid to the preface of his 1505 translation of the Elements , subsequent publications passed on this identification. Later Renaissance scholars, particularly Peter Ramus , reevaluated this claim, proving it false via issues in chronology and contradiction in early sources. Medieval Arabic sources give vast amounts of information concerning Euclid's life, but are completely unverifiable. Most scholars consider them of dubious authenticity; Heath in particular contends that

12852-399: The understanding of specific problems in vision, he identified three levels of analysis: the computational , algorithmic and implementational levels. Many vision scientists, including Tomaso Poggio , have embraced these levels of analysis and employed them to further characterize vision from a computational perspective. The computational level addresses, at a high level of abstraction,

12971-428: The visual signals at that location. Decoding is to infer or recognize the selected input signals, e.g., to recognize the object at the center of gaze as somebody's face. In this framework, attentional selection starts at the primary visual cortex along the visual pathway, and the attentional constraints impose a dichotomy between the central and peripheral visual fields for visual recognition or decoding. Transduction

13090-492: The visual system automatically groups elements into patterns: Proximity, Similarity, Closure, Symmetry, Common Fate (i.e. common motion), Continuity as well as Good Gestalt (pattern that is regular, simple, and orderly) and Past Experience. During the 1960s, technical development permitted the continuous registration of eye movement during reading, in picture viewing, and later, in visual problem solving, and when headset-cameras became available, also during driving. The picture to

13209-430: The visual system necessary for these higher-level tasks from developing properly. The general belief that a critical period lasts until age 5 or 6 was challenged by a 2007 study that found that older patients could improve these abilities with years of exposure. In the 1970s, David Marr developed a multi-level theory of vision, which analyzed the process of vision at different levels of abstraction. In order to focus on

13328-498: The work of Euclid from that of his predecessors, especially because the Elements essentially superseded much earlier and now-lost Greek mathematics. The classicist Markus Asper concludes that "apparently Euclid's achievement consists of assembling accepted mathematical knowledge into a cogent order and adding new proofs to fill in the gaps" and the historian Serafina Cuomo described it as a "reservoir of results". Despite this, Sialaros furthers that "the remarkably tight structure of

13447-419: The work of Ptolemy on binocular vision , and commented on the anatomical works of Galen. He was the first person to explain that vision occurs when light bounces on an object and then is directed to one's eyes. Leonardo da Vinci (1452–1519) is believed to be the first to recognize the special optical qualities of the eye. He wrote "The function of the human eye ... was described by a large number of authors in

13566-411: The world is (now) impacted by human activities. It is the common understanding of natural environment that underlies environmentalism — a broad political , social and philosophical movement that advocates various actions and policies in the interest of protecting what nature remains in the natural environment, or restoring or expanding the role of nature in this environment. While true wilderness

13685-826: The world, there are many lakes because of chaotic drainage patterns left over from the last ice age . All lakes are temporary over geologic time scales, as they will slowly fill in with sediments or spill out of the basin containing them. A pond is a body of standing water , either natural or human-made, that is usually smaller than a lake . A wide variety of human-made bodies of water are classified as ponds, including water gardens designed for aesthetic ornamentation, fish ponds designed for commercial fish breeding and solar ponds designed to store thermal energy. Ponds and lakes are distinguished from streams by their current speed . While currents in streams are easily observed, ponds and lakes possess thermally driven micro-currents and moderate wind-driven currents. These features distinguish

13804-465: The year. On the Earth's surface, temperatures usually range ±40 °C (100 °F to −40 °F) annually. Over thousands of years, changes in the Earth's orbit have affected the amount and distribution of solar energy received by the Earth and influenced long-term climate. Surface temperature differences in turn cause pressure differences. Higher altitudes are cooler than lower altitudes due to differences in compressional heating. Weather forecasting

13923-437: Was championed by scholars who were followers of Euclid 's Optics and Ptolemy 's Optics . The second school advocated the so-called 'intromission' approach which sees vision as coming from something entering the eyes representative of the object. With its main propagator Aristotle ( De Sensu ), and his followers, this theory seems to have some contact with modern theories of what vision really is, but it remained only

14042-520: Was incapable of producing a high-quality image. Insufficient information seemed to make vision impossible. He, therefore, concluded that vision could only be the result of some form of "unconscious inference", coining that term in 1867. He proposed the brain was making assumptions and conclusions from incomplete data, based on previous experiences. Inference requires prior experience of the world. Examples of well-known assumptions, based on visual experience, are: The study of visual illusions (cases when

14161-556: Was not felicitously done." The Elements is speculated to have been at least partly in circulation by the 3rd century BC, as Archimedes and Apollonius take several of its propositions for granted; however, Archimedes employs an older variant of the theory of proportions than the one found in the Elements . The oldest physical copies of material included in the Elements , dating from roughly 100 AD, can be found on papyrus fragments unearthed in an ancient rubbish heap from Oxyrhynchus , Roman Egypt . The oldest extant direct citations to

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