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Zemlja
Zemlja je planeta na kojoj živi čovjek i jedina nama poznata planeta na kojoj postoji život. Ona je treća planeta po udaljenosti od Sunca i najveća terestrijalna planeta u Sunčevom sistemu. Planeta Zemlja ima jedan prirodni satelit, Mjesec.
Smatra se da je Zemlja nastala prije otprilike 4,5 milijardi godina.
NAPOMENA: Riječ zemlja ima još dva značenja -
tlo i država
Atmosfera
Zemljina atmosfera sastoji se od više slojeva, a proteže se više stotina kilometara iznad površine. Sastavljena je od 78% dušika, 21% kisika, 1% argona, te nešto vodene pare, karbon dioksida i drugih plinova.
Slojevi atmosfere:
- troposfera je najdonji i najgušći dio atmosfere u kojem se događaju sve vremenske pojave. U ovom sloju temperatura opada s visinom. Sadrži velike količine vodene pare.
- stratosfera sadrži ozon koji nas štiti od štetnog zračenja iz Svemira. Temperatura je u nižim slojevima stratosfere stalna, a u višim slojevima raste. Vjetrovi koji pušu u stratosferi dostižu brzine od nekoliko stotina km/h.
- mezosfera je sloj u kojemu dolazi do naglog pada temperature.
- jonosfera (termosfera) sadrži jone, električki nabijene čestice. U ovom se sloju pod utjecajem Sunčevog vjetra stvara polarna svjetlost. Temperatura raste, sve do visine 400 km.
- egzosfera je prijelazno područje prema vakuumu. Ovo je sloj s vrlo razrijeđenim plinom, prostire se iznad 400 km visine.
Prelazna područja između slojeva atmosfere su tropopauza, stratopauza i mezopauza.
Biosfera
Koliko je do sada poznato, Zemlja je jedino mjesto na kojem postoji život. Životni oblici čine biosferu planete. Smatra se da je razvoj biosfere na Zemlji započeo prije otprilike 3,5 milijardi godina. Životne zajednice (biomi) nastanjuju gotovo cijelu površinu Zemlje, od vrlo rijetko nastanjenih arktičkih i antarktičkih područja, do gusto naseljenih područja oko ekvatora.
Hidrosfera
Zemlja je jedina planeta u Sunčevom sistemu na čijoj površini ima tečne vode. Voda pokriva 71% Zemljine površine. Najveći dio vodenih površina su morske (97%), a manji dio čini slatka voda (3%). Tekuća voda održava se na površini Zemlje zahvaljujući spoju odgovarajućih pogodnih uvjeta: orbite oko Sunca, vulkanizma, gravitacije, efekta staklenika, magnetskog polja i atmosfere bogate kisikom.
Zemljina orbita nalazi se izvan područja u kojem je dovoljno toplo da bi se održala tečna voda. Bez malog efekta staklenika koji zadržava toplotu u atmosferi, voda na Zemlji bi se zaledila. Paleontološki nalazi upućuju na razdoblje u Zemljinoj historiji u kojem je privremeno nestao efekt staklenika, a površina se smrznula tokom 10 do 100 miliona godina.
Na planetama poput Venere vodena para se pod uticajem ultraljubičastog svjetla razlaže na vodik i kisik, vodik se ionizira i (djelovanjem Sunčevog vjetra) odlazi iz vanjskih slojeva atmosfere. Oslobođeni kisik se veže u mineralne spojeve na površini. Ovaj proces je spor, ali se smatra da je glavni razlog zbog kojega na Veneri nema vode. Na Zemlji ozonski omotač apsorbira većinu ultraljubičastog zračenja u višim slojevima atmosfere i smanjuje opisani proces. Osim toga, magnetosfera štiti ionosferu od izravnog uticaja Sunčevog vjetra.
Vulkanski procesi stalno izbacuju vodenu paru iz unutrašnjosti. Procijenjeno je da minerali u Zemljinom plaštu sadrže 10 puta više vode nego je ima u oceanima, iako većina nje nikada neće biti oslobođena.
Unutrašnjost
Slično kao i kod drugih terestrijalnih planeta, unutrašnjost Zemlje je podijeljena u više slojeva:
- vanjska kruta kora
- tečni omotač (plašt)
- tečno vanjsko jezgro
- unutrašnje kruto jezgro
Kora
Kora je vanjski sloj Zemlje, dubine 5 do 35 km. Sastavljena je od silikatnih stijena. Na granici kore i omotača nalazi se Moho-sloj, poznat i kao Mohorovičićev diskontinuitet prema hrvatskom naučniku Andriji Mohorovičiću.
Materijal iz unutrašnjosti stalno izlazi na površinu kroz vulkanske otvore i pukotine na okeanskom dnu. Većina Zemljine površine je mlađa od 100 miliona godina, dok su najstariji dijelovi kore stari 4,4 milijarde godina.
Omotač
Ispod kore, do dubine 2900 km nalazi se omotač. Sastoji se od spojeva bogatih željezom i magnezijem. S dubinom raste i pritisak, a s pritiskom se mijenja i tačka topljenja. Stijene u višim slojevima nalaze se u polurastopljenom, plastičnom stanju, a u većim dubinama su krute. Materijal se kreće ("teče") vrlo sporo zbog visoke viskoznosti.
Jezgro
Kako je prosječna gustoća Zemlje 5515 kg/m3, a gustoća materijala na površini samo oko 3000 kg/m3, očito se gušći materijal mora nalaziti u jezgru. U vrijeme nastajanja Zemlje, prije 4.5 milijardi godina Zemlja je većinom bila rastopljena. U procesu koji nazivamo diferencijacija teži elementi su potonuli prema središtu, a lakši su se skupili uz površinu. Zato je jezgra sastavljena uglavnom od željeza (80%), nikla i silicija.
Jezgro dijelimo u dva dijela, unutrašnju kruto jezgro poluprečnika oko 1250 km i vanjsko rastopljeno jezgro koje se pruža do poluprečnika 3500 km. Smatra se da je unutrašnje jezgro u kristalnom obliku, a vanjska sastavljena od tekućeg željeza i nikla. Smatra se da strujanje ovog rastopljenog metala (i miješanje koje nastaje zbog Zemljine rotacije) stvara Zemljino magnetsko polje.
Category:Sunčev sistem
ja:地球
ko:지구
minnan:Tē-kiû
ms:Bumi
simple:Earth
Čovjek
Ljudi ili ljudska bića definišu sebe na biološki, sociološki i duhovni (spiritualni) način. Biološki, ljudi se klasifikuju kao vrsta Homo sapiens (na latinskom "mudri čovjek" ili "misleći čovjek"): dvonogi primat super-porodice Hominoidea, zajedno sa ostalim apes: čimpanze, gorile, orangutanii gibon.
Humans have an erect body carriage that frees their upper limbs for manipulating objects and a highly developed brain capable of abstract reasoning, speech, language, and introspection. Bipedal locomotion appears to have evolved before the development of a large brain. The origins of bipedal locomotion and of its role in the evolution of the human brain are topics of ongoing research.
The human mind has several distinct attributes. It is responsible for complex behaviour, especially language. Curiosity and observation have led to a variety of explanations for consciousness and the relation between mind and body. Psychology attempts to study behaviour from a scientific point of view. Religious perspectives emphasise a soul, qi or atman as the essence of being, and are often characterised by the belief in and worship of God, gods, spirits, or other people. Philosophy, especially philosophy of mind, attempts to fathom the depths of each of these perspectives. Art, music and literature are often used in expressing these concepts and feelings.
Like all primates, humans are inherently social. They create complex social structures composed of co-operating and competing groups. These range from nations and states down to families. Seeking to understand and manipulate the world around them has led to the development of technology and science. Artifacts, beliefs, myths, rituals, values, and social norms have all helped to form humanity's culture.
Terminology
In general, the word "people" is a collective or plural term for any specific group of individual persons. However, when used to refer to a group of humans possessing a common ethnic, cultural or national unitary characteristic or identity, "people" is a singular count noun, and as such takes an "s" in the plural (examples: "the English-speaking peoples of the world", "the indigenous peoples of Brazil").
ethnic
Juvenile males are called boys, adult males men, juvenile females girls, and adult females women. Humans are commonly referred to as persons or people, and collectively as Man (capital M), mankind, humankind, humanity, or the human race. Until the 20th century, "human" was only used adjectivally ("pertaining to mankind"). Nominal use of "human" (plural "humans") is short for "human being", and not considered good style in traditional English grammar. As an adjective, "human" is used neutrally (as in "human race"), but "human" and especially "humane" may also emphasise positive aspects of human nature, and can be synonymous with "benevolent" (versus "inhumane"; cf. humanitarian).
A distinction is maintained in philosophy and law between the notions "human being", or "man", and "person". The former refers to the species, while the latter refers to a rational agent (see, for example, John Locke's Essay concerning Human Understanding II 27 and Immanuel Kant's Introduction to the Metaphysic of Morals). The term "person" is thus used of non-human animals, and could be used of a mythical being, an artificial intelligence, or an extraterrestrial. An important question in theology and the philosophy of religion concerns whether God is a person.
In Latin, "humanus" is the adjectival form of the noun "homo", translated as "man" (to include males and females). The Old English word "man" could also have this generic meaning, as demonstrated by such compounds as "wifman" ("female person") → "wiman" → "woman". For the etymology of "man" see mannaz.
Biology
Anatomy and physiology
mannaz]
Humans exhibit fully bipedal locomotion. This leaves the forelimbs available for manipulating objects using opposable thumbs.
Humans vary substantially around the mean height and mean weight. Some of this variation is explained by locality and historical factors. Although body size is largely determined by genes, it is also significantly influenced by diet and exercise. The mean height of a North American adult female is 162 centimetres (5 feet 4 inches) and the mean weight is 62 kilograms (137 pounds). North American adult males are typically larger: 175 centimetres (5 feet 9 inches) and 78 kilograms (172 pounds).
Human skin appears to be relatively hairless in comparison to other primates; however, most humans have a larger number of hairs on their body than a chimpanzee. The main difference is that human hairs are shorter, finer, and less coloured then the average chimpanzee's, thus rendering them harder to see.
The colour of human hair and skin is determined by the presence of coloured pigments called melanins. Most researchers believe that skin darkening was an adaptation that evolved as a defence against UV solar radiation; melanin is an effective sunblock. The skin colour of contemporary humans can range from very dark brown to very pale pink. It is geographically stratified and in general correlates with the environmental level of UV. Human skin and hair colour is controlled in part by the MC1R gene. For example, the red hair and pale skin of some Europeans is the result of mutations in MC1R. Human skin has a capacity to darken (sun tanning) in response to UV exposure. Variation in the ability to sun tan is also controlled in part by MC1R.
sun tanning]
Because humans are bipedal, the pelvic region and spinal column tend to become worn, creating locomotion difficulties in old age.
The individual need for regular intake of food and drink is prominently reflected in human culture, and has led to the development of food science. Failure to obtain food leads to hunger and eventually starvation, while failure to obtain water leads to dehydration and thirst. Both starvation and dehydration cause death if not alleviated. In modern times, obesity amongst humans has increased to almost epidemic proportions, leading to health complications and increased mortality in some developed countries, and is becoming problematic elsewhere.
The average sleep requirement is between seven and eight hours a day for an adult and nine to ten hours for a child. Elderly people usually sleep for six to seven hours. It is common, however, in modern societies for people to get less sleep than they need, leading to a state of sleep deprivation.
The human body is subject to an ageing process and to illness. Medicine is the science that explores methods of preserving bodily health.
Life cycle
health]
The human life cycle is similar to that of other placental mammals. New human life develops from conception. An egg is usually fertilised inside the female by sperm from the male through sexual intercourse, though in vitro fertilisation methods are also used. The fertilised egg is called a zygote. The zygote divides inside the female's uterus to become an embryo which over a period of thirty-eight weeks becomes the foetus. At birth, the fully grown foetus is expelled from the female's body and breathes independently as a baby for the first time. At this point, most modern cultures recognise the baby as a person entitled to the full protection of the law, though some jurisdictions extend personhood to human foetuses while they remain in the uterus.
Compared with that of other species, human childbirth is relatively complicated. Painful labours lasting twenty-four hours or more are not uncommon, and may result in injury to the child or the death of the mother, although the chances of a successful labour increased significantly during the twentieth century in wealthier countries. Natural childbirth remains an arguably more dangerous ordeal in remote, underdeveloped regions of the world, though the women who live in these regions have argued that their natural childbirth methods are safer and less traumatic for mother and child.
Natural childbirth
Human children are born after a nine-month gestation period, with typically 3–4 kilograms (6–9 pounds) in weight and 50–60 centimetres (20–24 inches) in height in developed countries. [http://www.childinfo.org/eddb/lbw] Helpless at birth, they continue to grow for some years, typically reaching sexual maturity at twelve to fifteen years of age. Boys continue growing for some time after this, reaching their maximum height around the age of eighteen. These values vary too, depending on genes and environment.
The human lifespan can be split into a number of stages: infancy, childhood, adolescence, young adulthood, maturity and old age, though the lengths of these stages, especially the later ones, are not fixed.
There are striking differences in life expectancy around the world. The developed world is quickly getting older, with the median age around 40 years (highest in Monaco at 45.1 years), while in the developing world, the median age is 15–20 years (the lowest in Uganda at 14.8 years). Life expectancy at birth is 77.2 years in the U.S. as of 2001. [http://www.cdc.gov/nchs/fastats/lifexpec.htm] The expected life span at birth in Singapore is 84.29 years for a female and 78.96 years for a male, while in Botswana, due largely to AIDS, it is 30.99 years for a male and 30.53 years for a female. One in five Europeans, but one in twenty Africans, is 60 years or older, according to The World Factbook. [http://www.cia.gov/cia/publications/factbook]
African.]]
The number of centenarians in the world was estimated by the United Nations [http://www.un.org/ageing/note5713.doc.htm] at 210,000 in 2002. The maximum life span for humans is thought to be over 120 years. Worldwide, there are 81 men aged 60 or over for every 100 women, and among the oldest, there are 53 men for every 100 women.
The philosophical questions of when human personhood begins and whether it persists after death are the subject of considerable debate. The prospect of death may cause unease or fear. People who are near death sometimes have a near-death experience, in which they have visions. Burial ceremonies are characteristic of human societies, often inspired by beliefs in an afterlife. Institutions of inheritance or ancestor worship may extend an individual's presence beyond his physical lifespan (see immortality).
Genetics
Humans are a eukaryotic species. Each diploid cell has two sets of 23 chromosomes, each set received from one parent. There are 22 pairs of autosomes and one pair of sex chromosomes. At present estimate, humans have approximately 20,000–25,000 genes and share 95% of their DNA with their closest living evolutionary relatives, the two species of chimpanzees. [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=12368483] Like other mammals, humans have an XY sex determination system, so that females have the sex chromosomes XX and males have XY. The X chromosome is larger and carries many genes not on the Y chromosome, which means that recessive diseases associated with X-linked genes affect men more often than women. For example, genes that control the clotting of blood reside on the X chromosome. Women have a blood-clotting gene on each X chromosome so that one normal blood-clotting gene can compensate for a flaw in the gene on the other X chromosome. But men are hemizygous for the blood-clotting gene, since there is no gene on the Y chromosome to control blood clotting. As a result, men will suffer from haemophilia more often than women.
Race and ethnicity
haemophilia, Black, White (Hispanic), and Asian. Top row males, bottom row females.]]
Humans often categorise themselves and others in terms of race or ethnicity. In America, racial categories are primarily based on language and ethnicity, although biological qualities, such as skin colour, blood type, facial features, ancestry, and other genetic variances are also key factors. Self identification with an ethnic group is usually based on kinship and descent, as well as presumed advantage. When race and ethnicity lead to variant treatment it is thought to impact social identity, giving rise to the theory of identity politics.
Although most humans recognise that variances occur within a species, it is often a point of dispute as to what these differences entail, and if discrimination based on race (racism) is acceptable in the early twenty-first century. Race and intelligence, scientific racism, xenophobia and ethnocentrism are just a few of the many basis' for such practices.
Habitat
The view most widely accepted by the current anthropological community is that the human species originated in the African savanna between 100 and 200 thousand years BCE, colonised the rest of the Old World and Oceania by 40,000 years BCE, and finally colonised the Americas by 10,000 years BCE. Homo sapiens displaced groups such as Neanderthals and Homo floresiensis through more successful reproduction and competition for resources, and/or extermination. (See Human evolution, Vagina gentium, and Environment of Evolutionary Adaptedness.) Technology has allowed humans to colonise all of the continents and adapt to all climates. Within the last few decades, humans have been able to explore Antarctica, the ocean depths, and space, although long-term habitation of these environments are not yet possible. Humans, with a population of about six thousand million, are one of the most numerous mammals on Earth.
Most humans (61%) live in the Asian region. The vast majority of the remainder live in the Americas (14%), Africa (13%) and Europe (12%), with 5% in Oceania. (See list of countries by population and list of countries by population density.)
list of countries by population density (The arctic is at the centre of the map and the numbers are millennia before present).]]
The original human lifestyle is hunting-gathering, which is adapted to the savanna. Other human lifestyles are nomadism (often linked to animal herding) and permanent settlements made possible by the development of agriculture. Humans have a great capacity for altering their habitats by various methods, such as agriculture, irrigation, urban planning, construction, transport, and manufacturing goods.
Permanent human settlements are dependent on proximity to water and, depending on the lifestyle, other natural resources such as fertile land for growing crops and grazing livestock, or seasonally by populations of prey. With the advent of large-scale trade and transport infrastructure, immediate proximity to these resources has become unnecessary, and in many places these factors are no longer the driving force behind growth and decline of population.
Human habitation within closed ecological systems in hostile environments (Antarctica, outer space) is expensive, typically limited in duration, and restricted to scientific, military, or industrial expeditions. Life in space has been very sporadic, with a maximum of thirteen humans in space at any given time, starting with Yuri Gagarin's space flight in 1961. Between 1969 and 1974, up to two humans at a time spent brief intervals on the Moon. As of 2005, no other celestial body has been visited by human beings, although there has been a continuous human presence in space since the launch of the initial crew to inhabit the International Space Station on October 31, 2000.
Population
2000
From 1800 to 2000, the human population increased from one to six billion. It is expected to crest at around ten billion during the 21st century. In 2004, around 2.5 billion out of 6.3 billion people lived in urban centres, and this is expected to rise during the 21st century. Problems for humans living in cities include various forms of pollution, crime, and poverty, especially in inner city and suburban slums.
Geneticists Lynn Jorde and Henry Harpending of the University of Utah have concluded that the variation in the total stock of human DNA is minute compared to that of other species; and that around 74,000 years ago, human population was reduced to a small number of breeding pairs, possibly as small as 1000, resulting in a very small residual gene pool. Various reasons for this bottleneck have been postulated, the most popular, called the Toba catastrophe theory, being the eruption of a volcano at Lake Toba.
Human evolution
The study of human evolution encompasses many scientific disciplines, but most notably physical anthropology and genetics. The term "human", in the context of human evolution, refers to the genus Homo, but studies of human evolution usually include other hominids and hominines, such as the australopithecines.
Biologically, humans are defined as hominids of the species Homo sapiens, of which the only extant subspecies is Homo sapiens sapiens (Latin for "very wise man"); Homo sapiens idaltu (roughly translated as "elderly wise man") is the extinct subspecies. Modern humans are usually considered the only surviving species in the genus Homo, although some argue that the two species of chimpanzees should be reclassified from Pan troglodytes (Common Chimpanzee) and Pan paniscus (Bonobo/Pygmy Chimpanzee) to Homo troglodytes and Homo paniscus respectively, given that they share a recent ancestor with man. [http://news.nationalgeographic.com/news/2003/05/0520_030520_chimpanzees.html]
Full genome sequencing resulted in these conclusions: "After 6 [million] years of separate evolution, the differences between chimp and human are just 10 times greater than those between two unrelated people and 10 times less than those between rats and mice." [http://news.ft.com/cms/s/43445728-1a44-11da-b279-00000e2511c8.html Chimp and human DNA is 96% identical]
It has been estimated that the human lineage diverged from that of chimpanzees about five million years ago, and from gorillas about eight million years ago. However, in 2001 a hominine skull approximately seven million years old, classified as Sahelanthropus tchadensis, was discovered in Chad and seems to indicate an earlier divergence.
Two prominent scientific theories of the origins of contemporary humans exist. They concern the relationship between modern humans and other hominids:
The single-origin or "out of Africa" hypothesis proposes that modern humans evolved in Africa and later replaced hominids in other parts of the world.
The multiregional hypothesis proposes that modern humans evolved at least in part from independent hominid populations.
Human evolution is characterised by a number of important physiological trends:
- expansion of the brain cavity and brain itself, which is typically 1,400 cm³ in volume, over twice that of a chimpanzee or gorilla. The pattern of human postnatal brain growth differs from that of other apes (heterochrony), allowing for an extended period of social learning in juvenile humans. Physical anthropologists argue that a reorganisation of the structure of the brain is more important than cranial expansion itself;
- canine tooth reduction;
- bipedal locomotion;
- descent of the larynx, which makes speech possible.
Humans are classified as Homo sapiens sapiens. A camp of physical anthropologists see neanderthalensis as a subspecies and classify the neanderthals as Homo sapiens neanderthalensis. A second camp of physical anthropologists see the neanderthals as a distinct species diverging from the modern human lineage over 500,000 years ago. Under this classification, neaderthals are Homo neanderthalensis. Recent DNA analysis suggests that neanderthalensis were not a subspecies.
How these trends are related and what their role is in the evolution of complex social organisation and culture are matters of ongoing debate.
larynx]]
Intelligence
Most humans consider their species to be the most intelligent in the animal kingdom. Certainly, humans are the only technologically advanced animal. Along with the brain's internal complexity, the brain to body mass ratio is generally assumed to be a good indicator of relative intelligence. Humans have the second highest ratio, with the tree shrew having the highest [http://www.hindustantimes.com/news/181_935198,00300006.htm], and the bottlenose dolphin very similar to humans.
The human ability to abstract may be unparalleled in the animal kingdom. Human beings are one of five species to pass the mirror test — which tests whether an animal recognises its reflection as an image of itself — along with chimpanzees or bonobos, orangutans, and dolphins. Human beings under the age of four usually fail the test.
Culture
dolphin]]
Culture is defined here as a set of distinctive material, intellectual, emotional, and spiritual features of a social group, including art, literature, lifestyles, value systems, traditions, rituals, and beliefs.
Culture consists of at least three elements: values, social norms, and artifacts. A culture's values define what it holds to be important. Norms are expectations of how people ought to behave. Artifacts — things, or material culture — derive from the culture's values and norms together with its understanding of the way the world functions.
Origins
Essentially every culture has its characteristic origin beliefs. Creationism or creation theology is the belief that humans, the Earth, the universe and the multiverse were created by a supreme being or deity. The event itself may be seen either as an act of creation (ex nihilo) or the emergence of order from preexisting chaos (demiurge). Many who hold "creation" beliefs consider such belief to be a part of religious faith, and hence compatible with, or otherwise unaffected by scientific views while others maintain the scientific data is compatible with creationism. Proponents of evolutionary creationism may claim that understood scientific mechanisms are simply aspects of supreme creation. Otherwise, science-oriented believers may consider the scriptural account of creation as simply a metaphor.
Language
metaphor, Traditional Chinese, Korean, Hebrew and Greek]]
Values, norms and technology are dependent on the capacity for humans to share ideas. The faculty of speech may be a defining feature of humanity, probably predating phylogenetic separation of the modern population. (See Proto-World language, Origins of language.) Language is central to the communication between humans. Some scientists argue that non-human animals are able to use some form of language too, and that non-human primates are able to learn human sign language [http://www.mnsu.edu/emuseum/cultural/language/chimpanzee.html] [http://www.msubillings.edu/asc/PDF-WritingLab/3-Minute%20Spr05/APA%20sample%20paper.pdf] (pdf). Language is central to the sense of identity that unites cultures and ethnicities.
The invention of writing systems some 5000 years ago, allowing the preservation of speech, was a major step in cultural evolution. Language, especially written language, is sometimes thought to have supernatural status or powers. (See Magic, Mantra, Vac.)
The science of linguistics describes the structure of language and the relationship between languages. There are estimated to be some 6,000 different languages, including sign languages, used today.
Music
Music is a natural intuitive phenomenon operating in the three worlds of time, pitch, and energy, and under the three distinct and interrelated organisation structures of rhythm, harmony, and melody.
Composing, improvising and performing music are all art forms. Listening to music is perhaps the most common form of entertainment, while learning and understanding it are popular disciplines. There are a wide variety of music genres and ethnic musics.
Emotion and sexuality
Human emotion has a significant influence on, or can even be said to control, human behaviour. Emotional experiences perceived as pleasant, like love, admiration, or joy, contrast with those perceived as unpleasant, like hate, envy, or sorrow. There is often a distinction seen between refined emotions, which are socially learned, and survival oriented emotions, which are thought to be innate.
Human exploration of emotions as separate from other neurological phenomena is worth note, particularly in those cultures were emotion is considered separate from physiological state. In some cultural medical theories, to provide an example, emotion is considered so synonymous with certain forms of physical health that no difference is thought to exist. The Stoics believed excessive emotion was harmful, while some Sufi teachers (in particular, the poet and astronomer Omar Khayyám) felt certain extreme emotions could yield a conceptual perfection, what is often translated as ecstasy.
ecstasy"]] In modern scientific thought, certain refined emotions are considered to be a complex neural trait of many domesticated and a few non-domesticated mammals, developed commonly in reaction to superior survival mechanisms and intelligent interaction with each other and the environment; as such, refined emotion is not in all cases as discrete and separate from natural neural function as was once assumed. Still, when humans function in civilised tandem, it has been noted that uninhibited acting on extreme emotion can lead to social disorder and crime.
Human sexuality, besides ensuring reproduction, has important social functions, creating physical intimacy, bonds and hierarchies among individuals, and that may be directed to spiritual transcendence, and/or to the enjoyment of activity involving sexual gratification. Sexual desire, libido, is experienced as a bodily urge, often accompanied by strong emotions, both positive (such as love or ecstasy) and negative (such as jealousy).
As with other human self-descriptions, humans propose it is high intelligence and complex societies of humans that have produced the most complex sexual behaviors of any animal. Human sexual choices are usually made in reference to cultural norms, which vary widely. Restrictions are largely determined by religious beliefs.
Body image
norms, Japan]]The physical appearance of the human body is central to culture and art. In every human culture, people adorn their bodies with tattoos, cosmetics, clothing, and jewellery. Hairstyles and hair colour also have important cultural implications. The perception of an individual as physically beautiful or ugly can have profound implications for their lives. This is particularly true of women, whose external appearance is highly valued in most, if not all, human societies. Anthropologists believe this to be an important factor in the development of personality and social relations in particular physical attractiveness.
There is a relatively low sexual dimorphism between human males and females in comparison with other mammals.
Trade and economics
sexual dimorphism.]]
Trade is the voluntary exchange of goods, services, or both, and a form of economics. A mechanism that allows trade is called a market. The original form of trade was barter, the direct exchange of goods and services. Modern traders instead generally negotiate through a medium of exchange, such as money. As a result, buying can be separated from selling, or earning. The invention of money (and later credit, paper money and non-physical money) greatly simplified and promoted trade.
Trade exists for many reasons. Due to specialisation and division of labor, most people concentrate on a small aspect of manufacturing or service, trading their labour for products. Trade exists between regions because different regions have an absolute or comparative advantage in the production of some tradable commodity, or because different regions' size allows for the benefits of mass production. As such, trade between locations benefits both locations.
Economics is a social science that studies the production, distribution, trade and consumption of goods and services.
Economics, which focuses on measurable variables, is broadly divided into two main branches: microeconomics, which deals with individual agents, such as households and businesses, and macroeconomics, which considers the economy as a whole, in which case it considers aggregate supply and demand for money, capital and commodities. Aspects receiving particular attention in economics are resource allocation, production, distribution, trade, and competition. Economic logic is increasingly applied to any problem that involves choice under scarcity or determining economic value. Mainstream economics focuses on how prices reflect supply and demand, and uses equations to predict consequences of decisions.
Artifacts, technology, and science
supply and demand.]]
Human cultures are both characterised and differentiated by the objects that they make and use. Archaeology attempts to tell the story of past or lost cultures in part by close examination of the artifacts they produced. Early humans left stone tools, pottery and jewellery that are particular to various regions and times.
Improvements in technology are passed from one culture to another. For instance, the cultivation of crops arose in several different locations, but quickly spread to be an almost ubiquitous feature of human life. Similarly, advances in weapons, architecture and metallurgy are quickly disseminated.
Such techniques can be passed on by oral tradition. The development of writing, itself a type of artifact, made it possible to pass information from generation to generation and from region to region with greater accuracy.
Together, these developments made possible the commencement of civilisation and urbanisation, with their inherently complex social arrangements. Eventually this led to the institutionalisation of the development of new technology, and the associated understanding of the way the world functions. This science now forms a central part of human culture.
In recent times, physics and astrophysics have come to play a central role in shaping what is now known as physical cosmology, that is, the understanding of the universe through scientific observation and experiment. This discipline, which focuses on the universe as it exists on the largest scales and at the earliest times, begins by arguing for the big bang, a sort of cosmic explosion from which the universe itself is said to have erupted ~13.7 ± 0.2 billion (109) years ago. After its violent beginnings and until its very end, scientists then propose that the entire history of the universe has been an orderly progression governed by physical laws.
Mind
physical laws
Consciousness is a state of mind, said to possess qualities such as, self-awareness, sentience, sapience, and the ability to perceive the relationship between oneself and one's environment.
The way in which the world is experienced is the subject of much debate and research in philosophy of mind, psychology, brain biology, neurology, and cognitive science.
Humans (and often others as well) are variously said to possess consciousness, self-awareness, and a mind, the fruition of being our senses and perceptions. Each of us has a subjective view of existence, the passage of time, and free will.
There are many debates about the extent to which the mind constructs or experiences the outer world, and regarding the definitions and validity of many of the terms used above.
Cognitive scientist Daniel Dennett, for example, argues that there is no such thing as a narrative centre called mind, but that instead there is simply a collection of sensory inputs and outputs: different kinds of software running in parallel (Dennett, 1991).
Psychology and human ethology
Psychology (Classical Greek: psyche = "soul" or "mind", logos = "study of") is the study of behaviour, mind and thought and the neurological basis for them.
Psychoanalysis, the examination of the subconscious was, devised by Sigmund Freud and expanded and refined by the Swiss psychiatrist Carl Gustav Jung (initially one of Freud's followers and friends) and others.
Carl Gustav Jung
Freud divided the mind into the id (an individual's basic needs and instincts), the superego (personal and cultural values and norms), and the ego (the central, organising self, whose job it is to satisfy the id but not upset the superego). [http://allpsych.com/psychology101/ego.html]
C. G. Jung founded the school of analytical psychology and introduced the notion of the collective unconscious, a term taken from philosophy and used by Jung to describe symbols or archetypes that he believed might be common to all cultures.
There are also the Conscious, Subconscious, and Superconsciousness, a related but not identical set of categories.
The behaviour and mental processes of animals (human and non-human) can be described through animal cognition, ethology, and comparative psychology as well.
Human ecology is an academic discipline that investigates how humans and human societies interact with their environment, nature and the human social environment.
Philosophy
social environment in detail from Raphael's School of Athens]]
Philosophy is a discipline or field of study involving the investigation, analysis, and development of ideas at a general, abstract, or fundamental level. It is the discipline searching for a general understanding of values and reality by chiefly speculative rather than observational means comprising as its core logic, ontology or metaphysics, epistemology, and axiology which includes the branches of ethics and aesthetics. The term covers a very wide range of approaches, and is also used to refer to a worldview, to a perspective on an issue, or to the positions argued for by a particular philosopher or school of philosophy.
Metaphysics is a branch of philosophy concerned with the study of "first principles" and "being" (ontology). Problems that were not originally considered metaphysical have been added to metaphysics. Other problems that were considered metaphysical problems for centuries are now typically relegated to their own separate subheadings in philosophy, such as philosophy of religion, philosophy of mind, philosophy of perception, philosophy of language, and philosophy of science. In rare cases subjects of metaphysical research have been found to be entirely physical and natural.
The mind is the term most commonly used to describe the higher functions of the human brain, particularly those of which humans are subjectively conscious, such as personality, thought, reason, memory, intelligence and emotion. Other species of animals share some of these mental capacities, and it is also used in relation to supernatural beings, as in the expression "the mind of God." The term is used here only in relation to humans.
There are many Philosophies of mind, the most common relating to the nature of being, and ones way of being, or purpose.
Adi Shankara in the East proposed Advaita Vedanta, a popular argument for monism (the metaphysical view that all is of one essential essence, substance or energy).
Another type of monism is physicalism or
Sunčev sistem je područje u Svemiru koje čini barem jedna zvijezda i objekti koji se kreću u određenoj orbiti oko te zvijezde.
Ti objekti mogu biti: asteroidi, komete, prirodni sateliti, planete slično.
Izraz se obično koristi za naš sistem, u kojem je Zemlja. Da se izbjegne zabuna, drugi solarnisistemi nazivaju se planetarni sistemi.
U većini drugih jezika naziv je izveden iz riječi Sol, što je latinsko ime za Sunce.
Nebeska tijela koja čine Sunčev sistem
Sunce pripada zvijezdama spektralne klase G2, gdje 99.86% mase sistema otpada na masu zvijezde.
- Planete su devet tijela u Sunčevom sistemu. Navodimo ih prema udaljenosti od Sunca, od najbližeg do najdaljeg: Merkur, Venera, Zemlja, Mars, Jupiter, Saturn, Uran, Neptun i Pluton.
- Poveća tijela koja kruže oko planeta su prirodni sateliti ili mjeseci.
- Prašina i druga sitna tijela kruže oko planete, od čega nastaju planetarni prstenovi.
- Svemirski otpad su komadi ili tijela koja su ljudskog porijekla i većinom se nalaze u orbiti oko planeta Zemlje.
- Planetisimali.
- Asteroidi
- Komete
- Kentaurisu ledena nebeska tijela nalik na komete koja imaju nešto manje ekscentričnu orbitu, koja im omogućava da se zadrže u području između Jupitera i Neptuna.
- Trans-Neptunska tijela
- Kuiperov pojas je pojas u obliku diska koji se prostire iza planete Neptuna u širini od 30 AU do 50 AU od Sunca.
- Oortov oblak je hipotetični pojas koji se prostire od 50,000 do 100,000 AU od Sunca. Vjeruje se da je ova oblast izvor kometa s dugim periodima.
- Zodijačka svjetlost
- Svemirska prašina
Izvor planetarnih sistema i njihova evolucija
Uobičajeno mišljenje je da planetarni sistemi nastaju prilikom tvorbe zvijezda kao i prilikom slučajnih sudara zvjezdanih sistema. Postoji još jedna rasprostranjena teorija: da planetarni sistemi nastaju od zvjezdanih oblaka ili nebula.
Sunčev sistem i ostali planetarni sistemi
Krajem devedesetih godina dvadesetog stoljeća čovjek je uspio pronaći dokaze o postojanju planeta izvan Sunčevog sistema. Otkriće drugih planetarnih sistema postalo je moguće nakon izgradnje moćnih optičkih teleskopa na Zemlji i razvoja posebnih elektronskih naprava (digitalnih kamera), komjuterskih tehnika obrade podataka, i razvoja dostupnih i jeftinih računarskih mreža. Kroz posmatranje Dopplerovog efekta u sjaju dalekih zvijezda astronomi su uspjeli dokazati postojanje drugih planetarnih sistema. Pri tome su prilikom posmatranja uspjeli ustanoviti i masu kao i osobine orbite planeta izvan Sunčeva sistema.
Osobine glavnih planeta
Sve osobine i mjere u donjoj tablici su relativne u odnosu na planetu Zemlju:
| Planet |
Promjer
ekvatora |
Masa |
Promjer
orbite |
Godina |
Dan |
| Merkur |
0,382 |
0,06 |
0,38 |
0,241 |
58,6 |
| Venera |
0,949 |
0,82 |
0,72 |
0,615 |
-243 |
| Zemlja |
1,00 |
1,00 |
1,00 |
1,00 |
1,00 |
| Mars |
0,53 |
0,11 |
1,52 |
1,88 |
1,03 |
| Jupiter |
11,2 |
318 |
5,20 |
11,86 |
0,414 |
| Saturn |
9,41 |
95 |
9,54 |
29,46 |
0,426 |
| Uran |
3,98 |
14,6 |
19,22 |
84,01 |
0,718 |
| Neptun |
3,81 |
17,2 |
30,06 |
164,79 |
0,671 |
Pluton
- |
0,24 |
0,0017 |
39,5 |
248,5 |
6,5 |
- Međunarodni astronomski savez svrstao je Pluton u planete odmah nakon njegovog otkrića 1930. godine, ali ta klasifikacija je sada upitna zbog nedavnih otkrića.
Vanjski linkovi
- [http://www.michaelschultz.de/index_en.html Solar System] A interaktiv planets animation (145 zoom steps and time effects)
- [http://www.solarviews.com Solarviews]
Category:Sunčev sistem
ja:太陽系
ko:태양계
ms:Sistem suria
simple:Solar system
zh-cn:太阳系
zh-tw:太陽系
Prirodni satelitiZajednička imenica mjesec se koristi u smislu značenja pojma prirodni satelit drugih planeta. Postoji najmanje 140 mjeseca unutar našeg Sunčevog sistema, a vjerovatno i mnogi drugi koji orbitiraju oko planeta u drugim solarnim sistemima. Obično veći gasoviti giganti imaju obimne sisteme mjeseca. Merkur i Venera nemaju nikakvih mjeseca, Zemlja ima jedan svoj veliki Mjesec, Mars ima dva mala mjeseca (Fobos i Demos), i Pluton malog pratioca koji se zove Haron (pa se ponekad zajedno smatraju dvostrukom planetom).
Porijeklo
Za mnoge mjesece se pretpostavlja da su nastali iz iste oblasti protoplanetarnog diska koja se sažimala i koja je stvorila njegovo primarno tijelo. Ipak, postoje mnogi izuzeci i varijacije u ovom standardnom modelu nastajanja mjeseca koji su trenutno poznati ili se teoretišu. Za neke se mjesece misli da su zarobljeni strani objekti, fragmenti ili veći mjeseci raštrkani kao posljedica velikih udara (kometa), ili (kao u slučaju sa Zemljinim Mjesecom) dio planete čije je dijelove izbacio u njenu orbitu veliki udar. Budući da je većina mjeseca poznata samo na osnovu nekoliko dalekih opservacija preko proba i teleskopa, mnoge teorije o njima su još nepouzdane.
Fizikalne karakteristike
Mnogi mjeseci u Sunčevom sistemu su plimski povezani sa svojim primarnim tijelima, a izuzetak je Saturnov mjesec Hiperion, koji rotira haotično zbog raznih vanjskih uticaja. Nijedan poznati mjesec nema sopstveni mjesec, jer plimski efekti njihovih primarnih tijela stvaraju nestabilne orbite oko njih. Ipak, neki mjeseci imaju pratioce u svojim Lagrangeovim tačkama (npr. Saturnovi mjeseci Tetida i Diona).
Nedavno otkriće Idinog mjeseca Daktila potvrđuje da i neki asteroidi također imaju mjesece. Neki od njih, kao što je 90 Antiopa, su dvostruki asteroidi s komponentama iste veličine.
Mjeseci u Sunčevom sistemu
Najveći mjeseci u Sunčevom sistemu (veći od 3000 km) su Zemljin Mjesec, Jupiterovi Galilejanski mjeseci Io, Europa, Ganimed i Kalisto, Saturnov mjesec Titan, te Neptunov zarobljeni mjesec Triton.
Evo i komparativne tabele u kojoj su mjeseci u našem Sunčevom sistemu klasificirani prema dijametru, što uključuje i kolonu za neke poznate asteroide, planete i objekte iz Kuiperovog pojasa.
¹ Debatabilno je da li je Kruitne ustvari pravi mjesec; a ovdje je stavljen usporedbe radi.
Dodatno mjesecima raznih planeta postoji i oko 30 poznatih asteroidnih mjeseca, tj. asteroida koji orbitiraju oko drugih asteroida.
Također vidi
- Jupiterovi prirodni sateliti
- Saturnovi prirodni sateliti
- Uranovi prirodni sateliti
- Neptunovi prirodni sateliti
- Hronologija prirodnih satelita
- Imenovanje prirodnih satelita
- Kvazisateliti
Vanjski linkovi
- [http://www.infoplease.com/ipa/A0875452.html Kako su planete i sateliti dobili ime]
- [http://encyclopedia.thefreedictionary.com/natural%20satellite Farlexova Enciklopedija - poglavlje Prirodni satelit]
- [http://www.planetary.org/news/2005/saturn_names_0225.html Planetarno društvo, stranica Emily Lakdawalla]
- [http://planetarynames.wr.usgs.gov/append7.html USGS-ov Leksikon planetarne nomenklature]
- [http://www.ifa.hawaii.edu/~sheppard/satellites/jupsatdata.html Podaci o Jupiterovim satelitima]
- [http://www.ifa.hawaii.edu/faculty/jewitt/jmoons/jmoons.html Jupiterovi novi mjeseci (otkriveni 2000. god.)]
- [http://www.ifa.hawaii.edu/~sheppard/satellites/jup.html Jupiterovi novi mjeseci (otkriveni 2002. god.)]
- [http://www.ifa.hawaii.edu/~sheppard/satellites/jup2003.html Jupiterovi novi mjeseci (otkriveni 2003. god.)]
- [http://www.news.cornell.edu/releases/Oct00/Saturn.moons.deb.html Saturnovi novi mjeseci (otkriveni 2002. god.)]
- [http://www.ifa.hawaii.edu/~sheppard/satellites/sat2003.html Saturnovi novi mjeseci (otkriveni 2003. god.)]
- [http://sse.jpl.nasa.gov/whatsnew/pr/030113A.html Neptunovi novi mjeseci (otkriveni 2003. god.)]
- [http://www.planetary.org/learn/solarsystem/moons.html Mjeseci u Sunčevom sistemu (Planetarno društvo)]
- [http://www.ifa.hawaii.edu/~sheppard/satellites Stranica Scotta Shepparda]
- [http://ssd.jpl.nasa.gov JPL-ova Stranica o dinamici Sunčevog sistema]
- [http://nssdc.gsfc.nasa.gov/planetary/planetfact.html NASA-ini podaci o nebeskim tijelima]
- [http://www.nineplanets.org/ Bill Arnettova stranica Devet planeta]
Category:Astronomija
Category:Sunčev sistem
DržavaPrema međunarodnom pravu i međunarodnim odnosima, država je politički subjekt koji je suveren, tj. nije podložan nikakvoj višoj političkoj vlasti.
Postoje i savezne države, a taj naziv ističe postojanje federacije u kojoj vlade tih država imaju neke ovlasti neovisno o federalnoj vlasti.
Često su te države postojale prije udruživanja u federaciju.
U svakodnevnom govoru, riječi "država" i "zemlja" imaju isto značenje, ali "država" zvuči službenije.
O državi
Članak 1 Montevidejske konvencije navodi općeprihvaćene pravne kriterije za državu:
"Država, kao osoba prema međunarodnom pravu, mora imati sljedeće osobine: (a) stalno stanovništvo; (b) definirani teritorij; (c) vlast; i (d) sposobnost da stvara odnose s drugim državama."
(Montevidejska konvencija je regionalna američka konvencija, ali načela iz ovog članka prihvaćena su posvuda kao precizan izričaj običajnog međunarodnog prava.) Ipak, neki se pitaju jesu li ti kriteriji dovoljni.
Veliko pitanje je sukob između dvije teorije o priznavanju država: konstitutivne i deklarativne.
Konstitutivna teorija kaže da država postoji samo ako je priznaju druge države.
S druge strane, deklarativna teorija kaže da postojanje neke države ne zavisi o njezinu priznavanju od strane drugih država.
Koja teorija je ispravna? To je i danas kontroverzno pitanje u međunarodnom pravu. Praktičan primjer je urušavanje središnje vlasti u Somaliji početkom 1990ih godina: prema Konvenciji iz Montevidea, u tom slučaju država Somalija više ne postoji, a pritom stvorena republika Somaliland (koja sadrži jedan dio "bivše" Somalije) mogla bi ispunjavati kriterije za državnost. Međutim, tu samoproglašenu republiku nisu priznale druge države.
Drugo kontroverzno pitanje u političkoj filozofiji jest pitanje nastanka i osnovnih osobina države. Maks Veber i Norbert Elias definirali su državu kao ustanovu koja ima monopol na legitimno nasilje u određenom zemljopisnom području.
Jedna od temeljnih osobina države je reguliranje vlasničkih prava, investicija, trgovine i tržišta roba (hrane, goriva itd.), pri čemu država obično koristi vlastitu valutu.
Iako države sve više prenose te ovlasti na trgovinske saveze kao što su npr. NAFTA i Europska Unija, to je uvijek kontroverzna odluka koja otvara pitanje jesu li ti savezi zapravo samo veće države. Disciplina političke privrede detaljnije izučava ta pitanja.
Činjenica je da mnoge države u određenoj mjeri zavise o moćnijim državama i/ili dragovoljno ulaze u veće političke sile, kao što su Ujedinjeni narodi, Evropska Unija, Svjetska trgovinska organizacija i druge međunarodne organizacije.
Iako se mnoge države tako praktički stavljaju u podređen položaj, njihov je položaj u odnosu na međunarodne organizacije ili moćnije države ipak mnogo jači nego položaj državnih podjedinica u odnosu na državu.
U zadnje vrijeme sve više raste moć iznaddržavnih ustanova.
Zato mnogi ljudi (pogotovo oni koji zastupaju konstitutivnu teoriju međunarodnog prava) odbacuju pojam suvereniteta kao nešto zastarjelo i gledaju na državu samo kao na jedinicu političke podjele planeta.
Državni organi
- zakonodavna vlast - obično je to parlament, ali često i Vlade i predsjednici država imaju pravo donositi odluke i ukaze s zakonodavnom težinom
- sudska vlast - sudovi, od lokalnih do državnih, najviše sudsko tijelo u državi je Vrhovni sud (Ustavni sud je dio sudskog sustava, ali ne spada u hijerarhiju), brinu se za provođenje zakona
- izvršna vlast - Vlada, na čelu s predsjednikom Vlade (Premijerom), brine za vođenje države, članovi Vlade su ministri, tipično svaka država ima ministarstva policije, obrane (vojske), privrede, i vanjskih poslova
Tipovi državnih uređenja
- monarhija (donosi zakone, vlada jedna osoba - monarh, potpuno neograničena)
- ustavna monarhija]] (vladavina monarha ograničena Ustavom države)
- parlamentarna demokracija
- diktatura
Udruživanje država
Države se mogu udruživati u saveze (federacije), s većom ili manjom autonomijom članica. Primjeri su:
- Sjedinjene Američke Države
- SSSR
- SFRJ
- Čehoslovačka
Zanimljivo je da su se poslije 1990. tri navedene federacije raspale.
Također pogledajte: Popis država
ja:国家
ArgonArgon (Ar, latinski - argon) je plemeniti gas (ne stupa skoro ni u kakve hemijske raekcije).
Godine 2000 je dobijeno prvo jedinjenje argona, HArF
Stabilni izotopi su mu: 36Ar, 38Ar i 40Ar.
Argon koji se javlja na Zemlji ima veću atomsku masu od kalijuma koji se javlja poslije njega. To je prouzrokovano tim da nepostojan izotop kalijuma 40K prelazi u argon (skoro sav argon na zemlji je postao na taj način), dok je dominantan izotop kalijuma 39K stabilan.
Zastupljenost
Pošto od nastanka Zemlje na njoj postoji dosta kalijuma, a veoma malo plemenitih gasova, argon koji nastaje iz kalijuma svojom količinom nekoliko puta prevazilazi ostale plemenite gasove. Zastupljen je u atmosferi u količini od 0,934%.
Osobine
Pod normalnim uslovima je u gasovitom agregatnom stanju. Inertan je i ne reaguje ni pod kojim standardnim tehnološkim uslovima. Na -186°C i 1,013 bar je u tečnom stanju
Primjena
- U hemijskim reakcijama za dobijanje nereaktivne atmosfere (ako je i atmosfera azota suviše reaktivna.
- U tehnici zavarivanja, čist ili u gasnim smjesama sa CO, CO2, H2 i N2 ;
- U metalurgiji za termičku obradu i proizvodnju visokolegiranih čelika, za zaštitu odlivaka, za desulfurizaciju ...
- U elektronici za proizvodnju poluprovodnika, u proizvodnji rasvjetnih sredstava instrumentalnoj analitici, nuklearnoj tehnici ...
- U građevinarstvu za proizvodnju za toplotnu izolaciju prozora ...
Način proizvodnje i isporuke
- Dobija se rektifikacijom tečnog vazduha (kiseonične frakcije) na temperaturi ispod -185°C
- U čeličnim sudovima - bocama, pod pritiskom od 150 bara. Boce su pojedinačne ili u baterijama - paletama sa zajedničkim ventilom za punjenje i pražnjenje, u baterijama sudova - boca trajno ugrađenim na transportno vozilo ili u tečnom agregatnom stanju specijalnim transportnim vozilima do rezervoara korisnika argona
Postupak i materijali
- U gasovitom stanju pod pritiskom, u tečnom stanju se treba pridržavati propisanih normi i mjera zaštite.
- Za gasoviti argon se može primjeniti većina uobičajenih materijala. Tečni argon zahteva primjenu austenitnih legiranih čelika, aluminijuma, bakra i legura, teflon ...
Category:Hemijski element
ja:アルゴン
ko:아르곤
ms:Argon
simple:Argon
th:อาร์กอน
Sunčev sistem
Sunčev sistem je područje u Svemiru koje čini barem jedna zvijezda i objekti koji se kreću u određenoj orbiti oko te zvijezde.
Ti objekti mogu biti: asteroidi, komete, prirodni sateliti, planete slično.
Izraz se obično koristi za naš sistem, u kojem je Zemlja. Da se izbjegne zabuna, drugi solarnisistemi nazivaju se planetarni sistemi.
U većini drugih jezika naziv je izveden iz riječi Sol, što je latinsko ime za Sunce.
Nebeska tijela koja čine Sunčev sistem
Sunce pripada zvijezdama spektralne klase G2, gdje 99.86% mase sistema otpada na masu zvijezde.
- Planete su devet tijela u Sunčevom sistemu. Navodimo ih prema udaljenosti od Sunca, od najbližeg do najdaljeg: Merkur, Venera, Zemlja, Mars, Jupiter, Saturn, Uran, Neptun i Pluton.
- Poveća tijela koja kruže oko planeta su prirodni sateliti ili mjeseci.
- Prašina i druga sitna tijela kruže oko planete, od čega nastaju planetarni prstenovi.
- Svemirski otpad su komadi ili tijela koja su ljudskog porijekla i većinom se nalaze u orbiti oko planeta Zemlje.
- Planetisimali.
- Asteroidi
- Komete
- Kentaurisu ledena nebeska tijela nalik na komete koja imaju nešto manje ekscentričnu orbitu, koja im omogućava da se zadrže u području između Jupitera i Neptuna.
- Trans-Neptunska tijela
- Kuiperov pojas je pojas u obliku diska koji se prostire iza planete Neptuna u širini od 30 AU do 50 AU od Sunca.
- Oortov oblak je hipotetični pojas koji se prostire od 50,000 do 100,000 AU od Sunca. Vjeruje se da je ova oblast izvor kometa s dugim periodima.
- Zodijačka svjetlost
- Svemirska prašina
Izvor planetarnih sistema i njihova evolucija
Uobičajeno mišljenje je da planetarni sistemi nastaju prilikom tvorbe zvijezda kao i prilikom slučajnih sudara zvjezdanih sistema. Postoji još jedna rasprostranjena teorija: da planetarni sistemi nastaju od zvjezdanih oblaka ili nebula.
Sunčev sistem i ostali planetarni sistemi
Krajem devedesetih godina dvadesetog stoljeća čovjek je uspio pronaći dokaze o postojanju planeta izvan Sunčevog sistema. Otkriće drugih planetarnih sistema postalo je moguće nakon izgradnje moćnih optičkih teleskopa na Zemlji i razvoja posebnih elektronskih naprava (digitalnih kamera), komjuterskih tehnika obrade podataka, i razvoja dostupnih i jeftinih računarskih mreža. Kroz posmatranje Dopplerovog efekta u sjaju dalekih zvijezda astronomi su uspjeli dokazati postojanje drugih planetarnih sistema. Pri tome su prilikom posmatranja uspjeli ustanoviti i masu kao i osobine orbite planeta izvan Sunčeva sistema.
Osobine glavnih planeta
Sve osobine i mjere u donjoj tablici su relativne u odnosu na planetu Zemlju:
| Planet |
Promjer
ekvatora |
Masa |
Promjer
orbite |
Godina |
Dan |
| Merkur |
0,382 |
0,06 |
0,38 |
0,241 |
58,6 |
| Venera |
0,949 |
0,82 |
0,72 |
0,615 |
-243 |
| Zemlja |
1,00 |
1,00 |
1,00 |
1,00 |
1,00 |
| Mars |
0,53 |
0,11 |
1,52 |
1,88 |
1,03 |
| Jupiter |
11,2 |
318 |
5,20 |
11,86 |
0,414 |
| Saturn |
9,41 |
95 |
9,54 |
29,46 |
0,426 |
| Uran |
3,98 |
14,6 |
19,22 |
84,01 |
0,718 |
| Neptun |
3,81 |
17,2 |
30,06 |
164,79 |
0,671 |
Pluton
- |
0,24 |
0,0017 |
39,5 |
248,5 |
6,5 |
- Međunarodni astronomski savez svrstao je Pluton u planete odmah nakon njegovog otkrića 1930. godine, ali ta klasifikacija je sada upitna zbog nedavnih otkrića.
Vanjski linkovi
- [http://www.michaelschultz.de/index_en.html Solar System] A interaktiv planets animation (145 zoom steps and time effects)
- [http://www.solarviews.com Solarviews]
Category:Sunčev sistem
ja:太陽系
ko:태양계
ms:Sistem suria
simple:Solar system
zh-cn:太阳系
zh-tw:太陽系
VodikHidrogen (Vodonik, Vodik, Latinski: Hydrogenium, H) je najlakši hemijski element u periodnom sistemu elemenata koji ima simbol H i atomski broj 1, te atomsku težinu 1,00794. U njemu ima 99,98% običnog hidrogena (procijum), 0,02% teškog vodonika atomske težine 2 (deuterijum) koji je sastavni dio teške vode, i u tragovima superteškog vodonika atomske težine 3 (tricijum) koji je sastavni dio hidrogenske bombe. Paracelzus (Theophrastus Phillippus Aureolus Bombastus von Hohenheim - Paracelsus) je u 16. vijeku otkrio da se pri dobijanju metalnih acida razvija lahko zapaljiv gas, koji je nazvan zapaljivi vazduh. Englez Henri Kevendiš (Henry Cavendish) je 1760. odredio osobine hidrogena, a njegov zemljak Dž. Vorltajr (J. Warltire) je 1766. ustanovio da se sagorijevanjem hidrogena dobija voda, te mu je stoga Francuz A. Lavoazje (Antoine-Laurent Lavoisier) dao 1781. godine naziv hydrogen (od grčkog hydro-voda i genes-stvaranje). U slobodnom stanju hidrogen je u prirodi veoma rasprostranjen, ali u malim količinama (u atmosferi, zemnom gasu i dr.). Sastavni je dio mnogih organskih jedinjenja, kiselina i baza, a s kiseonikom čini cjelokupnu količinu vode na Zemlji.
Pri normalnoj temperaturi i pritisku hidrogen je gas bez boje, okusa i mirisa. Zagušljiv je ali nije otrovan. Lakši je 14,4 puta od vazduha. Temperatura ključanja mu je -252,81°C, temperatura topljenja -259,05°C, kritična temperatura -241°C, i kritični pritisak 20 atm.
Hidrogen se industrijski dobija najčešće rastvaranjem vodene pare usijanim ugljenikom ili rastvaranjem vode elektrolizom. Najviše se upotrebljava za sintezu amonijaka i metanola, i za proizvodnju goriva za motorna vozila hidrogenacijom ugljenika, nafte i katrana. Osim toga, upotrebljava se za zavarivanje i topljenje metala, za punjenje vazdušnih balona i vazdušnih brodova, za redukciju nekih metalnih oksida u metale i dr.
Category:Hemijski element
ŽeljezoŽeljezo (Fe, latinski ferrum) je metal VIIIB grupe.
Ima 16 izotopa čije se atomske mase nalaze između 49 - 63. Postojani izotopi su: 54, 56, 57 i 58. Najzastupljeniji je izotop 56 (91%).
Željezo je bilo poznato još prvobitnim civilizacijama.
Zastupljenost i jedinjenja
Zastupljen je u zemljinoj kori u količini od 0,41% u obliku sledećih minerala: crvenog hematita (Fe2O3, crnog magnezita (Fe3O4), siderita (FeCO3), limonita, halkopirita, pirita, arsenopirita...
Sem ovih minerala veliki tehnološki značaj imaju karboniklova kompleksna jedinjenja željeza koja se dobijaju iz hlorida željeza. Ta jedinjenja su katalizatori brojnih organskih reakcija. Zlatan hlorid (II)kiselog ukusa se upotrebljava za suzbijanje malokrvnosti.
Biološki značaj
Željezo je neophodno za očuvanje zdravlja. Atom željeza se nalazi u mnogim enzimima: hemoglobinu, mioglobinu ... Potrebe za željezom se razlikuju u zavisnosti od starosti, težine, pola, zdravlja minimalne količine koje je potrebno dnevno unijeti kreću se u širokim okvirima. Kod odraslih osoba od 10 miligrama dnevno do 20 kod žena, dok je za vrijeme dojenja potrebno 30. Iako čovjekov organizam ima solidne mehanizme za regulaciju količine željeza, u nekim situacijama može doći do oboljenja hemohromatoze. To oboljenje se javlja usljed prevelike doze željeza u organizmu. Velike količine željeza(II) su otrovne. Soli željeza(III-VI) su bezopasne, zato što ih organizam ne apsorbuje.
Pravilna koncentracija željeza u krvi:
- srednja vrednost
- muškarci 21,8 mikro mol po litru, 120 mikro grama po decilitru
- žene 18,5 mikro mol po litru, 100 mikro grama po decilitru
- minimalne i maksimalne koncentracije:
- muškarci 17,7 - 35,9 mikro mol po litru, 90 - 200 mikro grama po decilitru
- žene 11,1 - 30,1 mikro mol po litru, 60 - 170 mikro grama po decilitru
Osobine
Čisto željezo je sjajan, srebrnast, mekan metal koji veoma lako podleže koroziji.
Vijekovima se koristi u obliku legura kao što su čelik, legure sa manganom, hromom, molibdenom, vanadijumom i mnogim drugim elementima.
Alotropske modifikacije
Željezo se javlja u 3 alotropske modifikacije:
- željezo α
- željezo γ
- željezo δ
Samo alotropska modifikacija α posjeduje feromagnetične osobine
Željezo α u alotropsku modifikaciju željeza γ prelazi na temperaturi od 723°C pri hlađenju ili 728°C pri zagrijavanju.
Željezo γ u željezo δ prelazi pri temperaturi od 1400°C.
Category:Hemijski element
KisikKiseonik (O, latinski oxygenium) je nemetal z VIA. On je najrasprostranjeniji element na Zemlji - količina kiseonika u zemljinoj kori iznosi 45%. On takođe čini i 20,8% atmosfere zemlje.
Stabilni izotopi su mu 16O, 17O i18O
Osobine kiseonika
Pod normalnim uslovima je u gasovitom ]]|agregatnom stanju]]. Neophodan za opstanak živih bića. Snažan oksidans. U tečno stanje prelazi na -183°C (1.013 bara)
podržava gorenje, bez boje, ukusa i mirisa. Kiseonik u čistom obliku se javlja u vidu molekula
O2 i ozona O3
Primjena
- U procesima sagorjevanja radi postizanja viših temperatura.
- U metaloprerađivačkoj industriji i metalurgiji za sječenje i zavarivanje, za intenziviranje tehnoloških procesa.
- U industriji nemetala za postizanje viših temperatura.
- U hemijskoj industriji za proizvodnju sintenznih gasova, u pirolitičkim procesima ...
- U ostalim primjenama (medicina, biološke nauke, prehrambena industrija, naučnotehnička istraživanja).
Postupak sa gasom
Upotreba kiseonika pod pritiskom i upotreba tečnog kiseonika podležu posebnim propisima i mjerama zaštite.
Nije dozvoljen kontakt kiseonika sa organskim materijalima.
Za tečni kiseonik se preporučuje austenitni čelnici, aluminijum i legure, bakar i legure.
Dozvoljena upotreba fluornih polimera (teflon).
Za gasoviti kiseonik je pod određenim uslovima dozvoljena primjena ugljeničnih lako legiranih čelika i legura bakra i aluminijuma.
Način dobijanja i distribucije
U industriji se dobija se rektifikacijom tečnog vazduha na temperaturi ispod -185°C
Najčešće se isporučuje u čeličnim sudovima - bocama, pod pritiskom od 150 bara. Boce su pojedinačne ili u baterijama - paletama sa zajedničkim ventilom za punjenje i pražnjenje, u baterijama sudova - boca trajno ugrađenim na transportno vozilo ili u tečnom agregatnom stanju specijalnim transportnim vozilima do rezervoara korisnika kiseonika | | |
