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 and other inert gases, carbon dioxide, etc.; but air also contains a variable amount of water vapor. The atmospheric pressure declines steadily with altitude, and has a scale height of about 8 kilometres at the Earth's surface: the height at which the atmospheric pressure has declined by a factor of e (a mathematical constant equal to 2.71...).[31][32] The ozone layer of the Earth's atmosphere plays an important role in depleting 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.
A supercell thunderstorm
Terrestrial weather occurs almost exclusively in the lower part of the atmosphere, and serves as a convective system for redistributing heat. Ocean currents are another important factor in determining climate, particularly the major underwater thermohaline circulation which distributes heat energy from the equatorial oceans to the polar regions. These currents help to moderate the differences in temperature between winter and summer in the temperate zones. Also, without the redistributions of heat energy by the ocean currents and atmosphere, the tropics would be much hotter, and the polar regions much colder.
Tuesday, March 24, 2009
Nature beyond Earth
Outer space, also simply called space, refers to the relatively empty regions of the universe outside the atmospheres of celestial bodies. Outer space is used to distinguish it from airspace (and terrestrial locations). There is no discrete boundary between the Earth's atmosphere and space, as the atmosphere gradually attenuates with increasing altitude. Outer space within the solar system is called interplanetary space, which passes over into interstellar space at what is known as the heliopause.
Outer space is certainly spacious, but it is far from empty. Outer space is sparsely filled with several dozen types of organic molecules discovered to date by microwave spectroscopy, blackbody radiation left over from the big bang and the origin of the universe, and cosmic rays, which include ionized atomic nuclei and various subatomic particles. There is also some gas, plasma and dust, and small meteors. Additionally, there are signs of human life in outer space today, such as material left over from previous manned and unmanned launches which are a potential hazard to spacecraft. Some of this debris re-enters the atmosphere periodically.
Although the planet Earth is currently the only known body within the solar system to support life, current evidence suggests that in the distant past the planet Mars possessed bodies of liquid water on the surface.[75] For a brief period in Mars' history, it may have also been capable of forming life. At present though, most of the water remaining on Mars is frozen. If life exists at all on Mars, it is most likely to be located underground where liquid water can still exist.[76]
Conditions on the other terrestrial planets, Mercury and Venus, appear to be too harsh to support life as we know it. But it has been conjectured that Europa, the fourth-largest moon of Jupiter, may possess a sub-surface ocean of liquid water and could potentially host life.[77]
Recently, the team of Stéphane Udry have discovered a new planet named Gliese 581 c, which is an extrasolar planet orbiting the red dwarf star Gliese 581. Gliese 581 c appears to lie in the habitable zone of space surrounding the star, and therefore could possibly host life as we know it.
Outer space is certainly spacious, but it is far from empty. Outer space is sparsely filled with several dozen types of organic molecules discovered to date by microwave spectroscopy, blackbody radiation left over from the big bang and the origin of the universe, and cosmic rays, which include ionized atomic nuclei and various subatomic particles. There is also some gas, plasma and dust, and small meteors. Additionally, there are signs of human life in outer space today, such as material left over from previous manned and unmanned launches which are a potential hazard to spacecraft. Some of this debris re-enters the atmosphere periodically.
Although the planet Earth is currently the only known body within the solar system to support life, current evidence suggests that in the distant past the planet Mars possessed bodies of liquid water on the surface.[75] For a brief period in Mars' history, it may have also been capable of forming life. At present though, most of the water remaining on Mars is frozen. If life exists at all on Mars, it is most likely to be located underground where liquid water can still exist.[76]
Conditions on the other terrestrial planets, Mercury and Venus, appear to be too harsh to support life as we know it. But it has been conjectured that Europa, the fourth-largest moon of Jupiter, may possess a sub-surface ocean of liquid water and could potentially host life.[77]
Recently, the team of Stéphane Udry have discovered a new planet named Gliese 581 c, which is an extrasolar planet orbiting the red dwarf star Gliese 581. Gliese 581 c appears to lie in the habitable zone of space surrounding the star, and therefore could possibly host life as we know it.
Matter and energy
Some fields of science see nature as matter in motion, obeying certain laws of nature which science seeks to understand. For this reason the most fundamental science is generally understood to be "physics" – the name for which is still recognizable as meaning that it is the study of nature.
Matter is commonly defined as the substance of which physical objects are composed. It constitutes the observable universe. The visible components of the universe are now believed to compose only 4 percent of the total mass. The remainder is believed to consist of 23 percent cold dark matter and 73 percent dark energy.[72] The exact nature of these components is still unknown and is currently under intensive investigation by physicists.
The behavior of matter and energy throughout the observable universe appears to follow well-defined physical laws. These laws have been employed to produce cosmological models that successfully explain the structure and the evolution of the universe we can observe. The mathematical expressions of the laws of physics employ a set of twenty physical constants[73] that appear to be static across the observable universe.[74] The values of these constants have been carefully measured, but the reason for their specific values remains a mystery.
Matter is commonly defined as the substance of which physical objects are composed. It constitutes the observable universe. The visible components of the universe are now believed to compose only 4 percent of the total mass. The remainder is believed to consist of 23 percent cold dark matter and 73 percent dark energy.[72] The exact nature of these components is still unknown and is currently under intensive investigation by physicists.
The behavior of matter and energy throughout the observable universe appears to follow well-defined physical laws. These laws have been employed to produce cosmological models that successfully explain the structure and the evolution of the universe we can observe. The mathematical expressions of the laws of physics employ a set of twenty physical constants[73] that appear to be static across the observable universe.[74] The values of these constants have been carefully measured, but the reason for their specific values remains a mystery.
Natural history
Natural history is the scientific research of plants or animals, leaning more towards the observational than experimental methods of study, and encompasses more research that is published in magazines than in academic journals.[1] A person who studies natural history is known as a naturalist. Grouped among the natural sciences, Natural history is the systematic study of any category of natural objects or organisms. That is a very broad designation in a world filled with many narrowly focused disciplines, so while modern natural history dates historically from studies in the ancient Greco-Roman world and then the medieval Arabic world through to the scattered European Renaissance scientists working in near isolation, today's field is more of a cross discipline umbrella of many specialty sciences that like geobiology have a strong multi-disciplinary nature combining scientists and scientific knowledge of many specialty sciences.
History of natural history
The roots of natural history go back to Aristotle and other ancient philosophers who analyzed the diversity of the natural world. From the ancient Greeks until the work of Carolus Linnaeus and other 18th century naturalists, the central concept tying together the various domains of natural history was the scala naturae or Great Chain of Being, which arranged minerals, vegetables, more primitive or "lower" forms of animals, and more advanced or "higher" life forms on a linear scale of increasing "perfection", culminating in our species.
While natural history was basically static in medieval Europe, it continued to flourish in the medieval Arabic world during the Arab Agricultural Revolution. In zoology, Al-Jahiz described early evolutionary ideas[5] such as the struggle for existence.[6] He also introduced the idea of a food chain,[7] and was an early adherent of environmental determinism.[8] Al-Dinawari is considered the founder of Arabic botany for his Book of Plants, in which he described at least 637 plants and discussed plant evolution from its birth to its death, describing the phases of plant growth and the production of flowers and fruit.[9] Abu al-Abbas al-Nabati developed an early scientific method for botany, introducing empirical and experimental techniques in the testing, description and identification of numerous materia medica, and separating unverified reports from those supported by actual tests and observations.[10] His student Ibn al-Baitar wrote a pharmaceutical encyclopedia describing 1,400 plants, foods, and drugs, 300 of which were his own original discoveries. A Latin translation of his work was useful to European biologists and pharmacists in the 18th and 19th centuries.[11] Earth sciences such as geology were also studied extensively by Arabic geologists.
From the 13th century, the work of Aristotle was adapted rather rigidly into Christian philosophy, particularly by Thomas Aquinas, forming the basis for natural theology. In the Renaissance, scholars (herbalists and humanists, particularly) returned to direct observation of plants and animals for natural history, and many began to accumulate large collections of exotic specimens and unusual monsters. The rapid increase in the number of known organisms prompted many attempts at classifying and organizing species into taxonomic groups, culminating in the system of the Swedish naturalist Carl Linnaeus.
In the eighteenth century and well into the nineteenth century, natural history as a term was frequently used to refer to all descriptive aspects of the study of nature, as opposed to political, ecclesiastical or other human-related history; it was the counterpart to the analytical study of nature, natural philosophy. Roughly, it may be said that natural philosophy corresponded to modern physics and chemistry, while natural history included the biological and geological sciences, although the terminology was, and remains fairly flexible.
While natural history was basically static in medieval Europe, it continued to flourish in the medieval Arabic world during the Arab Agricultural Revolution. In zoology, Al-Jahiz described early evolutionary ideas[5] such as the struggle for existence.[6] He also introduced the idea of a food chain,[7] and was an early adherent of environmental determinism.[8] Al-Dinawari is considered the founder of Arabic botany for his Book of Plants, in which he described at least 637 plants and discussed plant evolution from its birth to its death, describing the phases of plant growth and the production of flowers and fruit.[9] Abu al-Abbas al-Nabati developed an early scientific method for botany, introducing empirical and experimental techniques in the testing, description and identification of numerous materia medica, and separating unverified reports from those supported by actual tests and observations.[10] His student Ibn al-Baitar wrote a pharmaceutical encyclopedia describing 1,400 plants, foods, and drugs, 300 of which were his own original discoveries. A Latin translation of his work was useful to European biologists and pharmacists in the 18th and 19th centuries.[11] Earth sciences such as geology were also studied extensively by Arabic geologists.
From the 13th century, the work of Aristotle was adapted rather rigidly into Christian philosophy, particularly by Thomas Aquinas, forming the basis for natural theology. In the Renaissance, scholars (herbalists and humanists, particularly) returned to direct observation of plants and animals for natural history, and many began to accumulate large collections of exotic specimens and unusual monsters. The rapid increase in the number of known organisms prompted many attempts at classifying and organizing species into taxonomic groups, culminating in the system of the Swedish naturalist Carl Linnaeus.
In the eighteenth century and well into the nineteenth century, natural history as a term was frequently used to refer to all descriptive aspects of the study of nature, as opposed to political, ecclesiastical or other human-related history; it was the counterpart to the analytical study of nature, natural philosophy. Roughly, it may be said that natural philosophy corresponded to modern physics and chemistry, while natural history included the biological and geological sciences, although the terminology was, and remains fairly flexible.
Description
Natural history involves the research and formation of statements that make elements of life and life styles comprehensible by describing the relevant structures, operations and circumstances of various species, such as diet, reproduction, and social grouping.[2] The term has grown to be an umbrella term for what are now often viewed as several distinct scientific disciplines of integrative organismal biology. Most definitions include the study of living things (e.g. biology, including botany and zoology); other definitions extend the topic to include paleontology, ecology or biochemistry, as well as parts of geology and climatology.
Today, well into the scientific revolution, natural history is sometimes considered an archaic term in the scientific community, since in its cross-discipline form usually leans toward the observational rather than the experimental, and encompasses more research that is published in general information (popular) magazines than in academic journals.[1] As an umbrella science, this is perhaps inevitable, and such cross disciplinary articles have their counterpart papers in many professional journals as well—which are frequently cited in the popular articles. That many advances, even in specialties, could not have been made without such cross-fertilization of strong points is beyond contestation. No one thirty years ago could have foreseen how genetics, has remade and impacted other science, nor radiometrics and other analytical methods that have proved useful in many fields.
In the past, during the heyday of the gentleman scientists, natural history was strongly associated with (and hardly distinguished from) natural philosophy for many figures contributed in both areas and early papers of both fields were commonly read at early professional science societies meetings such as the Royal Society and French Academy of Sciences—both founded during the early industrial revolution in the seventeenth century.
In the eighteenth century and well into the nineteenth century, natural history, as a term, was frequently used to refer to all descriptive aspects of the study of nature—what today are called natural sciences—as opposed to political, ecclesiastical or other human-related history. In that era, where knowledge was divided into two main branches, the humanities including theology—which was considered by far the most important discipline in the mindset of the age until about the late seventeenth century—and the studies of nature, it was the counterpart to the analytical study of nature, natural philosophy, which today we call the physical sciences. Spurred by the industrial revolution, the later became ascendant, natural history grew alongside it—mostly spurred by needs to analyze rock strata and find mineable mineral deposits, and the modern world gradually took place with a very different set of priorities and mindsets, as new sciences such as psychology emerged with expanding knowledge.
Furthermore, in modern usage as a term, natural history's sense has become narrowed and more tightly focused, and more often refers to matters relating to biology (the study of living organisms such as plants, animals, fungi, bacteria, etc. and their relationships in natural systems)—but such also encompasses paleobiology, paleozoology, etcetera and so weds the field strongly with many earth sciences like geology and its disciplines such as stratigraphy and petrology. In contrast, until the twentieth century, it had the designation as the study of all things in the natural world, such as rocks and minerals (geology), atoms and molecules (chemistry), and even the universe at large (astronomy, physics, astrophysics), etc.
It has historically been an often somewhat haphazard or less strictly organized study, description, and classification of natural objects, such as animals, plants, minerals, and placed an importance and significance on fieldwork as opposed to the more systematic scientific investigation such as experimental or lab work.[3] A person interested in natural history is known as a naturalist or natural historian. Natural History is not now commonly applied to the fields of astronomy, physics, or chemistry.,[3] as briefly discussed above. However, it sometimes even includes the disciplines of anthropology and archaeology.
Today, well into the scientific revolution, natural history is sometimes considered an archaic term in the scientific community, since in its cross-discipline form usually leans toward the observational rather than the experimental, and encompasses more research that is published in general information (popular) magazines than in academic journals.[1] As an umbrella science, this is perhaps inevitable, and such cross disciplinary articles have their counterpart papers in many professional journals as well—which are frequently cited in the popular articles. That many advances, even in specialties, could not have been made without such cross-fertilization of strong points is beyond contestation. No one thirty years ago could have foreseen how genetics, has remade and impacted other science, nor radiometrics and other analytical methods that have proved useful in many fields.
In the past, during the heyday of the gentleman scientists, natural history was strongly associated with (and hardly distinguished from) natural philosophy for many figures contributed in both areas and early papers of both fields were commonly read at early professional science societies meetings such as the Royal Society and French Academy of Sciences—both founded during the early industrial revolution in the seventeenth century.
In the eighteenth century and well into the nineteenth century, natural history, as a term, was frequently used to refer to all descriptive aspects of the study of nature—what today are called natural sciences—as opposed to political, ecclesiastical or other human-related history. In that era, where knowledge was divided into two main branches, the humanities including theology—which was considered by far the most important discipline in the mindset of the age until about the late seventeenth century—and the studies of nature, it was the counterpart to the analytical study of nature, natural philosophy, which today we call the physical sciences. Spurred by the industrial revolution, the later became ascendant, natural history grew alongside it—mostly spurred by needs to analyze rock strata and find mineable mineral deposits, and the modern world gradually took place with a very different set of priorities and mindsets, as new sciences such as psychology emerged with expanding knowledge.
Furthermore, in modern usage as a term, natural history's sense has become narrowed and more tightly focused, and more often refers to matters relating to biology (the study of living organisms such as plants, animals, fungi, bacteria, etc. and their relationships in natural systems)—but such also encompasses paleobiology, paleozoology, etcetera and so weds the field strongly with many earth sciences like geology and its disciplines such as stratigraphy and petrology. In contrast, until the twentieth century, it had the designation as the study of all things in the natural world, such as rocks and minerals (geology), atoms and molecules (chemistry), and even the universe at large (astronomy, physics, astrophysics), etc.
It has historically been an often somewhat haphazard or less strictly organized study, description, and classification of natural objects, such as animals, plants, minerals, and placed an importance and significance on fieldwork as opposed to the more systematic scientific investigation such as experimental or lab work.[3] A person interested in natural history is known as a naturalist or natural historian. Natural History is not now commonly applied to the fields of astronomy, physics, or chemistry.,[3] as briefly discussed above. However, it sometimes even includes the disciplines of anthropology and archaeology.
Natural history and naturalist societies
The term "natural history" alone, or sometimes together with archeology, forms the name of many national, regional and local natural history societies that maintain records for birds (ornithology), mammals (mammalogy), insects (entomology), fungi (mycology) and plants (botany). They may also have microscopical and geological sections.
Examples of these societies in Britain include the Natural History Society of Northumbria founded in 1829, British Entomological and Natural History Society founded in 1872, Birmingham Natural History Society, Glasgow Natural History Society, London Natural History Society founded in 1858, Manchester Microscopical and Natural History Society established in 1880, Scarborough Field Naturalists' Society and the Sorby Natural History Society, Sheffield, founded in 1918. The growth of natural history societies was also spurred due to the growth of British colonies in tropical regions with numerous new species to be discovered. Many civil servants took an interest in their new surroundings, sending specimens back to museums in Britain.
Examples of these societies in Britain include the Natural History Society of Northumbria founded in 1829, British Entomological and Natural History Society founded in 1872, Birmingham Natural History Society, Glasgow Natural History Society, London Natural History Society founded in 1858, Manchester Microscopical and Natural History Society established in 1880, Scarborough Field Naturalists' Society and the Sorby Natural History Society, Sheffield, founded in 1918. The growth of natural history societies was also spurred due to the growth of British colonies in tropical regions with numerous new species to be discovered. Many civil servants took an interest in their new surroundings, sending specimens back to museums in Britain.
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