Nature Nature

• The word The word naturenature is derived from the Latin word is derived from the Latin word naturanatura, or "essential qualities, , or "essential qualities, innate disposition", and literally means "birth".innate disposition", and literally means "birth".[1][1] NaturaNatura was a Latin translation was a Latin translation of the Greek word of the Greek word physisphysis (φύσις), which originally related to the intrinsic (φύσις), which originally related to the intrinsic characteristics that plants, animals, and other features of the world develop of characteristics that plants, animals, and other features of the world develop of their own accord.their own accord.[2][2][3][3] The concept of nature as a whole, the physical The concept of nature as a whole, the physical universeuniverse, is , is one of several expansions of the original notion; it began with certain core one of several expansions of the original notion; it began with certain core applications of the word φύσις by pre-Socratic philosophers, and has steadily applications of the word φύσις by pre-Socratic philosophers, and has steadily gained currency ever since. This usage was confirmed during the advent of gained currency ever since. This usage was confirmed during the advent of modern modern scientific methodscientific method in the last several centuries. in the last several centuries.[4][4][5][5]

• Within the various uses of the word today, "nature" may refer to the general Within the various uses of the word today, "nature" may refer to the general realm of various types of living plants and animals, and in some cases to the realm of various types of living plants and animals, and in some cases to the processes associated with inanimate objects–the way that particular types of processes associated with inanimate objects–the way that particular types of things exist and change of their own accord, such as the things exist and change of their own accord, such as the weatherweather and and geologygeology of of the Earth, and the the Earth, and the mattermatter and and energyenergy of which all these things are composed. It is of which all these things are composed. It is often taken to mean the "often taken to mean the "natural environmentnatural environment" or " or wildernesswilderness–wild animals, rocks, –wild animals, rocks, forest, beaches, and in general those things that have not been substantially forest, beaches, and in general those things that have not been substantially altered by human intervention, or which persist despite human intervention. altered by human intervention, or which persist despite human intervention. For, example, manufactured objects and human interaction generally are not For, example, manufactured objects and human interaction generally are not considered part of nature, unless qualified as, for example, "human nature" or considered part of nature, unless qualified as, for example, "human nature" or "the whole of nature". This more traditional concept of natural things which can "the whole of nature". This more traditional concept of natural things which can still be found today implies a distinction between the natural and the artificial, still be found today implies a distinction between the natural and the artificial, with the artificial being understood as that which has been brought into being with the artificial being understood as that which has been brought into being by a human by a human consciousnessconsciousness or a human or a human mindmind. Depending on the particular context, . Depending on the particular context, the term "natural" might also be distinguished from the the term "natural" might also be distinguished from the unnaturalunnatural, the , the supernaturalsupernatural, and the , and the artifactualartifactual..

EarthEarth• Earth (or, "the earth") is the only planet presently known to support life, and as such, its Earth (or, "the earth") is the only planet presently known to support life, and as such, its

natural features are the subject of many fields of scientific research. Within the natural features are the subject of many fields of scientific research. Within the solar systemsolar system, it is third nearest to the sun; it is the largest , it is third nearest to the sun; it is the largest terrestrial planetterrestrial planet and the fifth and the fifth largest overall. Its most prominent climatic features are its two large polar regions, two largest overall. Its most prominent climatic features are its two large polar regions, two relatively narrow relatively narrow temperatetemperate zones, and a wide zones, and a wide equatorialequatorial tropicaltropical to to subtropicalsubtropical region. region.[6][6] PrecipitationPrecipitation varies widely with location, from several varies widely with location, from several metresmetres of water per year to less of water per year to less than a than a millimetremillimetre. 71 percent of the Earth's surface is covered by salt-water oceans. The . 71 percent of the Earth's surface is covered by salt-water oceans. The remainder consists of continents and islands, with most of the inhabited land in the remainder consists of continents and islands, with most of the inhabited land in the Northern HemisphereNorthern Hemisphere..

• Earth has evolved through geological and biological processes that have left traces of Earth has evolved through geological and biological processes that have left traces of the original conditions. The the original conditions. The outer surfaceouter surface is divided into several gradually migrating is divided into several gradually migrating tectonic platestectonic plates, which have changed relatively quickly several times. The interior remains , which have changed relatively quickly several times. The interior remains active, with a thick layer of molten active, with a thick layer of molten mantlemantle and an iron-filled core that generates a and an iron-filled core that generates a magnetic fieldmagnetic field..

• The The atmosphericatmospheric conditions have been significantly altered from the original conditions by conditions have been significantly altered from the original conditions by the presence of life-forms,the presence of life-forms,[7][7] which create an ecological balance that stabilizes the which create an ecological balance that stabilizes the surface conditions. Despite the wide regional variations in climate by surface conditions. Despite the wide regional variations in climate by latitudelatitude and other and other geographic factors, the long-term average global climate is quite stable during geographic factors, the long-term average global climate is quite stable during interglacial periods,interglacial periods,[8][8] and variations of a degree or two of average global temperature and variations of a degree or two of average global temperature have historically had major effects on the ecological balance, and on the actual have historically had major effects on the ecological balance, and on the actual geography of the Earth.geography of the Earth.[9][9][10][10]

Picture of earth Picture of earth

• View of Earth, View of Earth, taken in 1972 by taken in 1972 by the the Apollo 17Apollo 17 crew. crew. This image is the This image is the only photograph of only photograph of its kind to date, its kind to date, showing a fully showing a fully sunlit hemisphere sunlit hemisphere of the Earth.of the Earth.

Historical perspective Historical perspective

• Earth is estimated to have formed 4.54 billion years ago from Earth is estimated to have formed 4.54 billion years ago from the the solar nebulasolar nebula, along with the , along with the SunSun and other and other planetsplanets..[12][12] The The moon formed roughly 20 million years later. Initially molten, the moon formed roughly 20 million years later. Initially molten, the outer layer of the planet cooled, resulting in the solid crust. outer layer of the planet cooled, resulting in the solid crust. Outgassing and Outgassing and volcanicvolcanic activity produced the primordial activity produced the primordial atmosphere. Condensing atmosphere. Condensing water vaporwater vapor, most or all of which , most or all of which came from came from iceice delivered by delivered by cometscomets, , produced the oceansproduced the oceans and and other water sources.other water sources.[13][13] The highly energetic chemistry is The highly energetic chemistry is believed to have produced a self-replicating molecule around 4 believed to have produced a self-replicating molecule around 4 billion years ago.billion years ago.[14][14]

• Continents formed, then broke up and reformed as the surface Continents formed, then broke up and reformed as the surface of Earth reshaped over hundreds of millions of years, of Earth reshaped over hundreds of millions of years, occasionally combining to make a occasionally combining to make a supercontinentsupercontinent. Roughly . Roughly 750 million years ago, the earliest known supercontinent 750 million years ago, the earliest known supercontinent RodiniaRodinia, began to break apart. The continents later recombined , began to break apart. The continents later recombined to form to form PannotiaPannotia which broke apart about 540 million years which broke apart about 540 million years ago, then finally ago, then finally PangaeaPangaea, which broke apart about 180 million , which broke apart about 180 million years ago.years ago.[15][15]

GeologyGeology• Geology (from Greek: γη, Geology (from Greek: γη, gêgê, "earth"; and , "earth"; and

λόγος, λόγος, logoslogos, "speech" lit. to talk about the , "speech" lit. to talk about the earth) is the earth) is the sciencescience and study of the solid and and study of the solid and liquid matter that constitutes the liquid matter that constitutes the EarthEarth. The . The field of geology encompasses the study of the field of geology encompasses the study of the composition, composition, structurestructure, , physical propertiesphysical properties, , dynamics, and dynamics, and historyhistory of of Earth materialsEarth materials, and the , and the processes by which they are formed, moved, processes by which they are formed, moved, and changed. The field is a major and changed. The field is a major academic disciplineacademic discipline, and is also important for , and is also important for mineralmineral and and hydrocarbonhydrocarbon extraction, knowledge extraction, knowledge about and mitigation of about and mitigation of natural hazardsnatural hazards, some , some engineeringengineering fields, and understanding fields, and understanding past climatespast climates and environments. and environments.

OceansOceans• An An oceanocean is a major body of is a major body of saline watersaline water, and a principal component of the , and a principal component of the

hydrosphere. Approximately 71% of the Earth's hydrosphere. Approximately 71% of the Earth's surfacesurface (an area of some 361 (an area of some 361 million square kilometers) is covered by ocean, a million square kilometers) is covered by ocean, a continuous body of watercontinuous body of water that is customarily divided into several principal oceans and smaller that is customarily divided into several principal oceans and smaller seasseas. . More than half of this area is over 3,000 meters (9,800 ft) deep. Average More than half of this area is over 3,000 meters (9,800 ft) deep. Average oceanic oceanic salinitysalinity is around 35 is around 35 parts per thousandparts per thousand (ppt) (3.5%), and nearly all (ppt) (3.5%), and nearly all seawater has a salinity in the range of 30 to 38 ppt. Though generally seawater has a salinity in the range of 30 to 38 ppt. Though generally recognized as several 'separate' oceans, these waters comprise one global, recognized as several 'separate' oceans, these waters comprise one global, interconnected body of salt water often referred to as the interconnected body of salt water often referred to as the World OceanWorld Ocean or or global ocean.global ocean.[29][29][30][30] This concept of a global ocean as a continuous body of This concept of a global ocean as a continuous body of water with relatively free interchange among its parts is of fundamental water with relatively free interchange among its parts is of fundamental importance to importance to oceanographyoceanography..[31][31]

• The major oceanic divisions are defined in part by the The major oceanic divisions are defined in part by the continentscontinents, various , various archipelagosarchipelagos, and other criteria: these divisions are (in descending order of , and other criteria: these divisions are (in descending order of size) the size) the Pacific OceanPacific Ocean, the , the Atlantic OceanAtlantic Ocean, the , the Indian OceanIndian Ocean, the , the Southern OceanSouthern Ocean (which is sometimes subsumed as the southern portions of (which is sometimes subsumed as the southern portions of the Pacific, Atlantic, and Indian Oceans), and the the Pacific, Atlantic, and Indian Oceans), and the Arctic OceanArctic Ocean (which is (which is sometimes considered a sometimes considered a seasea of the Atlantic). The Pacific and Atlantic may be of the Atlantic). The Pacific and Atlantic may be further subdivided by the further subdivided by the equatorequator into into northerlynortherly and and southerlysoutherly portions. portions. Smaller regions of the oceans are called Smaller regions of the oceans are called seasseas, , gulfsgulfs, , baysbays and other names. and other names. There are also There are also salt lakessalt lakes, which are smaller bodies of landlocked saltwater , which are smaller bodies of landlocked saltwater that are not interconnected with the World Ocean. Two notable examples of that are not interconnected with the World Ocean. Two notable examples of salt lakes are the salt lakes are the Aral SeaAral Sea and the and the Great Salt LakeGreat Salt Lake..

Matter and energy Matter and energy • Some fields of Some fields of sciencescience see nature as matter in motion, obeying certain see nature as matter in motion, obeying certain

laws of nature which science seeks to understand. For this reason the laws of nature which science seeks to understand. For this reason the most fundamental science is generally understood to be "most fundamental science is generally understood to be "physicsphysics" – " – the name for which is still recognizable as meaning that it is the study the name for which is still recognizable as meaning that it is the study of nature.of nature.

• Matter is commonly defined as the substance of which physical Matter is commonly defined as the substance of which physical objects are composed. It constitutes the objects are composed. It constitutes the observable universeobservable universe . The . The visible components of the universe are now believed to compose only 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 4 percent of the total mass. The remainder is believed to consist of 23 percent cold percent cold dark matterdark matter and 73 percent and 73 percent dark energydark energy..[73][73] The exact The exact nature of these components is still unknown and is currently under nature of these components is still unknown and is currently under intensive investigation by physicists.intensive investigation by physicists.

• The behavior of matter and energy throughout the observable The behavior of matter and energy throughout the observable universe appears to follow well-defined physical laws. These laws universe appears to follow well-defined physical laws. These laws have been employed to produce cosmological models that have been employed to produce cosmological models that successfully explain the structure and the evolution of the universe successfully explain the structure and the evolution of the universe we can observe. The mathematical expressions of the laws of physics we can observe. The mathematical expressions of the laws of physics employ a set of twenty physical constants[74] that appear to be static employ a set of twenty physical constants[74] that appear to be static across the observable universe.[75] The values of these constants across the observable universe.[75] The values of these constants have been carefully measured, but the reason for their specific values have been carefully measured, but the reason for their specific values remains a mystery.remains a mystery.