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Nature is an inherent character or constitution,
particularly of the
ecosphere or the
universe
The universe is all of space and time and their contents. It comprises all of existence, any fundamental interaction, physical process and physical constant, and therefore all forms of matter and energy, and the structures they form, from s ...
as a whole. In this general sense nature refers to the
laws
Law is a set of rules that are created and are law enforcement, enforceable by social or governmental institutions to regulate behavior, with its precise definition a matter of longstanding debate. It has been variously described as a Socia ...
, elements and
phenomena
A phenomenon ( phenomena), sometimes spelled phaenomenon, is an observable Event (philosophy), event. The term came into its modern Philosophy, philosophical usage through Immanuel Kant, who contrasted it with the noumenon, which ''cannot'' be ...
of the physical world, including
life
Life, also known as biota, refers to matter that has biological processes, such as Cell signaling, signaling and self-sustaining processes. It is defined descriptively by the capacity for homeostasis, Structure#Biological, organisation, met ...
. Although humans are part of nature, human activity or humans as a whole are often described as at times at odds, or outright
separate and even superior to nature.
During the advent of modern
scientific method
The scientific method is an Empirical evidence, empirical method for acquiring knowledge that has been referred to while doing science since at least the 17th century. Historically, it was developed through the centuries from the ancient and ...
in the last several centuries, nature became the passive
reality
Reality is the sum or aggregate of everything in existence; everything that is not imagination, imaginary. Different Culture, cultures and Academic discipline, academic disciplines conceptualize it in various ways.
Philosophical questions abo ...
, organized and moved by divine laws. With the
Industrial Revolution
The Industrial Revolution, sometimes divided into the First Industrial Revolution and Second Industrial Revolution, was a transitional period of the global economy toward more widespread, efficient and stable manufacturing processes, succee ...
, nature increasingly became seen as the part of reality deprived from intentional intervention: it was hence considered as sacred by some traditions (
Rousseau, American
transcendentalism) or a mere decorum for
divine providence or human history (
Hegel,
Marx
Karl Marx (; 5 May 1818 – 14 March 1883) was a German philosopher, political theorist, economist, journalist, and revolutionary socialist. He is best-known for the 1848 pamphlet '' The Communist Manifesto'' (written with Friedrich Engels) ...
). However, a
vitalist
Vitalism is a belief that starts from the premise that "living organisms are fundamentally different from non-living entities because they contain some non-physical element or are governed by different principles than are inanimate things." Wher ...
vision of nature, closer to the pre-Socratic one, got reborn at the same time, especially after
Charles Darwin
Charles Robert Darwin ( ; 12 February 1809 – 19 April 1882) was an English Natural history#Before 1900, naturalist, geologist, and biologist, widely known for his contributions to evolutionary biology. His proposition that all speci ...
.
Within the various uses of the word today, "nature" often refers to
geology
Geology (). is a branch of natural science concerned with the Earth and other astronomical objects, the rocks of which they are composed, and the processes by which they change over time. Modern geology significantly overlaps all other Earth ...
and
wildlife
Wildlife refers to domestication, undomesticated animals and uncultivated plant species which can exist in their natural habitat, but has come to include all organisms that grow or live wilderness, wild in an area without being species, introdu ...
. Nature can refer to the general realm of
living beings, and in some cases to the processes associated with inanimate objects—the way that particular types of things exist and change of their own accord, such as the weather and geology of the
Earth
Earth is the third planet from the Sun and the only astronomical object known to Planetary habitability, harbor life. This is enabled by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water. Almost all ...
. It is often taken to mean the "
natural environment
The natural environment or natural world encompasses all life, biotic and abiotic component, abiotic things occurring nature, naturally, meaning in this case not artificiality, artificial. The term is most often applied to Earth or some parts ...
" or
wilderness
Wilderness or wildlands (usually in the plurale tantum, plural) are Earth, Earth's natural environments that have not been significantly modified by human impact on the environment, human activity, or any urbanization, nonurbanized land not u ...
—wild animals, rocks, forest, and in general those things that have not been substantially altered by human intervention, or which persist despite human intervention. For example, manufactured objects and human interaction generally are not considered part of nature, unless qualified as, for example, "human nature" or "the whole of nature". This more traditional concept of natural things that can 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 by a human
consciousness
Consciousness, at its simplest, is awareness of a state or object, either internal to oneself or in one's external environment. However, its nature has led to millennia of analyses, explanations, and debate among philosophers, scientists, an ...
or a human
mind
The mind is that which thinks, feels, perceives, imagines, remembers, and wills. It covers the totality of mental phenomena, including both conscious processes, through which an individual is aware of external and internal circumstances ...
. Depending on the particular context, the term "natural" might also be distinguished from the
unnatural
Unnatural or The Unnatural(s) may refer to:
Film
* ''Alraune'' (1952 film), also known as ''Unnatural'', a West German science fiction horror film
*'' The Unnaturals'', a 1969 Italian-West German gothic horror film directed and written by Antonio ...
or the
supernatural
Supernatural phenomena or entities are those beyond the Scientific law, laws of nature. The term is derived from Medieval Latin , from Latin 'above, beyond, outside of' + 'nature'. Although the corollary term "nature" has had multiple meanin ...
.
Etymology
The word ''nature'' is borrowed from the
Old French
Old French (, , ; ) was the language spoken in most of the northern half of France approximately between the late 8th ''nature'' and is derived from the Latin">-4; we might wonder whether there's a point at which it's appropriate to talk of the beginnings of French, that is, when it wa ...
''nature'' and is derived from the Latin word ''natura'', or "essential qualities, innate disposition", and in ancient times, literally meant "birth".
In ancient philosophy, ''natura'' is mostly used as the Latin translation of the Greek word ''physis'' (φύσις), which originally related to the intrinsic characteristics of plants, animals, and other features of the world to develop of their own accord.
The concept of nature as a whole, the physical
universe
The universe is all of space and time and their contents. It comprises all of existence, any fundamental interaction, physical process and physical constant, and therefore all forms of matter and energy, and the structures they form, from s ...
, is one of several expansions of the original notion;
it began with certain core applications of the word φύσις by
pre-Socratic
Pre-Socratic philosophy, also known as early Greek philosophy, is ancient Greek philosophy before Socrates. Pre-Socratic philosophers were mostly interested in cosmology, the beginning and the substance of the universe, but the inquiries of the ...
philosophers (though this word had a dynamic dimension then, especially for
Heraclitus
Heraclitus (; ; ) was an Ancient Greece, ancient Greek Pre-Socratic philosophy, pre-Socratic philosopher from the city of Ephesus, which was then part of the Achaemenid Empire, Persian Empire. He exerts a wide influence on Western philosophy, ...
), and has steadily gained currency ever since.
Earth

Earth is the only
planet
A planet is a large, Hydrostatic equilibrium, rounded Astronomical object, astronomical body that is generally required to be in orbit around a star, stellar remnant, or brown dwarf, and is not one itself. The Solar System has eight planets b ...
known to support
life
Life, also known as biota, refers to matter that has biological processes, such as Cell signaling, signaling and self-sustaining processes. It is defined descriptively by the capacity for homeostasis, Structure#Biological, organisation, met ...
, and its natural features are the subject of many fields of scientific research. Within the
Solar System
The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Sola ...
, it is third closest to the Sun; it is the largest
terrestrial planet
A terrestrial planet, tellurian planet, telluric planet, or rocky planet, is a planet that is composed primarily of silicate, rocks or metals. Within the Solar System, the terrestrial planets accepted by the IAU are the inner planets closest to ...
and the fifth largest overall. Its most prominent climatic features are its two large polar regions, two relatively narrow
temperate
In geography, the temperate climates of Earth occur in the middle latitudes (approximately 23.5° to 66.5° N/S of the Equator), which span between the tropics and the polar regions of Earth. These zones generally have wider temperature ran ...
zones, and a wide
equator
The equator is the circle of latitude that divides Earth into the Northern Hemisphere, Northern and Southern Hemisphere, Southern Hemispheres of Earth, hemispheres. It is an imaginary line located at 0 degrees latitude, about in circumferen ...
ial tropical to
subtropical
The subtropical zones or subtropics are geographical zone, geographical and Köppen climate classification, climate zones immediately to the Northern Hemisphere, north and Southern Hemisphere, south of the tropics. Geographically part of the Ge ...
region.
Precipitation
In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls from clouds due to gravitational pull. The main forms of precipitation include drizzle, rain, rain and snow mixed ("sleet" in Commonwe ...
varies widely with location, from several metres of water per year to less than a millimetre. 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
Northern Hemisphere
The Northern Hemisphere is the half of Earth that is north of the equator. For other planets in the Solar System, north is defined by humans as being in the same celestial sphere, celestial hemisphere relative to the invariable plane of the Solar ...
.
Earth has evolved through geological and biological processes that have left traces of the original conditions. The
outer surface is divided into several gradually migrating
tectonic plates. The interior remains active, with a thick layer of plastic
mantle and an iron-filled core that generates a
magnetic field
A magnetic field (sometimes called B-field) is a physical field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular ...
. This iron core is composed of a solid inner phase, and a fluid outer phase. Convective motion in the core generates electric currents through dynamo action, and these, in turn, generate the geomagnetic field.
The
atmospheric conditions have been significantly altered from the original conditions by the presence of life-forms, which create an ecological balance that stabilizes the surface conditions. Despite the wide regional variations in climate by
latitude
In geography, latitude is a geographic coordinate system, geographic coordinate that specifies the north-south position of a point on the surface of the Earth or another celestial body. Latitude is given as an angle that ranges from −90° at t ...
and other geographic factors, the long-term average global climate is quite stable during interglacial periods, and variations of a degree or two of average global temperature have historically had major effects on the ecological balance, and on the actual geography of the Earth.
Geology
Geology is the science and study of the solid and liquid matter that constitutes the Earth. The field of geology encompasses the study of the composition,
structure
A structure is an arrangement and organization of interrelated elements in a material object or system, or the object or system so organized. Material structures include man-made objects such as buildings and machines and natural objects such as ...
,
physical properties, dynamics, and
history
History is the systematic study of the past, focusing primarily on the Human history, human past. As an academic discipline, it analyses and interprets evidence to construct narratives about what happened and explain why it happened. Some t ...
of
Earth materials, and the processes by which they are formed, moved, and changed. The field is a major
academic discipline
An academic discipline or academic field is a subdivision of knowledge that is taught and researched at the college or university level. Disciplines are defined (in part) and recognized by the academic journals in which research is published, a ...
, and is also important for
mineral
In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid substance with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2011): Mi ...
and
hydrocarbon
In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and Hydrophobe, hydrophobic; their odor is usually fain ...
extraction, knowledge about and mitigation of
natural hazard
A natural disaster is the very harmful impact on a society or community brought by natural phenomenon or hazard. Some examples of natural hazards include avalanches, droughts, earthquakes, floods, heat waves, landslides - including submarin ...
s, some
Geotechnical engineering
Geotechnical engineering, also known as geotechnics, is the branch of civil engineering concerned with the engineering behavior of earth materials. It uses the principles of soil mechanics and rock mechanics to solve its engineering problems. I ...
fields, and understanding
past climates and environments.
Geological evolution

The geology of an area evolves through time as rock units are deposited and inserted and deformational processes change their shapes and locations.
Rock units are first emplaced either by
deposition onto the surface or intrude into the
overlying rock. Deposition can occur when
sediment
Sediment is a solid material that is transported to a new location where it is deposited. It occurs naturally and, through the processes of weathering and erosion, is broken down and subsequently sediment transport, transported by the action of ...
s settle onto the surface of the Earth and later
lithify into
sedimentary rock
Sedimentary rocks are types of rock (geology), rock formed by the cementation (geology), cementation of sediments—i.e. particles made of minerals (geological detritus) or organic matter (biological detritus)—that have been accumulated or de ...
, or when as
volcanic material such as
volcanic ash
Volcanic ash consists of fragments of rock, mineral crystals, and volcanic glass, produced during volcanic eruptions and measuring less than 2 mm (0.079 inches) in diameter. The term volcanic ash is also often loosely used to r ...
or
lava
Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a Natural satellite, moon onto its surface. Lava may be erupted at a volcano or through a Fissure vent, fractu ...
flows, blanket the surface. Igneous
intrusions such as
batholiths,
laccoliths,
dikes, and
sills, push upwards into the overlying rock, and crystallize as they intrude.
After the initial sequence of rocks has been deposited, the rock units can be
deformed and/or
metamorphosed. Deformation typically occurs as a result of horizontal shortening,
horizontal extension, or side-to-side (
strike-slip) motion. These structural regimes broadly relate to
convergent boundaries,
divergent boundaries, and
transform boundaries, respectively, between
tectonic plates.
Historical perspective

Earth is estimated to have formed 4.54 billion years ago from the
solar nebula, along with the
Sun and other
planet
A planet is a large, Hydrostatic equilibrium, rounded Astronomical object, astronomical body that is generally required to be in orbit around a star, stellar remnant, or brown dwarf, and is not one itself. The Solar System has eight planets b ...
s. The Moon formed roughly 20 million years later. Initially molten, the outer layer of the Earth cooled, resulting in the solid crust. Outgassing and
volcanic activity produced the primordial atmosphere. Condensing
water vapor
Water vapor, water vapour, or aqueous vapor is the gaseous phase of Properties of water, water. It is one Phase (matter), state of water within the hydrosphere. Water vapor can be produced from the evaporation or boiling of liquid water or from th ...
, most or all of which came from
ice
Ice is water that is frozen into a solid state, typically forming at or below temperatures of 0 ° C, 32 ° F, or 273.15 K. It occurs naturally on Earth, on other planets, in Oort cloud objects, and as interstellar ice. As a naturally oc ...
delivered by
comet
A comet is an icy, small Solar System body that warms and begins to release gases when passing close to the Sun, a process called outgassing. This produces an extended, gravitationally unbound atmosphere or Coma (cometary), coma surrounding ...
s,
produced the oceans and other water sources. The highly energetic chemistry is believed to have produced a self-replicating molecule around 4 billion years ago.

Continents formed, then broke up and reformed as the surface of Earth reshaped over hundreds of millions of years, occasionally combining to make a
supercontinent
In geology, a supercontinent is the assembly of most or all of Earth's continent, continental blocks or cratons to form a single large landmass. However, some geologists use a different definition, "a grouping of formerly dispersed continents", ...
. Roughly 750 million years ago, the earliest known supercontinent
Rodinia
Rodinia (from the Russian родина, ''rodina'', meaning "motherland, birthplace") was a Mesoproterozoic and Neoproterozoic supercontinent that assembled 1.26–0.90 billion years ago (Ga) and broke up 750–633 million years ago (Ma). wer ...
, began to break apart. The continents later recombined to form
Pannotia which broke apart about 540 million years ago, then finally
Pangaea, which broke apart about 180 million years ago.
During the
Neoproterozoic
The Neoproterozoic Era is the last of the three geologic eras of the Proterozoic geologic eon, eon, spanning from 1 billion to 538.8 million years ago, and is the last era of the Precambrian "supereon". It is preceded by the Mesoproterozoic era an ...
era, freezing temperatures covered much of the Earth in
glacier
A glacier (; or ) is a persistent body of dense ice, a form of rock, that is constantly moving downhill under its own weight. A glacier forms where the accumulation of snow exceeds its ablation over many years, often centuries. It acquires ...
s and ice sheets. This hypothesis has been termed the "
Snowball Earth
The Snowball Earth is a historical geology, geohistorical hypothesis that proposes that during one or more of Earth's greenhouse and icehouse Earth, icehouse climates, the planet's planetary surface, surface became nearly entirely freezing, fr ...
", and it is of particular interest as it precedes the
Cambrian explosion in which multicellular life forms began to proliferate about 530–540 million years ago.
Since the Cambrian explosion there have been five distinctly identifiable
mass extinctions. The last mass extinction occurred some 66 million years ago, when a meteorite collision probably triggered the extinction of the
non-avian dinosaur
Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic Geological period, period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the #Evolutio ...
s and other large reptiles, but spared small animals such as
mammal
A mammal () is a vertebrate animal of the Class (biology), class Mammalia (). Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three ...
s. Over the past 66 million years, mammalian life diversified.
Several million years ago, a species of small African
ape gained the ability to stand upright.
The subsequent advent of human life, and the development of agriculture and further
civilization
A civilization (also spelled civilisation in British English) is any complex society characterized by the development of state (polity), the state, social stratification, urban area, urbanization, and symbolic systems of communication beyon ...
allowed humans to affect the Earth more rapidly than any previous life form, affecting both the nature and quantity of other organisms as well as global climate. By comparison, the
Great Oxygenation Event, produced by the proliferation of
algae
Algae ( , ; : alga ) is an informal term for any organisms of a large and diverse group of photosynthesis, photosynthetic organisms that are not plants, and includes species from multiple distinct clades. Such organisms range from unicellular ...
during the
Siderian period, required about 300 million years to culminate.
The present era is classified as part of a mass
extinction event
An extinction event (also known as a mass extinction or biotic crisis) is a widespread and rapid decrease in the biodiversity on Earth. Such an event is identified by a sharp fall in the diversity and abundance of multicellular organisms. It occ ...
, the
Holocene extinction
The Holocene extinction, also referred to as the Anthropocene extinction or the sixth mass extinction, is an ongoing extinction event caused exclusively by human activities during the Holocene epoch. This extinction event spans numerous families ...
event, the fastest ever to have occurred. Some, such as
E. O. Wilson of
Harvard University
Harvard University is a Private university, private Ivy League research university in Cambridge, Massachusetts, United States. Founded in 1636 and named for its first benefactor, the History of the Puritans in North America, Puritan clergyma ...
, predict that human destruction of the
biosphere
The biosphere (), also called the ecosphere (), is the worldwide sum of all ecosystems. It can also be termed the zone of life on the Earth. The biosphere (which is technically a spherical shell) is virtually a closed system with regard to mat ...
could cause the extinction of one-half of all species in the next 100 years. The extent of the current extinction event is still being researched, debated and calculated by biologists.
Atmosphere, climate, and weather

The Earth's atmosphere is a key factor in sustaining the
ecosystem
An ecosystem (or ecological system) is a system formed by Organism, organisms in interaction with their Biophysical environment, environment. The Biotic material, biotic and abiotic components are linked together through nutrient cycles and en ...
. The thin layer of gases that envelops the Earth is held in place by gravity. Air is mostly
nitrogen
Nitrogen is a chemical element; it has Symbol (chemistry), symbol N and atomic number 7. Nitrogen is a Nonmetal (chemistry), nonmetal and the lightest member of pnictogen, group 15 of the periodic table, often called the Pnictogen, pnictogens. ...
,
oxygen
Oxygen is a chemical element; it has chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen group (periodic table), group in the periodic table, a highly reactivity (chemistry), reactive nonmetal (chemistry), non ...
,
water vapor
Water vapor, water vapour, or aqueous vapor is the gaseous phase of Properties of water, water. It is one Phase (matter), state of water within the hydrosphere. Water vapor can be produced from the evaporation or boiling of liquid water or from th ...
, with much smaller amounts of carbon dioxide, argon, etc. The atmospheric pressure declines steadily with altitude. The
ozone layer
The ozone layer or ozone shield is a region of Earth's stratosphere that absorption (electromagnetic radiation), absorbs most of the Sun's ultraviolet radiation. It contains a high concentration of ozone (O3) in relation to other parts of the a ...
plays an important role in depleting the amount of
ultraviolet
Ultraviolet radiation, also known as simply UV, is electromagnetic radiation of wavelengths of 10–400 nanometers, shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight and constitutes about 10% of ...
(UV) radiation that reaches the surface. As
DNA
Deoxyribonucleic acid (; DNA) is a polymer composed of two polynucleotide chains that coil around each other to form a double helix. The polymer carries genetic instructions for the development, functioning, growth and reproduction of al ...
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.
Terrestrial weather occurs almost exclusively in the
lower part of the atmosphere, and serves as a convective system for redistributing heat.
Ocean current
An ocean current is a continuous, directed movement of seawater generated by a number of forces acting upon the water, including wind, the Coriolis effect, breaking waves, cabbeling, and temperature and salinity differences. Depth contours, sh ...
s 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.

Weather can have both beneficial and harmful effects. Extremes in weather, such as
tornado
A tornado is a violently rotating column of air that is in contact with the surface of Earth and a cumulonimbus cloud or, in rare cases, the base of a cumulus cloud. It is often referred to as a twister, whirlwind or cyclone, although the ...
es or
hurricane
A tropical cyclone is a rapidly rotating storm system with a low-pressure area, a closed low-level atmospheric circulation, strong winds, and a spiral arrangement of thunderstorms that produce heavy rain and squalls. Depending on its ...
s and
cyclones, can expend large amounts of energy along their paths, and produce devastation. Surface vegetation has evolved a dependence on the seasonal variation of the weather, and sudden changes lasting only a few years can have a dramatic effect, both on the vegetation and on the animals which depend on its growth for their food.
Climate is a measure of the long-term trends in the weather. Various factors are known to
influence the climate, including ocean currents, surface
albedo
Albedo ( ; ) is the fraction of sunlight that is Diffuse reflection, diffusely reflected by a body. It is measured on a scale from 0 (corresponding to a black body that absorbs all incident radiation) to 1 (corresponding to a body that reflects ...
,
greenhouse gas
Greenhouse gases (GHGs) are the gases in the atmosphere that raise the surface temperature of planets such as the Earth. Unlike other gases, greenhouse gases absorb the radiations that a planet emits, resulting in the greenhouse effect. T ...
es, variations in the solar luminosity, and changes to the Earth's orbit. Based on historical and geological records, the Earth is known to have undergone drastic
climate change
Present-day climate change includes both global warming—the ongoing increase in Global surface temperature, global average temperature—and its wider effects on Earth's climate system. Climate variability and change, Climate change in ...
s in the past, including
ice age
An ice age is a long period of reduction in the temperature of Earth's surface and atmosphere, resulting in the presence or expansion of continental and polar ice sheets and alpine glaciers. Earth's climate alternates between ice ages, and g ...
s.
The climate of a region depends on a number of factors, especially
latitude
In geography, latitude is a geographic coordinate system, geographic coordinate that specifies the north-south position of a point on the surface of the Earth or another celestial body. Latitude is given as an angle that ranges from −90° at t ...
. A latitudinal band of the surface with similar climatic attributes forms a climate region. There are a number of such regions, ranging from the
tropical climate
Tropical climate is the first of the five major climate groups in the Köppen climate classification identified with the letter A. Tropical climates are defined by a monthly average temperature of or higher in the coolest month, featuring hot te ...
at the equator to the
polar climate
The polar climate regions are characterized by a lack of warm summers but with varying winters. Every month a polar climate has an average temperature of less than . Regions with a polar climate cover more than 20% of the Earth's area. Most of ...
in the northern and southern extremes. Weather is also influenced by the seasons, which result from the
Earth
Earth is the third planet from the Sun and the only astronomical object known to Planetary habitability, harbor life. This is enabled by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water. Almost all ...
's
axis being
tilted relative to its
orbital plane. Thus, at any given time during the summer or winter, one part of the Earth is more directly exposed to the rays of the
sun. This exposure alternates as the Earth revolves in its orbit. At any given time, regardless of season, the
Northern and
Southern Hemispheres experience opposite seasons.
Weather is a
chaotic system that is readily modified by small changes to the
environment, so accurate
weather forecasting
Weather forecasting or weather prediction is the application of science and technology forecasting, to predict the conditions of the Earth's atmosphere, atmosphere for a given location and time. People have attempted to predict the weather info ...
is limited to only a few days. Overall, two things are happening worldwide: (1) temperature is increasing on the average; and (2) regional climates have been undergoing noticeable changes.
Water on Earth
Water is a
chemical substance
A chemical substance is a unique form of matter with constant chemical composition and characteristic properties. Chemical substances may take the form of a single element or chemical compounds. If two or more chemical substances can be com ...
that is composed of
hydrogen
Hydrogen is a chemical element; it has chemical symbol, symbol H and atomic number 1. It is the lightest and abundance of the chemical elements, most abundant chemical element in the universe, constituting about 75% of all baryon, normal matter ...
and
oxygen
Oxygen is a chemical element; it has chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen group (periodic table), group in the periodic table, a highly reactivity (chemistry), reactive nonmetal (chemistry), non ...
(H2O) and is vital for all known forms of life. In typical usage, "water" refers only to its liquid
form, but it also has a solid state,
ice
Ice is water that is frozen into a solid state, typically forming at or below temperatures of 0 ° C, 32 ° F, or 273.15 K. It occurs naturally on Earth, on other planets, in Oort cloud objects, and as interstellar ice. As a naturally oc ...
, and a
gaseous state,
water vapor
Water vapor, water vapour, or aqueous vapor is the gaseous phase of Properties of water, water. It is one Phase (matter), state of water within the hydrosphere. Water vapor can be produced from the evaporation or boiling of liquid water or from th ...
, or
steam
Steam is water vapor, often mixed with air or an aerosol of liquid water droplets. This may occur due to evaporation or due to boiling, where heat is applied until water reaches the enthalpy of vaporization. Saturated or superheated steam is inv ...
. Water covers 71% of the
Earth
Earth is the third planet from the Sun and the only astronomical object known to Planetary habitability, harbor life. This is enabled by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water. Almost all ...
's surface. On Earth, it is found mostly in oceans and other large bodies of water, with 1.6% of water below ground in
aquifer
An aquifer is an underground layer of water-bearing material, consisting of permeability (Earth sciences), permeable or fractured rock, or of unconsolidated materials (gravel, sand, or silt). Aquifers vary greatly in their characteristics. The s ...
s and 0.001% in the
air as
vapor
In physics, a vapor (American English) or vapour (Commonwealth English; American and British English spelling differences#-our, -or, see spelling differences) is a substance in the gas phase at a temperature lower than its critical temperature,R ...
, clouds, and
precipitation
In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls from clouds due to gravitational pull. The main forms of precipitation include drizzle, rain, rain and snow mixed ("sleet" in Commonwe ...
. Oceans hold 97% of surface water,
glacier
A glacier (; or ) is a persistent body of dense ice, a form of rock, that is constantly moving downhill under its own weight. A glacier forms where the accumulation of snow exceeds its ablation over many years, often centuries. It acquires ...
s, and polar
ice caps 2.4%, and other land surface water such as rivers, lakes, and ponds 0.6%. Additionally, a minute amount of the Earth's water is contained within biological bodies and manufactured products.
Oceans

An ocean is a major body of
saline water
Saline water (more commonly known as salt water) is water that contains a high concentration of dissolved salts (mainly sodium chloride). On the United States Geological Survey (USGS) salinity scale, saline water is saltier than brackish wat ...
, and a principal component of the hydrosphere. Approximately 71% of the Earth's surface (an area of some 361 million square kilometers) is covered by ocean, a
continuous body of water that is customarily divided into several principal oceans and smaller seas. More than half of this area is over deep. Average oceanic
salinity
Salinity () is the saltiness or amount of salt (chemistry), salt dissolved in a body of water, called saline water (see also soil salinity). It is usually measured in g/L or g/kg (grams of salt per liter/kilogram of water; the latter is dimensio ...
is around 35
parts per thousand (ppt) (3.5%), and nearly all seawater has a salinity in the range of 30 to 38 ppt. Though generally recognized as several 'separate' oceans, these waters comprise one global, interconnected body of salt water often referred to as the
World Ocean
The ocean is the body of salt water that covers approximately 70.8% of Earth. The ocean is conventionally divided into large bodies of water, which are also referred to as ''oceans'' (the Pacific, Atlantic, Indian, Antarctic/Southern, and ...
or global ocean.
[Distribution of land and water on the planet]
"
UN Atlas of the Oceans
This concept of a global ocean as a continuous body of water with relatively free interchange among its parts is of fundamental importance to
oceanography
Oceanography (), also known as oceanology, sea science, ocean science, and marine science, is the scientific study of the ocean, including its physics, chemistry, biology, and geology.
It is an Earth science, which covers a wide range of to ...
.
The major oceanic divisions are defined in part by the
continent
A continent is any of several large geographical regions. Continents are generally identified by convention (norm), convention rather than any strict criteria. A continent could be a single large landmass, a part of a very large landmass, as ...
s, various
archipelago
An archipelago ( ), sometimes called an island group or island chain, is a chain, cluster, or collection of islands. An archipelago may be in an ocean, a sea, or a smaller body of water. Example archipelagos include the Aegean Islands (the o ...
s, and other criteria: these divisions are (in descending order of size) the
Pacific Ocean
The Pacific Ocean is the largest and deepest of Earth's five Borders of the oceans, oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean, or, depending on the definition, to Antarctica in the south, and is ...
, the
Atlantic Ocean
The Atlantic Ocean is the second largest of the world's five borders of the oceans, oceanic divisions, with an area of about . It covers approximately 17% of Earth#Surface, Earth's surface and about 24% of its water surface area. During the ...
, the
Indian Ocean
The Indian Ocean is the third-largest of the world's five oceanic divisions, covering or approximately 20% of the water area of Earth#Surface, Earth's surface. It is bounded by Asia to the north, Africa to the west and Australia (continent), ...
, the
Southern Ocean
The Southern Ocean, also known as the Antarctic Ocean, comprises the southernmost waters of the world ocean, generally taken to be south of 60th parallel south, 60° S latitude and encircling Antarctica. With a size of , it is the seco ...
, and the
Arctic Ocean
The Arctic Ocean is the smallest and shallowest of the world's five oceanic divisions. It spans an area of approximately and is the coldest of the world's oceans. The International Hydrographic Organization (IHO) recognizes it as an ocean, ...
. Smaller regions of the oceans are called seas, gulfs,
bays and other names. There are also
salt lakes, which are smaller bodies of landlocked saltwater that are not interconnected with the World Ocean. Two notable examples of salt lakes are the
Aral Sea and the
Great Salt Lake.
Lakes

A lake (from Latin word ''lacus'') is a
terrain feature (or
physical feature), a body of liquid on the surface of a world that is localized to the bottom of
basin (another type of landform or terrain feature; that is, it is not global) and moves slowly if it moves at all. On Earth, a body of water is considered a lake when it is inland, not part of the ocean, is larger and deeper than a pond, and is fed by a river. The only world other than Earth known to harbor lakes is
Titan, Saturn's largest moon, which has lakes of
ethane
Ethane ( , ) is a naturally occurring Organic compound, organic chemical compound with chemical formula . At standard temperature and pressure, ethane is a colorless, odorless gas. Like many hydrocarbons, ethane is List of purification methods ...
, most likely mixed with
methane
Methane ( , ) is a chemical compound with the chemical formula (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The abundance of methane on Earth makes ...
. It is not known if Titan's lakes are fed by rivers, though Titan's surface is carved by numerous river beds. Natural lakes on Earth are generally found in mountainous areas,
rift zone
A rift zone is a feature of some volcanoes, especially shield volcanoes, in which a set of linear cracks (or rifts) develops in a volcanic edifice, typically forming into two or three well-defined regions along the flanks of the vent. Believed ...
s, and areas with ongoing or recent
glaciation
A glacial period (alternatively glacial or glaciation) is an interval of time (thousands of years) within an ice age that is marked by colder temperatures and glacier advances. Interglacials, on the other hand, are periods of warmer climate be ...
. Other lakes are found in
endorheic basin
An endorheic basin ( ; also endoreic basin and endorreic basin) is a drainage basin that normally retains water and allows no outflow to other external bodies of water (e.g. rivers and oceans); instead, the water drainage flows into permanent ...
s or along the courses of mature rivers. In some parts of the world, there are many lakes because of chaotic drainage patterns left over from the
last ice age. All lakes are temporary over geologic time scales, as they will slowly fill in with sediments or spill out of the basin containing them.
Ponds

A pond is a
body of
standing water
Water stagnation occurs when water stops Environmental flow, flowing for a long period of time. Stagnant water can be a significant environmental hazard.
Dangers
Malaria and dengue are among the main dangers of still water, which can become ...
, either natural or human-made, that is usually smaller than a lake. A wide variety of human-made bodies of water are classified as ponds, including
water gardens designed for aesthetic ornamentation,
fish ponds designed for commercial fish breeding, and
solar ponds designed to store thermal energy. Ponds and lakes are distinguished from streams via
current speed. While currents in streams are easily observed, ponds and lakes possess thermally driven micro-currents and moderate wind driven currents. These features distinguish a pond from many other aquatic terrain features, such as
stream pools and
tide pools.
Rivers

A river is a natural
watercourse
A stream is a continuous body of water, body of surface water Current (stream), flowing within the stream bed, bed and bank (geography), banks of a channel (geography), channel. Depending on its location or certain characteristics, a strea ...
, usually
freshwater
Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. The term excludes seawater and brackish water, but it does include non-salty mi ...
, flowing towards an ocean, a lake, a sea or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including stream, creek, brook, rivulet, and rill; there is no general rule that defines what can be called a river. Many names for small rivers are specific to geographic location; one example is ''Burn'' in Scotland and North-east England. Sometimes a river is said to be larger than a creek, but this is not always the case, due to vagueness in the language. A river is part of the
hydrological cycle. Water within a river is generally collected from
precipitation
In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls from clouds due to gravitational pull. The main forms of precipitation include drizzle, rain, rain and snow mixed ("sleet" in Commonwe ...
through
surface runoff
Surface runoff (also known as overland flow or terrestrial runoff) is the unconfined flow of water over the ground surface, in contrast to ''channel runoff'' (or ''stream flow''). It occurs when excess rainwater, stormwater, meltwater, or other ...
,
groundwater
Groundwater is the water present beneath Earth's surface in rock and Pore space in soil, soil pore spaces and in the fractures of stratum, rock formations. About 30 percent of all readily available fresh water in the world is groundwater. A unit ...
recharge,
springs, and the release of stored water in natural ice and snowpacks (i.e., from
glacier
A glacier (; or ) is a persistent body of dense ice, a form of rock, that is constantly moving downhill under its own weight. A glacier forms where the accumulation of snow exceeds its ablation over many years, often centuries. It acquires ...
s).
Streams

A stream is a flowing body of water with a
current, confined within a
bed and
stream banks. In the United States, a stream is classified as a watercourse less than wide. Streams are important as conduits in the
water cycle
The water cycle (or hydrologic cycle or hydrological cycle) is a biogeochemical cycle that involves the continuous movement of water on, above and below the surface of the Earth across different reservoirs. The mass of water on Earth remains fai ...
, instruments in
groundwater recharge, and they serve as corridors for fish and
wildlife
Wildlife refers to domestication, undomesticated animals and uncultivated plant species which can exist in their natural habitat, but has come to include all organisms that grow or live wilderness, wild in an area without being species, introdu ...
migration. The biological
habitat
In ecology, habitat refers to the array of resources, biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species' habitat can be seen as the physical manifestation of its ...
in the immediate vicinity of a stream is called a
riparian zone
A riparian zone or riparian area is the interface between land and a river or stream. In some regions, the terms riparian woodland, riparian forest, riparian buffer zone, riparian corridor, and riparian strip are used to characterize a ripari ...
. Given the status of the ongoing
Holocene extinction
The Holocene extinction, also referred to as the Anthropocene extinction or the sixth mass extinction, is an ongoing extinction event caused exclusively by human activities during the Holocene epoch. This extinction event spans numerous families ...
, streams play an important
corridor role in connecting
fragmented habitats and thus in conserving
biodiversity
Biodiversity is the variability of life, life on Earth. It can be measured on various levels. There is for example genetic variability, species diversity, ecosystem diversity and Phylogenetics, phylogenetic diversity. Diversity is not distribut ...
. The study of streams and waterways in general involves many branches of inter-disciplinary natural science and engineering, including
hydrology
Hydrology () is the scientific study of the movement, distribution, and management of water on Earth and other planets, including the water cycle, water resources, and drainage basin sustainability. A practitioner of hydrology is called a hydro ...
,
fluvial geomorphology,
aquatic ecology
An aquatic ecosystem is an ecosystem found in and around a body of water, in contrast to land-based terrestrial ecosystems. Aquatic ecosystems contain communities of organisms—aquatic life—that are dependent on each other and on their environ ...
,
fish biology,
riparian ecology, and others.
Ecosystems

Ecosystems are composed of a variety of
biotic and
abiotic components that function in an interrelated way. The structure and composition is determined by various environmental factors that are interrelated. Variations of these factors will initiate dynamic modifications to the ecosystem. Some of the more important components are
soil
Soil, also commonly referred to as earth, is a mixture of organic matter, minerals, gases, water, and organisms that together support the life of plants and soil organisms. Some scientific definitions distinguish dirt from ''soil'' by re ...
,
atmosphere
An atmosphere () is a layer of gases that envelop an astronomical object, held in place by the gravity of the object. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A stellar atmosph ...
, radiation from the
sun, water, and living organisms.
Central to the ecosystem concept is the idea that
living organism
An organism is any life, living thing that functions as an individual. Such a definition raises more problems than it solves, not least because the concept of an individual is also difficult. Many criteria, few of them widely accepted, have be ...
s interact with every other element in their local
environment. Eugene Odum, a founder of ecology, stated: "Any unit that includes all of the organisms (i.e.: the "community") in a given area interacting with the physical environment so that a flow of energy leads to clearly defined trophic structure, biotic diversity, and material cycles (i.e.: exchange of materials between living and nonliving parts) within the system is an ecosystem."
[Odum, EP (1971) ''Fundamentals of ecology'', 3rd edition, Saunders New York] Within the ecosystem, species are connected and dependent upon one another in the
food chain
A food chain is a linear network of links in a food web, often starting with an autotroph (such as grass or algae), also called a producer, and typically ending at an apex predator (such as grizzly bears or killer whales), detritivore (such as ...
, and exchange energy and
matter
In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All everyday objects that can be touched are ultimately composed of atoms, which are made up of interacting subatomic pa ...
between themselves as well as with their environment. The human ecosystem concept is based on the human/nature
dichotomy
A dichotomy () is a partition of a set, partition of a whole (or a set) into two parts (subsets). In other words, this couple of parts must be
* jointly exhaustive: everything must belong to one part or the other, and
* mutually exclusive: nothi ...
and the idea that all species are ecologically dependent on each other, as well as with the abiotic constituents of their
biotope
A biotope is an area of uniform environmental conditions providing a living place for a specific assemblage of flora (plants), plants and fauna (animals), animals. ''Biotope'' is almost synonymous with the term habitat (ecology), "habitat", which ...
.
A smaller unit of size is called a
microecosystem. For example, a microsystem can be a stone and all the life under it. A ''macroecosystem'' might involve a whole
ecoregion
An ecoregion (ecological region) is an ecological and geographic area that exists on multiple different levels, defined by type, quality, and quantity of environmental resources. Ecoregions cover relatively large areas of land or water, and c ...
, with its
drainage basin
A drainage basin is an area of land in which all flowing surface water converges to a single point, such as a river mouth, or flows into another body of water, such as a lake or ocean. A basin is separated from adjacent basins by a perimeter, ...
.
Wilderness

Wilderness is generally defined as areas that have not been significantly modified by human activity. Wilderness areas can be found in preserves, estates, farms, conservation preserves, ranches,
national forests,
national park
A national park is a nature park designated for conservation (ethic), conservation purposes because of unparalleled national natural, historic, or cultural significance. It is an area of natural, semi-natural, or developed land that is protecte ...
s, and even in urban areas along rivers, gulches, or otherwise undeveloped areas. Wilderness areas and protected
parks are considered important for the survival of certain
species
A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...
, ecological studies,
conservation, and solitude. Some nature writers believe wilderness areas are vital for the human spirit and creativity,
[Botkin, Daniel B. (2000) ''No Man's Garden'', Island Press, pp. 155–157, .] and some ecologists consider wilderness areas to be an integral part of the Earth's self-sustaining natural
ecosystem
An ecosystem (or ecological system) is a system formed by Organism, organisms in interaction with their Biophysical environment, environment. The Biotic material, biotic and abiotic components are linked together through nutrient cycles and en ...
(the
biosphere
The biosphere (), also called the ecosphere (), is the worldwide sum of all ecosystems. It can also be termed the zone of life on the Earth. The biosphere (which is technically a spherical shell) is virtually a closed system with regard to mat ...
). They may also preserve historic
genetic traits and that they provide
habitat
In ecology, habitat refers to the array of resources, biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species' habitat can be seen as the physical manifestation of its ...
for wild
flora
Flora (: floras or florae) is all the plant life present in a particular region or time, generally the naturally occurring (indigenous (ecology), indigenous) native plant, native plants. The corresponding term for animals is ''fauna'', and for f ...
and
fauna
Fauna (: faunae or faunas) is all of the animal life present in a particular region or time. The corresponding terms for plants and fungi are ''flora'' and '' funga'', respectively. Flora, fauna, funga and other forms of life are collectively ...
that may be difficult or impossible to recreate in
zoos,
arboretum
An arboretum (: arboreta) is a botanical collection composed exclusively of trees and shrubs of a variety of species. Originally mostly created as a section in a larger garden or park for specimens of mostly non-local species, many modern arbor ...
s, or
laboratories
A laboratory (; ; colloquially lab) is a facility that provides controlled conditions in which science, scientific or technological research, experiments, and measurement may be performed. Laboratories are found in a variety of settings such as s ...
.
Life

Although there is no universal agreement on the definition of life, scientists generally accept that the biological manifestation of life is characterized by
organization
An organization or organisation (English in the Commonwealth of Nations, Commonwealth English; American and British English spelling differences#-ise, -ize (-isation, -ization), see spelling differences) is an legal entity, entity—such as ...
,
metabolism
Metabolism (, from ''metabolē'', "change") is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run cellular processes; the co ...
,
growth,
adaptation
In biology, adaptation has three related meanings. Firstly, it is the dynamic evolutionary process of natural selection that fits organisms to their environment, enhancing their evolutionary fitness. Secondly, it is a state reached by the p ...
, response to
stimuli, and
reproduction
Reproduction (or procreation or breeding) is the biological process by which new individual organisms – "offspring" – are produced from their "parent" or parents. There are two forms of reproduction: Asexual reproduction, asexual and Sexual ...
. Life may also be said to be simply the characteristic state of
organism
An organism is any life, living thing that functions as an individual. Such a definition raises more problems than it solves, not least because the concept of an individual is also difficult. Many criteria, few of them widely accepted, have be ...
s.
Present day organisms from
virus
A virus is a submicroscopic infectious agent that replicates only inside the living Cell (biology), cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea. Viruses are ...
es to humans possess a self-replicating informational molecule (genome), either
DNA
Deoxyribonucleic acid (; DNA) is a polymer composed of two polynucleotide chains that coil around each other to form a double helix. The polymer carries genetic instructions for the development, functioning, growth and reproduction of al ...
or
RNA
Ribonucleic acid (RNA) is a polymeric molecule that is essential for most biological functions, either by performing the function itself (non-coding RNA) or by forming a template for the production of proteins (messenger RNA). RNA and deoxyrib ...
(as in some viruses), and such an informational molecule is probably intrinsic to life. It is likely that the earliest forms of life were based on a self-replicating informational molecule (
genome
A genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding genes, other functional regions of the genome such as ...
), perhaps RNA or a molecule more primitive than RNA or DNA. The specific
deoxyribonucleotide/
ribonucleotide sequence in each currently extant individual organism contains sequence information that functions to promotes survival,
reproduction
Reproduction (or procreation or breeding) is the biological process by which new individual organisms – "offspring" – are produced from their "parent" or parents. There are two forms of reproduction: Asexual reproduction, asexual and Sexual ...
, and the capacity to acquire resources necessary for reproduction, and such sequences probably emerged early in the evolution of life. Survival functions present early in the evolution of life likely also included genomic sequences that promote the avoidance of damage to the self-replicating molecule and also the capability to
repair such damages that do occur. Repair of some genome damages may have involved using information from another similar molecule by a process of
recombination (a primitive form of
sexual interaction).
Properties common to terrestrial organisms (plants, animals,
fungi
A fungus (: fungi , , , or ; or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified as one ...
,
protist
A protist ( ) or protoctist is any eukaryotic organism that is not an animal, land plant, or fungus. Protists do not form a natural group, or clade, but are a paraphyletic grouping of all descendants of the last eukaryotic common ancest ...
s,
archaea
Archaea ( ) is a Domain (biology), domain of organisms. Traditionally, Archaea only included its Prokaryote, prokaryotic members, but this has since been found to be paraphyletic, as eukaryotes are known to have evolved from archaea. Even thou ...
, and bacteria) are that they are cellular, carbon-and-water-based with complex organization, having a metabolism, a capacity to grow, respond to stimuli, and reproduce. An entity with these properties is generally considered life. However, not every definition of life considers all of these properties to be essential. Human-made
analogs of life may also be considered to be life.
The
biosphere
The biosphere (), also called the ecosphere (), is the worldwide sum of all ecosystems. It can also be termed the zone of life on the Earth. The biosphere (which is technically a spherical shell) is virtually a closed system with regard to mat ...
is the part of Earth's outer shell—including land, surface rocks, water, air and the atmosphere—within which life occurs, and which
biotic processes in turn alter or transform. From the broadest
geophysiological point of view, the biosphere is the global ecological system integrating all living beings and their relationships, including their interaction with the elements of the
lithosphere
A lithosphere () is the rigid, outermost rocky shell of a terrestrial planet or natural satellite. On Earth, it is composed of the crust and the lithospheric mantle, the topmost portion of the upper mantle that behaves elastically on time ...
(rocks),
hydrosphere
The hydrosphere () is the combined mass of water found on, under, and above the Planetary surface, surface of a planet, minor planet, or natural satellite. Although Earth's hydrosphere has been around for about 4 billion years, it continues to ch ...
(water), and
atmosphere
An atmosphere () is a layer of gases that envelop an astronomical object, held in place by the gravity of the object. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A stellar atmosph ...
(air). The entire Earth contains over 75 billion tons (150 ''trillion'' pounds or about 6.8×10
13 kilograms) of
biomass
Biomass is a term used in several contexts: in the context of ecology it means living organisms, and in the context of bioenergy it means matter from recently living (but now dead) organisms. In the latter context, there are variations in how ...
(life), which lives within various environments within the biosphere.
Over nine-tenths of the total biomass on Earth is plant life, on which animal life depends very heavily for its existence. More than 2 million species of plant and animal life have been identified to date, and estimates of the actual number of existing species range from several million to well over 50 million. The number of individual species of life is constantly in some degree of flux, with new species appearing and others ceasing to exist on a continual basis. The total number of species is in rapid decline.
Evolution

The
origin of life
Abiogenesis is the natural process by which life arises from abiotic component, non-living matter, such as simple organic compounds. The prevailing scientific hypothesis is that the transition from non-living to organism, living entities on ...
on Earth is not well understood, but it is known to have occurred at least 3.5 billion years ago,
during the
hadean or
archean
The Archean ( , also spelled Archaean or Archæan), in older sources sometimes called the Archaeozoic, is the second of the four geologic eons of Earth's history of Earth, history, preceded by the Hadean Eon and followed by the Proterozoic and t ...
eons on a
primordial Earth that had a substantially different environment than is found at present.
These life forms possessed the basic traits of self-replication and inheritable traits. Once life had appeared, the process of
evolution
Evolution is the change in the heritable Phenotypic trait, characteristics of biological populations over successive generations. It occurs when evolutionary processes such as natural selection and genetic drift act on genetic variation, re ...
by
natural selection
Natural selection is the differential survival and reproduction of individuals due to differences in phenotype. It is a key mechanism of evolution, the change in the Heredity, heritable traits characteristic of a population over generation ...
resulted in the development of ever-more diverse life forms.
Species that were unable to adapt to the changing environment and competition from other life forms became extinct. However, the
fossil
A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserve ...
record retains evidence of many of these older species. Current fossil and
DNA
Deoxyribonucleic acid (; DNA) is a polymer composed of two polynucleotide chains that coil around each other to form a double helix. The polymer carries genetic instructions for the development, functioning, growth and reproduction of al ...
evidence shows that all existing species can trace a continual ancestry back to the first primitive life forms.
[
When basic forms of plant life developed the process of ]photosynthesis
Photosynthesis ( ) is a system of biological processes by which photosynthetic organisms, such as most plants, algae, and cyanobacteria, convert light energy, typically from sunlight, into the chemical energy necessary to fuel their metabo ...
the sun's energy could be harvested to create conditions which allowed for more complex life forms. The resultant oxygen
Oxygen is a chemical element; it has chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen group (periodic table), group in the periodic table, a highly reactivity (chemistry), reactive nonmetal (chemistry), non ...
accumulated in the atmosphere and gave rise to the ozone layer
The ozone layer or ozone shield is a region of Earth's stratosphere that absorption (electromagnetic radiation), absorbs most of the Sun's ultraviolet radiation. It contains a high concentration of ozone (O3) in relation to other parts of the a ...
. The incorporation of smaller cells within larger ones resulted in the development of yet more complex cells called eukaryotes
The eukaryotes ( ) constitute the domain of Eukaryota or Eukarya, organisms whose cells have a membrane-bound nucleus. All animals, plants, fungi, seaweeds, and many unicellular organisms are eukaryotes. They constitute a major group of ...
. Cells within colonies became increasingly specialized, resulting in true multicellular organisms. With the ozone layer absorbing harmful ultraviolet radiation
Ultraviolet radiation, also known as simply UV, is electromagnetic radiation of wavelengths of 10–400 nanometers, shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight and constitutes about 10% of t ...
, life colonized the surface of Earth.
Microbes
The first form of life to develop on the Earth were unicellular, and they remained the only form of life until about a billion years ago when multi-cellular organisms began to appear. Microorganisms or microbes are microscopic, and smaller than the human eye can see. Microorganism
A microorganism, or microbe, is an organism of microscopic scale, microscopic size, which may exist in its unicellular organism, single-celled form or as a Colony (biology)#Microbial colonies, colony of cells. The possible existence of unseen ...
s can be single-celled, such as Bacteria
Bacteria (; : bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of Prokaryote, prokaryotic microorganisms. Typically a few micr ...
, Archaea
Archaea ( ) is a Domain (biology), domain of organisms. Traditionally, Archaea only included its Prokaryote, prokaryotic members, but this has since been found to be paraphyletic, as eukaryotes are known to have evolved from archaea. Even thou ...
, many Protist
A protist ( ) or protoctist is any eukaryotic organism that is not an animal, land plant, or fungus. Protists do not form a natural group, or clade, but are a paraphyletic grouping of all descendants of the last eukaryotic common ancest ...
a, and a minority of Fungi
A fungus (: fungi , , , or ; or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified as one ...
.
These life forms are found in almost every location on the Earth where there is liquid water, including in the Earth's interior.
Their reproduction is both rapid and profuse. The combination of a high mutation rate and a horizontal gene transfer
Horizontal gene transfer (HGT) or lateral gene transfer (LGT) is the movement of genetic material between organisms other than by the ("vertical") transmission of DNA from parent to offspring (reproduction). HGT is an important factor in the e ...
ability makes them highly adaptable, and able to survive in new and sometimes very harsh environments, including outer space. They form an essential part of the planetary ecosystem. However, some microorganisms are pathogen
In biology, a pathogen (, "suffering", "passion" and , "producer of"), in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a Germ theory of d ...
ic and can post health risk to other organisms.
Viruses
A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea. Viruses are found in almo ...
are infectious agents, but they are not autonomous life forms, as it is the case for viroids, satellites
A satellite or an artificial satellite is an object, typically a spacecraft, placed into orbit around a celestial body. They have a variety of uses, including communication relay, weather forecasting, navigation ( GPS), broadcasting, scientif ...
, DPIs and prions.
Plants and animals
Originally Aristotle
Aristotle (; 384–322 BC) was an Ancient Greek philosophy, Ancient Greek philosopher and polymath. His writings cover a broad range of subjects spanning the natural sciences, philosophy, linguistics, economics, politics, psychology, a ...
divided all living things between plants, which generally do not move fast enough for humans to notice, and animals. In Linnaeus
Carl Linnaeus (23 May 1707 – 10 January 1778), also known after ennoblement in 1761 as Carl von Linné,#Blunt, Blunt (2004), p. 171. was a Swedish biologist and physician who formalised binomial nomenclature, the modern system of naming o ...
' system, these became the kingdoms Vegetabilia (later Plant
Plants are the eukaryotes that form the Kingdom (biology), kingdom Plantae; they are predominantly Photosynthesis, photosynthetic. This means that they obtain their energy from sunlight, using chloroplasts derived from endosymbiosis with c ...
ae) and Animal
Animals are multicellular, eukaryotic organisms in the Biology, biological Kingdom (biology), kingdom Animalia (). With few exceptions, animals heterotroph, consume organic material, Cellular respiration#Aerobic respiration, breathe oxygen, ...
ia. Since then, it has become clear that the Plantae as originally defined included several unrelated groups, and the fungi
A fungus (: fungi , , , or ; or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified as one ...
and several groups of algae were removed to new kingdoms. However, these are still often considered plants in many contexts. Bacterial life is sometimes included in flora, and some classifications use the term ''bacterial flora'' separately from ''plant flora''.
Among the many ways of classifying plants are by regional flora
Flora (: floras or florae) is all the plant life present in a particular region or time, generally the naturally occurring (indigenous (ecology), indigenous) native plant, native plants. The corresponding term for animals is ''fauna'', and for f ...
s, which, depending on the purpose of study, can also include ''fossil flora'', remnants of plant life from a previous era. People in many regions and countries take great pride in their individual arrays of characteristic flora, which can vary widely across the globe due to differences in climate and terrain
Terrain (), alternatively relief or topographical relief, is the dimension and shape of a given surface of land. In physical geography, terrain is the lay of the land. This is usually expressed in terms of the elevation, slope, and orientati ...
.
Regional floras commonly are divided into categories such as ''native flora'' or ''agricultural and garden flora''. Some types of "native flora" actually have been introduced centuries ago by people migrating from one region or continent to another, and become an integral part of the native, or natural flora of the place to which they were introduced. This is an example of how human interaction with nature can blur the boundary of what is considered nature.
Another category of plant has historically been carved out for ''weeds''. Though the term has fallen into disfavor among botanists as a formal way to categorize "useless" plants, the informal use of the word "weeds" to describe those plants that are deemed worthy of elimination is illustrative of the general tendency of people and societies to seek to alter or shape the course of nature. Similarly, animals are often categorized in ways such as ''domestic'', ''farm animals'', ''wild animals'', ''pests'', etc. according to their relationship to human life.
Animals as a category have several characteristics that generally set them apart from other living things. Animals are eukaryotic
The eukaryotes ( ) constitute the Domain (biology), domain of Eukaryota or Eukarya, organisms whose Cell (biology), cells have a membrane-bound cell nucleus, nucleus. All animals, plants, Fungus, fungi, seaweeds, and many unicellular organisms ...
and usually multicellular
A multicellular organism is an organism that consists of more than one cell (biology), cell, unlike unicellular organisms. All species of animals, Embryophyte, land plants and most fungi are multicellular, as are many algae, whereas a few organism ...
, which separates them from bacteria, archaea
Archaea ( ) is a Domain (biology), domain of organisms. Traditionally, Archaea only included its Prokaryote, prokaryotic members, but this has since been found to be paraphyletic, as eukaryotes are known to have evolved from archaea. Even thou ...
, and most protist
A protist ( ) or protoctist is any eukaryotic organism that is not an animal, land plant, or fungus. Protists do not form a natural group, or clade, but are a paraphyletic grouping of all descendants of the last eukaryotic common ancest ...
s. They are heterotroph
A heterotroph (; ) is an organism that cannot produce its own food, instead taking nutrition from other sources of organic carbon, mainly plant or animal matter. In the food chain, heterotrophs are primary, secondary and tertiary consumers, but ...
ic, generally digesting food in an internal chamber, which separates them from plants and algae. They are also distinguished from plants, algae, and fungi
A fungus (: fungi , , , or ; or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified as one ...
by lacking cell wall
A cell wall is a structural layer that surrounds some Cell type, cell types, found immediately outside the cell membrane. It can be tough, flexible, and sometimes rigid. Primarily, it provides the cell with structural support, shape, protection, ...
s.
With a few exceptions—most notably the two phyla
Phyla, the plural of ''phylum'', may refer to:
* Phylum, a biological taxon between Kingdom and Class
* by analogy, in linguistics, a large division of possibly related languages, or a major language family which is not subordinate to another
Phy ...
consisting of sponge
Sponges or sea sponges are primarily marine invertebrates of the animal phylum Porifera (; meaning 'pore bearer'), a basal clade and a sister taxon of the diploblasts. They are sessile filter feeders that are bound to the seabed, and a ...
s and placozoa
Placozoa ( ; ) is a phylum of free-living (non-parasitic) marine invertebrates. They are blob-like animals composed of aggregations of cells. Moving in water by ciliary motion, eating food by Phagocytosis, engulfment, reproducing by Fission (biol ...
ns—animals have bodies that are differentiated into tissues. These include muscle
Muscle is a soft tissue, one of the four basic types of animal tissue. There are three types of muscle tissue in vertebrates: skeletal muscle, cardiac muscle, and smooth muscle. Muscle tissue gives skeletal muscles the ability to muscle contra ...
s, which are able to contract and control locomotion, and a nervous system
In biology, the nervous system is the complex system, highly complex part of an animal that coordinates its behavior, actions and sense, sensory information by transmitting action potential, signals to and from different parts of its body. Th ...
, which sends and processes signals. There is also typically an internal digestive chamber. The eukaryotic cells possessed by all animals are surrounded by a characteristic extracellular matrix composed of collagen
Collagen () is the main structural protein in the extracellular matrix of the connective tissues of many animals. It is the most abundant protein in mammals, making up 25% to 35% of protein content. Amino acids are bound together to form a trip ...
and elastic glycoproteins. This may be calcified to form structures like shells, bone
A bone is a rigid organ that constitutes part of the skeleton in most vertebrate animals. Bones protect the various other organs of the body, produce red and white blood cells, store minerals, provide structure and support for the body, ...
s, and spicules, a framework upon which cells can move about and be reorganized during development and maturation, and which supports the complex anatomy required for mobility.
Human interrelationship
Human impact
Although humans comprise a minuscule proportion of the total living biomass
Biomass is a term used in several contexts: in the context of ecology it means living organisms, and in the context of bioenergy it means matter from recently living (but now dead) organisms. In the latter context, there are variations in how ...
on Earth, the human effect on nature is disproportionately large. Because of the extent of human influence, the boundaries between what humans regard as nature and "made environments" is not clear cut except at the extremes. Even at the extremes, the amount of natural environment that is free of discernible human influence is diminishing at an increasingly rapid pace. A 2020 study published in ''Nature
Nature is an inherent character or constitution, particularly of the Ecosphere (planetary), ecosphere or the universe as a whole. In this general sense nature refers to the Scientific law, laws, elements and phenomenon, phenomena of the physic ...
'' found that anthropogenic mass (human-made materials) outweighs all living biomass on earth, with plastic
Plastics are a wide range of synthetic polymers, synthetic or Semisynthesis, semisynthetic materials composed primarily of Polymer, polymers. Their defining characteristic, Plasticity (physics), plasticity, allows them to be Injection moulding ...
alone exceeding the mass of all land and marine animals combined. And according to a 2021 study published in ''Frontiers in Forests and Global Change'', only about 3% of the planet's terrestrial surface is ecologically and fauna
Fauna (: faunae or faunas) is all of the animal life present in a particular region or time. The corresponding terms for plants and fungi are ''flora'' and '' funga'', respectively. Flora, fauna, funga and other forms of life are collectively ...
lly intact, with a low human footprint and healthy populations of native animal species. Philip Cafaro, professor of philosophy at the School of Global Environmental Sustainability at Colorado State University
Colorado State University (Colorado State or CSU) is a Public university, public Land-grant university, land-grant research university in Fort Collins, Colorado, United States. It is the flagship university of the Colorado State University Syst ...
, wrote in 2022 that "the cause of global biodiversity loss is clear: other species are being displaced by a rapidly growing human economy."
The development of technology
Technology is the application of Conceptual model, conceptual knowledge to achieve practical goals, especially in a reproducible way. The word ''technology'' can also mean the products resulting from such efforts, including both tangible too ...
by the human race has allowed the greater exploitation of natural resources and has helped to alleviate some of the risk from natural hazards. In spite of this progress, however, the fate of human civilization
A civilization (also spelled civilisation in British English) is any complex society characterized by the development of state (polity), the state, social stratification, urban area, urbanization, and symbolic systems of communication beyon ...
remains closely linked to changes in the environment. There exists a highly complex feedback loop between the use of advanced technology and changes to the environment that are only slowly becoming understood. Human-made threats to the Earth's natural environment include pollution
Pollution is the introduction of contaminants into the natural environment that cause harm. Pollution can take the form of any substance (solid, liquid, or gas) or energy (such as radioactivity, heat, sound, or light). Pollutants, the component ...
, deforestation
Deforestation or forest clearance is the removal and destruction of a forest or stand of trees from land that is then converted to non-forest use. Deforestation can involve conversion of forest land to farms, ranches, or urban use. Ab ...
, and disasters such as oil spills. Humans have contributed to the extinction
Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...
of many plants and animals, with roughly 1 million species threatened with extinction within decades. The loss of biodiversity and ecosystem functions over the last half century have impacted the extent that nature can contribute to human quality of life, and continued declines could pose a major threat to the existence of human civilization, unless a rapid course correction is made. The value of natural resources to human society is poorly reflected in market prices because except for labour costs the natural resources are available free of charge. This distorts market pricing of natural resources and at the same time leads to underinvestment in our natural assets. The annual global cost of public subsidies that damage nature is conservatively estimated at $4–6 trillion (million million). Institutional protections of these natural goods, such as the oceans and rainforests, are lacking. Governments have not prevented these economic externalities.
Humans employ nature for both leisure and economic activities. The acquisition of natural resources for industrial use remains a sizable component of the world's economic system
An economic system, or economic order, is a system of production, resource allocation and distribution of goods and services within an economy. It includes the combination of the various institutions, agencies, entities, decision-making proces ...
. Some activities, such as hunting and fishing, are used for both sustenance and leisure, often by different people. Agriculture
Agriculture encompasses crop and livestock production, aquaculture, and forestry for food and non-food products. Agriculture was a key factor in the rise of sedentary human civilization, whereby farming of domesticated species created ...
was first adopted around the 9th millennium BCE
The 9th millennium BC spanned the years 9000 BC to 8001 BC (11 to 10 thousand years ago). In chronological terms, it is the first full millennium of the current Holocene epoch that is generally reckoned to have begun by 9700 BC (11.7 thousan ...
. Ranging from food production to energy, nature influences economic wealth.
Although early humans gathered uncultivated plant materials for food and employed the medicinal properties of vegetation for healing, most modern human use of plants is through agriculture
Agriculture encompasses crop and livestock production, aquaculture, and forestry for food and non-food products. Agriculture was a key factor in the rise of sedentary human civilization, whereby farming of domesticated species created ...
. The clearance of large tracts of land for crop
A crop is a plant that can be grown and harvested extensively for profit or subsistence. In other words, a crop is a plant or plant product that is grown for a specific purpose such as food, Fiber, fibre, or fuel.
When plants of the same spe ...
growth has led to a significant reduction in the amount available of forestation and wetlands
A wetland is a distinct semi-aquatic ecosystem whose groundcovers are flooded or saturated in water, either permanently, for years or decades, or only seasonally. Flooding results in oxygen-poor ( anoxic) processes taking place, especially ...
, resulting in the loss of habitat for many plant and animal species as well as increased erosion
Erosion is the action of surface processes (such as Surface runoff, water flow or wind) that removes soil, Rock (geology), rock, or dissolved material from one location on the Earth's crust#Crust, Earth's crust and then sediment transport, tran ...
.
Aesthetics and beauty
Beauty in nature has historically been a prevalent theme in art and books, filling large sections of libraries and bookstores. That nature has been depicted and celebrated by so much art, photography, poetry, and other literature shows the strength with which many people associate nature and beauty. Reasons why this association exists, and what the association consists of, are studied by the branch of philosophy called aesthetics
Aesthetics (also spelled esthetics) is the branch of philosophy concerned with the nature of beauty and taste (sociology), taste, which in a broad sense incorporates the philosophy of art.Slater, B. H.Aesthetics ''Internet Encyclopedia of Ph ...
. Beyond certain basic characteristics that many philosophers agree about to explain what is seen as beautiful, the opinions are virtually endless. Nature and wildness have been important subjects in various eras of world history. An early tradition of landscape art
Landscape painting, also known as landscape art, is the depiction in painting of natural scenery such as mountains, valleys, rivers, trees, and forests, especially where the main subject is a wide view—with its elements arranged into a coh ...
began in China during the Tang Dynasty
The Tang dynasty (, ; zh, c=唐朝), or the Tang Empire, was an Dynasties of China, imperial dynasty of China that ruled from 618 to 907, with an Wu Zhou, interregnum between 690 and 705. It was preceded by the Sui dynasty and followed ...
(618–907). The tradition of representing nature ''as it is'' became one of the aims of Chinese painting
Chinese painting () is one of the oldest continuous artistic traditions in the world. Painting in the traditional style is known today in Chinese as , meaning "national painting" or "native painting", as opposed to Western styles of art which b ...
and was a significant influence in Asian art.
Although natural wonders are celebrated in the Psalms
The Book of Psalms ( , ; ; ; ; , in Islam also called Zabur, ), also known as the Psalter, is the first book of the third section of the Tanakh (Hebrew Bible) called ('Writings'), and a book of the Old Testament.
The book is an anthology of B ...
and the Book of Job
The Book of Job (), or simply Job, is a book found in the Ketuvim ("Writings") section of the Hebrew Bible and the first of the Poetic Books in the Old Testament of the Christian Bible. The language of the Book of Job, combining post-Babylonia ...
, wilderness
Wilderness or wildlands (usually in the plurale tantum, plural) are Earth, Earth's natural environments that have not been significantly modified by human impact on the environment, human activity, or any urbanization, nonurbanized land not u ...
portrayals in art became more prevalent in the 1800s, especially in the works of the Romantic movement
Romanticism (also known as the Romantic movement or Romantic era) was an artistic and intellectual movement that originated in Europe towards the end of the 18th century. The purpose of the movement was to advocate for the importance of subjec ...
. British
British may refer to:
Peoples, culture, and language
* British people, nationals or natives of the United Kingdom, British Overseas Territories and Crown Dependencies.
* British national identity, the characteristics of British people and culture ...
artists John Constable
John Constable (; 11 June 1776 – 31 March 1837) was an English landscape painter in the Romanticism, Romantic tradition. Born in Suffolk, he is known principally for revolutionising the genre of landscape painting with his pictures of Dedha ...
and J. M. W. Turner turned their attention to capturing the beauty of the natural world in their paintings. Before that, paintings had been primarily of religious scenes or of human beings. William Wordsworth
William Wordsworth (7 April 177023 April 1850) was an English Romantic poetry, Romantic poet who, with Samuel Taylor Coleridge, helped to launch the Romanticism, Romantic Age in English literature with their joint publication ''Lyrical Balla ...
's poetry described the wonder of the natural world, which had formerly been viewed as a threatening place. Increasingly the valuing of nature became an aspect of Western culture.[History of Conservation]
BC Spaces for Nature. Accessed: May 20, 2006. This artistic movement also coincided with the Transcendentalist movement in the Western world. A common classical idea of beautiful art involves the word mimesis
Mimesis (; , ''mīmēsis'') is a term used in literary criticism and philosophy that carries a wide range of meanings, including '' imitatio'', imitation, similarity, receptivity, representation, mimicry, the act of expression, the act of ...
, the imitation of nature. Also in the realm of ideas about beauty in nature is that the perfect is implied through perfect mathematical forms and more generally by patterns in nature
Patterns in nature are visible regularities of form found in the natural world. These patterns recur in different contexts and can sometimes be modelled mathematically. Natural patterns include symmetries, trees, spirals, meanders, wave ...
. As David Rothenburg writes, "The beautiful is the root of science and the goal of art, the highest possibility that humanity can ever hope to see".
Matter and energy
The natural science
Natural science or empirical science is one of the branches of science concerned with the description, understanding and prediction of natural phenomena, based on empirical evidence from observation and experimentation. Mechanisms such as peer ...
s view matter as obeying certain laws of nature which scientists seek to understand.
Matter is commonly defined as the substance of which physical objects are composed. It constitutes the observable universe
The observable universe is a Ball (mathematics), spherical region of the universe consisting of all matter that can be observation, observed from Earth; the electromagnetic radiation from these astronomical object, objects has had time to reach t ...
. The visible components of the universe are now believed to compose only 4.9 percent of the total mass. The remainder is believed to consist of 26.8 percent cold dark matter and 68.3 percent dark energy
In physical cosmology and astronomy, dark energy is a proposed form of energy that affects the universe on the largest scales. Its primary effect is to drive the accelerating expansion of the universe. It also slows the rate of structure format ...
. The exact arrangement of these components is still unknown and is under intensive investigation by physicists.
The behaviour of matter and energy throughout the observable universe appears to follow well-defined physical law
Scientific laws or laws of science are statements, based on repeated experiments or observations, that describe or predict a range of natural phenomena. The term ''law'' has diverse usage in many cases (approximate, accurate, broad, or narrow) ...
s. These laws have been employed to produce cosmological
Cosmology () is a branch of physics and metaphysics dealing with the nature of the universe, the cosmos. The term ''cosmology'' was first used in English in 1656 in Thomas Blount's ''Glossographia'', with the meaning of "a speaking of the wo ...
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 that appear to be static across the observable universe. The values of these constants have been carefully measured, but the reason for their specific values remains a mystery.
Beyond Earth
Outer space, also simply called ''space'', refers to the relatively empty regions of the Universe
The universe is all of space and time and their contents. It comprises all of existence, any fundamental interaction, physical process and physical constant, and therefore all forms of matter and energy, and the structures they form, from s ...
outside the atmosphere
An atmosphere () is a layer of gases that envelop an astronomical object, held in place by the gravity of the object. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A stellar atmosph ...
s of celestial bodies. ''Outer'' space is used to distinguish it from airspace (and terrestrial locations). There is no discrete boundary between Earth's atmosphere and space, as the atmosphere gradually attenuates with increasing altitude. Outer space within the Solar System
The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Sola ...
is called interplanetary space, which passes over into interstellar space at what is known as the heliopause.
Outer space is sparsely filled with several dozen types of organic molecule
A molecule is a group of two or more atoms that are held together by Force, attractive forces known as chemical bonds; depending on context, the term may or may not include ions that satisfy this criterion. In quantum physics, organic chemi ...
s discovered to date by microwave spectroscopy, blackbody radiation left over from the Big Bang
The Big Bang is a physical theory that describes how the universe expanded from an initial state of high density and temperature. Various cosmological models based on the Big Bang concept explain a broad range of phenomena, including th ...
and the origin of the universe, and cosmic ray
Cosmic rays or astroparticles are high-energy particles or clusters of particles (primarily represented by protons or atomic nuclei) that move through space at nearly the speed of light. They originate from the Sun, from outside of the ...
s, which include ionized atomic nuclei and various subatomic particle
In physics, a subatomic particle is a particle smaller than an atom. According to the Standard Model of particle physics, a subatomic particle can be either a composite particle, which is composed of other particles (for example, a baryon, lik ...
s. There is also some gas, plasma and dust
Dust is made of particle size, fine particles of solid matter. On Earth, it generally consists of particles in the atmosphere that come from various sources such as soil lifted by wind (an aeolian processes, aeolian process), Types of volcan ...
, and small meteor
A meteor, known colloquially as a shooting star, is a glowing streak of a small body (usually meteoroid) going through Earth's atmosphere, after being heated to incandescence by collisions with air molecules in the upper atmosphere,
creating a ...
s. Additionally, there are signs of human life in outer space today, such as material left over from previous crewed and uncrewed launches which are a potential hazard to spacecraft. Some of this debris re-enters the atmosphere periodically.
Although Earth is the only body within the Solar System
The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Sola ...
known to support life, evidence suggests that in the distant past the planet Mars
Mars is the fourth planet from the Sun. It is also known as the "Red Planet", because of its orange-red appearance. Mars is a desert-like rocky planet with a tenuous carbon dioxide () atmosphere. At the average surface level the atmosph ...
possessed bodies of liquid water on the surface. 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.
Conditions on the other terrestrial planets, Mercury and Venus
Venus is the second planet from the Sun. It is often called Earth's "twin" or "sister" planet for having almost the same size and mass, and the closest orbit to Earth's. While both are rocky planets, Venus has an atmosphere much thicker ...
, 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
Jupiter is the fifth planet from the Sun and the List of Solar System objects by size, largest in the Solar System. It is a gas giant with a Jupiter mass, mass more than 2.5 times that of all the other planets in the Solar System combined a ...
, may possess a sub-surface ocean of liquid water and could potentially host life.
Astronomers have started to discover extrasolar Earth analogs – planets that lie in the habitable zone
In astronomy and astrobiology, the habitable zone (HZ), or more precisely the circumstellar habitable zone (CHZ), is the range of orbits around a star within which a planetary surface can support liquid water given sufficient atmospheric pressu ...
of space surrounding a star
A star is a luminous spheroid of plasma (physics), plasma held together by Self-gravitation, self-gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night sk ...
, and therefore could possibly host life as we know it.
See also
* Biophilic design
* Force of nature
* Human nature
Human nature comprises the fundamental dispositions and characteristics—including ways of Thought, thinking, feeling, and agency (philosophy), acting—that humans are said to have nature (philosophy), naturally. The term is often used to denote ...
* Natural building
* Natural history
Natural history is a domain of inquiry involving organisms, including animals, fungi, and plants, in their natural environment, leaning more towards observational than experimental methods of study. A person who studies natural history is cal ...
* Natural landscape
* Natural law
Natural law (, ) is a Philosophy, philosophical and legal theory that posits the existence of a set of inherent laws derived from nature and universal moral principles, which are discoverable through reason. In ethics, natural law theory asserts ...
* Natural resource
Natural resources are resources that are drawn from nature and used with few modifications. This includes the sources of valued characteristics such as commercial and industrial use, aesthetic value, scientific interest, and cultural value. ...
* Natural science
Natural science or empirical science is one of the branches of science concerned with the description, understanding and prediction of natural phenomena, based on empirical evidence from observation and experimentation. Mechanisms such as peer ...
* Natural theology
* Naturalism
* Nature reserve
A nature reserve (also known as a wildlife refuge, wildlife sanctuary, biosphere reserve or bioreserve, natural or nature preserve, or nature conservation area) is a protected area of importance for flora, fauna, funga, or features of geologic ...
* Nature versus nurture
* Nature worship
* Nature-based solutions
* Naturism
* Rewilding
Media:
* '' National Wildlife'', a publication of the National Wildlife Federation
* ''Natural History
Natural history is a domain of inquiry involving organisms, including animals, fungi, and plants, in their natural environment, leaning more towards observational than experimental methods of study. A person who studies natural history is cal ...
'', by Pliny the Elder
Gaius Plinius Secundus (AD 23/24 79), known in English as Pliny the Elder ( ), was a Roman Empire, Roman author, Natural history, naturalist, and naval and army commander of the early Roman Empire, and a friend of the Roman emperor, emperor Vesp ...
* '' Natural World'' (TV series)
* ''Nature
Nature is an inherent character or constitution, particularly of the Ecosphere (planetary), ecosphere or the universe as a whole. In this general sense nature refers to the Scientific law, laws, elements and phenomenon, phenomena of the physic ...
'', by Ralph Waldo Emerson
Ralph Waldo Emerson (May 25, 1803April 27, 1882), who went by his middle name Waldo, was an American essayist, lecturer, philosopher, minister, abolitionism, abolitionist, and poet who led the Transcendentalism, Transcendentalist movement of th ...
* ''Nature
Nature is an inherent character or constitution, particularly of the Ecosphere (planetary), ecosphere or the universe as a whole. In this general sense nature refers to the Scientific law, laws, elements and phenomenon, phenomena of the physic ...
'', a prominent scientific journal
* ''Nature
Nature is an inherent character or constitution, particularly of the Ecosphere (planetary), ecosphere or the universe as a whole. In this general sense nature refers to the Scientific law, laws, elements and phenomenon, phenomena of the physic ...
'' (TV series)
* '' The World We Live In (Life magazine)''
Organizations:
* Nature Detectives
* The Nature Conservancy
The Nature Conservancy (TNC) is a global environmental organization headquartered in Arlington, Virginia, United States. it works via affiliates or branches in 79 countries and territories, as well as across every state in the US.
Founded in ...
Philosophy:
* Balance of nature (biological fallacy), a discredited concept of natural equilibrium in predator–prey dynamics
* Mother Nature
Mother Nature (sometimes known as Mother Earth or the Earth Mother) is a personification of nature that focuses on the life-giving and nurturing aspects of nature by embodying it, in the form of a mother or mother goddess.
European concept tr ...
* Naturalism, any of several philosophical stances, typically those descended from materialism
Materialism is a form of monism, philosophical monism according to which matter is the fundamental Substance theory, substance in nature, and all things, including mind, mental states and consciousness, are results of material interactions. Acco ...
and pragmatism
Pragmatism is a philosophical tradition that views language and thought as tools for prediction, problem solving, and action, rather than describing, representing, or mirroring reality. Pragmatists contend that most philosophical topics� ...
that do not distinguish the supernatural from nature;[Papineau, David (2016]
"Naturalism"
The Stanford Encyclopedia of Philosophy, Edward N. Zalta (ed.), > this includes the ''methodological naturalism'' of natural science, which makes the methodological assumption that observable
In physics, an observable is a physical property or physical quantity that can be measured. In classical mechanics, an observable is a real-valued "function" on the set of all possible system states, e.g., position and momentum. In quantum ...
events in nature are explained only by natural causes, without assuming either the existence or non-existence of the supernatural
* Nature (philosophy)
Nature has two inter-related meanings in philosophy and natural philosophy. On the one hand, it means the set of all things which are natural, or subject to the normal working of the Physical law, laws of nature. On the other hand, it means the es ...
Notes and references
Further reading
*
*
*
* Farber, Paul Lawrence (2000), ''Finding Order in Nature: The Naturalist Tradition from Linnaeus to E. O. Wilson''. Johns Hopkins University Press: Baltimore.
*
*
*
*
External links
The IUCN Red List of Threatened Species (iucnredlist.org)
*
{{Authority control
Environmental science
Environmental social science concepts
Main topic articles