Changes

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Much attention has been given to preserving the [[flora]] and other natural characteristics of the view, while allowing ample access for visitors to this popular site.]]

[[Image:Hopetoun falls.jpg|thumb|right|300px|A more steady-state view of nature: [[Hopetoun Falls]], [[Victoria (Australia)|Victoria]], [[Australia]]. Much attention has been given to preserving the [[flora]] and other natural characteristics of the view, while allowing ample access for visitors to this popular site.]]

'''Nature''', in the broadest sense, is equivalent to the '''natural world''', '''physical universe''', '''material world''' or '''material universe'''. "Nature" refers to the [[phenomenon|phenomena]] of the physical world, and also to [[life]] in general. The term generally does not include manufactured objects and human interaction unless qualified in ways such as, e.g., "[[human nature]]" or "the whole of nature". Nature is also generally distinguished from the [[supernatural]].  It ranges in scale from the [[subatomic]] to the [[galaxy|galactic]].

'''Nature''', in the broadest sense, is equivalent to the '''natural world''', '''physical universe''', '''material world''' or '''material universe'''. "Nature" refers to the [[phenomenon|phenomena]] of the physical world, and also to [[life]] in general. The term generally does not include manufactured objects and human interaction unless qualified in ways such as, e.g., "[[human nature]]" or "the whole of nature". Nature is also generally distinguished from the [[supernatural]].  It ranges in scale from the [[subatomic]] to the [[galaxy|galactic]].

== Earth ==

== Earth ==

'''Earth''' (or, "the earth") is the fifth largest [[planet]] in the [[solar system]], third in order of distance from the [[Sun]]. It is the largest of its [[planetary system]]'s [[terrestrial planet]]s and the only place in the [[universe]] known to support life.  

'''Earth''' (or, "the earth") is the fifth largest [[planet]] in the [[solar system]], third in order of distance from the [[Sun]]. It is the largest of its [[planetary system]]'s [[terrestrial planet]]s and the only place in the [[universe]] known to support life.  

===Historical perspective===

===Historical perspective===

 

Based on the available evidence, scientists have reconstructed detailed information about the planet's past. Earth is estimated to have formed approximately 4.55 billion years ago out of the [[solar nebula]], along with the Sun and other planets.<ref>{{cite book |first=G. Brent |last=Dalrymple |year=1991 |title=The Age of the Earth |publisher=Stanford University Press |location=Stanford |id=ISBN 0-8047-1569-6}}</ref> The moon formed relatively soon afterwards (roughly 20 million years later, or 4.53 billion years ago).

Based on the available evidence, scientists have reconstructed detailed information about the planet's past. Earth is estimated to have formed approximately 4.55 billion years ago out of the [[solar nebula]], along with the Sun and other planets.<ref>{{cite book |first=G. Brent |last=Dalrymple |year=1991 |title=The Age of the Earth |publisher=Stanford University Press |location=Stanford |id=ISBN 0-8047-1569-6}}</ref> The moon formed relatively soon afterwards (roughly 20 million years later, or 4.53 billion years ago).

Continents formed, then broke up and re-formed as the surface of Earth reshaped itself over the course of hundreds of millions of years, occasionally combining to make a [[supercontinent]]. Roughly 750 million years ago, the earliest known supercontinent [[Rodinia]], 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.<ref>{{cite journal |first=J.B. |last=Murphy |coauthors=R.D. Nance |year=2004 |url=http://www.americanscientist.org/template/AssetDetail/assetid/34004;jsessionid=aaa4W2jLnnG9QG |title=How do supercontinents assemble? |journal=American Scientist |volume=92 |issue=4 |id={{doi|10.1511/2004.4.324}} |pages=pp. 324-333}}</ref>  

Continents formed, then broke up and re-formed as the surface of Earth reshaped itself over the course of hundreds of millions of years, occasionally combining to make a [[supercontinent]]. Roughly 750 million years ago, the earliest known supercontinent [[Rodinia]], 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.<ref>{{cite journal |first=J.B. |last=Murphy |coauthors=R.D. Nance |year=2004 |url=http://www.americanscientist.org/template/AssetDetail/assetid/34004;jsessionid=aaa4W2jLnnG9QG |title=How do supercontinents assemble? |journal=American Scientist |volume=92 |issue=4 |id={{doi|10.1511/2004.4.324}} |pages=pp. 324-333}}</ref>  

There is significant evidence, still being discussed among scientists, that a severe [[Glacier|glacial]] action during the [[Neoproterozoic]] era covered much of the planet in a sheet of ice. This hypothesis has been termed the "[[Snowball Earth]]", 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.<ref>{{cite book |first=J.L. |last=Kirschvink |year=1992 |chapter=Late Proterozoic Low-Latitude Global Glaciation: The Snowball Earth |chapterurl=http://www.gps.caltech.edu/~jkirschvink/pdfs/firstsnowball.pdf |title=The Proterozoic Biosphere |editor=J.W. Schopf, C. Klein eds. |publisher=Cambridge University Press |location=Cambridge |pages=pp. 51-52 |id=ISBN 0-521-36615-1}}</ref>

There is significant evidence, still being discussed among scientists, that a severe [[Glacier|glacial]] action during the [[Neoproterozoic]] era covered much of the planet in a sheet of ice. This hypothesis has been termed the "[[Snowball Earth]]", 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.<ref>{{cite book |first=J.L. |last=Kirschvink |year=1992 |chapter=Late Proterozoic Low-Latitude Global Glaciation: The Snowball Earth |chapterurl=http://www.gps.caltech.edu/~jkirschvink/pdfs/firstsnowball.pdf |title=The Proterozoic Biosphere |editor=J.W. Schopf, C. Klein eds. |publisher=Cambridge University Press |location=Cambridge |pages=pp. 51-52 |id=ISBN 0-521-36615-1}}</ref>

}}</ref><ref>{{cite journal | last = Pelletier | first = Jon D. | title=Natural variability of atmospheric temperatures and geomagnetic intensity over a wide range of time scales | journal=Proceedings of the National Academy of Sciences | year=2002 | volume=99 | pages=2546-2553 | url=http://www.pnas.org/cgi/content/full/99/suppl_1/2546 | accessdate = 2007-01-07 }}</ref> The [[ozone layer]] of the Earth's atmosphere plays an important role in depleting the amount of [[ultraviolet]] (UV) radiation that reaches the surface. As [[DNA]] is readily damaged by UV light, this serves to protect life at the surface. The atmosphere also retains heat during the night, thereby reducing the daily temperature extremes.   

}}</ref><ref>{{cite journal | last = Pelletier | first = Jon D. | title=Natural variability of atmospheric temperatures and geomagnetic intensity over a wide range of time scales | journal=Proceedings of the National Academy of Sciences | year=2002 | volume=99 | pages=2546-2553 | url=http://www.pnas.org/cgi/content/full/99/suppl_1/2546 | accessdate = 2007-01-07 }}</ref> The [[ozone layer]] of the Earth's atmosphere plays an important role in depleting the amount of [[ultraviolet]] (UV) radiation that reaches the surface. As [[DNA]] is readily damaged by UV light, this serves to protect life at the surface. The atmosphere also retains heat during the night, thereby reducing the daily temperature extremes.   

Terrestrial weather occurs almost exclusively in the [[troposphere|lower part of the atmosphere]], and serves as a convective system for redistributing heat. Ocean currents are another important factor in determining climate, particularly the major underwater [[thermohaline circulation]] which distributes heat energy from the equatorial oceans to the polar regions. These currents help to moderate the differences in temperature between winter and summer in the temperate zones. Also, without the redistributions of heat energy by the ocean currents and atmosphere, the tropics would be much hotter, and the polar regions much colder.

Terrestrial weather occurs almost exclusively in the [[troposphere|lower part of the atmosphere]], and serves as a convective system for redistributing heat. Ocean currents are another important factor in determining climate, particularly the major underwater [[thermohaline circulation]] which distributes heat energy from the equatorial oceans to the polar regions. These currents help to moderate the differences in temperature between winter and summer in the temperate zones. Also, without the redistributions of heat energy by the ocean currents and atmosphere, the tropics would be much hotter, and the polar regions much colder.

== Life ==  

== Life ==  

 

Although there is no universal agreement on the definition of life, scientists generally accept that the biological manifestation of life is characterized by [[Organism|organization]], [[metabolism]], [[cell growth|growth]], [[adaptation]], response to [[stimulus (physiology)|stimuli]] and [[reproduction]].<ref>{{cite web | year = 2006 | url = http://www.calacademy.org/exhibits/xtremelife/what_is_life.php | title = Definition of Life  | publisher = California Academy of Sciences | accessdate = 2007-01-07 }}</ref> Life may also be said to be simply the characteristic state of [[organism]]s.

Although there is no universal agreement on the definition of life, scientists generally accept that the biological manifestation of life is characterized by [[Organism|organization]], [[metabolism]], [[cell growth|growth]], [[adaptation]], response to [[stimulus (physiology)|stimuli]] and [[reproduction]].<ref>{{cite web | year = 2006 | url = http://www.calacademy.org/exhibits/xtremelife/what_is_life.php | title = Definition of Life  | publisher = California Academy of Sciences | accessdate = 2007-01-07 }}</ref> Life may also be said to be simply the characteristic state of [[organism]]s.

===Plants and animals===

===Plants and animals===

 

The distinction between plant and animal life is not sharply drawn, with some categories of life that stand between or across the two. Originally [[Aristotle]] divided all living things between plants, which generally do not move, and animals. In [[Carolus Linnaeus|Linnaeus]]' system, these became the [[kingdom (biology)|Kingdoms]] [[Vegetabilia]] (later [[Plantae]]) and [[Animal]]ia. Since then, it has become clear that the Plantae as originally defined included several unrelated groups, and the [[fungus|fungi]] and several groups of [[alga]]e were removed to new kingdoms. However, these are still often considered plants in many contexts. Bacterial life is sometimes included in flora,<ref>{{cite web |title=flora |url=http://webster.com/cgi-bin/dictionary?va=flora |work=Merriam-Webster Online Dictionary |publisher=Merriam-Webster |accessmonthday=September 27|accessyear=2006 }}</ref><ref>{{cite book |year=1998 |title=Status and Trends of the Nation's Biological Resources |chapter=Glossary |chapterurl=http://biology.usgs.gov/s+t/SNT/noframe/zy198.htm#F |publisher=Department of the Interior, Geological Survey |location=Reston, VA |id=SuDocs No. I 19.202:ST 1/V.1-2}}</ref> and some classifications use the term ''bacterial flora'' separately from ''plant flora''.

The distinction between plant and animal life is not sharply drawn, with some categories of life that stand between or across the two. Originally [[Aristotle]] divided all living things between plants, which generally do not move, and animals. In [[Carolus Linnaeus|Linnaeus]]' system, these became the [[kingdom (biology)|Kingdoms]] [[Vegetabilia]] (later [[Plantae]]) and [[Animal]]ia. Since then, it has become clear that the Plantae as originally defined included several unrelated groups, and the [[fungus|fungi]] and several groups of [[alga]]e were removed to new kingdoms. However, these are still often considered plants in many contexts. Bacterial life is sometimes included in flora,<ref>{{cite web |title=flora |url=http://webster.com/cgi-bin/dictionary?va=flora |work=Merriam-Webster Online Dictionary |publisher=Merriam-Webster |accessmonthday=September 27|accessyear=2006 }}</ref><ref>{{cite book |year=1998 |title=Status and Trends of the Nation's Biological Resources |chapter=Glossary |chapterurl=http://biology.usgs.gov/s+t/SNT/noframe/zy198.htm#F |publisher=Department of the Interior, Geological Survey |location=Reston, VA |id=SuDocs No. I 19.202:ST 1/V.1-2}}</ref> and some classifications use the term ''bacterial flora'' separately from ''plant flora''.

Another category of plant has historically been carved out for ''weeds''. Though the term has fallen into disfavor among [[botanist]]s 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.

Another category of plant has historically been carved out for ''weeds''. Though the term has fallen into disfavor among [[botanist]]s 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, though not traced by scientists to having legs or wings instead of roots and leaves.  Animals are [[eukaryote|eukaryotic]] and usually [[multicellular]] (although see [[Myxozoa]]), which separates them from [[bacteria]], [[archaea]] and most [[protist]]s.  They are [[heterotroph]]ic, generally digesting food in an internal chamber, which separates them from [[plant]]s and [[alga]]e. They are also distinguished from plants, algae, and [[fungus|fungi]] by lacking [[cell wall]]s.

[[Animals]] as a category have several characteristics that generally set them apart from other living things, though not traced by scientists to having legs or wings instead of roots and leaves.  Animals are [[eukaryote|eukaryotic]] and usually [[multicellular]] (although see [[Myxozoa]]), which separates them from [[bacteria]], [[archaea]] and most [[protist]]s.  They are [[heterotroph]]ic, generally digesting food in an internal chamber, which separates them from [[plant]]s and [[alga]]e. They are also distinguished from plants, algae, and [[fungus|fungi]] by lacking [[cell wall]]s.

With a few exceptions, most notably the [[sea sponge|sponge]]s (Phylum Porifera), animals have bodies differen­tiated into separate [[biological tissue|tissues]]. These include [[muscle]]s, which are able to contract and control locomotion, and a [[nervous system]], which sends and processes signals. There is also typically an internal [[digestion|digestive]] chamber. The eukaryotic cells possessed by all animals are surrounded by a characteristic extracellular matrix composed of [[collagen]] and elastic [[glycoprotein]]s. This may be calcified to form structures like [[Animal shell|shell]]s, [[bone]]s, and [[spicule]]s, a framework upon which cells can move about and be reorganized during development and maturation, and which supports the complex anatomy required for mobility.  

With a few exceptions, most notably the [[sea sponge|sponge]]s (Phylum Porifera), animals have bodies differen­tiated into separate [[biological tissue|tissues]]. These include [[muscle]]s, which are able to contract and control locomotion, and a [[nervous system]], which sends and processes signals. There is also typically an internal [[digestion|digestive]] chamber. The eukaryotic cells possessed by all animals are surrounded by a characteristic extracellular matrix composed of [[collagen]] and elastic [[glycoprotein]]s. This may be calcified to form structures like [[Animal shell|shell]]s, [[bone]]s, and [[spicule]]s, a framework upon which cells can move about and be reorganized during development and maturation, and which supports the complex anatomy required for mobility.  

[[Loch Lomond]] in Scotland forms a relatively isolated ecosystem. The fish community of this lake has remained unchanged over a very long period.<ref>{{cite journal | last=Adams | first=C.E. | title=The fish community of Loch Lomond, Scotland : its history and rapidly changing status | journal=Hydrobiologia | year=1994 | volume=290 | issue=1-3 | pages=91-102 | url=http://cat.inist.fr/?aModele=afficheN&cpsidt=3302548 }}</ref>]]

[[Image:View of loch lomond.JPG|thumb|260px|right|[[Loch Lomond]] in Scotland forms a relatively isolated ecosystem. The fish community of this lake has remained unchanged over a very long period.<ref>{{cite journal | last=Adams | first=C.E. | title=The fish community of Loch Lomond, Scotland : its history and rapidly changing status | journal=Hydrobiologia | year=1994 | volume=290 | issue=1-3 | pages=91-102 | url=http://cat.inist.fr/?aModele=afficheN&cpsidt=3302548 }}</ref>]]

{{main|Ecology|Ecosystem}}

{{main|Ecology|Ecosystem}}

All forms of life interact with the environment in which they exist, and also with other life forms.  In the 20th century this premise gave rise to the concept of '''ecosystems''', which can be defined as any situation where there is interaction between organisms and their environment.

All forms of life interact with the environment in which they exist, and also with other life forms.  In the 20th century this premise gave rise to the concept of '''ecosystems''', which can be defined as any situation where there is interaction between organisms and their environment.

Each living organism has a continual relationship with every other element that makes up its environment. Within the ecosystem, species are connected and dependent upon one another in the [[food chain]], and exchange [[energy]] and [[matter]] between themselves as well as with their environment.<ref>{{cite web |last=Pidwirny |first=Michael |year=2006 |work=Fundamentals of Physical Geography (2nd Edition) |title=Introduction to the Biosphere: Organization of Life |url=http://www.physicalgeography.net/fundamentals/9d.html |accessmonthday=September 28|accessyear=2006}}</ref></blockquote>

Each living organism has a continual relationship with every other element that makes up its environment. Within the ecosystem, species are connected and dependent upon one another in the [[food chain]], and exchange [[energy]] and [[matter]] between themselves as well as with their environment.<ref>{{cite web |last=Pidwirny |first=Michael |year=2006 |work=Fundamentals of Physical Geography (2nd Edition) |title=Introduction to the Biosphere: Organization of Life |url=http://www.physicalgeography.net/fundamentals/9d.html |accessmonthday=September 28|accessyear=2006}}</ref></blockquote>

Every species has limits of tolerance to factors that affect its survival, reproductive success and ability to continue to thrive and interact sustainably with the rest of its environment, which in turn may have effects on these factors for many other species or even on the whole of life.<ref>{{cite web |last=Pidwirny |first=Michael |year=2006 |work=Fundamentals of Physical Geography (2nd Edition) |title=Introduction to the Biosphere: Abiotic Factors and  the Distribution of Species |url=http://www.physicalgeography.net/fundamentals/9e.html |accessmonthday=September 28|accessyear=2006}} esp. section on "Abiotic Factors and Tolerance Limits."</ref> The concept of an ecosystem is thus an important subject of study, as such study provides information needed to make decisions about how human life may interact in a way that allows the various ecosystems to be sustained for future use rather than used up or otherwise rendered ineffective. For the purpose of such study, a unit of smaller size is called a ''[[microecosystem]]''. For example, an ecosystem can be a stone and all the life under it. A ''macroecosystem'' might involve a whole [[ecoregion]], with its [[drainage basin]].<ref>{{cite journal |last=Bailey |first=Robert G. |year=2004 |month=April |title=Identifying Ecoregion Boundaries |journal=Environmental Management |volume=34 |issue=Supplement 1 |url=http://www.fs.fed.us/institute/news_info/Identifying_ecoregion_boundaries.pdf |id={{doi|10.1007/s00267-003-0163-6}} }}</ref>  

Every species has limits of tolerance to factors that affect its survival, reproductive success and ability to continue to thrive and interact sustainably with the rest of its environment, which in turn may have effects on these factors for many other species or even on the whole of life.<ref>{{cite web |last=Pidwirny |first=Michael |year=2006 |work=Fundamentals of Physical Geography (2nd Edition) |title=Introduction to the Biosphere: Abiotic Factors and  the Distribution of Species |url=http://www.physicalgeography.net/fundamentals/9e.html |accessmonthday=September 28|accessyear=2006}} esp. section on "Abiotic Factors and Tolerance Limits."</ref> The concept of an ecosystem is thus an important subject of study, as such study provides information needed to make decisions about how human life may interact in a way that allows the various ecosystems to be sustained for future use rather than used up or otherwise rendered ineffective. For the purpose of such study, a unit of smaller size is called a ''[[microecosystem]]''. For example, an ecosystem can be a stone and all the life under it. A ''macroecosystem'' might involve a whole [[ecoregion]], with its [[drainage basin]].<ref>{{cite journal |last=Bailey |first=Robert G. |year=2004 |month=April |title=Identifying Ecoregion Boundaries |journal=Environmental Management |volume=34 |issue=Supplement 1 |url=http://www.fs.fed.us/institute/news_info/Identifying_ecoregion_boundaries.pdf |id={{doi|10.1007/s00267-003-0163-6}} }}</ref>  

==Human interrelationship==

==Human interrelationship==

 

Although humans currently comprise only about one-half of one percent of the total living biomass on Earth,<ref> For an example of a range of opinions, see: {{cite web |url=http://www.wilderness.org/Library/Documents/Beauty_Quotes.cfm |title=On the Beauty of Nature |publisher=The Wilderness Society |accessmonthday=September 29|accessyear=2006 }} and [[Ralph Waldo Emerson]]'s analysis of the subject: {{cite book |last=Emerson |first=Ralph Waldo |year=1849 |title=Nature; Addresses and Lectures |chapter=Beauty |chapterurl=http://www.emersoncentral.com/beauty.htm}}</ref> the human effect on nature is disproportionately large. Because of the extent of human influence, the boundaries between what we 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 presently diminishing at an increasingly rapid pace, or, according to some, has already disappeared.

Although humans currently comprise only about one-half of one percent of the total living biomass on Earth,<ref> For an example of a range of opinions, see: {{cite web |url=http://www.wilderness.org/Library/Documents/Beauty_Quotes.cfm |title=On the Beauty of Nature |publisher=The Wilderness Society |accessmonthday=September 29|accessyear=2006 }} and [[Ralph Waldo Emerson]]'s analysis of the subject: {{cite book |last=Emerson |first=Ralph Waldo |year=1849 |title=Nature; Addresses and Lectures |chapter=Beauty |chapterurl=http://www.emersoncentral.com/beauty.htm}}</ref> the human effect on nature is disproportionately large. Because of the extent of human influence, the boundaries between what we 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 presently diminishing at an increasingly rapid pace, or, according to some, has already disappeared.

===Wilderness===

===Wilderness===

'''Wilderness''' is generally defined as a [[natural environment]] on [[Earth]] that has not been directly modified by [[human]] activity. [[Ecologist]]s consider wilderness areas to be an integral part of the planet's self-sustaining natural [[ecosystem]] (the [[biosphere]]).   

'''Wilderness''' is generally defined as a [[natural environment]] on [[Earth]] that has not been directly modified by [[human]] activity. [[Ecologist]]s consider wilderness areas to be an integral part of the planet's self-sustaining natural [[ecosystem]] (the [[biosphere]]).   

==Beauty in nature==

==Beauty in nature==

 

Beauty in nature is has long been a common theme in life and in art, and books emphasizing beauty in nature fill 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. Why this association exists, and what the association consists of, is studied by the branch of philosophy called [[aesthetics]].  Beyond certain basic characteristics that many philosophers agree about to explain what is seen as beautiful, the opinions are virtually endless.<ref> For an example of a range of opinions, see: {{cite web |url=http://www.wilderness.org/Library/Documents/Beauty_Quotes.cfm |title=On the Beauty of Nature |publisher=The Wilderness Society |accessmonthday=September 29|accessyear=2006 }} and [[Ralph Waldo Emerson]]'s analysis of the subject: {{cite book |last=Emerson |first=Ralph Waldo |year=1849 |title=Nature; Addresses and Lectures |chapter=Beauty |chapterurl=http://www.emersoncentral.com/beauty.htm}}</ref>

Beauty in nature is has long been a common theme in life and in art, and books emphasizing beauty in nature fill 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. Why this association exists, and what the association consists of, is studied by the branch of philosophy called [[aesthetics]].  Beyond certain basic characteristics that many philosophers agree about to explain what is seen as beautiful, the opinions are virtually endless.<ref> For an example of a range of opinions, see: {{cite web |url=http://www.wilderness.org/Library/Documents/Beauty_Quotes.cfm |title=On the Beauty of Nature |publisher=The Wilderness Society |accessmonthday=September 29|accessyear=2006 }} and [[Ralph Waldo Emerson]]'s analysis of the subject: {{cite book |last=Emerson |first=Ralph Waldo |year=1849 |title=Nature; Addresses and Lectures |chapter=Beauty |chapterurl=http://www.emersoncentral.com/beauty.htm}}</ref>

== Matter and energy ==

== Matter and energy ==

Some fields of [[science]] see nature as matter in motion, obeying certain laws of nature which science seeks to understand. For this reason the most fundamental science is generally understood to be "[[physics]]"&mdash;the name for which is still recognizable as meaning that it is the study of nature.  

Some fields of [[science]] see nature as matter in motion, obeying certain laws of nature which science seeks to understand. For this reason the most fundamental science is generally understood to be "[[physics]]"&mdash;the name for which is still recognizable as meaning that it is the study of nature.  

The behavior of matter and energy throughout the [[observable universe]] appears to follow well-defined [[physical law]]s. These laws have been employed to produce [[Physical cosmology|cosmological]] models that successfully explain the structure and the evolution of the universe we can observe. The mathematical expressions of the laws of physics employ a set of twenty [[physical constant]]s<ref>{{cite web | last = Taylor | first = Barry N. | year = 1971 | url = http://www.physics.nist.gov/cuu/Constants/introduction.html | title = Introduction to the constants for nonexperts | publisher = National Institute of Standards and Technology | accessdate = 2007-01-07

The behavior of matter and energy throughout the [[observable universe]] appears to follow well-defined [[physical law]]s. These laws have been employed to produce [[Physical cosmology|cosmological]] models that successfully explain the structure and the evolution of the universe we can observe. The mathematical expressions of the laws of physics employ a set of twenty [[physical constant]]s<ref>{{cite web | last = Taylor | first = Barry N. | year = 1971 | url = http://www.physics.nist.gov/cuu/Constants/introduction.html | title = Introduction to the constants for nonexperts | publisher = National Institute of Standards and Technology | accessdate = 2007-01-07

}}</ref> that appear to be static across the observable universe.<ref>{{cite journal | author=D. A. Varshalovich, A. Y. Potekhin, A. V. Ivanchik | title=Testing cosmological variability of fundamental constants | journal=AIP Conference Proceedings | year=2000 | volume=506 | pages=503 | url=http://arxiv.org/abs/physics/0004062 }}</ref> The values of these constants have been carefully measured, but the reason for their specific values remains a mystery.  

}}</ref> that appear to be static across the observable universe.<ref>{{cite journal | author=D. A. Varshalovich, A. Y. Potekhin, A. V. Ivanchik | title=Testing cosmological variability of fundamental constants | journal=AIP Conference Proceedings | year=2000 | volume=506 | pages=503 | url=http://arxiv.org/abs/physics/0004062 }}</ref> The values of these constants have been carefully measured, but the reason for their specific values remains a mystery.  

==Nature beyond Earth==

==Nature beyond Earth==

'''Outer space''', also simply called ''space'', refers to the relatively empty regions of the [[universe]] outside the [[celestial body's atmosphere|atmosphere]]s of celestial bodies. ''Outer'' space is used to distinguish it from [[airspace]] (and terrestrial locations). There is no discrete boundary between the [[Earth's atmosphere]] and space, as the atmosphere gradually attenuates with increasing altitude. Outer space within the [[solar system]] is called [[interplanetary space]], which passes over into [[interstellar medium|interstellar space]] at what is known as the [[heliopause]].

'''Outer space''', also simply called ''space'', refers to the relatively empty regions of the [[universe]] outside the [[celestial body's atmosphere|atmosphere]]s of celestial bodies. ''Outer'' space is used to distinguish it from [[airspace]] (and terrestrial locations). There is no discrete boundary between the [[Earth's atmosphere]] and space, as the atmosphere gradually attenuates with increasing altitude. Outer space within the [[solar system]] is called [[interplanetary space]], which passes over into [[interstellar medium|interstellar space]] at what is known as the [[heliopause]].