World
"World" is a common noun for the planet Earth seen from a human point of view, as a place inhabited by human beings. It is often used to signify the sum of human experience and history, or the 'human condition' in general.
In a metaphysical context, World may refer to the Universe, everything that constitutes reality: see World (philosophy)
Etymology
In English, world may be parsed as rooted in a compound of the obsolete words were, "man", and eld, "age"; thus, its etymology may be semantically rendered as "age or life of man". Compare to the word for "world" in a closely related language to English, Dutch, which is "wereld."
Usage
World' distinguishes the entire planet or population from any particular country or region: world affairs are those which pertain not just to one place but to the whole world, and world history is a field of history which examines events from a global (rather than a national or a regional) perspective. Earth, on the other hand, refers to the planet as a physical entity, and distinguishes it from other planets and physical objects.
'World' can also be used attributively, as an adjective, to mean 'global', 'relating to the whole world', forming usages such as World community. See World (adjective).
By extension, a 'world' may refer to any planet or heavenly body, especially when it is thought of as inhabited.
'World', when qualified, can also refer to a particular domain of human experience.
* The world of work describes paid work and the pursuit of a career, in all its social aspects, to distinguish it from home life and academic study.
* The fashion world describes the environment of the designers, fashion houses and consumers that make up the fashion industry.
* The New World is a part of the world discovered or colonized by Europeans later than other parts; it usually refers to the American continents or to Australia. Native Americans and Native Australians tend to dislike this usage. For them America and Australia are not new. Their ancestors have lived there since time immemorial. The Old World refers, by contrast, to the continents of Europe, Asia and north Africa.
Earth
Earth is the only place in the universe where life is known by humanity to exist at this time. Most scientific evidence indicates that the planet formed 4.6 billion years ago, and life appeared on its surface within a billion years. Since then, Earth's biosphere has significantly altered the atmosphere and other abiotic conditions on the planet, enabling the proliferation of aerobic organisms as well as the formation of the ozone layer which, together with Earth's magnetic field, blocks harmful radiation, permitting life on land.
Earth's outer surface is divided into several rigid segments, or tectonic plates, that gradually migrate across the surface over periods of many millions of years. About 71% of the surface is covered with salt-water oceans, the remainder consisting of continents and islands; liquid water, necessary for all known life, is not known to exist on any other planet's surface. Earth's interior remains active, with a thick layer of relatively solid mantle, a liquid outer core that generates a magnetic field, and a solid iron inner core.
The earth consists of seven continents listed as follows: North America, South America, Antarctica, Africa, Europe, Asia and Australia; the largest of which is Asia. There are several other methods of determining the continents.
Earth is impacted upon by other objects in outer space, including the Sun and the Moon. At present, Earth orbits the Sun once for every roughly 365.26 times it rotates about its axis. This length of time is a sidereal year, which is equal to 365.26 solar days. The Earth's axis of rotation is tilted 23.4° away from the perpendicular to its orbital plane, producing seasonal variations on the planet's surface with a period of one tropical year (365.24 solar days). Earth's only known natural satellite, the Moon, which began orbiting it about 4.53 billion years ago, provides ocean tides, stabilizes the axial tilt and gradually slows the planet's rotation. A cometary bombardment during the early history of the planet played a role in the formation of the oceans. Later, asteroid impacts caused significant changes to the surface environment.
Humanity
Humans, or human beings, are bipedal primates belonging to the mammalian species Homo sapiens. Compared to animals, humans have a highly developed brain capable of abstract reasoning, language, and introspection. This mental capability, combined with an erect body carriage that frees their upper limbs for manipulating objects, has allowed humans to make far greater use of tools than any other species. DNA evidence indicates that modern humans originated in Africa about 200,000 years ago. Humans now inhabit every continent and low Earth orbit, with a total population of over 6.73 billion humans as of January 2009.
Like most primates, humans are social by nature. However, humans are particularly adept at utilizing systems of communication for self-expression, the exchange of ideas, and organization. Humans create complex social structures composed of many cooperating and competing groups, from families to nations. Social interactions between humans have established an extremely wide variety of traditions, rituals, ethics, values, social norms, and laws which form the basis of human society. Humans have a marked appreciation for beauty and aesthetics which, combined with the human desire for self-expression, has led to cultural innovations such as art, literature and music.
Humans are noted for their desire to understand and influence the world around them, seeking to explain and manipulate natural phenomena through science, philosophy, mythology and religion. This natural curiosity has led to the development of advanced tools and skills.
