A tower is a tall

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 ...

, taller than it is wide, often by a significant factor. Towers are distinguished from masts by their lack of guy-wires and are therefore, along with tall buildings, self-supporting structures. Towers are specifically distinguished from

building A building or edifice is an enclosed Structure#Load-bearing, structure with a roof, walls and window, windows, usually standing permanently in one place, such as a house or factory. Buildings come in a variety of sizes, shapes, and functions, a ...

s in that they are built not to be habitable but to serve other functions using the

height Height is measure of vertical distance, either vertical extent (how "tall" something or someone is) or vertical position (how "high" a point is). For an example of vertical extent, "This basketball player is 7 foot 1 inches in height." For an e ...

of the tower. For example, the height of a clock tower improves the visibility of the clock, and the height of a tower in a fortified building such as a

castle A castle is a type of fortification, fortified structure built during the Middle Ages predominantly by the nobility or royalty and by Military order (monastic society), military orders. Scholars usually consider a ''castle'' to be the private ...

increases the visibility of the surroundings for defensive purposes. Towers may also be built for

observation Observation in the natural sciences is an act or instance of noticing or perceiving and the acquisition of information from a primary source. In living beings, observation employs the senses. In science, observation can also involve the percep ...

, leisure, or

telecommunication Telecommunication, often used in its plural form or abbreviated as telecom, is the transmission of information over a distance using electronic means, typically through cables, radio waves, or other communication technologies. These means of ...

purposes. A tower can stand alone or be supported by adjacent buildings, or it may be a feature on top of a larger structure or building.

Etymology

Old English Old English ( or , or ), or Anglo-Saxon, is the earliest recorded form of the English language, spoken in England and southern and eastern Scotland in the Early Middle Ages. It developed from the languages brought to Great Britain by Anglo-S ...

''torr'' is from

Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...

''turris'' via

Old French Old French (, , ; ) was the language spoken in most of the northern half of France approximately between the late 8th Greek τύρσις was loaned from a pre-Indo-European Mediterranean language, connected with the Illyrian toponym Βου-δοργίς. With the Lydian language">Lydian toponyms Τύρρα, Τύρσα, it has been connected with the ethnonym Tyrrhenians">Τυρρήνιοι as well as with ''Tusci'' (from ''*Turs-ci''), the Greek and Latin names for the Etruscans (Kretschmer Glotta 22, 110ff.)

History

Towers have been used by humankind since prehistoric times. The oldest known may be the circular stone tower in walls of Wall of Jericho (Neolithic), Neolithic Jericho (8000 BC). Some of the earliest towers were ziggurats, which existed in Sumerian architecture since the 4th millennium BC. The most famous ziggurats include the Sumerian Ziggurat of Ur, built in the 3rd millennium BC, and the Etemenanki, one of the most famous examples of Babylonian architecture. Some of the earliest surviving examples are the

broch In archaeology, a broch is an British Iron Age, Iron Age drystone hollow-walled structure found in Scotland. Brochs belong to the classification "complex Atlantic roundhouse" devised by Scottish archaeologists in the 1980s. Brochs are round ...

structures in northern

Scotland Scotland is a Countries of the United Kingdom, country that is part of the United Kingdom. It contains nearly one-third of the United Kingdom's land area, consisting of the northern part of the island of Great Britain and more than 790 adjac ...

, which are conical tower houses. These and other examples from

Phoenicia Phoenicians were an Ancient Semitic-speaking peoples, ancient Semitic group of people who lived in the Phoenician city-states along a coastal strip in the Levant region of the eastern Mediterranean, primarily modern Lebanon and the Syria, Syrian ...

n and Roman cultures emphasised the use of a tower in fortification and sentinel roles. For example, the name of the Moroccan city of

Mogador Essaouira ( ; ), known until the 1960s as Mogador (, or ), is a port city in the western Morocco, Moroccan region of Marrakesh-Safi, on the Atlantic Ocean, Atlantic coast. It has 77,966 inhabitants as of 2014. The foundation of the city of Essao ...

, founded in the first millennium BC, is derived from the Phoenician word for watchtower ('migdol'). The Romans utilised octagonal towers as elements of Diocletian's Palace in

Croatia Croatia, officially the Republic of Croatia, is a country in Central Europe, Central and Southeast Europe, on the coast of the Adriatic Sea. It borders Slovenia to the northwest, Hungary to the northeast, Serbia to the east, Bosnia and Herze ...

, which monument dates to approximately 300 AD, while the Servian Walls (4th century BC) and the Aurelian Walls (3rd century AD) featured square ones. The Chinese used towers as integrated elements of the

Great Wall of China The Great Wall of China (, literally "ten thousand ''li'' long wall") is a series of fortifications in China. They were built across the historical northern borders of ancient Chinese states and Imperial China as protection against vario ...

in 210 BC during the

Qin dynasty The Qin dynasty ( ) was the first Dynasties of China, imperial dynasty of China. It is named for its progenitor state of Qin, a fief of the confederal Zhou dynasty (256 BC). Beginning in 230 BC, the Qin under King Ying Zheng enga ...

. Towers were also an important element of castles. Other well known towers include the Leaning Tower of Pisa in Pisa, Italy built from 1173 until 1372, the Two Towers in Bologna, Italy built from 1109 until 1119 and the Towers of Pavia (25 survive), built between 11th and 13th century. The Himalayan Towers are stone towers located chiefly in

Tibet Tibet (; ''Böd''; ), or Greater Tibet, is a region in the western part of East Asia, covering much of the Tibetan Plateau and spanning about . It is the homeland of the Tibetan people. Also resident on the plateau are other ethnic groups s ...

built approximately 14th to 15th century. Dana Thomas, "Towers to the Heavens"
''Newsweek'', 2003-11-15

Mechanics

Up to a certain height, a tower can be made with the supporting structure with parallel sides. However, above a certain height, the compressive load of the material is exceeded, and the tower will fail. This can be avoided if the tower's support structure tapers up the building. A second limit is that of buckling—the structure requires sufficient stiffness to avoid breaking under the loads it faces, especially those due to winds. Many very tall towers have their support structures at the periphery of the building, which greatly increases the overall stiffness. A third limit is dynamic; a tower is subject to varying winds, vortex shedding, seismic disturbances etc. These are often dealt with through a combination of simple strength and stiffness, as well as in some cases tuned mass dampers to damp out movements. Varying or tapering the outer aspect of the tower with height avoids vibrations due to vortex shedding occurring along the entire building simultaneously.

Functions

Although not correctly defined as towers, many modern high-rise buildings (in particular

skyscraper A skyscraper is a tall continuously habitable building having multiple floors. Most modern sources define skyscrapers as being at least or in height, though there is no universally accepted definition, other than being very tall high-rise bui ...

) have 'tower' in their name or are colloquially called 'towers'. Skyscrapers are more properly classified as 'buildings'. In the

United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Northwestern Europe, off the coast of European mainland, the continental mainland. It comprises England, Scotlan ...

, tall domestic buildings are referred to as tower blocks. In the

United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...

, the original World Trade Center had the nickname the Twin Towers, a name shared with the Petronas Twin Towers in

Kuala Lumpur Kuala Lumpur (KL), officially the Federal Territory of Kuala Lumpur, is the capital city and a Federal Territories of Malaysia, federal territory of Malaysia. It is the largest city in the country, covering an area of with a census population ...

. In addition some of the structures listed below do not follow the strict criteria used at List of tallest towers.

Strategic advantages

The tower throughout history has provided its users with an advantage in surveying defensive positions and obtaining a better view of the surrounding areas, including battlefields. They were constructed on defensive walls, or rolled near a target (see siege tower). Today, strategic-use towers are still used at prisons, military camps, and defensive perimeters.

Potential energy

By using gravity to move objects or substances downward, a tower can be used to store items or liquids like a storage silo or a

water tower A water tower is an elevated structure supporting a water tank constructed at a height sufficient to pressurize a water distribution system, distribution system for potable water, and to provide emergency storage for fire protection. Water towe ...

, or aim an object into the earth such as a drilling tower. Ski-jump ramps use the same idea, and in the absence of a natural mountain slope or hill, can be human-made.

Communication enhancement

In history, simple towers like

lighthouse A lighthouse is a tower, building, or other type of physical structure designed to emit light from a system of lamps and lens (optics), lenses and to serve as a beacon for navigational aid for maritime pilots at sea or on inland waterways. Ligh ...

s, bell towers, clock towers, signal towers and

minaret A minaret is a type of tower typically built into or adjacent to mosques. Minarets are generally used to project the Muslim call to prayer (''adhan'') from a muezzin, but they also served as landmarks and symbols of Islam's presence. They can h ...

s were used to communicate information over greater distances. In more recent years, radio masts and cell phone towers facilitate communication by expanding the range of the transmitter. The CN Tower in

Toronto, Ontario Toronto ( , locally pronounced or ) is the List of the largest municipalities in Canada by population, most populous city in Canada. It is the capital city of the Provinces and territories of Canada, Canadian province of Ontario. With a p ...

, Canada was built as a communications tower, with the capability to act as both a transmitter and repeater.

Transportation support

Towers can also be used to support bridges, and can reach heights that rival some of the tallest buildings above-water. Their use is most prevalent in suspension bridges and cable-stayed bridges. The use of the pylon, a simple tower structure, has also helped to build railroad bridges, mass-transit systems, and harbors. Control towers are used to give visibility to help direct aviation traffic.

Other

* To access tall or high objects: launch tower, service tower, service structure, scaffold,

tower crane A crane is a machine used to move materials both vertically and horizontally, utilizing a system of a boom, hoist, wire ropes or chains, and sheaves for lifting and relocating heavy objects within the swing of its boom. The device uses on ...

* To access atmospheric conditions aloft:

wind turbine A wind turbine is a device that wind power, converts the kinetic energy of wind into electrical energy. , hundreds of thousands of list of most powerful wind turbines, large turbines, in installations known as wind farms, were generating over ...

, meteorological measurement tower, tower telescope,

solar power Solar power, also known as solar electricity, is the conversion of energy from sunlight into electricity, either directly using photovoltaics (PV) or indirectly using concentrated solar power. Solar panels use the photovoltaic effect to c ...

station * To lift high tension cables for electrical power distribution transmission tower * To take advantage of the temperature gradient inherent in a height differential:

cooling tower A cooling tower is a device that rejects waste heat to the atmosphere through the cooling of a coolant stream, usually a water stream, to a lower temperature. Cooling towers may either use the evaporation of water to remove heat and cool the ...

* To expel and disperse potentially harmful gases and particulates into the atmosphere:

chimney A chimney is an architectural ventilation structure made of masonry, clay or metal that isolates hot toxic exhaust gases or smoke produced by a boiler, stove, furnace, incinerator, or fireplace from human living areas. Chimneys are typical ...

* To protect from exposure: BREN Tower, lightning rod tower * For industrial production: shot tower * For surveying: Survey tower * To drop objects: Drop tube (drop tower), bomb tower, diving platform * To test height-intensive applications: elevator test tower * To improve structural integrity: thyristor tower * To mimic towers or provide height for training purposes: fire tower, parachute tower * As art: Shukhov Tower * For recreation: rock climbing tower * As a symbol: Tower of Babel, The Tower (Tarot card), church tower The term "tower" is also sometimes used to refer to firefighting equipment with an extremely tall ladder designed for use in firefighting/rescue operations involving high-rise buildings.

Gallery

References

External links

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