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 A guy-wire, guy-line, guy-rope, or stay, also called simply a guy, is a tensioned cable designed to add stability to a free-standing structure. They are used commonly for ship masts, radio masts, wind turbines, utility poles, and tents. A thin ...

and are therefore, along with tall buildings, self-supporting structures. Towers are specifically distinguished from

building A building, or edifice, is an enclosed structure with a roof and walls standing more or less permanently in one place, such as a house or factory (although there's also portable buildings). Buildings come in a variety of sizes, shapes, and fun ...

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 example, "The height of that building is 50 m" or "The height of an airplane in-flight is abou ...

of the tower. For example, the height of a

clock tower Clock towers are a specific type of structure which house a turret clock and have one or more clock faces on the upper exterior walls. Many clock towers are freestanding structures but they can also adjoin or be located on top of another buildi ...

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 fortified structure built during the Middle Ages predominantly by the nobility or royalty and by military orders. Scholars debate the scope of the word ''castle'', but usually consider it to be the private fortified r ...

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

observation Observation is the active acquisition of information from a primary source. In living beings, observation employs the senses. In science, observation can also involve the perception and recording of data via the use of scientific instruments. The ...

, leisure, or

telecommunication Telecommunication is the transmission of information by various types of technologies over wire, radio, optical, or other electromagnetic systems. It has its origin in the desire of humans for communication over a distance greater than that fe ...

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 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 was brought to Great Britain by Anglo-Saxon settlement of Britain, Anglo ...

''torr'' is from

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...

''turris'' via

Old French Old French (, , ; Modern French: ) was the language spoken in most of the northern half of France from approximately the 8th to the 14th centuries. Rather than a unified language, Old French was a linkage of Romance dialects, mutually intelligib ...

''tor''. The Latin term together with Greek τύρσις was loaned from a pre-Indo-European Mediterranean language, connected with the Illyrian toponym Βου-δοργίς. With the Lydian toponyms Τύρρα, Τύρσα, it has been connected with the ethnonym Τυρρήνιοι as well as with ''Tusci'' (from ''*Turs-ci''), the Greek and Latin names for the

Etruscans The Etruscan civilization () was developed by a people of Etruria in ancient Italy with a common language and culture who formed a federation of city-states. After conquering adjacent lands, its territory covered, at its greatest extent, rou ...

(Kretschmer Glotta 22, 110ff.)

History

Towers have been used by mankind since prehistoric times. The oldest known may be the circular stone tower in walls of Neolithic Jericho (8000 BC). Some of the earliest towers were

ziggurat A ziggurat (; Cuneiform: 𒅆𒂍𒉪, Akkadian: ', D-stem of ' 'to protrude, to build high', cognate with other Semitic languages like Hebrew ''zaqar'' (זָקַר) 'protrude') is a type of massive structure built in ancient Mesopotamia. It has ...

s, which existed in

Sumerian architecture The architecture of Mesopotamia is ancient architecture of the region of the Tigris–Euphrates river system (also known as Mesopotamia), encompassing several distinct cultures and spanning a period from the 10th millennium BC (when the first perm ...

since the 4th millennium BC. The most famous ziggurats include the Sumerian

Ziggurat of Ur The Ziggurat (or Great Ziggurat) of Ur ( Sumerian: "Etemenniguru", meaning "temple whose foundation creates aura") is a Neo-Sumerian ziggurat in what was the city of Ur near Nasiriyah, in present-day Dhi Qar Province, Iraq. The structure wa ...

, built in the 3rd millennium BC, and the

Etemenanki Etemenanki ( Sumerian: "temple of the foundation of heaven and earth") was a ziggurat dedicated to Marduk in the ancient city of Babylon. It now exists only in ruins, located about south of Baghdad, Iraq. Etemenanki has been suggested to be th ...

, one of the most famous examples of Babylonian architecture. Some of the earliest surviving examples are the

broch A broch is an Iron Age drystone hollow-walled structure found in Scotland. Brochs belong to the classification "complex Atlantic roundhouse" devised by Scottish archaeologists in the 1980s. Their origin is a matter of some controversy. Origin ...

structures in northern

Scotland Scotland (, ) is a country that is part of the United Kingdom. Covering the northern third of the island of Great Britain, mainland Scotland has a border with England to the southeast and is otherwise surrounded by the Atlantic Ocean to the ...

, which are conical

tower house A tower house is a particular type of stone structure, built for defensive purposes as well as habitation. Tower houses began to appear in the Middle Ages, especially in mountainous or limited access areas, in order to command and defend strateg ...

s. These and other examples from

Phoenicia Phoenicia () was an ancient thalassocratic civilization originating in the Levant region of the eastern Mediterranean, primarily located in modern Lebanon. The territory of the Phoenician city-states extended and shrank throughout their histor ...

n and

Roman Roman or Romans most often refers to: *Rome, the capital city of Italy *Ancient Rome, Roman civilization from 8th century BC to 5th century AD *Roman people, the people of ancient Rome *''Epistle to the Romans'', shortened to ''Romans'', a letter ...

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

Mogador Essaouira ( ; ar, الصويرة, aṣ-Ṣawīra; shi, ⵜⴰⵚⵚⵓⵔⵜ, Taṣṣort, formerly ''Amegdul''), known until the 1960s as Mogador, is a port city in the western Morocco, Moroccan region of Marrakesh-Safi, Marakesh-Safi, on the ...

, 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 , image_flag = Flag of Croatia.svg , image_coat = Coat of arms of Croatia.svg , anthem = "Lijepa naša domovino"("Our Beautiful Homeland") , image_map = , map_caption = , capit ...

, 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'' wall") is a series of fortifications that were built across the historical northern borders of ancient Chinese states and Imperial China as protection against various nomadic grou ...

in 210 BC during the

Qin Dynasty The Qin dynasty ( ; zh, c=秦朝, p=Qín cháo, w=), or Ch'in dynasty in Wade–Giles romanization ( zh, c=, p=, w=Ch'in ch'ao), was the first Dynasties in Chinese history, dynasty of Imperial China. Named for its heartland in Qin (state), ...

. Towers were also an important element of castles. The Eiffel Tower, Paris, France

Other well known towers include the Leaning Tower of Pisa in

Pisa, Italy Pisa ( , or ) is a city and ''comune'' in Tuscany, central Italy, straddling the Arno just before it empties into the Ligurian Sea. It is the capital city of the Province of Pisa. Although Pisa is known worldwide for its leaning tower, the cit ...

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 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 building A tower block, high-rise, apartment tower, residential tower, apartment block, block of flats, or office tower is a tall building, as opposed to a low-rise building and is defined differently in terms of height depending on the jurisdictio ...

s (in particular

skyscraper A skyscraper is a tall continuously habitable building having multiple floors. Modern sources currently define skyscrapers as being at least or in height, though there is no universally accepted definition. Skyscrapers are very tall high-ris ...

) have 'tower' in their name or are colloquially called 'towers'. Skyscrapers are more properly classified as 'buildings'. In the United Kingdom, tall domestic buildings are referred to as tower blocks. In the United States, the original World Trade Center had the nickname the Twin Towers, a name shared with the Petronas Twin Towers in Kuala Lumpur. 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, 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 lenses and to serve as a beacon for navigational aid, for maritime pilots at sea or on inland waterways. Lighthouses mar ...

bell tower A bell tower is a tower that contains one or more bells, or that is designed to hold bells even if it has none. Such a tower commonly serves as part of a Christian church, and will contain church bells, but there are also many secular bell tower ...

s, signal towers and

minaret A minaret (; ar, منارة, translit=manāra, or ar, مِئْذَنة, translit=miʾḏana, links=no; tr, minare; fa, گل‌دسته, translit=goldaste) is a type of tower typically built into or adjacent to mosques. Minarets are generall ...

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, 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 bridge A suspension bridge is a type of bridge in which the deck (bridge), deck is hung below suspension wire rope, cables on vertical suspenders. The first modern examples of this type of bridge were built in the early 1800s. Simple suspension bridg ...

s 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. * To access atmospheric conditions aloft: wind turbine, meteorological measurement tower, tower telescope, solar power 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 * 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 typic ...

* To protect from exposure: BREN Tower, lightning rod tower * For industrial production: shot tower * For surveying: Survey tower * To drop objects:

Drop tube In physics and materials science, a drop tower or drop tube is a structure used to produce a controlled period of weightlessness for an object under study. Air bags, polystyrene pellets, and magnetic or mechanical brakes are sometimes used to ...

(drop tower), bomb tower, diving platform * To test height-intensive applications:

elevator test tower An elevator test tower is a structure usually 100 to over 200 metres (300 feet to over 600 feet) tall that is designed to evaluate the stress and fatigue limits of specific elevator cars in a controlled environment. Tests are also carried out in ...

* To improve structural integrity:

thyristor tower A valve hall is a building which contains the valves of the static inverters of a high-voltage direct current plant. The valves consist of thyristors, or at older plants, mercury arc rectifiers. Mercury arc rectifiers are usually supported by i ...

* 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 Church may refer to: Religion * Church (building), a building for Christian religious activities * Church (congregation), a local congregation of a Christian denomination * Church service, a formalized period of Christian communal worship * Chris ...

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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