Dome

Dome (pronounced dohm)

(1) In architecture, a vault, having a circular plan and usually in the form of a portion of a sphere, so constructed as to exert an equal thrust in all directions.

(2) A domical roof or ceiling; a polygonal vault, ceiling, or roof.

(3) Any covering thought to resemble the hemispherical vault of a building or room; anything shaped like a hemisphere or inverted bowl.

(4) In water management, (usually in dam design), a semidome having its convex surface toward the impounded water.

(5) In crystallography, a form having planes that intersect the vertical axis and are parallel to one of the lateral axes.

(6) In geology, an upwarp (a broad anticline (a fold with strata sloping downwards on each side) caused by local uplift).

(7) In geology, a mountain peak having a rounded summit (a structure in which rock layers slope away in all directions from a central point).

(8) As vistadome, in passenger vehicles (usually railroad cars), a raised, glass-enclosed section of the roof of, placed over an elevated section of seats to afford passengers a full view of scenery (not usually truly in the hemispherical shape of a dome).

(9) In horology, the inner cover for the works of a watch which snaps into the rim of the case.

(10) A building; a house; an edifice (obsolete except as a literary device).

(11) As heat dome, a meteorological phenomenon in which the interplay of high & low pressure atmospheric systems interact to produce static, warm air over a large area.

(12) To cover with or as if with a dome; to shape like a dome.

(13) To rise or swell as a dome.

(14) In slang, a person's head (the form chrome dome used of the bald).

(15) In slang (both military and in some criminal classes), to shoot in the head (often in the form “got domed”).

(16) In African-American slang, to perform fellatio upon.

1505–1515: From the Middle French domme & dome (a town-house; a dome, a cupola) (which persists in modern French as dôme), from the Provençal doma, from the Italian duomo (cathedral), from the Medieval Latin domus (ecclesiae; literally “house (of the church)”), a calque of the Ancient Greek οἶκος τῆς ἐκκλησίας (oîkos tês ekklēsías).  Dome is a noun & verb, domed & doming are verbs and domelike, domical, domish & domesque are adjectives; the noun plural is domes.

By the 1650s, the formalized use in architecture ensured the meaning was (more or less) standardized as “a round, vaulted roof, a hemispherical covering of a building” and thus the ultimate specialized evolution from the Greek dōma (a house, housetop (used especially of those with a roof “in the eastern style”), from domos (house), from the primitive Indo-European root dem- (house, household).  The medieval use of the German dom and Italian duomo as verbal shorthand for “cathedral” (essentially a clipping from “house of God”) was picked up in the imperfect way so many words entered English to describe architectural features in the style of hemispherical cupolas, the domes at the intersection of the nave and the transept, or over the sanctuary, characteristic architectural feature of Italian cathedrals.  The sense in English of “a building, a house” had been borrowed in English as early as the 1510s and was used mostly of stately homes and it endures but only as a literary device and it’s rarely seen outside of poetry.

The shape occurs to one degree or another in nature and is common in man-made objects and the built environment so dome is an often seen modifier (cake dome, pleasure dome, lava dome; onion dome et al) and appears in the opening lines of one of the most cherished fragments of English verse: Kubla Khan (1797) by Samuel Taylor Coleridge (1772-1834).

In Xanadu did Kubla Khan
A stately pleasure-dome decree:
Where Alph, the sacred river, ran
Through caverns measureless to man
Down to a sunless sea.

Some of the use has also been opportunistic and not especially domical.  Vistadomes were raised, glass-enclosed sections built into the roofs of railway carriages, placed over an elevated section of seats to afford passengers a better view of the scenery.  The idea was picked up by General Motors, the Oldsmobile Vista Cruiser station wagon (1964-1977), the Buick Roadmaster Estate (1991-1996) and the Scenicruiser busses (1954-1956 and made famous in the Greyhound livery some wore until the 1970s) all used raised, partially-windowed sections although none were officially described as “domes”.

The Hagia Sophia, now the main mosque in Istanbul; the minarets were added after the fall of Constantinople to the Ottoman Turks in 1453 and there are many architectural critics who maintain visually they improve the balance of the structure.  The illustration on the right shows how the Byzantine engineers used pendentives to make the construction of domes possible.     

Domes however are most associated with grand-scale, representational architecture (although quite a few builders of McMansions found them hard to resist).  One intriguing aspect of structural engineering upon which the integrity of a dome depends on what are called pendentives (the triangular segments of the lower part of a hemispherical dome left by the penetration of the dome by two semicircular vaults intersection at right angles).  Dating from 1727, pendentive was from the mid-sixteenth century French pendentif, from the Latin pendentem (nominative pendens) (hanging and the source of the English “pendulous”), the present participle of pendere (to hang) from the primitive Indo-European roots pen & spen- (to draw, stretch, spin).  What pendentives permit is the use of a circular dome over a square void square room or an elliptical one over something rectangular room.  Pendentives, (geometrically the triangular segments of a sphere), taper to points at the bottom and spread at the top to establish the continuous circular or elliptical base as required.  As structural supports, pendentives distribute the bulk of a dome’s weight to the four corners (the strongest points) and ultimately to the piers and the foundations below.  The classic example is the Hagia Sophia, the sixth century Byzantine cathedral at Constantinople (modern day Istanbul).  It was converted into a mosque when Constantinople fell to the Ottoman Turks in 1453 and, after a century-odd as a museum, is again a mosque.

Scale model of Germania.  Hitler would spend hours pondering the details but in 1945, he spent even longer looking at the model of what was planned for the Austrian city of Linz where he'd decided to have his tomb installed.

Domes have long been a favorite of emperors, dictators and those other megalomaniacs: architects.  A truly monumental one would have been the Volkshalle (People's Hall and known also as the Große Halle (Great Hall) & Ruhmeshalle (Hall of Glory), the centerpiece of Adolf Hitler’s (1889-1945; Führer (leader) and German head of government 1933-1945 & head of state 1934-1945) never realized plan to re-built Berlin as Germania, a worthy Welthauptstadt (world capital) of his “thousand year Reich”.  Although Albert Speer (1905–1981; Nazi court architect 1934-1942; Nazi minister of armaments and war production 1942-1945) was Germania’s chief architect, in some aspects he was really a glorified draftsman, correcting the technical errors in the drawings passed to him by the Führer who had be sketching parts of the design since the early 1920s.

Even by the standards of the super-dimensionality which was characteristic of the Third Reich, the domed hall would have been extraordinary.  The oculus would have been 46 m (151 feet) in diameter which would have accommodated the entire rotunda of Hadrian's Pantheon and the dome of St Peter's Basilica.  The  250 m (820 feet) diameter of the dome was (and this was a signature of Speer’s approach), bigger even than Hitler had requested and he was much displeased to learn of a rival architect’s plans for a dome 15 m (49 feet) greater in diameter to sit atop the city’s new railway station.  As things turned out, none of the grandiose structures were ever built and although a tinge of regret can be found in Speer’s post-war thoughts, even he admitted the designs were a failure because of “their lack of human scale”.

Berlin's rebuilt Reichstag with steel & glass dome.

Berlin did however eventually get a new dome, albeit it one rendered not in granite but the glass and steel the Führer thought was fine for factories and warehouses but which would have appalled him as a method of construction for public, representational architecture.  Plonked atop the rebuilt Reichstag, it was said to symbolize the reunification of Germany although quite how it managed that has never really been explained although the distinctive structure has become a city landmark and people seem to like it.  A clever design, it sits directly above the chamber of the Bundestag (the lower house of the bicameral federal parliament) and permits public observation, the clever design also reducing energy use by optimizing the input of natural light while moving shrouds minimize glare and heat-soak.

Cinerama Dome, Los Angeles in 1965, the year of its greatest commercial success.

The Cinerama Dome movie theatre sits on Hollywood’s Sunset Boulevard.  Opened in 1963, the Cinerama Dome introduced a new concept for film projection, a curved screen which sat inside a geodesic dome based on the design developed by US systems theorist & architect Richard Buckminster Fuller (1895–1983), one attraction of which was such things could be built at lower coast and in much less time than a conventional theatre building.  Intended to be the first of perhaps thousands around the planet, it was built in a still remarkable four months but it remains the only concrete geodesic on the planet and while it has operated intermittently since being closed during the COVID-19 pandemic, its future is uncertain and although it will probably be preserved as a historic building, it’s likely to be re-purposed as retail or restaurant space.

Lindsay Lohan at the Scary Movie V premiere, Cinerama Dome, April 2013.

The end of the line for Cinerama is another marker in the evolution of the technology which underpinned the evolution of the US economy from one based on agriculture, to one increasingly industrial to one geared around the military & entertainment.  In the 1950s, cinema’s greatest challenge came from television and the film studios fought back by creating differentiation in their products.  The venture into 3D proved a cul-de-sac for a number of reasons but one thing cinemas could do was make their big screens huge and during the 1950s the wide-screen Cinemascope enjoyed a boom.  However, there was a limit to how much screens could grow, hence the interest in Cinerama which projected onto a curved screen designed to take advantage of the way the human eye sees and processes images, the system at its best when provided by three synchronized projectors.  The idea lives on in the curved screens which have become popular among gaming freaks who enjoy the sense of “envelopment”.  It was also the era during which populations moved further from city centres into suburbs and thus, cinemas also needed to move, more of which (but often smaller) would be required.  Thus the attraction of the geodesic dome came which, largely pre-fabricated, was cheap to produce and quick to assemble.  However, Cinerama was expensive to film, to print, to produce and the sheer size and weight of the prints meant it was costly even to ship the material to venues and the conversion process to something which could be used with conventional projection.

Heat Domes

July 2023 Global heat map from the Climate Change Institute, University of Maine, USA.  For those unconvinced, Fox News continues to provide alternative facts.

The “heat dome” is a weather phenomenon, the physics of which has for decades been understood but of late the term has entered general use as much of the northern hemisphere has suffered from prolonged, unusually high temperatures, July 2023 measured as the hottest month ever recorded.  A heat dome occurs when a large, high-pressure system traps and concentrates hot air in a specific region, leading to prolonged and extremely high temperatures. Under a heat dome, the atmospheric pressure aloft prevents the hot air from rising and dissipating, effectively acting as a lid or cap over the area, thus the image of a dome sitting over the land.

The UK's Royal Meteorological Service's simple illustration of the physics of a heat dome.  Heat domes are also their own feedback loop.  A static areas of high pressure which already contains warm or hot air trapped under the high will become hotter and hotter, creating a heat dome.  Hot air will rise into the atmosphere, but high pressure acts as a lid and causes the air to subside or sink; as the air sinks, it warms by compression, and the heat builds. The ground also warms, losing moisture and making it easier to heat even more.