Dome

A dome is a special kind of curved roof that looks like the top half of a ball or sphere. It is an important part of many buildings and has been used for thousands of years. Domes can sit on round or square spaces, and they are made in many different ways using many kinds of materials.

People have built domes since very old times. You can find domes in buildings from ancient Mesopotamia, Persian, Hellenistic, Roman, and Chinese cultures. They were also used a lot in Byzantine architecture and Sasanian architecture, and later in Renaissance architecture, Ottoman architecture, Baroque, and Neoclassical architecture.

Today, domes are used in all sorts of buildings, from churches and government buildings to sports arenas and even everyday structures. They are made from many materials, including stone, wood, brick, concrete, metal, glass, and plastic. Domes often have special meanings, such as representing the sky or serving as important symbols in different cultures.

Etymology

The word "dome" comes from the ancient Greek and Latin word domus, meaning "house." Long ago, it was used to describe important buildings like churches, no matter their shape. Over time, especially in the 18th century, the word began to mean a rounded roof shape, especially for big, impressive buildings. In French, a similar word, dosme, also came to mean a rounded roof or vault, influencing how we use the word today.

Main article: cupola

Definitions

Domes are curved-roof structures that have been used for thousands of years. In ancient times, people made roofs with curved shapes using materials like wood and stone. The most common dome shape, like half of a sphere, came from Greek and Roman designs, but other shapes were used too, especially in early Islamic buildings.

Today, the word "dome" can mean many things. Sometimes it refers only to dome shapes that are half of a sphere, and other times it includes any rounded roof shape. Engineers and architects often use the word differently—one group focuses on how the structure stays up, while the other focuses on how it looks. With new building materials, domes can now be made in many new ways, making the definition even broader.

Elements

The word "cupola" is another word for "dome", usually used for a small dome on top of a roof or turret. The top part of a dome is called the "crown". Domes can be supported by a round or oval wall called a "drum". If the drum reaches the ground, the building might be called a "rotunda".

When a dome's shape doesn't match the walls below it, special techniques are used to connect them. One way is to use diagonal lintels to create an octagonal base. Another method uses arches to support the dome's weight. These methods help spread the weight of the dome evenly.

Materials

The earliest domes in the Middle East were built using mud-brick, and later with baked brick and stone. Wooden domes were also used because wood is light and flexible, allowing for wide spaces, and were often protected by copper or lead roofing. Stone domes were more expensive and smaller, while brick became a popular choice for large buildings until the Industrial Age.

New materials like iron, steel, and concrete in the 19th and 20th centuries allowed for thinner and lighter domes, which could cover much larger spaces. These advances also made it possible to create movable domes for modern sports stadiums. In 1983, experimental domes made from rammed earth were created at the University of Kassel as part of research into sustainable architecture.

Shapes and internal forces

A masonry dome creates forces that push downward and outward. These forces can be thought of in two directions: like lines of longitude on a globe, which only push in, and like lines of latitude, which push in at the top but stretch at the bottom. The strength of these forces depends on how heavy the dome's materials are.

Domes are built in layers, with each layer forming a complete ring that supports itself. This makes them stable as they are built. Because of this, domes can be thinner than similar arches. The best shape for a dome allows it to push in perfectly without stretching, which helps it stay strong.

Symbolism

Main article: Symbolism of domes

Domes have held special meaning throughout history. In ancient times, dome-shaped tombs were built to honor ancestors, linking the dome shape to ideas of a permanent home. In places like India and Iberia, domes appeared in tombs and were seen as sacred.

Later, domes were also linked to the idea of the heavens. In buildings, a dome over a square base showed a special meaning: the circle stood for the sky and perfection, while the square stood for the earth. This idea was used by rulers and became important in religious buildings, where domes symbolized the sky and the sacred.

Acoustics

Domes can affect how we hear sounds because of their curved shapes. They can reflect sound and sometimes create echoes. Some domes have special areas called "whispering galleries" where a person can whisper and be heard clearly from far away. This shape can help carry music, like in old churches, but it might make speaking harder to understand.

To improve sound, some domes have small hollow spaces built inside them. These spaces can spread out sound waves so that echoes are reduced and the atmosphere feels special. This idea of using special shapes and spaces to control sound has been known for a very long time.

Types

Domes come in many different shapes and styles, each with its own unique features. One common type is the beehive dome, which is made of horizontal layers that slightly lean toward the center as they rise, meeting at the top. A famous example is the Treasury of Atreus from the Bronze Age.

Another type is the geodesic dome, which is made of a framework of triangles forming a pattern based on shapes like icosahedrons or octahedrons. These domes are efficient and can be built using simple elements. Bulbous and onion domes are known for their swollen, curved shapes and are often seen in Islamic and Russian architecture. Oval domes have an egg-like shape and were used as early as 4000 B.C. Each type of dome serves different purposes and reflects the creativity of the cultures that built them.

Main article: Cloister vault

Main article: Ellipsoidal dome

Main article: Geodesic dome

History

Cultures from prehistoric times to the present have built domed dwellings using whatever materials were available. Early examples include small homes made from mammoth tusks and bones, discovered in Ukraine and dating back thousands of years. Indigenous peoples around the world also created dome-like structures, such as wigwams made by Native Americans and igloos built by the Inuit from snow blocks.

Over time, domes evolved from these simple forms into more complex architectural features. Ancient civilizations like Mesopotamia, China, and the Roman Empire developed their own styles of domes. The Romans, in particular, built large domes in baths, palaces, and tombs, with the famous Pantheon in Rome being a prime example. These early domes laid the groundwork for future architectural developments.