Globe

A globe is a spherical model of a celestial body or the celestial sphere.

While flat maps must use projections that distort shapes or sizes, globes avoid this issue. They represent the surface accurately by simply scaling it down. A model of the Earth is known as a terrestrial globe. These models show landmasses, water bodies, nations, and major cities.

They often include a network of latitude and longitude lines to provide coordinates. Some terrestrial globes feature raised relief to represent mountains and other large landforms.

Celestial globes represent a different subject: the stars and the celestial sphere. These models show notable stars and the positions of prominent astronomical objects. They also divide the sky into different constellations.

Celestial globes typically exclude the Sun, Moon, and planets because their locations change constantly. Instead, they mark the ecliptic, which is the apparent path of the Sun. Creating these models involves complex geometry. Because of how we view the sky, some celestial globes use reversed constellations so they appear correct when viewed in a mirror.

Historically, celestial globes were used to reflect geocentric models of the universe. In the 2nd century, Ptolemy used systems like epicycles and equants to explain how planets moved. Medieval astronomers built globes based on these ideas, assuming the Earth was static. They believed rotating celestial spheres encircled the Earth. This view lasted until Copernicus proposed a heliocentric system. This new model changed our understanding of the cosmic structure.

The earliest known mention of a globe comes from the writer Strabo. He described the Globe of Crates from approximately 150 BC.

Terrestrial globe making has a long and diverse history across many cultures. The oldest surviving terrestrial globe is the Erdapfel, created by Martin Behaim in 1492.

Behaim was a German merchant and navigator who worked in Nuremberg. In the Islamic world, terrestrial globes were constructed that depicted the Old World. In 1276, the Persian astronomer Jamal ad-Din introduced a globe to China. Other notable historical examples include the Hunt–Lenox Globe from around 1510. This copper cast is thought to be related to an ostrich egg globe from 1504.

Manufacturing methods for globes have changed significantly over the centuries. Traditionally, makers glued paper gores onto a sphere, often made of wood. Gores are long, thin strips of paper that narrow at the poles. Using more gores helps the paper fit the sphere without too much stretching.

Modern globes are frequently made from thermoplastic. Machines mold flat plastic disks into hemispherical shapes. These two halves are then joined to complete the sphere. Most globes are mounted on an axis tilted at 23.5 degrees. This specific angle helps people visualize how the Earth's seasons change.

Globes come in many different scales and sizes to serve different purposes. Many common globes have a circumference of one metre, creating a 1:40 million scale. Others use a one-foot diameter, resulting in a 1:42 million scale. Some specialized globes use exaggerated topography to make mountains visible. One manufacturer produces a relief globe where Mount Everest appears 57 times higher than its actual scale. Large-scale globes also exist for public display. The Unisphere in New York is the world's largest geographical globe, with a scale of 1:350,000.

Specific famous globes highlight the variety of this medium. Eartha, located in Yarmouth, Maine, is the world's largest rotating globe.

It has a diameter of 12 meters and a scale of 1:1.1 million. In London, Wyld's Great Globe was a massive hollow structure from the mid-1800s. The P-I Globe in Seattle was a 30-foot neon model made in 1948. There is even a 40-ton stone globe at Durlston Castle in England. Even in space exploration, globes have played a role. Soviet and Russian spacecraft used small electro-mechanical globes for navigation until 2002.