Globe

Painting a globe

A globe is a scale model with the shape of a sphere. Globes can be scale models of the Earth (terrestrial globes) or of other planets. Globes can also be models of the celestial sphere (celestial globes). The English word "globe" comes from the Latin: globus, meaning round mass or sphere.

Most globes are maps of the Earth. They have the advantage of avoiding the distortions of flat map projections. The most common types are political and physical. Political globes show countries. Physical globes show landscape like mountains and rivers. Some globes are star charts and some are maps of distant worlds.

Global as an adjective is used to mean the entire world rather than any special place on the Earth. It is also used in fields like computers to mean dealing with a whole larger system, rather than its individual little parts.

History

Aureus (gold coin) of the Roman emperor Carus, with a personification of Victory standing on a terrestrial globe

That the Earth is a sphere was established by Hellenistic astronomy in the 3rd century BC. The terrestrial globe appeared in that period. Now, there are no terrestrial globes from Classical Antiquity or the Middle Ages in existence. The first example of terrestrial globe known was the one the ancient Greek Crates of Mallus made in the middle of the 2nd century BC. The Greek geographer Strabo wrote about Crates's terrestrial globe during the early years of the Roman Empire.

A celestial globe from Classical Antiquity is in the Naples National Archaeological Museum, Italy. The globe is part of a sculpture – the globe is held up by a statue of Atlas, a Titan from Greek mythology. The ancient Romans made the globe and statue in the 2nd century AD. They may have copied the sculpture from Hellenistic art (art of the ancient Greek type) from the Hellenistic period (the 1st, 2nd, and 3rd centuries BC). The sculpture's name is the Farnese Atlas.

Early globes of the Earth that show all of the Old World were constructed in the Islamic Golden Age. One such example was made in the 9th century AD by Muslim geographers and cartographers working under the Abbasid caliph, al-Ma'mun. Another example was the globe introduced to Beijing by the Persian astronomer, Jamal ad-Din, in 1267.

Olivier van Deuren: A Young Astronomer

Martin Behaim designed a globe in 1492, in Nuremberg, Bavaria (Germany). Georg Glockendon was the artist who created the actual map drawings following Behaim's specifications. This globe is the oldest terrestrial globe still in existence. A copy of the globe showing America was made by Martin Waldseemueller in 1507. Another early globe, the Hunt-Lenox Globe, ca. 1507, is thought to be the source of the phrase "Here be dragons". Another "remarkably modern-looking" globe of the Earth was made in Constantinople (Istanbul) by Taqi al-Din at his Constantinople Observatory during the 1570s.

Manufacture

Gores for making a globe of Mars, with polar disks, 1892

Mass-produced globes are typically covered by a printed paper map. The most common type has long, thin gores (strips) of paper. These strips narrow to a point at the North Pole and the South Pole. Then a small disk is used to paper over the irregularities at the poles. The more gores there are, the less stretching and crumpling is needed to make the paper map fit the sphere.

From a geometric point of view, all points on a sphere are the same. One could select any point on the planet, and create a paper map that covers the globe with strips that come together at that point and the opposite point.

A globe that represents the Earth is usually mounted at a 23.5° angle on bearings. This mounting represents the axial tilt of the spinning planet, in relation to the Sun. This makes it easy to visualize how days and seasons change.