is a curve representing the changing angular offset of a celestial body (usually the Sun) from its mean position on the celestial sphere as viewed from another celestial body (usually the Earth). The term is used when the observed body appears, as seen from the viewing body, to move in a way that is repeated at regular intervals, such as once a year or once a day. The analemma is then a closed curve, which does not change.
Because of the Earth’s annual revolution around the Sun in an orbit that is elliptical and tilted relative to the plane of the equator, an observer at a fixed point on the Earth sees the Sun appear to move in an analemma around a mean position, taking a year to do so. The mean position appears to revolve around the Earth once every mean solar day, because of the Earth’s rotation. This daily revolution is not considered to be averaged out to get the mean. The mean position of the Sun is therefore at the same place in the sky at the same time every day, but not at other times. Therefore if the observed position of the Sun in the sky is plotted or photographed at the same time every day, or every few days, for a year, the points trace out the analemma.
The word “analemma” is most commonly used to mean the analemma of the Sun’s apparent motion, observed from a fixed position on the Earth as described above. Except where stated otherwise (mostly in items 5 and 6 of the table of contents), this common usage is employed in this article. For clarity, when the figure refers to the Sun, the term “solar analemma” is sometimes used in place of the single word “analemma”.
The analemma is an abstract concept. It has no physical existence except in diagrams and time-lapse photographs. Nevertheless, in common, convenient language, it is often described as if it were a real, visible celestial object. This common usage is followed in this article.
A model of objects in the sky (in the celestial sphere), consisting of a spherical framework of rings, centred on Earth, that represent lines of celestial longitude and latitude and other astronomically important features such as the ecliptic. As such, it differs from a celestial globe, which is a smooth sphere whose principal purpose is to map the constellations.
A skilled craft worker who makes or creates things by hand that may be functional or strictly decorative, for example furniture, decorative arts, sculptures, jewellery, household items and tools or even mechanical mechanisms such as the handmade clockwork movement of a watchmaker. Artisans practice a craft and may through experience and aptitude reach the expressive levels of an artist.
The axis is the rod or shaft at the centre of the globe. It represents the imaginary line around which the earth rotates or spins. At the two ends of the axis are the North Pole at the top and the South Pole at the bottom.
An adjective for anything commissioned to a particular specification. It may be altered or tailored to the customs, tastes, or usage of an individual purchaser.
Impression formed when a liquid substance is poured into a form or mould, and then hardens into that shape.
More often seen in European globes, polar calottes are two round pieces of paper that cover the poles instead of paper gores.
Map cartouches may contain the title, the printer’s address, date of publication, the scale of the map and legends, and sometimes a dedication.
The design of cartouches varies according to cartographer and period style. On 15th-century maps they are modelled afterItalian precedent (simple strapwork), by the 16th century architectural and figurative elements (like coats of arms) are added. The cartographic cartouche had its heyday in the Baroque period. Toward the end of the 18th century ornamental effects in cartography became less popular, their style developed to simple oval or rectangular fields with inscriptions.
The celestial globe is a three-dimensional map of the stars, and has been used since classical times. The stars were thought to sit on the surface of a giant sphere around the Earth, and the constant movement of the stars every night and throughout the year seemed to be caused by this giant sphere slowly turning overhead. Just like a terrestrial globe, the celestial sphere is mapped by a North and South Pole, an Equator, and lines of longitude and latitude.
Celestial globes were produced first by Greek astronomers, and later also in the Islamic world, where the earliest known globes date from the late eleventh century. Islamic astronomers built upon many of the achievements of classical Greek science, further refining concepts and the design of astronomical instruments, such as the celestial globe and the astrolabe. This is why an Islamic globe depicts the classical constellations, such as the Great Bear, Pegasus, Orion and the twelve signs of the zodiac.
The cradle mount is a type of mount that allows the globe to be disengaged for closer viewing. The globe is cradled and as such, has no axis.
A unit of measurement used in globes, known as 1/360th of the circumference of a circle.
A line that passes through the globes centre, measuring the diameter. If you know the radius of the circle, double it to get the diameter. The radius is the distance from the center of the circle to its edge. For example, if the radius of the circle is 4 cm, then the diameter of the circle is 4 cm x 2, or 8 cm.
If you know the circumference of the circle, divide it by π to get the diameter. π is equal to approximately 3.14 but you should use your calculator to get the most accurate results. For example, if the circumference of the circle is 10 cm, then the diameter is 10 cm/π, or 3.18 cm.
If you know the area of the circle, divide the result by π and find its square root to get the radius; then multiply by 2 to get the diameter. This goes back to manipulating the formula for finding the area of a circle, A = πr2, to get the diameter. You can transform this into r = √(A/π) cm. For example, if the area of the circle is 25 cm2, divide that by π and find the square root. This equals cm 2.82cm, so the diameter of the circle is 2.82 x 2 = 5.64cm.
Oldest globe in the world, made in 1492 by Martin Behaim.
It is so valuable, authorities in Germany keep it at a secret location to prevent damage and theft.
Erdapfel.. meaning Earth apple is now a German word for potato. At the time Behaim made his globe, potatoes were unknown in Europe. (Potatoes are native to North and South America, which hadn’t been discovered by Europeans yet.)
The half of the earth generally recognised as being composed of Europe, Africa, Asia, Australia, and their nearby oceans.
The great imaginary circle that runs around the earth precisely between the poles, effectively dividing the world into the Northern and Southern Hemispheres.
The band applied to the equator, working also to cover the seam of the globe.
The two events of the year, often around March 21 and September 23, when the sun’s rays are perpendicular to the Equator, resulting in day and night being of equal length all over the world.
A globe which can sit on the floor and still be viewed, refers to the base design.
The truest representation of the Earth; a map imprinted on an orb/round ball in the shape of the earth.
Also referred to as the Prime Meridian
It is the network of parallels and meridians on a globe.
Any of the halves on the earths surface (i.e. Northern hemisphere, Southern hemisphere, Western hemisphere, Eastern hemisphere)
The ring attached to many globes. This ring represents the celestial horizon, which divides the globe into the hemispheres.
A decoration, interpretation or visual explanation of a text, concept or process, designed for integration (in this case) into the cartography of a globe.
Inclination of the Earth’s Axis
Also known as the earths axis tilt 23.5
The tilt of the Earths axis, which is angled at 23.5 in relation to its orbital plane.
International Colouring Scheme
It is the system of contour layer colouring for showing elevation on globes and maps. Green represents lower elevations, yellows medium elevations, and orange and brown for extreme elevations.
International Date Line
The imaginary line used as a reference to determine the beginning and end of the day. While arbitrary variations exist for local convenience, it follows the 180th meridian.
Latitude & Longitude
Latitude and longitude are horizontal and vertical lines that crisscross each other on maps and globes, helping establish reference points and creating a navigation system. Combine, these lines form a grid.
Represented by horizontal lines on globes, with the equator being the middle-most line. All points north of the equator are called north latitude, while lines south of the equator are South latitude. Latitude also identifies zones such as the tropical and arctic zone.
A reference that identifies symbols and details on globes and maps like railways, flight routes, and more.
Represented by vertical lines on globes, with the prime meridian found at 0. All meridians to the left and right are west and east respectively, and are in 15 intervals.
(1459-1507) German geographer. His maps are sometimes held to have been influential on the Age of Discovery but he is now best known for his Erdapfel, the world’s oldest surviving globe, which he produced for the Imperial City of Nuremberg.
Meridian (Half Meridian / Full Meridian)
The metal band that encircles half or the entire globe, normally attached to the globe on both poles and the base.
The structure to which the globe is attached to and is what keeps the globe in place. See the definition of the many types of mounts (Plain Mount , Cradle mount, Stationary mount).
The Western Hemisphere, made up of the Americas and their islands.
The half of the worlds surface situated north of the Equator.
Another word used for globe, sphere, or round ball.
The cartouches overlay, or when a label is applied to cover the original cartouche.
Parallels of Latitude
East-west lateral lines around the globe that are parallel to the Equator.
A globe mounted onto its base with no form of meridian present.
Also known as the zero meridian, the basis of measurement for east and west longitude. The Prime Meridian (00 longitude) runs through Greenwich and is the basis from which standard times are calculated.
A bearing which carries a load by placing rolling elements (such as balls or rollers) between two bearing rings called races. The relative motion of the races causes the rolling elements to roll with very little rolling resistance and with little sliding.
The earths turning on its axis.
Line formed by two pieces of joined material.
The numerical relationship between an actual distance on the earth and the distance which represents it on a map.
Either of the two points on the ecliptic at which its distance from the celestial equator is greatest and which is reached by the sun each year about june 22 and december 22.
The half of the worlds surface situated south of the Equator.
Another word used for globe, orb, or round ball. Spherical = rounded and three-dimensional.
A type of mount that keeps the sphere and full meridian affixed to the globes base.
A globe which is designed to sit on a desk, table or shelf.
Spherical model of the Earth.
Having the appearance of width, height, and depth.
Most maps are static two-dimensional, geometrically accurate (or approximately accurate) representations of three-dimensional space. Globes are three-dimensional.
Commonly found on most 20th century US Globes, a time dial is a thin metal circle at the top of the globe. It is divided into 24 parts, and is engraved or printed with the hours of day and night. It allows viewers to calculate the difference in time between the different time zones on the globe.
The half of the earth generally recognised as being composed of North America and South America.
An imaginary belt in the nighttime sky and divided into 12 parts, each section represented by a symbol of a constellation.
In both astrology and historical astronomy, the zodiac is a circle of twelve 30° divisions of celestial longitude that are centred upon the ecliptic, the apparent path of the Sun across the celestial sphere over the course of the year. The paths of the Moon and visible planets also remain close to the ecliptic, within the belt of the zodiac, which extends 8-9° north or south of the ecliptic, as measured in celestial latitude. Because the divisions are regular, they do not correspond exactly to the twelve constellations after which they are named.
Historically, these twelve divisions are called signs. Essentially, the zodiac is a celestial coordinate system, or more specifically an ecliptic coordinate system, which takes the ecliptic as the origin of latitude, and the position of the Sun at vernal equinox as the origin of longitude.