A globe is a three-dimensional scale model of a spheroid celestial body such as a planet, star or moon, in particular Earth, or, alternatively, a spherical representation of the sky with the stars (but without the Sun, Moon, or planets, because their positions vary relative to those of the stars; however, the ecliptic, along which the Sun moves, is indicated). The word globe comes from the Latin word globus, meaning round mass or sphere.
How is a globe made?
Background
Globes fall into two broad categories: terrestrial and celestial. Terrestrial globes are spherical maps of the world, and celestial globes use the earth as an imaginary center of the universe to map the stars in spherical form. A globe is the only "true" map of the world because there is no distortion in relationships of areas, directions, or distances. The actual flattening of the true earth at its poles and "fattening" around the equator are such small, real distortions that they don't appear at the scale of most globes. The sphere constituting the globe is mounted on an axle and stand so it can be rotated like the earth. The axle's tilt (23.5°) is the same as Earth's rotation on its axis (relative to the plane in which it orbits the Sun).
There are many types of globes within the classification of terrestrial globes. A physical globe depicts Earth as the astronauts see it (except that they also see the intervening clouds and the shadows cast by the sun). Although physical globes emphasize natural land features (sometimes showing them in relief), the features of the bottom of the sea can also be shown. A political globe shows the nations of the world in a variety of colors as well as other features of civilization like locations of cities. Varieties of celestial globes extend to globes of the planets and the moon. Thanks to satellite imagery and other technological advances, the physical features of the world are now available in globe form on CD-ROM as the digital globe.
History
The ancient Greeks never gave credence to "flat earth" theories. They knew the world was spherical and made the first globes to depict their understanding of it. A Greek named Crates is credited with making the first globe in about 150 B.C. Our ancient ancestors were quick to adapt the principle of the globe to mapping the skies. The Romans made a celestial globe called the Farnese globe in 25 A.D. Because they used local marble for this feat, the globe survives today.
German geographer Martin Behaim made the earliest terrestrial globe that has survived. Behaim's accomplishment was timely; he made his globe in 1492, and Christopher Columbus was almost certainly aware of it and strengthened by it in his conviction to sail West to find the Orient. Today's globes would not be the same without the Flemish geographer Gerhard Kremer who is better known by the Latin form of his name, Gerardus Mercator. Mercator lived from 1512-1594 and was also a cartographer, mathematician, astronomer, and engraver. He is best known for having developed the type of map, now called a Mercator projection, in which all the meridians and longitudinal lines are parallel and the lines of latitude intersect these at right angles and are also parallel to each other. The Mercator projection simplified map reading; for instance, a navigator can plot a ship's course between any two points in a straight line and follow that course without changing compass direction. Mercator also widely influenced all other aspects of mapmaking; the world atlas is also his invention. He made Louvain, Belgium, the center of the world of cartography and scientific instruments; and, there, he and Myrica Frisius constructed terrestrial and celestial globes in 1535-1537.
Raw Materials
In the past, globes were generally solid and made of a variety of materials including glass, marble, wood, and metal. Hollow globes, including those made in Mercator's day, were produced from thin metal sheets including copper. Today, globes are almost always hollow and can be made of any material that is both strong and lightweight. Cardboard, plastic, or metal can be used. A three-dimensional jigsaw puzzle with paper pieces backed with foam rubber is manufactured for puzzle fanatics, plastic globes with snap-on continents and other features are learning tools for children, decorative globes of Waterford crystal can ornament desk tops, and inflatable globes (both terrestrial and celestial) are useful tools and toys.
The George F. Cram Company and Replogle Globes Inc. are the only two manufacturers of traditional globes in the United States. The George F. Cram Company has made maps since 1867 and globes since 1929. The company's manufacturing processes for producing the two basic types of globe remain largely unchanged in 70 years. One type is made of fiberboard or cardboard, and the illuminated globe is made of plastic that will withstand the heat from a light bulb that is placed inside the sphere to light it from the inside out. Recycled cardboard is used for the cardboard globes. Injection molding plastic is also used to partially fill the plastic globe. Specialty manufacturers produce all other parts for the globe. These include tape required to join the two globe hemispheres ("Equator tape"); the axis, stand, base, or other mounting; and electrical wiring and the bulb socket for the illuminated version.
diff. b/w map and globe-
globe is 3-d but map is 2-d.
Flat maps can be more useful than globes in many situations: they are more compact and easier to store; they readily accommodate an enormous range of scales; they are viewed easily on computer displays; they can facilitate measuring properties of the terrain being mapped; they can show larger portions of the earth's surface at once; and they are cheaper to produce and transport.
2007-06-29 20:43:18
·
answer #2
·
answered by diya h 2
·
0⤊
0⤋