Map it Out!
D. Maya and friends, Chennai
The Earth is a globe, but in every map, we represent it on a flat piece of paper. There are many ways to show a map of the countries of the world. It all depends on what you want to highlight. However, the famous scientist Carl Friedrich Gauss proved that each representation distorts the true facts in some way or the other.
Some maps are drawn so that the area of a given region is preserved. That is, the shape is distorted so that the area of (say) India and China are shown correctly in proportion. For instance, two longitudes and two (parallel) latitudes are used to describe a fixed area, and then rendered on the Albers equal area projection map. As the name suggests, the area is preserved (so if a country looks big on this map, it is big) but the scale and direction is not preserved, especially as you go away from the standard parallels. The picture shows the Albers world map using the standard parallels 20o and 50o North. So the region between these two is hardly distorted, while the regions outside these latitudes are badly stretched. See for instance, Australia in the southern hemisphere, which is nearly unrecognisable. However, the areas of these countries is correctly represented.
Sometimes, it may be more important to preserve the shape of the region and then it may be shown as having more or less area than the actual value. For instance, in the most common Mercator projection, countries near the North Pole are usually shown to be very large. This is because the projection is like that of a cylinder: places near the equator are more or less represented correctly, but Greenland near the North Pole and Antarctica near the South Pole are stretched from being the small end-cap of a sphere to the width of the entire cylinder.
If you want to see how close the eastern end of Russia is to the western end of the United States (Alaska), see the Pacific-centric map! This map is preferred for obvious reasons in countries around the Pacific ocean. They obviously will not prefer a map where their country is squeezed somewhere in the corner of the map. This happens because a globe has to be "cut open" to fit on a flat surface, otherwise you will be able to see only the "front half".
A more popular version is the Mollweide projection. It is also an equal area map. You can see that instead of the map being rectangular, it is like a flattened circle. This reduces the enormous distortion near the poles that you see in Mercator projections. You must remember, though, that this is the entire Earth and not the "front part" of it that you would see on a 3D globe (see the picture, where India is completely hidden). The Mollweide projection is very useful to see global parameters at a glance, for instance, the mean sea surface temperatures around the world in 2009.
An exotic use of the Mollweide projection is to represent not countries on the Earth but galaxies on the spherical Universe itself. The PLANCK telescope has been observing the Universe for more than 10 years now. Shown in the map are the observations of light coming from different parts of our Universe from very early times. Red and blue spots indicate where the Universe is slightly hotter or cooler than the average value of 2.7 K (or -270oC).
There are many more types of maps in use for different reasons. For instance, can you spot India on this map? Does this map seem familiar to you? Where have you seen it before? For answers, see page 35.