Hi,
That's an interesting question. Back in the days when I was in
school, it was the norm for classrooms to have a wall map using a
Mercator projection. Now when I go to my children's classrooms, the
maps typically use other projections that more accurately portray the
relative sizes of the continents.
A brief background: All flat global maps, simply by being flat,
introduce some distortion because they are trying to portray a curved
surface. The Mercator projection, developed by Flemish cartographer
Gerardus Mercator in 1569, has the advantage that north and south are
up and down, and east and west are horizontal lines. So if you were
piloting a ship across the ocean, the projection would be great for
helping you head in the right direction (although not necessarily in
following the shortest route).
But the projection (which can be visualized by imagining that there's
a light in the middle of a translucent globe, then placing a cylinder
around the earth and making the resulting projection into a map before
unrolling the cylinder) introduces a serious distortion -- objects
closer to the poles appear to be larger in area than they are. In
fact, Greenland (much of which is near the North Pole) appears to be
much larger than South America. In actuality, South America, which
straddles the equator, is eight times as large in area as Greenland.
Greenland is an extreme case, because it's so far north. But the same
is true for other continents that are away from the equator. In
general, it can be said that the projection provides the illusion that
Europe, Asia, Australia and North America (none of which straddle the
equator) are proportionately larger than they actually are, while
South America and Africa (both of which do) are proportionately
smaller than they appear. Among the areas that appear particularly
large are Greenland, Russia, Alaska, Antarctica and northern Canada.
(Antarctica is partly or wholly cut off of most Mercator maps because
it is so distorted.)
Here's a good introductory lesson to the Mercator projection:
Exploring Maps
http://interactive2.usgs.gov/learningweb/teachers/exploremaps_lesson2.htm
You can see samples of how various other projections look like on this
page:
Map Projections
http://www.seaspace.com/service/support/TeraScan_Docs/doc/terapgs/map_projections.html
And here's an excellent explanation of the Mercator projection and one
of its competitors (follow the links to read all three parts of the
article). This article is particularly relevant to your question,
since people tend to think that continents that are larger are more
important, and the Peters projection has been promoted by some groups
for purposes that have as much to do with politics and fairness as
they do with geography:
Peters Projection vs. Mercator Projection
http://geography.about.com/library/weekly/aa030201a.htm
I hope this helps.
Sincerely,
mvguy
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