Grid and Bear It - Geography - page 29

meaning length. This makes sense because when viewed on a globe, lines of longitude are
generally lengthier than lines of latitude.
Similar to the roads in Gridville, the global grid contains a principal line of latitude ( the equator ) and
a principal line of longitude ( the prime meridian ). All other lines of latitude and longitude are named
and numbered respectively from these starting lines. It makes sense, therefore, that if you want to
make like Hipparchus and draw a grid on a globe, then these are the first two lines you would draw.
But where would you put them, and why?
The equator
Because Earth is sphere-like, no compelling locale cries out and says, “Use me to locate the equator!”
So where to put it? Old Hipparchus might simply have said, “It's Greek to me!” and placed it any-
where. Instead, he wrestled with the challenge and came up with an ingenious solution.
He knew that the Earth is sphere-like and that it rotates around an imaginary line called the axis. Look
on a globe and you find two fixed points, halfway around the earth from each other, where the axis
intersects the Earth's surface: the North Pole and the South Pole. So Hipparchus drew a line that ran
all the way around the globe and was always an equal distance (hence, equator) from the two Poles.
The result is a latitudinal “starting line” from which all others could be placed on the globe.
The prime meridian
Thelongitudinal “starting line” iscalled the prime meridian, whichsignifies itsimportance astheline
from which all other lines of longitude are numbered. Locating this line proved more problematical
than locating the equator. Quite simply, no logical equivalent of the equator exists with respect to lon-
gitude. Thus, while the equator came into general use as the latitudinal starting line, mapmakers were
perfectly free to draw the longitudinal starting line anywhere they pleased. And that is what they did.
Typically, mapmakers drew the prime meridian right through their country's capital city. By the late
1800s, lack of a universal prime meridian had become a real pain in the compass. International trade
and commerce were growing. Countries were claiming territory that would become colonial empires.
But one country's world maps did not agree with another's, and the international climate made it in-
creasingly advisable that they do so.
As a result, in 1884 the International Meridian Conference was convened in Washington, D.C. to
promote the adoption of a common prime meridian. Out of that was born an agreement to adopt the
British system of longitude as the world standard. Thus, the global grid's prime meridian passes right