Ursula Tillmanj, age 13,, of Williamsport,PA:

What is the prime meridian?

The surface of the earth has been measured off in sections. These sections are bounded by the lines of latitude and longitude you will find criss‑crossing the maps in your  atlas, The lines of latitude run around the globe in parallel circles. The widest is the equator, half way between the two poles. This division was a natural one.

It was not so easy to find a starting place to draw the lines of longitude that run up and down through the poles. These are the meridians, And who was to say where the first one should be put? It was decided to place this first or prime meridian at Greenwich England where there is a fine observatory. This was important for astronomical instruments are needed to check the location of a meridian. Once the prime meridian was agreed upon, the rest could be measured from it.

The prime meridian runs directly north to the north pole and directly, south to the south pole. Everything located on this line is on longitude zero. At the north pole, the meridian swoops down in a direct line to the south pole, so forming a complete circle around the globe. This section of

the Greenwich meridians however, is called longitude 160 degrees, The circles between are noted as east or west of the prime meridian, Longitude 60 degrees west is exactly the same distance from the prime meridian as is longitude 60 degrees east ‑ only in the opposite direction.