**Maps and globes are guidelines for exploring the earth not exploring outer space. This project is to make a model of the meridians (longitued) on a globe.**

**science.aksiografi.com** – A map is a representation of all or part of a region of the Earth’s surface. Maps can be spherical like the Earth or flat. They all have crisscrossing lines that are used to indicate the coordinates of any specific location. These reference lines are called meridians (or lines of longitude) and parallels (or lines of latitude).

In this project, you will study and model the meridians and parallels. You will learn a technique for measuring latitude and determine the latitude where you live. Planar projection, a method of preparing flat maps, will also be demonstrated.

**Learning Objective**

The Learning objective of this project of The nature school is to model meridians (lines of longitude) on a globe.

**Materials**

lemon-size ball of modeling clay pencil dental floss

**Procedure**

1. Shape the clay into a sphere.

2. Use the pencil to draw a circle around the center of the clay sphere.

3. Draw a second circle perpendicular to the first one.

4. Hold the sphere so the lines cross at its top and bottom ends.

5. Observe the position of the lines and the distance between them at (1) the ends of the sphere where the lines cross, and (2) the center of the sphere, midway between the ends.

6. Wrap the ends of the dental floss around your index fingers, then use your thumbs to press the floss into one of the circles. Press the floss through the clay sphere, cutting the sphere in half (see Figure above).

**Results** of Nature School

The lines you drew with the pencil are not parallel. They approach and cross each other at opposite ends of the sphere and are farthest apart around the center of the sphere. Cutting through the clay creates a plane that passes through the center of the sphere.

**Why?**

The circles around the clay sphere are called **great circles** (circles on a sphere, with the center of the circle and the center of the sphere being the same). A **meridian **is defined as a great circle, or half of a great circle passing through the Earth’s **North **and **South Poles **(northernmost and southernmost points on the Earth). In this book, meridian will refer to half of a great circle. Thus, the clay model has four meridians from pole to pole. While there is no limit to the number of meridians that may be on a globe, a common number of meridians is 24.

Meridians are also called **lines of longitude** because they measure longitude. Longitude is the distance in degrees east and west of the meridian running through Greenwich, England, called the prime meridian. The prime **meridian **is located at 0° longitude. Longitudes 0° and 180° divide a globe into the Eastern and Western Hemispheres, as demonstrated by cutting the clay model in half. (The word hemisphere means half a sphere.)

In the **Eastern Hemisphere** the longitudes are 0° to 180° and are labeled with an E, such as 90° E. The **Western Hemisphere** longitudes making up the other half of the sphere also start at 0° and end at 180° they are labeled with a W, such as 90° W. Note that 90° E and 90° W are on opposite sides of the sphere from each other and that 0° E and 0° W are the same meridian, as are 180° E and 180° W. The lines on the clay sphere, like the meridians on a globe, are not parallel. The distance between the meridians is greatest at the middle of the globe and decreases toward the poles (ends). One degree (1°) of longitude is about 69 miles (110 km) wide at the equator and gradually narrows to 0 miles (0 km) wide at the North and South Poles.