Straight On!: How Does the Curved Shape of the Earth Affect the Climate Throughout the World?

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Author: Janice VanCleave


How does the curved shape of the earth affect the climate throughout the world?


  • Sheet of typing paper
  • modeling clay
  • Two new, unsharpened pencils
  • Pen


Straight On!

Straight On!

  1. Turn the paper sideways on a table.
  2. Mold a walnut-sized piece of clay into a 1 1/2-inch (3.75-cm) column.
  3. Place the clay on the top left edge of the paper.
  4. Lay the eraser of one pencil on top of the clay column so that the end of the pencil rests on the paper.
  5. Hold the second pencil on top of the first one and slide it downward along the top of the first pencil until its tip just touches the paper, as shown in the diagram.
  6. Use the pen to mark where each pencil touches the paper.
  7. Move the two pencils to a vertical position so that they stand side by side on the paper.
  8. Use the pen to mark where the left side of each pencil touches the paper.
  9. Compare the distance between the first two marks to the distance between the second two marks.


The marks made when the pencils were slanted are farther apart than the marks made when the pencils were in a vertical position.


Variations in weather are caused by changing conditions throughout the atmosphere (blanket of gases known as air surrounding the earth), including changes in temperature, pressure, humidity (amount of water vapor in the air), wind, and precipitation (liquid or solid particles that form in the atmosphere and then fall to the earth's surface}. The heat of the sun warms the earth and its atmosphere. Because the earth is curved, some regions and materials heat up more quickly than others, creating warmer air masses and cooler air masses. The movement of these air masses causes changes in weather. Thus, the sun's energy is the fuel that keeps the atmosphere in a state of constant change.

The sun's rays hit different regions of the earth at different angles, creating distinct climates (average weather over long periods of time) throughout the world. Generally, the hottest places on earth are near the equator (the imaginary line around the center of the earth), which receive the most direct rays from the sun (the areas from A to B in the diagram). Places farther from the equator tend to be cooler because the sun's rays strike the ground there at an angle. The same amount of sunlight is spread over a larger area in other places on the earth (B to C and C to D in the diagram).

Straight On!

The pencils in this experiment represent the sun's rays. The vertical pencils are direct rays received at the equator, and the slanted pencils are angled rays received near the north and south poles (areas farthest north and south, respectively, from the equator). The marks on the paper indicate the areas heated by the rays. The slanted rays mark off a wider area. Places that receive slanted rays from the sun are cooler because the same amount of heat is spread over a larger area.

Let's Explore

Repeat the original experiment twice, changing the height of the clay first to 3 inches (7.5 cm) and then to 5 inches (12.5 cm). Science Fair Hint: Take photographs with the pencils being held at different angles against a map of the earth. These photos can be used as part of a project display to represent how the sun's rays strike the earth at different angles in different locations between the earth's equator and its poles.

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