Atmospheric Energy: Unequal Heating by the Earth's Surface (page 2)

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Author: Janice VanCleave

Try New Approaches

How does the curvature of the Earth affect the spreading of the Sun's light rays? Use the flashlight from the experiment; lay it on a table with the attached ruler extending over the table edge. Make a large cylinder out of the graph paper by overlapping the short ends. Hold the cylinder vertically at the end of the ruler. Observe the number of illuminated squares on the curved paper. Then move the cylinder slightly to the left or right so that the light grazes the edge of the cylinder. Again, observe the number of illuminated squares.

Design Your Own Experiment


    Cut a diagonal line from corner to corner across a 2-inch (5-cm) square of cardboard. Discard one of the triangles. Tape the second triangle upright to a block of wood. Set the wooden block in the center of the long side of a sheet of white poster board so that the edge of the block with the tip of the triangle is even with the edge of the poster board. As soon after sunrise as possible, place the poster board outdoors where it will receive direct sunlight all day. Using a compass, point the vertical side of the triangle north. Every hour, or as often as possible, mark a line along the edge of the triangle's shadow from the shadow's tip to the vertical end of the triangle. Mark the time of day on the poster board (see Figure 24.2). Determine the time of day when the sunlight is most direct.

    Atmospheric Energy: Unequal Heating by the Earth's Surface

    1. The temperature of the Earth's surface and thus its atmospheric temperature also change because the Earth rotates on its axis. As the Earth turns, sunlight hits a given region from different directions throughout the day. The length of shadows corresponds to the angle of sunlight. The shorter the shadow, the more direct the sunlight and the smaller the angle. A sundial tells time by casting shadows. Use a gnomon (raised part of a sundial that casts a shadow) to compare shadows during the day.
    2. Determine how the angle of sunlight affects atmospheric temperature by repeating the previous experiment and using a thermometer to measure air temperature each time a shadow is measured. It is best to place the thermometer out of direct sunlight to measure the air temperature.

Get the Facts

  1. The number of daylight hours changes during the year. The more daylight hours during the day, the more radiant energy the Earth's surface receives. The day with the most daylight hours in the Northern Hemisphere is the first day of summer, which is on or about June 21. This day is the summer solstice. Find out more about the changing number of daylight hours during the year. What and when are the spring and fall equinoxes, and the winter solstice? How does the Earth's tilt cause different seasons? What is the difference between the angle of the Sun's rays in the Northern and Southern Hemispheres on these dates? What is the general difference in their atmospheric temperatures?
  2. The earth's atmosphere is divided into layers. Each layer differs from the other in distance from the Earth, content, temperature, and what occurs in it. Find out more about these layers. What are their names, distances from Earth, and temperature? Where is the ozone layer, and how does it affect the type of energy that the Earth receives?
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