Read pages indicated by Z-13 and study Behavioral Objective 17. Let us consider how the amount of energy from the sun varies from place to place on the surface of the Earth and why this is so. Examine the figure below. Now examine the figure indicated by Z-13 showing which areas of the Earth receive the most solar energy. The solar energy striking the earth near one of the poles, that is the South or the North pole must pass through a greater amount of atmosphere before striking the surface of the earth compared to a similar beam striking the earth at the equator. The more atmosphere the solar energy must travel through, the less solar energy reaches the surface of the earth. The Earth receives from the sun an average of two calories of radiant energy per minute for every square centimeter - 13x10²³ calories every year.

Now, we know the earth revolves on its own axis once every 24 hours, and also that the axis of the earth tilted away from perpendicular 23 1/2 degrees. Now this tilt in the surface of the earth causes the solar energy to fall differently on different parts of the earth during its orbit around the sun once every year. Winter in the northern hemisphere, from December 21st or 22nd until March the 20th or 21st is caused by the axis of the earth, being the northern axis of earth or the North Pole, being pointed away from the sun. Now what does this mean in terms of energy reaching the surface of the earth? It means just this, that the sun's energy is dissipated over a wider area because of the inclination away from the sun, and that the sun's energy has to pass through a greater amount of atmosphere before it reaches the surface of the earth, and because the amount of atmosphere it has to pass through, much of the solar energy never reaches the surface of the earth. Therefore, it never warms the surface of the earth, at least in the northern hemisphere.

Which of the following statements is not true?

a. Near the equator the sunlight falls perpendicular to the Earth's surface.

b. Towards the poles the same amount of sunlight falls over a much larger surface.

c. The tilt of the Earth on its axis causes variation in sunlight directness.

d. The poles receive direct sunlight only during six months of the year.