Universe Cycle - Earth (6)
 Lab 

   
OBJECTIVES:
  • Exploring rotation and revolution.
  • Discovering how the tilt of the axis causes the seasons.
VOCABULARY:
  • axis
  • northern hemisphere
  • season
  • southern hemisphere
  • Tropic of Capricorn
  • Tropic of Cancer
MATERIALS:

Students use models to recreate the reason for seasons.


Summer in the Southern Hemisphere: the North Po
le tilts away from the Sun. 

BACKGROUND:

The seasons are caused by the positioning of the Earth with respect to the Sun as it revolves around the Sun, and by the tilt of its axis. This will cause different seasonal climates throughout the Earth. For example, during June 21, it will be the summer solstice in the northern hemisphere, but in the southern hemisphere it will be the winter solstice.

The varying distance of the Earth from the Sun is not an important factor in seasonal changes as much as is the intensity of solar energy that strikes the earth's surface. The intensity depends mostly on the angle at which it strikes the Earth's surface. The steeper the angle, the more it is concentrated. Solar energy is concentrated most on the Northern Hemisphere during its summer season when the north axis is titled toward the Sun. More hours of daylight also occur at this time (hence, summers are warmer than winter). Simultaneously, the Southern Hemisphere is experiencing winter. Six months later, when the Earth is on the opposite side of its orbit, the north end of the axis is tilted away from the Sun and it has its winter. Fall and spring occur in between these two extremes when the axis is tilted neither toward or away from the Sun.

PROCEDURE:
  1. Explain the origin of the seasons to the students. Remember seasons are caused by the quality of sunlight, and not climatic conditions.
     
  2. In the lab, students first draw pictures showing summer and winter in the Northern Hemisphere. They should then use the model planetarium to understand the motions which create the seasons. Be sure the students can find the locations on the globe that are listed in the chart.
     
  3. ANSWERS:
     
    Part 1.
    1. opposite; 2. opposite; 3. No, because the Moon does not radiate heat; 4. Yes, in summer the rays are direct, in winter they are indirect; 5. angle, because the Earth’s axis is tilted.

    Part 2.

 

Dec. 21

Mar. 21

June 21

Sept. 23

North Pole

24 hrs darkness

12/12

24 hrs light

12/12

Arctic

24 hrs darkness

12/12

24 hrs light

12/12

Tropic of Cancer

more night than day

12/12

more day than night

12/12

Equator

12/12

12/12

12/12

12/12

Tropic of Capricorn

more day than night

12/12

more night than day

12/12

Antarctica

24 hrs light

12/12

24 hrs darkness

12/12

South Pole

24 hrs light

12/12

24 hrs darkness

12/12

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