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:
- Explain the origin of the seasons to the students.
Remember seasons are caused by the quality of sunlight, and not climatic
conditions.
- 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.
- 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.
