LESSON 8
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Inquiry Master 8
Sun-Earth-Moon System Review (Anticipated Responses)
1. Why do we experience day and night?
(Half of Earth is always illuminated by the Sun,
while the other half of Earth is in its own shadow, and is dark. As an area on Earth rotates into
the Sun’s light, that area experiences daylight.
As an area on Earth rotates away from the Sun’s
light, that area experiences night. The length of
day and night for an area changes depending on
Earth’s position relative to the Sun during
Earth’s revolution. During the equinoxes, all
areas on Earth experience 12 hours of daylight
and 12 hours of nighttime.)
2. Define the terms “rotation” and “revolution”
as they relate to space science. (Rotation
defines a planet’s or moon’s spin on its axis.
Revolution defines a planet’s or moon’s orbit
around another solar system body.)
3. Describe the Moon’s period of rotation and
revolution. (The Moon’s period of rotation on
its spin axis is 27.3 days. This is equal to its
period of revolution around Earth [27.3 days];
therefore, only one side of the Moon faces Earth
[the “near side”].)
4. Describe the relative size and distance relationships among the Sun, Earth, and Moon.
(The Moon is 384,000 km away from Earth, or
30 Earth-diameters away. The Earth is 150
million km away from the Sun. The Sun is
1,392,000 km in diameter, which is 400 times
greater than the Moon’s diameter of 3,500 km.
The Sun is also 400 times larger in diameter
than the Moon. The Moon is approximately
one-fourth [0.27] the size of Earth, whose
equatorial diameter is 12,756 km. Nearly 109
Earth-diameters would fit across the diameter
of the Sun.)
© 2003 National Academy of Sciences
5. Why can the Moon appear as large as the
Sun even though we know the Moon is much
smaller than the Sun? (The Sun is 400 times
farther away from Earth than the Moon, and the
Sun is also 400 times larger in diameter than
the Moon. This causes the two bodies to appear
to be the same size.)
6. Why do shadows change during the day?
You may draw a picture to show changes in
shadow length relative to the Sun’s position in
the sky. (As Earth rotates on its axis, the Sun
appears to move across the sky. Shadow lengths
depend on the apparent position of the Sun in
the sky. When the Sun’s apparent position in
the sky is high [solar noon], shadows are short.
When the Sun’s apparent position in the sky is
lower, shadows are longer.)
7. Explain why shadow lengths change
throughout the year. (Shadow lengths change
throughout the year as Earth orbits the Sun
and Earth’s position on its tilted axis changes
relative to the Sun. When an area on Earth is
tilted toward the Sun [summer in that hemisphere], the apparent position of the Sun is
highest in the sky and solar-noon shadows are
shortest. When an area on Earth is tilted away
from the Sun [winter in that hemisphere], the
apparent position of the Sun is lowest and
shadows are longest.)
8. What causes seasons? (Seasons occur due
to the tilt of Earth’s axis relative to the Sun. As
Earth orbits the Sun, different parts of Earth get
more or less direct sunlight.)
(continued)
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Inquiry Master 8 (continued)
9. What factors (other than the one you listed
in Question 8) affect how hot or cold it is in
any one place on Earth? (The atmosphere and
its weather, angle of sunlight, length of day, surface composition, and oceans all play a key role
in daily temperatures.)
10. Looking at the Moon from space, how much
of the Moon always receives light from the
Sun? Explain your answer. (Looking at the
Moon from space, half of the Moon is always
illuminated by the Sun, unless there is a lunar
eclipse. Students may draw a picture of this as
well. See Figure 5.3 and the inner circles of
Inquiry Master 5.2 for an example.)
11. Sketch and label the phases of the Moon.
Waning
Crescent
Third
Quarter
Waning
Gibbous
New
Moon
SUN
EARTH
Waxing
Crescent
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First
Quarter
Full
Moon
Waxing
Gibbous
© 2003 National Academy of Sciences
LESSON 8
SUNSPOTS
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Inquiry Master 8 (continued)
12. Draw a diagram of each eclipse listed below. Make certain to show the lighter and darker
portions of the eclipse shadow. Label the Moon, Sun, and Earth, umbra and penumbra, and
indicate where there is a partial or total eclipse.
Partial
solar
eclipse
Total
solar
eclipse
Earth
Penumbra
Umbra
Moon
Sun
Solar eclipse
Penumbra
Umbra
Earth
Moon (in total lunar eclipse)
Sun
Lunar eclipse
(continued)
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Inquiry Master 8 (continued)
13. Why do solar and lunar eclipses occur?
(Although the Moon’s orbit is tilted, two to five
times a year the Moon crosses over Earth’s
orbital plane at the same time that the Moon,
Earth, and Sun align. During this alignment, the
Moon’s shadow falls on Earth and causes a solar
eclipse, or the Moon passes into Earth’s shadow
and a lunar eclipse results. The type of eclipse
that occurs depends upon the position of the
Moon or Earth within the umbra and penumbra
of the shadow.)
14. During which phase of the Moon does a
solar eclipse occur? During which phase of
the Moon does a lunar eclipse occur? (A solar
eclipse occurs during a new moon. A lunar
eclipse occurs during a full moon.)
15. Why don’t we have eclipses every month?
(The Moon’s orbital plane is tilted. This means
that when the Moon passes between the Sun
and Earth, its shadow normally falls into space
below or above Earth. The same occurs when
the Earth is between the Moon and Sun; the
Moon normally passes above or below Earth’s
shadow.)
16. What is the source of energy for the Earth?
(The Sun provides the primary source of energy
for Earth.)
18. What can you conclude from your observations of sunspots? (Sunspots are part of the
Sun’s surface and move across the Sun’s surface
from west to east, which indicates that the Sun
rotates on its axis counterclockwise relative to
its northern pole. Sunspot groups can be tracked
over days. The number of sunspots changes from
day to day and from year to year. Sunspot maximums and minimums occur on 11-year cycles.)
19. What is space weather? How does it affect
Earth, including its space environment?
(The term “space weather” includes conditions
on the Sun and in the Sun’s extended atmosphere. Space weather affects our atmosphere,
equipment, and space operations. The particles
energized by the solar winds affect spacecraft,
humans in space, and occasionally human
activities on Earth. They even cause changes
in the space environment, which we see as
auroras.)
20. What are auroras and how do they form?
(If you haven’t done so already, read ahead to
“Auroras” in Lesson 8 to answer this question.)
(Auroras are light displays that occur mostly
near the poles when gases in Earth’s atmosphere
glow when hit by charged particles carried by
solar winds.)
17. How is Earth protected from receiving too
much solar radiation? (Earth’s atmosphere
absorbs, reflects, and scatters the Sun’s incoming
radiation.)
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