EARTH SCIENCE
Geology, the Environment and the Universe
Chapter 27: The Sun-Earth-Moon
System
CHAPTER
27
Table Of Contents
Section 27.1 Tools of Astronomy
Section 27.2 The Moon
Section 27.3 The Sun-Earth-Moon
System
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SECTION
27.1
Tools of Astronomy
Essential Questions
• What is electromagnetic radiation?
• How do telescopes work?
• How does space exploration help scientists
learn about the universe?
SECTION
27.1
Tools of Astronomy
• Radiation emitted or reflected by distant
objects allows scientists to study the universe.
Review Vocabulary
• refraction: occurs when a light ray changes
direction as it passes from one material into
another
SECTION
27.1
Tools of Astronomy
New Vocabulary
electromagnetic
spectrum
refracting telescope
reflecting telescope
interferometry
SECTION
Tools of Astronomy
27.1
Radiation
• The radiation from bodies throughout the
universe that scientists study is called
electromagnetic radiation.
• This includes visible light, infrared and
ultraviolet radiation, radio waves, microwaves,
X rays, and gamma rays.
SECTION
Tools of Astronomy
27.1
Radiation
• The electromagnetic spectrum consists of all
types of electromagnetic radiation arranged
according to wavelength and frequency.
SECTION
Tools of Astronomy
27.1
Radiation
Wavelength and frequency
• Electromagnetic radiation is classified by
wavelength, the distance between peaks on a
wave, and frequency, the number of waves or
oscillations that pass a given point per second.
SECTION
Tools of Astronomy
27.1
Radiation
Wavelength and frequency
• Frequency is related to wavelength by the
mathematical relationship c = λf, where c is
the speed of light (3.0 × 108 m/s), λ is the
wavelength, and f is the frequency.
SECTION
Tools of Astronomy
27.1
Telescopes
• Telescopes provide the ability to observe
wavelengths beyond what the human eye can
detect. They collect electromagnetic radiation
from distant objects and focus it so that an
image of the object can be recorded.
• Telescopes can also collect light over periods
of minutes or hours.
SECTION
Tools of Astronomy
27.1
Telescopes
Refracting and reflecting telescopes
• Refracting telescopes use lenses to focus
visible light.
SECTION
Tools of Astronomy
27.1
Telescopes
Refracting and reflecting telescopes
• Reflecting telescopes use mirrors to focus
visible light.
SECTION
Tools of Astronomy
27.1
Telescopes
Telescopes using non-visible wavelengths
• For all telescopes, the goal is to bring as
much electromagnetic radiation as possible
into focus.
• Infrared and ultraviolet radiation can be
focused by mirrors in a way similar to that
used for visible light.
SECTION
Tools of Astronomy
27.1
Telescopes
Telescopes using non-visible wavelengths
• X rays cannot be focused by normal mirrors,
and thus special designs must be used.
• Gamma rays cannot be focused, so
telescopes designed to detect this type of
radiation can determine only the direction
from which the rays come.
SECTION
Tools of Astronomy
27.1
Telescopes
Telescopes using non-visible wavelengths
• A radio telescope collects the longer
wavelengths of radio waves with a large dish
antenna and reflects them to a point above
the dish. There, a receiver converts the radio
waves into electric signals that can be stored
in a computer for analysis.
SECTION
Tools of Astronomy
27.1
Telescopes
Telescopes using non-visible wavelengths
• The data collected from radio telescopes are
converted into visual images by a computer.
The image resolution can be improved using
interferometry, a process that links
separate telescopes so they act as one
telescope, producing more detailed images
as the distance between the telescopes
increases.
SECTION
27.1
Tools of Astronomy
Space-Based Astronomy
• Space-based telescopes allow astronomers to
study radiation that would be blurred by our
atmosphere.
SECTION
27.1
Tools of Astronomy
Space-Based Astronomy
Hubble Space Telescope
• The Hubble Space Telescope was designed
to obtain sharp visible-light images without
atmospheric interference and to make
observations in infrared and ultraviolet
wavelengths.
SECTION
27.1
Tools of Astronomy
Please click the image above to view the interactive table.
SECTION
Tools of Astronomy
27.1
Space-Based Astronomy
Spacecraft
• Spacecraft make observations from above
Earth’s atmosphere and can also be sent
directly to the bodies being observed.
• Robotic probes are spacecraft that can make
close-up observations and sometimes land to
collect information directly.
SECTION
27.1
Tools of Astronomy
Space-Based Astronomy
Human spaceflight
• The most recent human studies have been
accomplished with the space shuttle program
between 1981 and 2011.
• The space shuttle provides an environment
for scientists to study the effects of
weightlessness on humans, plants, the
growth of crystals, and other phenomena.
SECTION
27.1
Tools of Astronomy
Space-Based Astronomy
Spinoff technology
• Many technologies that were originally
developed for use in space programs are now
used by people around the world. More than
1400 different NASA technologies, such as
memory foam, have been passed on to
commercial industries for common use; these
are called spinoffs.
SECTION
Section Check
27.1
Gamma rays move through space at a
greater speed than do radio waves.
a. true
b. false
SECTION
Section Check
27.1
Which objects produce the image in a
refracting telescope?
a. mirrors
b. lamps
c. lenses
d. prisms
SECTION
27.1
Section Check
What advantage do telescopes in space
have over similar instruments on Earth’s
surface?
a. The telescopes are closer to the object.
b. The telescopes are above the atmosphere.
c. The telescopes are safe from damage.
d. The telescopes are always in the dark.
SECTION
27.2
The Moon
Essential Questions
• What is the history of lunar exploration?
• How are lunar properties and structures
described?
• What are the features of the Moon?
• What is the theory of the Moon’s origin and
formation?
SECTION
27.2
The Moon
• The Moon, Earth’s nearest neighbor in space,
is unique among the moons in our solar
system.
Review Vocabulary
• lava: magma that flows onto the surface from
the interior of an astronomical body
SECTION
The Moon
27.2
New Vocabulary
albedo
highland
maria
impact crater
ejecta
ray
rille
regolith
SECTION
27.2
The Moon
Exploring the Moon
• Astronomers have learned much about the
Moon from observations with telescopes.
However, most knowledge of the Moon comes
from explorations by space probes and from
landings by astronauts.
SECTION
27.2
The Moon
Exploring the Moon
• The first step toward reaching the Moon was
in 1957, when the Soviet Union launched the
first artificial satellite, Sputnik I.
• Four years later, Soviet cosmonaut Yuri A.
Gagarin became the first human in space.
SECTION
27.2
The Moon
Exploring the Moon
• In 1957, the United States launched the first
American, Alan B. Shepard, Jr., into space
during Project Mercury.
• This was followed by Project Gemini that
launched two-person crews.
SECTION
27.2
The Moon
Exploring the Moon
• On July 20, 1969, the Apollo program landed
Neil Armstrong and Edwin “Buzz” Aldrin on the
Moon during the Apollo 11 mission.
• Scientists hope to return to the Moon someday
and eventually establish a permanent base
there.
SECTION
27.2
The Moon
The Lunar Surface
• The albedo of the Moon, the percentage of
incoming sunlight that its surface reflects, is
very small—only about 7 percent.
• In contrast, Earth has an average albedo of
nearly 31 percent.
SECTION
27.2
The Moon
The Lunar Surface
• Lunar highlands are heavily cratered regions
of the Moon that are light in color and
mountainous.
• Maria are dark, smooth plains, which average
3 km lower in elevation and have few craters.
SECTION
The Moon
27.2
The Lunar Surface
Lunar craters
• The craters on the Moon, called impact
craters, formed when objects from space
crashed into the lunar surface.
• The material blasted out during these impacts
fell back to the Moon’s surface as ejecta.
SECTION
The Moon
27.2
The Lunar Surface
Lunar craters
• Some craters have long trails of ejecta, called
rays, that radiate outward from the impact
site.
• Rilles are meandering structures that might
be collapsed lava tubes.
SECTION
The Moon
27.2
The Lunar Surface
Lunar properties
• Earth’s moon is unique among all the moons
in the solar system. It is the largest moon
compared to the radius and mass of the
planet it orbits. It is a solid, rocky body, in
contrast with the icy compositions of most
other moons of the solar system.
SECTION
The Moon
27.2
The Lunar Surface
Lunar properties
• The Moon’s orbit is farther from Earth relative
to the distance of many moons from the
planets they orbit.
SECTION
The Moon
27.2
The Lunar Surface
Lunar properties
• The Moon is made up of minerals similar
to those of Earth—mostly silicates.
• The highlands are mostly lunar breccias, which
are rocks formed by the fusion of smaller rocks
during impacts. The maria are predominantly
basalt that contains no water.
SECTION
27.2
The Moon
Please click the image above to view the interactive table.
SECTION
27.2
The Moon
History of the Moon
• The Moon is approximately 3.8 to 4.6 billion
years old, about the same age as Earth.
• Scientists theorize that the Moon was heavily
bombarded during its first 800 million years.
This caused the breaking and heating of
surface rocks and resulted in a layer of loose,
ground-up rock called regolith on the surface.
SECTION
The Moon
27.2
History of the Moon
Layered structure
• Scientists infer from
seismic data that the
Moon, like Earth, has a
layered structure,
which consists of the
crust, upper mantle,
lower mantle, and
core.
SECTION
27.2
The Moon
History of the Moon
Formation of maria
• After the period of intense bombardment that
formed the highlands, lava welled up from the
Moon’s interior and filled in the large impact
basins.
• This lava fill created the dark, smooth plains of
the maria.
SECTION
The Moon
27.2
History of the Moon
Tectonics
• Scientists think that the Moon is not
tectonically active because the Moon has no
active volcanoes and no significant magnetic
field.
SECTION
The Moon
27.2
Formation
• The Moon probably formed as the result of a
collision between Earth and a Mars-sized
object about 4.5 bya when the solar system
was forming.
SECTION
The Moon
27.2
Formation
• The impact theory of the Moon’s formation
states that material ejected from Earth and
from the striking object eventually merged to
form the Moon.
SECTION
27.2
The Moon
Please click the image above to view the video.
SECTION
Section Check
27.2
The Moon has a lower density than that
of Earth.
a. true
b. false
SECTION
Section Check
27.2
Which term refers to meandering
structures on the Moon that might be
lava tubes?
a. ejecta
b. rays
c. rilles
d. highlands
SECTION
27.2
Section Check
Which theory about how the Moon
formed is most accepted?
a. The Moon was captured by Earth.
b. The Moon condensed with Earth.
c. A Mars-sized object struck Earth.
d. A piece broke off of Earth.
SECTION
27.3
The Sun-Earth-Moon System
Essential Questions
• What are the relative positions and motions of
the Sun, Earth, and Moon?
• What are the phases of the Moon?
• What are the differences between solstices
and equinoxes?
• How are eclipses of the Sun and Moon
explained?
SECTION
27.3
The Sun-Earth-Moon System
• Motions of the Sun-Earth-Moon system define
Earth’s day, month, and year.
Review Vocabulary
• revolution: the time it takes for a planetary
body to make one orbit around another, larger
body
SECTION
27.3
The Sun-Earth-Moon System
New Vocabulary
ecliptic plane
solstice
equinox
synchronous rotation
solar eclipse
perigee
apogee
lunar eclipse
SECTION
27.3
The Sun-Earth-Moon System
Daily Motions
• The Sun, the Moon, planets, and stars do not
orbit around Earth every day. It appears that
way because we observe the sky from a planet
that rotates.
SECTION
27.3
The Sun-Earth-Moon System
Daily Motions
Earth’s rotation
• Both a Foucault pendulum and the Coriolis
effect demonstrate that Earth is rotating.
SECTION
27.3
The Sun-Earth-Moon System
Daily Motions
Earth’s rotation
• The time period from one noon to the next is
called a solar day. As Earth rotates, it moves
in its orbit and has to turn a little farther each
day to align with the Sun.
SECTION
27.3
The Sun-Earth-Moon System
Annual Motions
• Earth orbits the Sun in a slightly elliptical orbit.
The plane of Earth’s orbit is called the ecliptic
plane.
SECTION
27.3
The Sun-Earth-Moon System
Annual Motions
The effects of Earth’s tilt
• Earth’s axis is tilted relative to the ecliptic at
approximately 23.5. As Earth orbits the Sun,
the orientation of Earth’s axis remains fixed.
SECTION
27.3
The Sun-Earth-Moon System
Annual Motions
The effects of Earth’s tilt
• Earth’s tilt and orbital motion around the Sun
result in a cycle of the seasons.
• Another effect is the changing angle of the
Sun above the horizon from summer to winter.
SECTION
27.3
The Sun-Earth-Moon System
Annual Motions
The effects of Earth’s tilt
• At a solstice, the Sun is overhead at its
farthest distance either north or south of the
equator.
• The lines of latitude that correspond to these
positions on Earth have been identified as the
Tropic of Cancer and the Tropic of Capricorn.
SECTION
27.3
The Sun-Earth-Moon System
Annual Motions
The effects of Earth’s tilt
• The summer solstice
occurs in the northern
hemisphere when the
Sun is directly
overhead at the Tropic
of Cancer, 23.5 north
latitude.
SECTION
27.3
The Sun-Earth-Moon System
Annual Motions
The effects of Earth’s tilt
• The winter solstice
occurs in the
northern
hemisphere when
the Sun is directly
overhead at the
Tropic of Capricorn,
23.5 south latitude.
SECTION
27.3
The Sun-Earth-Moon System
Annual Motions
The effects of Earth’s tilt
• At an equinox, Earth’s axis is perpendicular to
the Sun’s rays and at noon the Sun is directly
overhead at the equator.
SECTION
27.3
The Sun-Earth-Moon System
Annual Motions
The effects of Earth’s tilt
• The Sun’s maximum height, called its zenith,
varies throughout the year depending on the
viewer’s location.
SECTION
27.3
The Sun-Earth-Moon System
Annual Motions
The effects of Earth’s tilt
• For a person standing
on the 23.5 north
latitude, the Sun would
be at zenith on the
summer solstice. It
would be at its lowest
position at the winter
solstice.
SECTION
27.3
The Sun-Earth-Moon System
Phases of the Moon
• The Moon changes position relative to the
ecliptic plane as it orbits Earth.
SECTION
27.3
The Sun-Earth-Moon System
Phases of the Moon
Waxing and waning
• Starting at the new moon, as the Moon moves
in its orbit around Earth, more of the sunlit
side of the Moon becomes visible. This
increase in the visible sunlit surface of the
Moon is called the waxing phase.
SECTION
27.3
The Sun-Earth-Moon System
Phases of the Moon
Waxing and waning
• The waxing phases are called waxing
crescent, first quarter, and waxing gibbous.
• As the Moon moves to the far side of Earth
from the Sun, the entire sunlit side of the Moon
faces Earth. This is known as a full moon.
SECTION
27.3
The Sun-Earth-Moon System
Phases of the Moon
Waxing and waning
• After the full moon, the portion of the sunlit side
that is visible begins to decrease. This is called
the waning phase. The waning phases are
waning gibbous and waning crescent. When
exactly half of the sunlit portion is visible, it is
called the third quarter.
SECTION
27.3
The Sun-Earth-Moon System
Visualizing the Phases of the Moon
• One-half of the Moon is always illuminated by
the Sun’s light, but the entire lighted half is
visible from Earth only at full moon. The rest of
the time you see portions of the lighted half.
These portions are called lunar phases.
SECTION
27.3
The Sun-Earth-Moon System
Please click the image above to view the video.
SECTION
27.3
The Sun-Earth-Moon System
Phases of the Moon
Synchronous rotation
• The state at which the Moon’s orbital and
rotational periods are equal is called
synchronous rotation.
SECTION
27.3
The Sun-Earth-Moon System
Lunar Motions
• The length of time it takes for the Moon to go
through a complete cycle of phases is called a
lunar month.
SECTION
27.3
The Sun-Earth-Moon System
Lunar Motions
• The length of a lunar
month is about 29.5
days, which is longer
than the 3 days it takes
for one revolution, or
orbit, around Earth.
SECTION
27.3
The Sun-Earth-Moon System
Lunar Motions
• The Moon rotates as
it revolves, keeping
the same side facing
Earth.
SECTION
The Sun-Earth-Moon System
27.3
Lunar Motions
Tides
• The Moon’s gravity pulls on Earth along an
imaginary line connecting Earth and the
Moon, and this creates bulges of ocean water
on both the near and far sides of Earth.
SECTION
The Sun-Earth-Moon System
27.3
Lunar Motions
Tides
• Alignment of the Sun and the Moon produces
the spring tides, shown on the left.
• Neap tides, shown on
the right, occur when
the Sun and the Moon
are at right angles.
SECTION
27.3
The Sun-Earth-Moon System
Solar Eclipses
• A solar eclipse occurs when the Moon
passes directly between the Sun and Earth
and blocks the Sun from view.
SECTION
27.3
The Sun-Earth-Moon System
Solar Eclipses
How solar eclipses occur
• During a solar eclipse, the Moon passes
between Earth and the Sun. Those on Earth
within the darkest part of the Moon’s shadow
(umbra) see a total eclipse. Those within the
lighter part, or penumbral shadow, see only a
partial eclipse.
SECTION
27.3
The Sun-Earth-Moon System
Please click the image above to view the video.
SECTION
27.3
The Sun-Earth-Moon System
Solar Eclipses
How solar eclipses occur
• Solar eclipses can take place only when
Earth, the Moon, and the Sun are perfectly
aligned.
SECTION
27.3
The Sun-Earth-Moon System
Solar Eclipses
How solar eclipses occur
• Solar eclipses can happen only when the
Moon’s orbital plane and ecliptic plane intersect
along the Sun-Earth line, shown on the right. In
the left diagram, this does not happen, and the
Moon’s shadow misses Earth.
SECTION
27.3
The Sun-Earth-Moon System
Solar Eclipses
How solar eclipses occur
• The closest point in the Moon’s orbit to Earth
is called perigee.
• The farthest point is called apogee.
• An annular eclipse takes place when the
Moon is too far away for its umbral shadow to
reach Earth.
SECTION
27.3
The Sun-Earth-Moon System
Lunar Eclipses
• A lunar eclipse occurs when the Moon
passes through Earth’s shadow.
• A total lunar eclipse occurs when the entire
Moon is within Earth’s umbra. This lasts for
approximately two hours.
SECTION
27.3
The Sun-Earth-Moon System
Lunar Eclipses
• Lunar eclipses do not occur every full moon
because the Moon in its orbit usually passes
above or below the Sun as seen from Earth.
SECTION
Section Check
27.3
How much time elapses between one
moon rise and the next moon rise?
a. 24 hours
b. 25 hours
c. 23 hours 10 minutes
d. 24 hours 50 minutes
SECTION
Section Check
27.3
Which location on Earth receives
sunlight at the highest angle on the day
of the northern hemisphere summer
solstice?
a. the equator
b. the Tropic of Cancer
c. the Tropic of Capricorn
d. the Arctic Circle
SECTION
Section Check
27.3
What lunar phase appears when Earth
is between the Sun and Moon?
a. full moon
b. new moon
c. first quarter
d. third quarter
CHAPTER
27
The Sun-Earth-Moon System
Resources
Earth Science Online
Study Guide
Chapter Assessment Questions
Standardized Test Practice
Click on a hyperlink to view the corresponding feature.
SECTION
Tools of Astronomy
27.1
Study Guide
• Radiation emitted or reflected by distant
objects allows scientists to study the universe.
• Telescopes collect and focus electromagnetic
radiation emitted or reflected from distant
objects.
• Electromagnetic radiation is classified by
wavelength and frequency.
SECTION
Tools of Astronomy
27.1
Study Guide
• The two main types of optical telescopes are
refractors and reflectors.
• Space-based astronomy includes the study
of orbiting telescopes, satellites, and probes.
• Technology originally developed to explore
space is now used by people on Earth.
SECTION
The Moon
27.2
Study Guide
• The Moon, Earth’s nearest neighbor in space,
is unique among the moons in our solar
system.
• Astronomers have gathered information about
the Moon using telescopes, space probes, and
astronaut exploration.
• Like Earth’s crust, the Moon’s crust is
composed mostly of silicates.
SECTION
The Moon
27.2
Study Guide
• Surface features on the Moon include
highlands, maria, ejecta, rays, and rilles. It is
heavily cratered.
• The Moon probably formed about 4.5 bya in a
collision between Earth and a Mars-size
object.
SECTION
27.3
The Sun-Earth-Moon System
Study Guide
• Motions of the Sun-Earth-Moon system
define Earth’s day, month, and year.
• Earth’s rotation defines one day, and Earth’s
revolution around the Sun defines one year.
• Seasons are caused by the tilt of Earth’s spin
axis relative to the ecliptic plane.
SECTION
27.3
The Sun-Earth-Moon System
Study Guide
• The gravitational attraction of both the Sun
and the Moon causes tides.
• The Moon’s phases result from our view of its
lighted side as it orbits Earth.
• Solar and lunar eclipses occur when the
Sun’s light is blocked.
CHAPTER
27
The Sun-Earth-Moon System
Chapter Assessment
Which type of electromagnetic radiation
has the shortest wavelength?
a. radio waves
b. ultraviolet rays
c. infrared waves
d. gamma rays
CHAPTER
27
The Sun-Earth-Moon System
Chapter Assessment
Examine the illustration. Which layer of the
Moon is shown by the letter C?
a. the lower mantle
C
B
D
b. the upper mantle
c. the core
d. the crust
A
CHAPTER
27
The Sun-Earth-Moon System
Chapter Assessment
During which lunar phase could a solar
eclipse occur?
a. new moon
b. full moon
c. first quarter
d. third quarter
CHAPTER
27
The Sun-Earth-Moon System
Chapter Assessment
How did the maria on the Moon’s surface
form?
a. The Moon’s crust was stretched.
b. Water transported sediment into basins.
c. Regolith fell on the lunar surface.
d. Volcanic eruptions filled impact craters.
CHAPTER
27
The Sun-Earth-Moon System
Chapter Assessment
Why are lunar phases seen from Earth?
Answer: Half of the Moon is always
lighted by sunlight. As the Moon revolves
around Earth, different amounts of the
near side of the Moon, which always faces
Earth, are illuminated.
CHAPTER
27
The Sun-Earth-Moon System
Standardized Test Practice
During which moon phases do spring tides
occur?
a. first quarter and full moon
b. new moon and third quarter
c. full moon and new moon
d. first quarter and third quarter
CHAPTER
27
The Sun-Earth-Moon System
Standardized Test Practice
How old are the lunar highlands?
a. between 1.2 and 1.7 billion years
b. between 2.3 and 2.9 billion years
c. between 3.8 and 4.6 billion years
d. between 5.1 and 5.9 billion years
CHAPTER
27
The Sun-Earth-Moon System
Standardized Test Practice
Examine the illustration. Which season is
occurring in the northern hemisphere?
a. summer
b. autumn
c. winter
d. spring
CHAPTER
27
The Sun-Earth-Moon System
Standardized Test Practice
How does the plane of the Moon’s orbit
compare to the ecliptic?
a. It is the same as the ecliptic.
b. It is tilted 5 degrees to the ecliptic.
c. It is tilted 10 degrees to the ecliptic.
d. It is tilted 25 degrees to the ecliptic.
CHAPTER
27
The Sun-Earth-Moon System
Standardized Test Practice
How is a lunar eclipse different from a solar
eclipse?
CHAPTER
27
The Sun-Earth-Moon System
Standardized Test Practice
Answer: A lunar eclipse is an eclipse of the
Moon. During a lunar eclipse, Earth blocks
sunlight from striking all or part of the Moon’s
surface. The eclipse can be seen by anyone on
Earth who can see the Moon. A solar eclipse is
an eclipse of the Sun. During a solar eclipse,
the Moon blocks some or all sunlight from
reaching a portion of Earth. The eclipse can be
seen by only the people in the affected region.