Download Motions of the Earth–Moon System 22.2 The Earth–Moon–Sun System

Prentice Hall
EARTH SCIENCE
Tarbuck

Lutgens
STARTER
• Using figure 3 on page 616 answer
the following questions
–What is the main difference
between these two models of the
solar system?
–How do changing models of the
solar system demonstrate the selfcorrecting nature of science?
•22.1 Early Astronomy
• Key Concepts
• How does the geocentric model of the solar
system differ from the heliocentric model?
• What were the accomplishments of early
astronomers?
• Vocabulary
• astronomy, geocentric, heliocentric,
retrograde motion, ellipse, astronomical unit
(AU)
22.1 Early Astronomy
Ancient Greeks
 Astronomy is the science that studies the
universe. It includes the observation and
interpretation of celestial bodies and
phenomena.
 The Greeks used philosophical arguments
to explain natural phenomena.
 The Greeks also used some observational
data.
Astrolabe
Early astronomers
often used
instruments called
astrolabes to track
the positions on the
sun and stars.
Calculating Earth’s Circumference
This diagram
shows the
orientation of the
sun’s rays at Syene
(Aswan) and
Alexandria in
Egypt on June 21
when Erastothenes
calculted Earth’s
circumfrence.
22.1 Early Astronomy
Ancient Greeks
 Geocentric Model
• In the ancient Greeks’ geocentric model, the
moon, sun, and the known planets—Mercury,
Venus, Mars, and Jupiter—orbit Earth.
 Heliocentric Model
• In the heliocentric model, Earth and the other
planets orbit the sun.
Geocentric and Heliocentric Models
A Geocentric Model of the
Universe
A Heliocentric Model of the
Universe
22.1 Early Astronomy
Ancient Greeks
 Ptolemaic System
• Ptolemy created a model of the universe that
accounted for the movement of the planets.
• Retrograde motion is the apparent westward
motion of the planets with respect to the stars.
Retrograde Motion
When viewed from Earth, Mars moves eastward among the stars each
day. Then periodically it appears to stop and reverse direction. This
apparent movement, called retrograde motion occurs because Earth has
a faster orbital speed than Mars and overtakes it.
Reading Checkpoint
• What is retrograde motion??
22.1 Early Astronomy
The Birth of Modern Astronomy
 Nicolaus Copernicus
• Copernicus concluded that Earth is a planet. He
proposed a model of the solar system with the
sun at the center.
22.1 Early Astronomy
The Birth of Modern Astronomy
 Tycho Brahe
• Tycho Brahe designed and built instruments to
measure the locations of the heavenly bodies.
Brahe’s observations, especially of Mars, were
far more precise than any made previously.
22.1 Early Astronomy
The Birth of Modern Astronomy
 Johannes Kepler
• Kepler discovered three laws of planetary motion:
1. Orbits of the planets are elliptical.
2. Planets revolve around the sun at varying
speed.
3. There is a proportional relationship between
a planet’s orbital period and its distance to
the sun.
22.1 Early Astronomy
The Birth of Modern Astronomy
 Johannes Kepler
• An ellipse is an oval-shaped path.
• An astronomical unit (AU) is the average
distance between Earth and the sun; it is about
150 million kilometers.
Planet Revolution
A line connecting
a planet to the
sun would move
in such a manner
that equal areas
are swept out in
equal times.
Thus, planets
revolve slower
when they are
farther from the
sun and faster
when they are
closer.
22.1 Early Astronomy
The Birth of Modern Astronomy
 Galileo Galilei
• Galileo’s most important contributions were his
descriptions of the behavior of moving objects.
• He developed his own telescope and made
important discoveries:
1. Four satellites, or moons, orbit Jupiter.
2. Planets are circular disks, not just points of light.
3. Venus has phases just like the moon.
4. The moon’s surface is not smooth.
5. The sun has sunspots, or dark regions.
The Solar System Model Evolves
In the Ptolemaic
system, the orbit of
Venus lies between
the sun and Earth.
In the Copernicus
system, Venus orbits
the sun and all its
phases are visible
from Earth
As Galileo observed,
Venus goes through
phases similar to the
moon.
22.1 Early Astronomy
The Birth of Modern Astronomy
 Sir Isaac Newton
• Although others had theorized the existence of
gravitational force, Newton was the first to
formulate and test the law of universal
gravitation.
 Universal Gravitation
• Gravitational force decreases with distance.
• The greater the mass of an object, the greater is
its gravitational force.
Gravity’s Influence on Orbits
Without the influence of gravity, planets would move in a
straight line out into space.
Review of 22.1
• Create three review questions
with answers from section
22.1.
• Hold you paper up so I can
come by and check off when
you are finished.
Who am I?
• I built instruments called pointers
to measure the location of
heavenly bodies. I came up with
the most precise location of Mars
than had ever been made.
Tycho Brahe
Who am I?
• I was the first to formulate and
test the Law of Universal
Gravitation.
Sir Isaac Newton
Who am I?
• I determined that Earth is a
planet, not the center of the
universe.
Copernicus
Who am I?
• I invented the telescope and made
other discoveries such as:
–Planets are circular disks
–Venus has phases like the moon
–The moon’s surface is not smooth
–The are dark regions called
sunspots
Galileo
Who am I?
• I came up with the three laws
of planetary motion.
Johannes Kepler
Who am I?
• I came up with the concept of
retrograde motion, which is the
apparent westward drift of
planets.
Ptolemy
Who am I?
• I was credited for determining
the circumference of Earth.
Eratosthenes
Who am I?
• I determined that the Earth was
round because it always cast a
curved shadow when it passed
between the sun and the moon.
Aristotle
A. built instruments called pointers to measure
the location of heavenly bodies
B. Earth is a planet, not the center of the solar
system
C. credited for finding the circumference of the
Earth
D. formulated and tested the Law of Universal
Gravitation
E. concluded the Earth is round
F. retrograde motion
G. 3 laws of planetary motion
H. telescope, sunspots, planets are circular disks,
discovered the moon’s surface is not smooth
•22.2 The Earth-Moon-Sun System
• Key Concepts
• In what ways does Earth move?
• What causes the phases of the moon?
• Why are eclipses relatively rare events?
• Vocabulary
• Rotation, revolution, precession, perihelion,
aphelion, perigee, apogee, phases of the
moon, solar eclipse, lunar eclipse
22.2 The Earth–Moon–Sun System
Motions of Earth
 The two main motions of Earth are rotation
and revolution. Precession is a third and
very slow motion of Earth’s axis.
Stonehenge, an Ancient Observatory
22.2 The Earth–Moon–Sun System
Motions of Earth
 Rotation
• Rotation is the turning, or spinning, of a body on
its axis.
• Two measurements for rotation:
1. Mean solar day is the time interval from one
noon to the next, about 24 hours.
2. Sidereal day is the time it takes for Earth to
make one complete rotation (360º) with
respect to a star other than the sun—23 hours,
56 minutes, 4 seconds.
Sidereal Day
22.2 The Earth–Moon–Sun System
Motions of Earth
 Revolution
• Revolution is the motion of a body, such as a
planet or moon, along a path around some point
in space.
• Perihelion is the time in January when Earth is
closest to the sun.
• Aphelion is the time in July when Earth is
farthest from the sun.
22.2 The Earth–Moon–Sun System
Motions of Earth
 Earth’s Axis and Seasons
• The plane of the ecliptic is an imaginary plane
that connects Earth’s orbit with the celestial
sphere.
• Because of the inclination of Earth’s axis to the
plane of the ecliptic, Earth has its yearly cycle of
seasons.
Spring Equinox- March 20 or 21
Autumn Equinox- September 22 or 23
Summer Solstice- June 21 or 22
Winter Solstice- December 21 or 22
The Ecliptic
22.2 The Earth–Moon–Sun System
Motions of Earth
 Precession
• Precession traces out a cone over a period of
26,000 years.
 Earth–Sun Motion
• The solar system speeds in the direction of the
star Vega.
• The sun revolves around the galaxy.
• Earth is presently approaching one of its
nearest galactic neighbors, the Great Galaxy in
Andromeda.
Precession
Reading Checkpoint
• What is precession?
22.2 The Earth–Moon–Sun System
Motions of the Earth–Moon System
 Perigee is the point at which the moon is
closest to Earth.
 Apogee is the point at which the moon is
farthest from Earth.
22.2 The Earth–Moon–Sun System
Motions of the Earth–Moon System
 Phases of the Moon
• The phases of the moon are the progression of
changes in the moon’s appearance during the
month.
• Lunar phases are a result of the motion of the
moon and the sunlight that is reflected from its
surface.
Phases of the Moon
22.2 The Earth–Moon–Sun System
Motions of the Earth–Moon System
 Lunar Motions
• The synodic month is based on the cycle of the
moon’s phases. It lasts 29 1/2 days.
• The sidereal month is the true period of the
moon’s revolution around Earth. It lasts 27 1/3
days.
22.2 The Earth–Moon–Sun System
Motions of the Earth–Moon System
 Lunar Motions
• The difference of two days between the synodic
and sidereal cycles is due to the Earth–moon
system also moving in an orbit around the sun.
• The moon’s period of rotation about its axis and
its revolution around Earth are the same, 27 1/3
days. It causes the same lunar hemisphere to
always face Earth.
Lunar Motions
Reading Checkpoint
• Why does the same side of the moon
always face Earth?
22.2 The Earth–Moon–Sun System
Eclipses
 Solar eclipses occur when the moon
moves in a line directly between Earth and
the sun, casting a shadow on Earth.
 Lunar eclipses occur when the moon
passes through Earth’s shadow.
 During a new-moon or full-moon phase,
the moon’s orbit must cross the plane of
the ecliptic for an eclipse to take place.
Solar Eclipse
Lunar Eclipse
22.3 Earth’s Moon
• Key Concepts
• What processes create surface features on
the moon?
• How did the moon form?
• Vocabulary
• Crater, ray, mare, rille, lunar regolith
22.3 Earth’s Moon
The Lunar Surface
 Craters
• A crater is the depression at the summit of a
volcano or a depression produced by a
meteorite impact.
• Most craters were produced by the impact of
rapidly moving debris.
• Rays are any of a system of bright, elongated
streaks, sometimes associated with a crater on
the moon.
The Moon’s Surface
Mare Imbrium
(Sea of Rains)
Kepler
Crater
Copernicus
Crater
Mare Tranquillitatus
(Sea of Tranquility)
Formation of a Crater
22.3 Earth’s Moon
The Lunar Surface
 Highlands
• Most of the lunar surface is made up of densely
pitted, light-colored areas known as highlands.
 Maria
• Maria, ancient beds of basaltic lava, originated
when asteroids punctured the lunar surface,
letting magma bleed out.
• A rille is a long channel associated with lunar
maria. A rille looks similar to a valley or a trench.
1st
22.3 Earth’s Moon
The Lunar Surface
 Regolith
• The lunar regolith is a thin, gray layer on the
surface of the moon, consisting of loosely
compacted, fragmented material believed to
have been formed by repeated impacts of
meteorites.
Major Topographic Features of the Moon
22.3 Earth’s Moon
Lunar History
 The most widely accepted model for the
origin of the moon is that when the solar
system was forming, a body the size of
Mars impacted Earth. The resulting debris
was ejected into space, began orbiting
around Earth, and eventually united to form
the moon.
Formation of Earth’s Moon
STARTER
• Draw a simple illustration for
the motions of Earth: rotation,
revolution, & precession
Classwork
• Draw, color, and label the Major topographic features of the
moon’s surface.
• List facts about the Lunar Surface and Lunar History.
• Using complete sentences answer 1-5 on the section
assessment.
• Read Foucalt’s Experiment on page 635. Answer the following
questions.
– Once the pendulum is set in motion, it will continue to swing in the
same direction unless it is pushed or pulled by a force. Why is
this true?
– What outside force is acting on the pendulum?
– Why does the pendulum change position over time?
– How does this prove that Earth is rotating?
Homework: Study & write a paragraph explaining what evidence
scientists use to reconstruct the history of the moon.
Classwork
• Based on the you vocabulary definitions can
you determing the meaning of the following
word parts:
1. helios 2. ge or gee 3. peri- 4. ap- or
apo• Using Figure 12 on page 623 answer the
following questions
– What are the reference points for a mean solar day
and a sidereal day?
– Why do these two reference points give two
different results?
– Why do astronomers choose to use the sidereal day
instead of the mean solar day?
Classwork
• Complete the reading strategy.
• Using figure 17 answer the following
questions
– During a solar eclipse, why do observers
in the umbra see a total solar eclipse?
– Why do observers in the penumbra see a
partial eclipse?
– When does a total lunar eclipse occur?
– When does a partial lunar eclipse occur?
• Using complete sentences answer 1-6 on
the section assessment.
Classwork
• Create a Venn diagram on geocentric and
heliocentric models
• Using Figure 4 answer the following
questions
– Why does Mars appear to have retrograde
motion?
– Using Newton’s laws of motion, explain
why retrograde motion is impossible.
• Using complete sentences answer 1-6 on
the section assessment.
•22.1 Mini-Quiz
1.
2.
3.
4.
5.
What is astronomy?
What is the heliocentric model?
What is retrograde motion?
What is Kepler’s 2nd law of motion?
What does Newton’s Law of Universal
gravitation take into account that Kepler’s
3rd law doesn’t?
22.2 Mini-Quiz
1.
2.
3.
4.
What the two main motions of Earth?
What is precession?
What causes the phases of the moon?
Why does one side of the moon always
face Earth?
5. Which shadow do you have to be in to
see a total eclipse?
22.3 Mini-Quiz
1. How did the moon most likely form?
2. Why are craters more likely on the moon
than on Earth?
3. How old are the maria?
4. What are rilles?
5. What is lunar regolith?