Transcript Earth in Space Conceptest

Chapter 2: Earth in Space
1. Old Ideas, New Ideas
2. Origin of the Universe
3. Stars and Planets
4. Our Solar System
5. Earth, the Sun, and
the Seasons
6. The Unique
Composition of Earth
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Learning Objectives
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Students will explain concepts related to Earth in space.
Students will compare and contrast the characteristics that are
present in geocentric and heliocentric models of the solar system.
Students will describe the Big Bang theory and key developments
in the history of the universe.
Students will describe components of the solar system and
features of the Sun.
Students will analyze the similarities and differences between
terrestrial and Jovian planets.
Students will explain how insolation varies with the seasons.
Students will describe the three main boundaries in Earth.
Students will explain why the Earth system allows life to flourish.
Students will give examples of how scientific ideas change with
time.
Earth in Space Concept Survey
Explain how we are influenced
by Earth’s position in space on
a daily basis.
The Good Earth, Chapter 2: Earth in Space
Old Ideas, New Ideas
• Why is Earth the only
planet known to support
life?
• How have our views of
Earth’s position in space
changed over time?
“Earthrise” taken by astronauts
aboard Apollo 8, December 1968
• Why is it warmer in
summer and colder in
winter? (or, How does
Earth’s position relative to
the sun control the
climate?)
The Good Earth, Chapter 2: Earth in Space
Old Ideas, New Ideas
From a Geocentric to
Heliocentric System
sun
Earth pictured at the center of a
geocentric planetary system
• Geocentric orbit
hypothesis - Ancient
civilizations interpreted
rising of sun in east
and setting in west to
indicate the sun (and
other planets) revolved
around Earth
– Remained dominant
idea for more than 2,000
years
The Good Earth, Chapter 2: Earth in Space
Old Ideas, New Ideas
From a Geocentric to Heliocentric System
• Geocentric and heliocentric models could both
explain the relative positions of planets and sun
– Geocentric model required additional revolutions
around smaller orbits
Heliocentric
model
Geocentric
model
The Good Earth, Chapter 2: Earth in Space
Old Ideas, New Ideas
From a Geocentric to Heliocentric System
• Heliocentric orbit hypothesis – 16th century
idea suggested by Copernicus
• Confirmed by Galileo’s early 17th century
observations of the phases of Venus
– Changes in the size and shape of Venus as observed
from Earth
The Good Earth, Chapter 2: Earth in Space
Old Ideas, New Ideas
From a Geocentric to Heliocentric System
• Galileo used early telescopes to observe
changes in the size and shape of Venus as it
revolved around the sun
The Good Earth, Chapter 2: Earth in Space
Earth in Space Conceptest
The moon has what type of orbit?
A. Geocentric
B. Heliocentric
C. Neither
The Good Earth, Chapter 2: Earth in Space
Go back to the Table of Contents
Go to the next section: Origin of the Universe
The Good Earth, Chapter 2: Earth in Space
Earth in Space Conceptest
List these cosmic features in order
of size, beginning with the largest:
A. universe, galaxy, star, planet
B. star, galaxy, universe, planet
C. universe, planet, star, galaxy
D. galaxy, universe, star, planet
The Good Earth, Chapter 2: Earth in Space
Origin of the Universe
Earth, a small, rocky planet, orbits the
. . . the sun, a medium sized star,
. . one of billions of stars in the Milky Way galaxy,
. . one of billions of galaxies in the universe.
The Good Earth, Chapter 2: Earth in Space
Origin of the Universe
Size of the Universe: Luminosity
Brightness of pulsating stars – cepheid variables
– was used to determine distance from Earth
– Brighter stars = closer to Earth
– Dimmer stars = farther from Earth
Repeated measurements determined cepheid
variables were moving away from Earth
– Interpretation  the universe is expanding
The Good Earth, Chapter 2: Earth in Space
Origin of the Universe
Size of the Universe: Doppler Effect
Doppler Effect: The apparent change in the
frequency of sound waves or light waves due to
the motion of a source relative to an observer
– Example: change in frequency (pitch) of a siren
from passing police car
The Good Earth, Chapter 2: Earth in Space
Origin of the Universe
Doppler Effect Example: The change in
frequency (pitch) of a siren from passing police car
No change in
frequency for sound
waves when police
siren and observer
are stationary
Higher frequency
when sound waves
are compressed for
objects moving
toward an observer
Lower frequency
when sound waves
are stretched out for
objects moving away
from an observer
The Good Earth, Chapter 2: Earth in Space
Origin of the Universe
Size of the Universe: Doppler Effect
Doppler Effect: The apparent change in the
frequency of sound waves or light waves due to
the motion of a source relative to an observer
– Sound/light waves are compressed for objects
moving toward an observer
– Sound/light waves are stretched out for objects
moving away from an observer
• The change in frequency of a passing siren
can be used to determine the speed of the
police car
The Good Earth, Chapter 2: Earth in Space
Origin of the Universe
Size of the Universe: Doppler Effect
Light on Earth is a form of solar radiation and occurs
at specific wavelengths from 380-750 nanometers
• The color of
light from
distant stars
is stretched
(“shifted”)
toward
wavelengths
at the red
end of the
spectrum
Shorter wavelength
Longer wavelength
The Good Earth, Chapter 2: Earth in Space
Origin of the Universe
Size of the Universe: Doppler Effect
Astronomers use the degree of “red shift” to
determine the distance to far away galaxies
• more than 13 billion light years (distance) from Earth
The Good Earth, Chapter 2: Earth in Space
Origin of the Universe
Size and Age of the Universe
• If the color of light from other stars is “shifted”
toward the red end of the spectrum
– Other objects in the universe are moving away from
Earth and from each other
– The farther away the star, the greater the red shift
and the faster the star is moving away from us
– The universe must be expanding
– Light from the most distant stars has traveled more
than 13 billion light years (distance) in 13 billion
years (time)
The Good Earth, Chapter 2: Earth in Space
Earth in Space Conceptest
What is the Doppler Effect as used in
exploration of the universe?
A. A change in the speed of light as the source
moves relative to the observer
B. A change in luminosity of light as the source
moves relative to the observer
C. A change in the frequency of light as the
source moves relative to the observer
The Good Earth, Chapter 2: Earth in Space
Earth in Space Conceptest
Suppose the light spectrum from a distant
star shifted toward the blue end of the
light spectrum. What would this imply?
A. The star is moving away from us
B. The star is moving toward us
C. The star is not moving relative to us
The Good Earth, Chapter 2: Earth in Space
Earth in Space Conceptest
Suppose you and a friend are tossing a ball back
and forth. The ball has a speaker that lets off a
constant noise. How does the frequency of the
noise you hear vary from when you throw the
ball to when you catch the ball?
A. The frequency increases
B. The frequency decreases
C. The frequency does not change
The Good Earth, Chapter 2: Earth in Space
Origin of the Universe
The Big Bang Theory
• Reversing the expansion of the universe
suggests the universe began with an
episode of rapid expansion from a much
more compact form
• The almost instantaneous period of rapid
expansion is known as the Big Bang
• Within hours of the Big Bang, simple
elements (hydrogen, helium) formed as
subatomic particles combined
− Hydrogen – 1 proton + 1 electron
− Helium – 2 protons + 2 neutrons + 2 electrons
The Good Earth, Chapter 2: Earth in Space
Earth in Space Concept Survey
Scientists often suggest that the expansion of the
Universe is similar to the expansion of raisin bread
as it bakes in an oven. The loaf increases in size
and individual raisins move farther apart in the
expanding bread.
During a homework assignment, two students
suggest two more analogies (see below) for the
universe. These answers are not considered as
good as the raisin bread analogy. Why?
a) The universe expands similarly to the concentric
ripples formed when a rock is thrown into a pond.
b) The universe is similar to a Jell-O mold enclosing
pieces of fruit (galaxies).
The Good Earth, Chapter 2: Earth in Space
Go back to the Table of Contents
Go to the next section: Stars and Planets
The Good Earth, Chapter 2: Earth in Space
Stars and Planets
• Just 3 elements – hydrogen, oxygen,
carbon - make up 90% of the human body
(by weight)
– Five more – nitrogen, calcium, phosphorus,
potassium, sulfur – make up 9% more
– Small amounts of many other elements needed
for life
• Hydrogen formed soon after the Big Bang
• Other elements and complex compounds
formed during the life cycle of stars
The Good Earth, Chapter 2: Earth in Space
Stars and Planets
• Gravity pulled together irregular clouds of
gas and dust generated from the Big Bang
to form galaxies (systems of stars)
Stars and
galaxies in a
small section of
the universe.
Image taken by
Hubble space
telescope
The Good Earth, Chapter 2: Earth in Space
Stars and Planets
• Gas and dust material
clumped together to
form millions of stars
(ongoing process)
− Very high temperatures
and pressures in the
interiors of stars fuses
hydrogen atoms
together – nuclear
fusion – to form helium
− Stars burn out when
hydrogen is used up
Clouds of hydrogen gas and dust in Eagle Nebula
are incubators for the formation of new stars.
The Good Earth, Chapter 2: Earth in Space
Stars and Planets
• Stars vary in size, age
− Giant stars are 1001,000 times brighter
than the sun but burn
out faster
− Giant stars burn out in
10-20 million years
− Intermediate-sized
stars such as the sun
will last approximately
10 billion years
Life cycle stages and types of stars
(Hertsprung-Russell diagram).
The Good Earth, Chapter 2: Earth in Space
Stars and Planets
• The sun will collapse when hydrogen is
used up
− resulting in a temporary temperature rise and
expansion (to form a red giant star)
− higher temperatures would fuel more fusion
converting helium  carbon
• Fusion would end when helium is used up
• The loss of the heat of fusion would form a
smaller white dwarf star that will cool to a
black dwarf star
The Good Earth, Chapter 2: Earth in Space
Stars and Planets
• Giant stars collapse over
multiple stages, initially
forming red supergiant
stars
− Collapse forms increasingly
complex elements (e.g.,
carbon  oxygen)
Kepler’s supernova. Astronomer Kepler
noted the appearance of a new star (the
supernova) on October 9, 1604.
• Final stage is a massive
explosion – supernova –
that fuses heavier elements
together and blasts them
through the universe
The Good Earth, Chapter 2: Earth in Space
Stars and Planets
• When stars form they are surrounded by a
rotating disk of cosmic debris
• Gravity pulls debris together to form planets that
revolve in a consistent direction around star
− Heavier, rocky planets closer to star
− Lighter, gas-rich planets farther from star
• Potentially thousands or millions of extra-solar
planets revolve around other stars
The Good Earth, Chapter 2: Earth in Space
Earth in Space Conceptest
Which of the following statements is most
accurate? Explain the reason for your answer as well
as why you did not choose either of the other two answers.
A. All stars and planets are about the same age.
B. Stars are approximately the same age as their
orbiting planets.
C. The number of stars is declining as stars burn
out.
The Good Earth, Chapter 2: Earth in Space
Go back to the Table of Contents
Go to the next section: Our Solar System
The Good Earth, Chapter 2: Earth in Space
Earth in Space Quiz
What are the principal
components of the sun?
A. Hydrogen and helium
B. Carbon and oxygen
C. Silicon and nitrogen
D. Nickel and iron
The Good Earth, Chapter 2: Earth in Space
Our Solar System
The Good Earth, Chapter 2: Earth in Space
Our Solar System
• Solar system - sun and
surrounding planets
Sunspots – dark spots
on surface of sun
• Sun = 99.8% of total mass
of the solar system
− Sun 150,000,000 km from
Earth
• Sun undergoes differential
rotation
Solar
flare
− Sun’s equatorial region
rotates faster (25 days) than
polar regions (36 days)
− Results in disruption of sun’s
magnetic field to produce
sunspots and solar flares
The Good Earth, Chapter 2: Earth in Space
Our Solar System
Sunspot cycle
solar
maximum
− Variation in the
number of
sunspots over
an 11-year cycle
− Few sunspots
visible during
solar minimum
solar
minimum
− More than 100
sunspots during
solar maximum
11-year sunspot cycle
The Good Earth, Chapter 2: Earth in Space
Our Solar System
• The solar wind is a stream of charged particles
emitted from sun’s magnetic field (1,600,000 km/hr)
• The solar wind affects an volume of space known
as the heliosphere
• Earth’s magnetic field deflects the solar wind
The Good Earth, Chapter 2: Earth in Space
Our Solar System
Aurora from Earth
Aurora from space
• Interactions of solar wind
with Earth’s magnetic
field generates aurora in
the upper atmosphere of
polar regions
• Occasional solar
eruptions can disrupt
Earth’s magnetic field to
produce electrical
blackouts
− Satellites in greater
danger from solar flares
than features on surface
The Good Earth, Chapter 2: Earth in Space
Earth in Space Conceptest
Sunspots, flares, and other emissions from
the sun’s surface can have a negative
impact on electrical systems on Earth. What
would be the implications for this type of
solar activity if the sun did not rotate?
A. There would be less sunspot activity
B. There would be more sunspot activity
C. There would be no change in sunspot activity
The Good Earth, Chapter 2: Earth in Space
Earth in Space Conceptest
The sun is located approximately
150,000,000 km from Earth. If scientists
identified a solar flare leaving the sun’s
surface, how long would it take to
affect electrical systems on Earth?
A. A few minutes
B. A few hours
C. A few days
D. A few weeks
The Good Earth, Chapter 2: Earth in Space
Earth in Space Conceptest
Which satellite view shows the sun
approaching a maximum in the
sunspot cycle?
A
B
C
The Good Earth, Chapter 2: Earth in Space
Our Solar System
The Good Earth, Chapter 2: Earth in Space
Our Solar System
The Good Earth, Chapter 2: Earth in Space
Our Solar System
Eight Planets
• 4 terrestrial planets
(Mercury, Venus,
Earth, Mars)
• Jovian planets
(Jupiter, Saturn,
Uranus, Neptune)
The Good Earth, Chapter 2: Earth in Space
Our Solar System
What about Pluto?
• Improved technology resulted in recent discoveries
of several distant objects that were similar size or
larger than Pluto
• International Astronomical Union (IAU) could either
1. Consider the new objects as new planets
OR
2. Classify the new objects – and Pluto – as a new group of
objects
• IAU chose option #2
The Good Earth, Chapter 2: Earth in Space
Our Solar System
What about Pluto?
• IAU adopted a new definition of the term planet:
A planet is an object that orbits a star and is
massive enough (~400 km radius) for gravity to pull
its material into an approximately spherical shape.
A planet would have cleared the neighborhood
around its orbit.
• Pluto does not meet the last part of the definition
and was considered a founding member of a new
class of objects - dwarf planets
The Good Earth, Chapter 2: Earth in Space
Our Solar System
Terrestrial Planets
• Composed of rocks
• Divided into compositional layers
− Crust – composed of lighter
elements (e.g., silicon, oxygen)
− Mantle
− Core – composed of heavier
elements (e.g., iron, nickel) found in
metallic meteorites
The Good Earth, Chapter 2: Earth in Space
Our Solar System
Jovian Planets
• Large, gas giants
• Much of the volume of the
planets is a thick atmosphere
overlying oceans of liquid gases
• Characterized by many moons
and ring systems
Jupiter and four of
its largest moons.
Saturn’s ring system.
The gravitational pull
of the moon’s keep
the ring systems in
place.
The Good Earth, Chapter 2: Earth in Space
Go back to the Table of Contents
Go to the next section: Earth, the Sun, and
the Seasons
The Good Earth, Chapter 2: Earth in Space
Earth in Space Conceptest
How do we define the length of a year
on Earth?
A.
B.
A year is related to the revolution of Earth around the sun.
C.
D.
A year is related to the rotation of the sun on its axis.
A year is related to the rotation of Earth on its axis.
A year is related to the revolution of the sun around Earth.
The Good Earth, Chapter 2: Earth in Space
Earth, the Sun, and the Seasons
What patterns must the Earth-Sun
relationship be able to explain?
• Why is it hotter at the equator and colder at
the Poles?
• Why is it colder in winter (January) than in
summer (July)?
• Why is it summer in Australia when it is
winter in the U.S.?
The Good Earth, Chapter 2: Earth in Space
Earth, the Sun, and the Seasons
Why is it colder in winter
and warmer in summer?
• Common misconception
that Earth is closer to the
sun during summer and
farther away in winter
• But Earth is actually
closer to sun in winter (in
the northern hemisphere)
and farther away in
summer.
Distance from sun does not contribute to
temperature differences between winter
and summer
The Good Earth, Chapter 2: Earth in Space
Earth, the Sun, and the Seasons
Why is it colder in winter
and warmer in summer?
• Seasonal temperature
contrasts are due to the
tilt of Earth’s axis and
angle of Sun’s rays
• Tilt = 23.5 degrees
Earth is tilted on an imaginary axis
oriented 23.5 degrees to vertical. The
tropics of Cancer and Capricorn are 23.5
degrees of latitude north and south of the
equator.
The Good Earth, Chapter 2: Earth in Space
Earth, the Sun, and the Seasons
• Amount of solar energy
(insolation) reaching
Earth’s surface depends
on the angle the Sun’s
rays strike Earth
• More heat delivered by
insolation where the Sun
is directly overhead
− As sunlight is distributed
over a smaller area
− Total annual insolation is
least at Poles, greatest at
the Equator
Solar energy is diluted over a larger area
when sunlight strikes at a low angle (at
high latitudes).
The Good Earth, Chapter 2: Earth in Space
Earth, the Sun, and the Seasons
• Sun is directly overhead
at different places (tropics,
equator) during different
seasons
− During summer in the
northern hemisphere, the
sun is directly overhead at
the Tropic of Cancer
− During winter in the
northern hemisphere, the
Sun is directly overhead at
the Tropic of Capricorn in
the southern hemisphere
Note that Earth’s axis is always tilted in
the same direction causing the
distribution of solar radiation to change
with the seasons.
The Good Earth, Chapter 2: Earth in Space
Earth, the Sun, and the Seasons
• Sun is directly overhead
at different places
(tropics, equator) during
different seasons
− During spring and fall in
the northern hemisphere,
the sun is directly
overhead at the Equator
Note that Earth’s axis is always tilted in
the same direction causing the
distribution of solar radiation to change
with the seasons.
The Good Earth, Chapter 2: Earth in Space
Earth, the Sun, and the Seasons
Why day length changes
• Hours of daylight change
• With latitude – higher
latitudes have more
daylight than low latitudes
in summer, less in winter
• With time of year – all
locations have more
daylight in summer and
less in winter
High latitudes in the Northern
Hemisphere experience nearly
continuous daylight in summer
(top) and almost perpetual
darkness in winter.
The Good Earth, Chapter 2: Earth in Space
Earth in Space Conceptest
What would happen to the average
temperature at the equator during our
summer if the tilt angle of Earth’s axis
increased to 27º?
A. Temperatures would decrease
B. Temperatures would increase
C. Temperatures would stay the same
The Good Earth, Chapter 2: Earth in Space
Earth in Space Conceptest
How would the amount of incoming solar
radiation change at the equator if Earth’s
axis was vertical instead of tilted?
A. Incoming solar radiation would decrease.
B. Incoming solar radiation would be the
same as at present.
C. Incoming solar radiation would increase.
The Good Earth, Chapter 2: Earth in Space
Earth in Space Conceptest
What must happen to the tilt angle of
Earth’s axis in order to have vertical rays
where you live on the summer solstice
(June 21)?
A. Tilt would increase
B. Tilt would decrease
C. Tilt would stay the same
The Good Earth, Chapter 2: Earth in Space
Earth in Space Concept Survey
Mars has a more asymmetric orbit of the sun
than Earth. Mars is 20% closer to the sun
during its winter than during its summer.
How would Earth’s climate be affected if
Earth had a similarly eccentric orbit, being
20% closer to the sun during winter months
in the Northern Hemisphere?
The Good Earth, Chapter 2: Earth in Space
Go back to the Table of Contents
Go to the next section: The Unique
Composition of Earth
The Good Earth, Chapter 2: Earth in Space
The Unique Composition of Earth
• Earth’s interior can be
divided into three major
compositional layers
− Crust – composed of lighter
elements (e.g., silicon, oxygen)
− Mantle – composed of rocks
made up of 3 key elements
(oxygen, silicon, magnesium)
− Core – iron and nickel
− solid inner core
− partially melted outer core is
source of Earth’s magnetic
field
The Good Earth, Chapter 2: Earth in Space
The Unique Composition of Earth
• Scientists recognize two
layers with different
properties near the surface
− Lithosphere – rigid outer layer
composed of crust and upper
mantle
− Asthenosphere – plastic, slowly
flowing layer in uppermost part of
mantle
The Good Earth, Chapter 2: Earth in Space
The Unique Composition of Earth
• Lithosphere divided into large slabs known as
tectonic plates
− Plates move over Earth’s surface to produce earthquakes,
volcanoes, mountain belts, and various features on the
seafloor
The Good Earth, Chapter 2: Earth in Space
The Unique Composition of Earth
Geothermal gradient
• Earth’s temperature increases with depth
• Average temperature rise is 25oC/kilometer
• Heat generated by the:
− Formation of the planet – all terrestrial planets
cooled following formation
 Only large planets still retain heat
− Radioactive decay of elements in Earth’s interior
The Good Earth, Chapter 2: Earth in Space
The Unique Composition of Earth
Earth shares many
features with other
planets, so what
makes it so special?
• Liquid water
• Gravity and a
protective atmosphere
• Life-sustaining gases
• A strong magnetic field
The Good Earth, Chapter 2: Earth in Space
The Unique Composition of Earth
Liquid water is essential for life on Earth and
is maintained by appropriate temperature
range (0-100oC)
Venus
− Too close to Sun, original water evaporated to
atmosphere
− Water vapor molecules (H2O)split by ultraviolet
radiation and hydrogen lost to space
Mars
− Too cold today to have liquid water, some frozen
The Good Earth, Chapter 2: Earth in Space
The Unique Composition of Earth
Earth’s size is sufficient
to produce enough
gravity to hold a thick
atmosphere of gases
in place
Atmosphere protects
us from:
• Incoming
asteroids/comets
• Harmful solar radiation
(x-rays, UV)
The Good Earth, Chapter 2: Earth in Space
The Unique Composition of Earth
Earth’s biosphere has altered the
composition of the atmosphere to add
oxygen and extract toxic carbon dioxide
Atmosphere composition effects temperature:
− Higher carbon dioxide content on Venus produces
temperatures of 464oC
The Good Earth, Chapter 2: Earth in Space
The Unique Composition of Earth
Composition of Earth’s atmosphere just
right to absorb enough heat to keep
average temperature of 15oC
Greenhouse effect:
− Water vapor, carbon dioxide (0.038%)
gases absorb heat
− Without greenhouse effect, temperatures
would be -18oC
The Good Earth, Chapter 2: Earth in Space
The Unique Composition of Earth
Earth’s magnetic field protects Earth
from harmful solar wind that would strip
away atmosphere
Magnetic field due to molten rocks in
the outer core and relatively rapid
planetary rotation:
− Smaller planets or slowly rotating planets
have lost heat and have weak magnetic
fields
The Good Earth, Chapter 2: Earth in Space
Earth in Space Conceptest
If Earth were farther from the sun, the
planet would be, __________.
A. warmer
B. colder
The Good Earth, Chapter 2: Earth in Space
Earth in Space Conceptest
If Earth’s biosphere were younger, we
would have _____ oxygen in the
atmosphere.
A. less
B. more
The Good Earth, Chapter 2: Earth in Space
Earth in Space Conceptest
If Earth were smaller, its atmosphere
would be ________.
A. thicker
B. thinner
The Good Earth, Chapter 2: Earth in Space
The End
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The Good Earth, Chapter 2: Earth in Space