Upload
denis-fletcher
View
230
Download
0
Tags:
Embed Size (px)
Citation preview
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
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Learning Objectives• 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?
• 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
“Earthrise” taken by astronauts aboard Apollo 8, December 1968
Old Ideas, New Ideas
Earth pictured at the center of a geocentric planetary system
From a Geocentric to Heliocentric System
sun • 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
The Good Earth, Chapter 2: Earth in Space
Heliocentric model
Geocentric model
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
The Good Earth, Chapter 2: Earth in Space
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
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
The Good Earth, Chapter 2: Earth in Space
A. universe, galaxy, star, planet
B. star, galaxy, universe, planet
C. universe, planet, star, galaxy
D. galaxy, universe, star, planet
List these cosmic features in order of size, beginning with the largest:
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
The Good Earth, Chapter 2: Earth in Space
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
Origin of the Universe
The Good Earth, Chapter 2: Earth in Space
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
Origin of the Universe
The Good Earth, Chapter 2: Earth in Space
Doppler Effect Example: The change in frequency (pitch) of a siren from passing police car
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
No change in frequency for sound waves when police siren and observer are stationary
Origin of the Universe
The Good Earth, Chapter 2: Earth in Space
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
Origin of the Universe
The Good Earth, Chapter 2: Earth in Space
Size of the Universe: Doppler EffectLight on Earth is a form of solar radiation and occurs at specific wavelengths from 380-750 nanometers
Longer wavelengthShorter wavelength
• The color of light from distant stars is stretched (“shifted”) toward wavelengths at the red end of the spectrum
Origin of the Universe
The Good Earth, Chapter 2: Earth in Space
Size of the Universe: Doppler EffectAstronomers use the degree of “red shift” to determine the distance to far away galaxies
• more than 13 billion light years (distance) from Earth
Origin of the Universe
The Good Earth, Chapter 2: Earth in Space
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)
Earth in Space Conceptest
The Good Earth, Chapter 2: Earth in Space
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
Earth in Space Conceptest
The Good Earth, Chapter 2: Earth in Space
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
Earth in Space Conceptest
The Good Earth, Chapter 2: Earth in Space
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
Origin of the Universe
The Good Earth, Chapter 2: Earth in Space
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
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.
The Good Earth, Chapter 2: Earth in Space
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).
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
The Good Earth, Chapter 2: Earth in Space
• 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
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
The Good Earth, Chapter 2: Earth in Space
• 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.
Stars and Planets
The Good Earth, Chapter 2: Earth in Space
• Stars vary in size, age
− Giant stars are 100-1,000 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).
Stars and Planets
The Good Earth, Chapter 2: Earth in Space
• 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
Stars and Planets
The Good Earth, Chapter 2: Earth in Space
• Giant stars collapse over multiple stages, initially forming red supergiant stars
− Collapse forms increasingly complex elements (e.g., carbon oxygen)
• Final stage is a massive explosion – supernova – that fuses heavier elements together and blasts them through the universeKepler’s supernova. Astronomer Kepler
noted the appearance of a new star (the supernova) on October 9, 1604.
Stars and Planets
The Good Earth, Chapter 2: Earth in Space
• 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
Earth in Space Conceptest
The Good Earth, Chapter 2: Earth in Space
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.
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
The Good Earth, Chapter 2: Earth in Space
What are the principal components of the sun?
A. Hydrogen and helium
B. Carbon and oxygen
C. Silicon and nitrogen
D. Nickel and iron
Our Solar System
The Good Earth, Chapter 2: Earth in Space
Our Solar System
The Good Earth, Chapter 2: Earth in Space
• Solar system - sun and surrounding planets
• Sun = 99.8% of total mass of the solar system
− Sun 150,000,000 km from Earth
• Sun undergoes differential rotation
− 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
Sunspots – dark spots on surface of sun
Solar flare
Our Solar System
The Good Earth, Chapter 2: Earth in Space
Sunspot cycle− Variation in the
number of sunspots over an 11-year cycle
− Few sunspots visible during solar minimum
− More than 100 sunspots during solar maximum
solar minimum
solar maximum
11-year sunspot cycle
Our Solar System
The Good Earth, Chapter 2: Earth in Space
• 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
Our Solar System
The Good Earth, Chapter 2: Earth in 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
Aurora from Earth
Aurora from space
Earth in Space Conceptest
The Good Earth, Chapter 2: Earth in Space
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
Earth in Space Conceptest
The Good Earth, Chapter 2: Earth in Space
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
Earth in Space Conceptest
The Good Earth, Chapter 2: Earth in Space
Which satellite view shows the sun approaching a maximum in the sunspot cycle?
A B C
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
The Good Earth, Chapter 2: Earth in Space
Eight Planets
• 4 terrestrial planets (Mercury, Venus, Earth, Mars)
• Jovian planets (Jupiter, Saturn, Uranus, Neptune)
Our Solar System
The Good Earth, Chapter 2: Earth in Space
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 either1. 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
Our Solar System
The Good Earth, Chapter 2: Earth in Space
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
Our Solar System
The Good Earth, Chapter 2: Earth in Space
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
Our Solar System
The Good Earth, Chapter 2: Earth in Space
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.
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
The Good Earth, Chapter 2: Earth in Space
How do we define the length of a year on Earth?
A. A year is related to the revolution of Earth around the sun.
B. A year is related to the rotation of Earth on its axis.
C. A year is related to the rotation of the sun on its axis.
D. A year is related to the revolution of the sun around Earth.
Earth, the Sun, and the Seasons
The Good Earth, Chapter 2: Earth in Space
• 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.?
What patterns must the Earth-Sun relationship be able to explain?
Earth, the Sun, and the Seasons
The Good Earth, Chapter 2: Earth in Space
• 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.
Why is it colder in winter and warmer in summer?
Distance from sun does not contribute to temperature differences between winter and summer
Earth, the Sun, and the Seasons
The Good Earth, Chapter 2: Earth in Space
• 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.
Why is it colder in winter and warmer in summer?
Earth, the Sun, and the Seasons
The Good Earth, Chapter 2: Earth in Space
Solar energy is diluted over a larger area when sunlight strikes at a low angle (at high latitudes).
• 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
Earth, the Sun, and the Seasons
The Good Earth, Chapter 2: Earth in Space
• 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.
Earth, the Sun, and the Seasons
The Good Earth, Chapter 2: Earth in Space
• 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.
Earth, the Sun, and the Seasons
The Good Earth, Chapter 2: Earth in Space
• 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
Why day length changes
High latitudes in the Northern Hemisphere experience nearly continuous daylight in summer (top) and almost perpetual darkness in winter.
Earth in Space Conceptest
The Good Earth, Chapter 2: Earth in Space
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
Earth in Space Conceptest
The Good Earth, Chapter 2: Earth in Space
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.
Earth in Space Conceptest
The Good Earth, Chapter 2: Earth in Space
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
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
The Good Earth, Chapter 2: Earth in Space
• 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 Unique Composition of Earth
The Good Earth, Chapter 2: Earth in Space
• 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 Unique Composition of Earth
The Good Earth, Chapter 2: Earth in Space
• 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 Unique Composition of Earth
The Good Earth, Chapter 2: Earth in Space
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 Unique Composition of Earth
The Good Earth, Chapter 2: Earth in Space
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 Unique Composition of Earth
The Good Earth, Chapter 2: Earth in Space
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
Liquid water is essential for life on Earth and is maintained by appropriate temperature range (0-100oC)
The Unique Composition of Earth
The Good Earth, Chapter 2: Earth in Space
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 Unique Composition of Earth
The Good Earth, Chapter 2: Earth in Space
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 Unique Composition of Earth
The Good Earth, Chapter 2: Earth in Space
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 Unique Composition of Earth
The Good Earth, Chapter 2: Earth in Space
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
Earth in Space Conceptest
The Good Earth, Chapter 2: Earth in Space
If Earth were farther from the sun, the planet would be, __________.
A. warmer
B. colder
Earth in Space Conceptest
The Good Earth, Chapter 2: Earth in Space
If Earth’s biosphere were younger, we would have _____ oxygen in the atmosphere.
A. less
B. more
Earth in Space Conceptest
The Good Earth, Chapter 2: Earth in Space
If Earth were smaller, its atmosphere would be ________.
A. thicker
B. thinner
The End
The Good Earth, Chapter 2: Earth in Space
Go back to the Table of Contents