chapter 2: earth in space 1.old ideas, new ideasold ideas, new ideas 2.origin of the universeorigin...

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?)


“Earthrise” taken by astronauts aboard Apollo 8, December 1968


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




• 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



• 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





• 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


Go back to the Table of Contents

Go to the next section: Origin of the Universe




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.




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



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



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



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



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



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



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)



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



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



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 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


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).


Go to the next section: Stars and Planets


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

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


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.

Stars and Planets


• 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 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


• 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


• 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



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 to the next section: Our Solar System


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

Our Solar System


Our Solar System


• 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


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 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


• 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



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 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



Which satellite view shows the sun approaching a maximum in the sunspot cycle?

A B C

Our Solar System


Our Solar System


Eight Planets

• 4 terrestrial planets (Mercury, Venus, Earth, Mars)

• Jovian planets (Jupiter, Saturn, Uranus, Neptune)

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 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


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


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


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 to the next section: Earth, the Sun, and the Seasons




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


• 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?



• 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



• 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?



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



• 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.



• 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.



• 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.



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



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.



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


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?



Go to the next section: The Unique Composition of Earth


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



• 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



• 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



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



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



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)



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)



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



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



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



If Earth were farther from the sun, the planet would be, __________.

A. warmer

B. colder



If Earth’s biosphere were younger, we would have _____ oxygen in the atmosphere.

A. less

B. more



If Earth were smaller, its atmosphere would be ________.

A. thicker

B. thinner

The End



chapter 2: earth in space 1.old ideas, new ideasold ideas, new ideas 2.origin of the universeorigin...

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