Astronomy a beginners guide to the universe 8th CHaisson mcmillan chapter 05

TO THE UNIVERSEEIGHTH EDITION CHAPTER 5 Earth and Its Moon Lecture Presentation © 2017 Pearson Education, Inc... Chapter 5 Earth and Its Moon© 2017 Pearson Education, Inc... • Earth and

TO THE UNIVERSE

EIGHTH EDITION

CHAPTER 5 Earth and Its Moon Lecture Presentation

© 2017 Pearson Education, Inc.

Chapter 5 Earth and Its Moon

© 2017 Pearson Education, Inc.

• Earth and the Moon in Bulk

• The Tides

• Atmospheres

• Internal Structure of Earth and the Moon

• Surface Activity on Earth

• The Surface of the Moon

5.1 Earth and the Moon in Bulk

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• Tides are due to gravitational force

on Earth from the Moon; the force on near side of Earth

is greater than force on far side Water can flow freely in response

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• Tides tend to exert a “drag” force on Earth, slowing its rotation.

• This will continue until Earth rotates synchronously with the Moon so that the same side of Earth always points toward the Moon

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5.2 The Tides

• This has already happened with the Moon, whose near side is always toward Earth

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• The blue curve shows the

temperature at each altitude

• Troposphere is where convection takes place It is responsible for weather

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5.3 Atmospheres

• Convection depends on warming of the ground by the Sun

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• Ionosphere is ionized by solar radiation and is good conductor.

• It reflects radio waves in the AM range, but it is transparent to FM and TV

• Ozone layer absorbs ultraviolet radiation

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Discovery 5.1: Earth’s Growing Ozone Hole

• Chlorofluorocarbons (CFCs) have been damaging the ozone layer, resulting in an ozone hole

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• Surface heating:

– Sunlight that is not reflected is absorbed by Earth’s surface, warming it.– Surface reradiates as infrared thermal radiation.

– Atmosphere absorbs some infrared, causing further heating.

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5.3 Atmospheres

• This is known as the greenhouse effect

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• There is extremely strong evidence that Earth is getting warmer The cause of this warming is a subject of intense debate; many scientists believe it is related to the corresponding increase in atmospheric carbon dioxide.

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5.4 Internal Structure of Earth and the Moon

– Earthquakes produce both pressure and shear waves

– Pressure waves will travel through both liquids and solids.

– Shear waves will not travel through liquids, as liquids do not resist shear forces.– Wave speed depends on density of material.

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• The pressure wave

5.4 Internal Structure of Earth and the Moon

• We can use the pattern of waves measured by seismometers during earthquakes to deduce the interior structure of Earth

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• Currently accepted model

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5.4 Internal Structure of Earth and the Moon

• Mantle is much less dense than core

• Mantle is rocky; core is metallic, consisting of iron and nickel

• Outer core is liquid; inner core is solid, due to pressure

• Volcanic lava comes from mantle, allowing analysis of the mantle’s composition

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• Continental drift: Earth’s entire surface is covered with crustal plates, which can move independently At plate boundaries, earthquakes and volcanoes

can occur

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5.5 Surface Activity on Earth

• Plates moving away from each other create rifts

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• If we follow the continental drift backward, the continents merge into one, called Pangaea.

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5.6 The Surface of the Moon

• The Moon has large dark flat areas, called maria (early observers thought they were oceans), due to lava flow

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• The far side of the Moon is heavily cratered but contains few maria.

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5.6 The Surface of the Moon

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• Craters are typically about 10 times as wide as the meteoroid creating them, and twice as deep.

• Rock is pulverized to a much greater depth

• Most lunar craters date to at least 3.9 billion years ago; there has been much less

bombardment since then

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5.6 The Surface of the Moon

• Very large and very small lunar craters

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• Regolith: Thick layer

this slowly erodes

and softens features

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• These charged particles are trapped in areas called the Van Allen belts, where they spiral around the magnetic field lines.

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• Current theory of the Moon’s origin:

Glancing impact of Mars-sized body

on the still-liquid Earth caused enough material, mostly from the mantle, to be ejected to form the Moon Computer

model

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5.8 History of the Earth–Moon System

• Four billion years ago, the Moon had many craters but no maria By 3 billion years ago, the maria had formed Now, they also are covered with craters

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• Earth’s structure, from inside out: core, mantle, crust, hydrosphere, atmosphere, magnetosphere

• Tides are caused by gravitational effects of the Moon and Sun

• Atmosphere is mostly nitrogen and oxygen; it thins rapidly with increasing altitude

• Greenhouse effect keeps Earth warmer than it would be otherwise

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Summary of Chapter 5, cont.

• We can study Earth’s interior by studying seismic waves

• Crust is made of plates that move independently

• Movement at plate boundaries can cause earthquakes, volcanic activity, mountain ranges, and rifts

• New crust formed at rifts shows evidence of magnetic field reversals

• Earth’s magnetic field traps charged particles from solar wind

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• Main surface features on Moon are maria and highlands.

• The moon is heavily cratered

• No atmosphere and large day–night temperature variation

• Tidal interactions are responsible for synchronicity of Moon’s orbit

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Summary of Chapter 5, cont.

• The Moon’s surface has both rocky and dusty material

• There is evidence for ancient volcanic activity

• The Moon apparently formed as a result of a large object colliding with Earth

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