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

Astronomy
A BEGINNER’S GUIDE
TO THE UNIVERSE
EIGHTH EDITION

CHAPTER 5

Earth and Its Moon
Lecture Presentation

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Chapter 5 Earth and Its Moon

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Units of Chapter 5

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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
Magnetospheres
History of the Earth–Moon System
Summary of Chapter 5

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5.1 Earth and the Moon in Bulk

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5.2 The Tides

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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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5.2 The Tides

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The Sun has less effect, but it does
modify the lunar tides.

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5.2 The Tides

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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

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

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5.3 Atmospheres

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The blue curve shows the
temperature at each altitude.

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

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5.3 Atmospheres

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Convection depends on warming of the ground by the Sun.

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5.3 Atmospheres

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Ionosphere is ionized by solar
radiation and is good conductor.

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

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Ozone layer absorbs ultraviolet
radiation.

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Discovery 5.1: Earth’s Growing Ozone Hole

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

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5.3 Atmospheres

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Surface heating:

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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

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This is known as the greenhouse effect.

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Discovery 5.2: The Greenhouse Effect and Global Warming

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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

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Seismic waves:

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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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5.4 Internal Structure of Earth and the Moon

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The pressure wave
is a longitudinal
wave, whereas the
shear wave is a
transverse wave.
A shear wave
cannot propagate
within a liquid.

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5.4 Internal Structure of Earth and the Moon

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

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5.4 Internal Structure of Earth and the Moon

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Currently accepted model

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5.4 Internal Structure of Earth and the Moon

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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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5.5 Surface Activity on Earth

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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

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Plates moving away from each other create rifts.

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5.5 Surface Activity on Earth

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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

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

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5.6 The Surface of the Moon

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

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