12.1 Earth in Space

1
Table of Contents

• 12.1 Earth in Space
• 12.2 Gravity and Motion
• 12.3 Phases, Eclipses, and Tides
• 12.4 Earths Moon

Chapter Preview 12.1 Earth in Space 12.2
Gravity and Motion 12.3 Phases, Eclipses, and
Tides 12.4 Earths Moon


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Chapter Preview Questions

• What is the source of most of Earths heat and
  natural light?
• a. the moon
• b. Earth itself
• c. the sun
• d. stars other than the sun

3
Chapter Preview Questions

• What is the source of most of Earths heat and
  natural light?
• a. the moon
• b. Earth itself
• c. the sun
• d. stars other than the sun

4
Chapter Preview Questions

• 2. What force keeps Earth in motion around the
  sun?
• a. friction between Earth and the planets
• b. gravity between Earth and the moon
• c. friction between Earth and the sun
• d. gravity between Earth and the sun

5
Chapter Preview Questions

• 2. What force keeps Earth in motion around the
  sun?
• a. friction between Earth and the planets
• b. gravity between Earth and the moon
• c. friction between Earth and the sun
• d. gravity between Earth and the sun

6
Chapter Preview Questions

• 3. How many natural satellites does Earth have?
• a. one
• b. two
• c. six
• d. dozens

7
Chapter Preview Questions

• 3. How many natural satellites does Earth have?
• a. one
• b. two
• c. six
• d. dozens

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Chapter Preview Questions

• 4. What causes day and night?
• a. the tilt of Earths axis
• b. the sun moving behind the moon
• c. Earths movement around the sun
• d. Earths rotation on its axis

9
Chapter Preview Questions

• 4. What causes day and night?
• a. the tilt of Earths axis
• b. the sun moving behind the moon
• c. Earths movement around the sun
• d. Earths rotation on its axis

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What events are caused by the motion of Earth and
the moon?

• Imagine that you are looking up at a full moon in
  the sky. Why is the moon so bright? Does the moon
  produce its own light, like a flashlight, or does
  its light come from somewhere else? Explain your
  reasoning.

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Latin Word Origins
equal
equinox
12
Latin Word Origins
large mixing bowl
crater
13
Latin Word Origins
weight, heaviness
gravity, gravitation
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Latin Word Origins
moon
lunar eclipse, lunar highlands
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Latin Word Origins
sea
mare, maria
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Latin Word Origins
sun
solar eclipse
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Latin Word Origins
shade, shadow
umbra, penumbra
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• Apply It!
• Review the Latin words and meanings in the chart.
  Look at the
• meaning of crater. Predict what a crater might be
  if it were seen
• on the surface of the moon. Revise your
  definition as needed.
• Sample I have seen photographs of the moon and
  have seen large
• holes in the surface that are probably craters
  and have a bowl shape.

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End of Chapter Preview
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Section 1Earth in Space

• How does Earth move in space?
• What causes the cycle of seasons on Earth?

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How Earth Moves

• Earth moves through space in two major ways
  rotation and revolution.

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How Earth Moves

• Earth moves through space in two major ways
  rotation and revolution.

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Sunlight Striking Earths Surface

• Near the equator, sunlight strikes Earths
  surface more directly and is less spread out than
  near the poles.

24
Seasons on Earth

• Earth has seasons because its axis is tilted as
  it revolvesaround the sun.

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Seasons on Earth

• The height of the sun above the horizon varies
  with the season.

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Seasons Activity

• Click the Active Art button to open a browser
  window and access Active Art about the seasons.

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End of SectionEarth in Space
28
Section 2Gravity and Motion

• What determines the strength of the force of
  gravity between two objects?
• What two factors combine to keep the moon and
  Earth in orbit?

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Gravity, Mass, and Distance

• The strength of the force of gravity between two
  objects depends on two factors the masses of the
  objects and the distance between them.

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Gravity Versus Distance

• As a rocket leaves a planets surface, the force
  of gravity between the rocket and the planet
  changes. Use the graph to answer the following
  questions.

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Gravity Versus Distance

• Reading Graphs
• What is the force of gravity on the rocket at the
  planets surface?

• Four million newtons

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Gravity Versus Distance

• Reading Graphs
• What is the force of gravity on the rocket at a
  distance of two units (twice the planets radius
  from its center)?

• One million newtons

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Gravity Versus Distance

• Making Generalizations
• According to the graph, is the relationship
  between gravity and distance linear or nonlinear?
  Explain.

• Nonlinear. The graph is a curve.

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Gravity Versus Distance

• Drawing Conclusions
• In general, how does the force of gravity pulling
  on the rocket change as the distance between it
  and the planet increases?

• It decreases.

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Gravity Versus Distance

• Predicting
• What would the force of gravity on the rocket be
  at a distance of five units?

• 0.16 million newtons, or 160,000 newtons

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Gravity and Inertia

• Newton concluded that two factorsinertia and
  gravitycombine to keep Earth in orbit around the
  sun and the moon in orbit around Earth.

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Links on Gravity

• Click the SciLinks button for links on gravity.

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End of SectionGravity and Motion
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Section 3Phases, Eclipses,and Tides

• What causes the phases of the moon?
• What are solar and lunar eclipses?
• What causes the tides?

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Motions of the Moon

• The changing relative positions of the moon,
  Earth, and sun cause the phases of the moon,
  eclipses, and tides.

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Phases of the Moon

• The phase of the moon you see depends on how much
  of the sunlit side of the moon faces Earth.

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The Moons Orbit

• The moons orbit is tilted about 5 degrees
  relative to Earths orbit around the sun.

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Solar Eclipse

• A solar eclipse occurs when the moon passes
  directly between Earth and the sun, blocking
  sunlight from Earth.

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Lunar Eclipse

• During a lunar eclipse, Earth blocks sunlight
  fromreaching the moons surface.

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Moon Phases and Eclipses Activity

• Click the Active Art button to open a browser
  window and access Active Art about moon phases
  and eclipses.

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Tides

• Tides occur mainly because of differences in the
  force of gravity between the moon and different
  parts of Earth.

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Spring and Neap Tides

• When Earth, the sun, and the moon are in a
  straight line, a spring tide occurs. When the
  moon is at a right angle to the sun, a neap tide
  occurs.

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End of SectionPhases, Eclipses,and Tides
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Section 4Earths Moon

• What causes the phases of the moon?
• What are solar and lunar eclipses?
• What causes the tides?

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The Moons Surface

• Features on the moons surface include maria,
  craters, and highlands.

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The Moons Size

• The moon is 3,476 km in diameter, a little less
  than the distance across the contiguous Untied
  States.

52
The Origin of the Moon

• Scientists theorize that a planet-sized object
  collided with earth to form the moon.

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Links on Earths Moon

• Click the SciLinks button for links on Earths
  moon.

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End of SectionEarths Moon
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QuickTake Quiz

• Click to start quiz.