World Geography Today
Earth in Space
Preview
Section 1: The Solar System
Section 2: Earth-Sun Relationships
Section 3: The Earth System
Chapter Wrap-Up
Chapter 2
World Geography Today
Chapter 2
Section 1: The Solar System
Read to Discover
• What is Earth’s position in the solar
system?
• How do rotation and revolution affect
Earth?
World Geography Today
Chapter 2
Section 1: The Solar System
Mercury
Jupiter
Earth
Uranus
Sun
Venus
Mars
Saturn
Neptune
World Geography Today
Chapter 2
Section 1: The Solar System
Earth’s Position in the Solar System
• One of eight planets
• Third planet from the Sun
• Fifth-largest planet
• In elliptical orbit around the Sun
World Geography Today
Chapter 2
Section 1: The Solar System
Rotation and Revolution
• Rotation and revolution affect the amount of
solar energy Earth receives at different
locations.
• Rotation of Earth on its axis produces day and
night.
• Revolution around the Sun takes one year.
• Revolution and the tilt of Earth on its axis
determine seasons.
World Geography Today
Chapter 2
Section 2: Earth-Sun Relationships
Read to Discover
• How does the angle of the Sun’s rays
affect the amount of solar energy received
at different locations on Earth?
• What are solstices and equinoxes?
World Geography Today
Chapter 2
Section 2: Earth-Sun Relationships
Angle of the Sun’s Rays
• Direct vertical rays of sunlight concentrate solar
energy in a smaller area, making more heat.
• Angled rays spread solar energy out, making
less heat.
• Earth’s tilt makes direct rays most common near
the equator and less common at high latitudes.
• Change in the Earth’s tilt creates seasons.
World Geography Today
Chapter 2
1
Section 2: Earth-Sun Relationships
Solstice
Equinox
Time twice a year when
Earth’s poles point at their
greatest angle toward or
away from the Sun
Time twice a year when
Earth’s poles are both at
a 90° angle from the Sun
World Geography Today
Chapter 2
Section 2: Earth-Sun Relationships
Solstices and Equinoxes
• Solstices—About December 21 and June 21
 Earth’s poles tilted toward or away from the Sun
 Longest or shortest days of the year, depending on
hemisphere
• Equinoxes—About March 21 and September 22
 Earth’s poles not tilted toward or away from the Sun
 Equal amount of sunlight in both hemispheres
World Geography Today
Chapter 2
Section 3: The Earth System
Read to Discover
• What are Earth’s four spheres?
• How is Earth’s environment unique in the
solar system?
World Geography Today
Chapter 2
Section 3: The Earth System
Earth’s Four Spheres
• Atmosphere—Envelope of gases surrounding Earth;
least dense and outermost sphere
• Lithosphere—Solid crust of the planet; forms
continents, islands, and ocean floor
• Hydrosphere—Earth’s water; 70 percent of Earth’s
surface, including water in liquid, solid, and gaseous
forms
• Biosphere—All life-forms; overlaps other three spheres
World Geography Today
Chapter 2
Section 3: The Earth System
Earth’s Unique Environment
• No other planet in the solar system has
such a complex environment.
• Earth’s environment is the key to human
survival and quality of life.