eyes that allow them to see in all directions
at once.
Most grasshoppers eat only plants. Some
kinds, such as locusts, move in swarms
and destroy farmers’ crops.
Usually only male grasshoppers chirp or
sing. They make their song by rubbing
their wings together or by rubbing their
hind legs against their front wings. The
song is the male’s way of calling females.
#More to explore
Cricket • Insect • Locust
Grassland
Grasses grow in wide, open spaces
around the world. Large areas covered
with grasses are called grasslands. Tropical
grasslands grow close to the equator.
Temperate grasslands grow in regions
farther from the equator.
Features
Many different kinds of grass grow on
the world’s grasslands. Grasslands may
have no trees or only a scattered few.
Usually the land is flat. Sometimes it has
rolling hills.
Grasslands are good for grazing livestock.
Grasslands also have good soil for
farming. Wheat, oats, corn, and other
crops have replaced many wild grasses.
Grasshoppers use their long hind legs for
jumping.
142 Grasshopper BRITANNICA STUDENT ENCYCLOPEDIA
Types of Grasslands
Tropical grasslands are often called
savannas. Africa, India, Southeast Asia,
Brazil, and Australia all have areas of
tropical grassland. The climate of savannas
is extreme. Temperatures are high,
and there are wet and dry seasons.
The climate in temperate grasslands is
less extreme. The prairies of North
America are temperate grasslands. So are
the pampas of Argentina, the veld of
southern Africa, and the steppes of central
Asia. The huge rangelands in Australia’s
southeastern corner are also
temperate grasslands.
Life in the Grasslands
The large animals that live in tropical
grasslands include zebras, gazelles, lions,
and kangaroos. Horses, antelope, hawks,
and prairie dogs are a few of the animals
that live in temperate grasslands.
In the past wandering peoples lived on
many of the world’s grasslands. For
example, the Mongols lived on the
steppes of central Asia. The Plains Indians
lived on the prairies of North
America.
Changing Grasslands
In the 1800s farmers moved onto the
grasslands of southern Africa, Australia,
South America, and North America.
They began changing the grasslands into
farmland. In North America the prairies
once extended down the middle of the
continent, from Canada to Texas. Now
most of this land is farmland. The Australian
grasslands and the South American
pampas have also become mostly
farming and grazing lands. Grasslands
have also disappeared as cities and towns
have expanded.
But much grassland still exists. The veld
still carpets large parts of southern
Africa. Steppes extend 5,000 miles
(8,000 kilometers) from eastern Europe
to eastern China. They are mostly
unspoiled wilderness, and few people
live there.
#More to explore
Grass
The grasslands in central North America
are called prairies.
The sun sets on a savanna in the African
country of Kenya.
BRITANNICA STUDENT ENCYCLOPEDIA Grassland 143
Gravity
All objects attract other objects because
of a force called gravity. Gravity is a
pulling force that works across space.
That is, objects do not have to touch
each other for the force of gravity to
affect them. For example, the sun, which
is millions of miles from Earth, pulls on
Earth and the other planets and objects
in the solar system.
Gravity on Earth
On Earth gravity pulls objects toward the
center of Earth. This is what makes
objects fall. It is also what gives an object
weight.Weight is a measurement of the
force of gravity between an object and
the surface it stands on. If a person stands
on a scale, gravity pulls the person against
the scale. The scale shows the strength of
this force, or the person’s weight.
Gravity in Space
In the solar system the planets all orbit,
or travel around, the sun in a constant
path. They would move in a straight
line, but the force of gravity pulls them
toward the sun. At the same time, the
speed of the planets in their orbits keeps
them from falling into the sun.
Spacecraft and satellites travel around
Earth in a similar way. Earth’s gravity
keeps them in orbit, and their speed
keeps them from falling back to Earth.
When astronauts are inside a spacecraft
in orbit, they experience weightlessness.
The astronauts float freely because they
are traveling around Earth at the same
speed as the spacecraft. But even though
Earth’s gravity does not pull them
toward the floor—as it does on Earth—
they have not escaped it. Earth’s gravity
Gravity keeps the Moon moving in an orbit
around Earth.
Gravity is what gives weight to objects on
Earth. Scales measure the pull of gravity as
weight.
144 Gravity BRITANNICA STUDENT ENCYCLOPEDIA
keeps the astronauts in orbit, just as it
does the spacecraft.
Newton’s Law of Gravity
Isaac Newton, an English scientist, discovered
a law, or truth, about gravity in
the late 1600s. Newton said that the
force of gravity between objects depends
on their mass, or the amount of material
they contain. The greater the mass of an
object, the greater is its force of gravity.
For example, the sun, which has a very
large mass, has a greater force of gravity
than Earth, which has a much smaller
