called the zodiac. These are Aries,
Taurus, Gemini, Cancer, Leo, Virgo,
Libra, Scorpius, Sagittarius,
Capricornus, Aquarius, and Pisces.
A person looking at the sky from the
same point every night will see different
constellations at different times of year.
This happens because Earth moves
around the sun, while the stars do not.
Earth completes one trip around the sun
The constellation Orion is associated
with a character in Greek
mythology who was a hunter. An
illustration shows how the stars
of the constellation might be
seen as the image of a hunter.
The sky above
the Southern
Hemisphere
(half of the
world) and the
sky above the
Northern
Hemisphere
have different
sets of constellations.
188 Constellation BRITANNICA STUDENT ENCYCLOPEDIA
each year, so different stars are visible
from Earth in the course of a year.
#More to explore
Astronomy • Star
Constitution
A constitution is a set of rules that
guides how a country, state, or other
political organization works. The constitution
may tell what the branches of the
government are, what powers they have,
and how they work. It may also state the
rights of citizens. The government’s
other laws are not allowed to disagree
with its constitution. The constitution
may be amended, or changed, but this is
generally more difficult to do than passing
an ordinary law.
Development of Constitutions
The first people to think about constitutions
were the ancient Greeks. They
established a form of democracy, in
which some of the people had a say in
how the government was run. For hundreds
of years after this, however, most
people were ruled by kings or queens.
The people had no rights, and they had
no say in how they were governed. Eventually
that began to change. In 1215 the
landowners in England were upset with
their cruel and greedy ruler, King John.
They banded together and forced the
king to sign a document that guaranteed
them certain rights. The document was
called the Magna Carta. The Magna
Carta served as a model for many future
constitutions.
In the 1600s and 1700s thinkers like
John Locke in England and Jean-Jacques
Rousseau in France wrote about an idea
called the social contract. This idea
states that people give up their freedom
to do anything they want in return for
the protection of a stable government.
These thinkers influenced the writing of
the U.S. Constitution in 1787.
Modern Constitutions
The U.S. Constitution took effect in
1789. It is now the oldest written constitution.
It has set a pattern for many
other countries. Today almost all countries
have written constitutions. Many
have had several in their history.
One country without a written constitution
is Saudi Arabia. Its uses the Koran
and other Islamic teachings as its highest
law. The most famous example of a
country without a written constitution
The original signed copy of the U.S. Constitution
is one of the treasures of the National
Archives in Washington, D.C.
BRITANNICA STUDENT ENCYCLOPEDIA Constitution 189
is the United Kingdom. The British
constitution is a group of laws that have
built up throughout history. Its elements
include the Magna Carta, the English
Bill of Rights of 1689, laws passed by
Parliament, court decisions, and other
sources.
Not all constitutions come from the
people of the country. For example, the
United States set up the Japanese constitution
of 1947 after it defeated Japan in
WorldWar II. And even the finest constitution
does not guarantee that the
government will follow it. Dictators, or
rulers who take unlimited power, often
ignore their country’s constitution.
#More to explore
Amendment • Government • Magna
Carta • United States Constitution
Continent
On a globe, continents are the easiest
things to spot. A continent is a large
solid area of land. Earth has seven continents.
In order from largest to smallest,
they are Asia, Africa, North America,
South America, Antarctica, Europe, and
Australia. Sometimes people think of
Europe and Asia as a single continent
called Eurasia.
The continents have different kinds of
weather, landscapes, and populations.
For instance, Antarctica is icy and has
very little plant and animal life. Africa,
though, tends to be very warm and has a
great variety of plants and animals.
Most of the continents are also divided
into political units called countries. Parts
of Antarctica are claimed by several
countries, but there are no permanent
settlements on the continent. Australia is
the only continent that is occupied by a
single country.
In 1912 a German scientist named
AlfredWegener came up with the idea
that the continents were once all joined
together. He called this large body of
land Pangaea. He suggested that more
190 Continent BRITANNICA STUDENT ENCYCLOPEDIA
than 200 million years ago Pangaea split
apart to form the continents. The continents
then drifted apart to their current
locations.
Scientists since then have found evidence
that this idea is correct. They now
believe that the continents sit on a number
of large plates. The plates float on a
layer of melted rock. As the plates slide
over the melted rock, the continents also
move. This idea is called plate tectonics.
