DAY
NIGHT
!
1
14
Important
Sunrise (in the east) and
sunset (in the west) allows
us to orient ourselves; to
identify east and to find
the
cardinal points
: north,
south, east and west.
In the Middle Ages, the
compass was invented in
China. A compass indicates
north, and its opposite,
south.
The magnetised needles of the
compass point to magnetic north
2
tilted:
inclined
3
orbit:
the trajectory or path an object
travels around another object in space
2. THE EARTH’S MOVEMENTS
Just like the other planets, the Earth moves in two different ways:
rotation
and
revolution
.
2.1. Rotation
Rotation is the movement of the Earth as it turns on its own
axis
, once every 24
hours (one day).
The Earth rotates on an imaginary line called the
Earth’s axis
. The axis is a little tilted
2
and runs through the centre of the planet between the North and South Poles.
DAYS AND NIGHTS
Revolution is the movement of the Earth around the Sun, creating an elongated
or
elliptical orbit
3
.
In the diagram, you can see that the Sun’s rays only reach part of the Earth’s surface.
As the Earth turns on its axis during the course of the day, different parts of the planet
are gradually illuminated. This is what causes
days
and
nights
.
2.2. Revolution
It takes the Earth
365 days
and
6 hours
to complete one revolution. A calendar
year is 365 days, so the 6 hours accumulate. Every 4 years we add one day to the
month of February, which goes from 28 days to 29. A year with 366 days is called
a
leap year
.
Because the Earth’s axis is tilted, the Sun’s rays hit the Earth differently depending
on the time of year, causing variations in temperature and the length of the day.
So, as the Earth revolves around the Sun, we get different seasons: spring, summer,
autumn and winter. The seasons in the Northern and Southern Hemispheres are
opposite: when it is summer in the Northern Hemisphere, it is winter in the Southern
Hemisphere.
angle of Earth’s tilt
(23.5°)
axis of rotation
South Pole
North Pole
SUN
