Rotation and revolution

Rotation of the Earth
Ana Borrajo Castanedo. Social Sciences' teacher. IES El Pinar. Alcorcón.

ROTATION
• The Earth spins (or rotates) on an
imaginary axis that runs from the
North Pole to the South Pole.
• The Earth completes a single
rotation every 24 hours. This
rotation explains the sequence of
days and nights.
• The rotation of the Earth also
stops the planet from becoming
too hot or too cold and allows life
on Earth to exist.
Ana Borrajo Castanedo. Social Sciences'
teacher. IES El Pinar. Alcorcón.

A day=24 hours
• At what time of the year are the days longer?
• In summer, the first day of summer, the 21st
of June (Northern hemisphere)
• How long is that day?
• It’s 16hours,7 minutes long
• Work out how long is that night.

• The day is 16h 7’ long on the 21st of June,
consequently the night must be 7 h 53’ long.
• A day= 23 h + 60’
23h 60’ (The whole day: light and night)
16h 07’ (The day)
____________
7h 53’ (The night)
That means 16 h 07’+7h 53’= 23 h 60’= 24 h (a
day)

• Now, work out how long is the night on
the first day of winter, and how long is
the night on the first day of spring and
automn (fall)

• Winter’s night is…. Long.
• The day is 8h 10’
• The whole day is 23h60’-8h10’= 15h 50’ is
the night long.
• 15h50’+8h10’= 23h 60’, that means 24h,
a day.

Spring and Automn nights.
• The 21st of March and the 23rd the day is 12 h
long, consequently the night is 12 h long.
• 24h-12h= 12 h
• 12h+12h= 24h
• Both day and night are exactly the same.

TIME ZONES
Because of the Earth’s rotation when it is
night-time in some places, it is day-time
in others.
In order to establish an official time in
every country, the Earth’s sphere
(360º) is divided into 24 equal
sections of 15º (24x15º=360º)These
sections are called time zones and
each one equals one hour.
The time we use as a reference is called
Greenwich Mean Time (GMT)

As we move east
from the Greenwich
meridian, cloks move
forward the same
number of hours as time
zones travelled.
I As we move west
from the Greenwich
meridian, cloks go back
the same number of
hours as time zones
travelled.

What time is it?
• It is ------- in------, what time is it in--------?
• It is------- in----------.

Questions
• It is 12:00 AM in London, what time is it in
Madrid?
• It is 2:00 PM in Madrid, what time is it in
India?
• It is 5:00 PM in Madrid, what time is it in
Brazil?

Answers
• It is 1:00 PM in Madrid.
• It is 6:30 PM in India
• It is 1:00 PM in Brazil

• The movement of the revolution
of the Earth: The Earth´s orbit

The consequences of the Earth´s
orbit:
The seasons of the year due to the different
exposure to the Sun´s rays.
Different duration of nights and days
The different climate zones.

The seasons
• The tilting of the Earth´s axis
causes variations on the duration
of days and nights and the
different seasons.
• There are some places on the
Earth where the Sun is directly
overhead, at this time the midday
sun forms a 90º angle with the
Eart surface.
• The overhead Sun points the
Equator twice a year (the
equinoxes) and the overhead Sun
points the Tropics once a year
(the solstices).

Spring equinox (On the 20 or 21 of March)
• The overhead Sun is over the equator.
• The Equator receives the largest amount of
solar radiation.
• At this time the Northern Hemisphere is in
the Spring equinox, while the Southern
Hemisphere is in the Autumn equinox.
• The angle of the Sun decreases towards
the Poles.
• On this day the two hemispheres receive a
similar amount of solar radiation and the
lenght of day and night it is the same at all
places on the Earth.
• After this day it is Spring in the Northern
Hemisphere where the day is longer than
the night. In the Southern hemisphere it
becomes Autumn where the day is shorter
than the night.

Summer Solstice (On the 21 or 22 of June)
• The overhead Sun is over the Tropic of
Cancer, it receives the largest amount of
solar radiation. At this time the Northern
Hemisphere is in the Summer Solstice ,
while the Southern Hemisphere is in the
winter solstice.
• The angle of the sun decreases towards
the Poles.
• On this day the length of daytime of the
Northern Hemisphere is the largest in the
year, while that of the Southern
Hemisphere is the shortest in the year.
• Besides there are 24 hours of daylight at
the Artic Circle and 24 hours of darkness at
the Antartic Circle.

Autumn equinox (On the 22 or 23 of September)
• The overhead Sun is over the equator.
• The Equator receives the largest amount of
solar radiation.
• At this time the Northern Hemisphere is in the
Autumn equinox, while the Southern
Hemisphere is in the Spring equinox.
• The angle of the Sun decreases towards the
Poles.
• On this day the two hemispheres receive a
similar amount of solar radiation and the
lenght of day and night it is the same at all
places on the Earth.
• After this day it is Autumn in the Northern
Hemisphere where the day is shorter than the
night. In the Southern hemisphere it becomes
Spring where the day is longer than the night.

Winter solstice (On the 21 or 22 of December)
• The overhead Sun is over the Tropic of
Capricorn, it receives the largest
amount of solar radiation. At this time
the Northern Hemisphere is in the
Winter Solstice , while the Southern
Hemisphere is in the Summer solstice.
• The angle of the sun decreases towards
the Poles.
• On this day the length of daytime of
the Northern Hemisphere is the
shortest in the year, while that of the
Southern Hemisphere is the largest in
the year.
• Besides there are 24 hours of darkness
at the Artic Circle and 24 hours of
daylight at the Antartic Circle.

REMEMBER…
ROTATION
The Earth rotates
constantly on its axis
in a west-to-east
direction.
The main consequence
of it is the sucession
of days and nights.

REMEMBER…
REVOLUTION
It is the west-to-east orbit
of the Earth around the
Sun.
It takes 365 days and 6
hours. Every four years
we have a leap year
(366 days).
It causes the seasons:
spring, summer,
autumn (fall) and
winter. Ana Borrajo Castanedo. Social Sciences'

SOLSTICE
• Time of year when the Sun is directly over
one of the tropics.
• When the Sun’s rays strike vertically in one
hemisphere, it is summer (high temperatures
and many hours of light), at the same time it
is winter in the other hemisphere (low
temperatures and few hours of light).
• The greatest difference between day and
night occurs on the two solstices.

EQUINOX
• There are two (spring and automn).
• The Sun’s rays strike vertically over the
Equator, and day and night are the same
lenght

REMEMBER…
TIME ZONES

Meridian 0º or Greenwich Meridian is our reference point:
We put the clock forward one hour for every time zone we move towards
the east.
We put the clock back one hour for every time zone we move towards west.

Rotation and revolution

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