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.


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.

Ana Borrajo Castanedo. Social Sciences'

teacher. IES El Pinar. Alcorcón.

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'

teacher. IES El Pinar. Alcorcón.

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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