1 hrly gs ch 02 earth movement

Earth Movement

Axis of Earth

• What is Axis?

Earth's axis is the imaginary line which goes through the north and south poles and around which Earth spins.

• Think of Earth as a Giant

Spin top

Tilted Axis

• Earth axis is Tilted/Inclined at an angle of 66.5 degrees to the plane of its orbit.

Angle from Plane is 66.5 Degree

Earth’s Hemispheres

NORTHERN HEMISPHERE

SOUTHERN HEMISPHERE

EARTH MOVEMENT• Earth is in a constant motion and performs

two different movements:

• Rotation around it’sAxis.

• Revolution aroundSun

Rotation of Earth

• Causes Day & Night

• It takes approx. 24 Hours for earth to complete one rotation around it’s Axis.

• The side of Earth facing Sun has Day while the side away has Night.

• Earth rotation is anti-clockwise

• Because of which:

- Sunrises in the east

- Sun travels across

the sky

- Sunsets in the west

Effects of Tilt

• Difference in the Length

of Day & Night.

• Different

Seasons

at same

time.

Revolution of Earth

• Revolution is the movement of one object around another object.

• Earth is revolving around Sun and completes one Revolution In 365 Days and 6 Hours

• Solar year = 365 and ¼ days

• Calendar = 365 days

• Difference = ¼ days or 6 hours in a year

¼ + ¼ + ¼ + ¼ = 1 day

Leap Year

• To compensate for every extra 6 Hours, a day is added to the calendar after every four years as 29th February:

Leap Year = Last two Figure of Desired Year

4

• If answer has no remainder it is a leap year.

Leap Year or not?

• 1934

• 1956

• 1978

• 1994

Not a leap year

Leap year

Not a leap year

Not a leap year

Seasons• This revolution of Earth is constant along

with the Axial Tilt which gives us different seasons

• As Earth revolves, at different places the seasons

occur.

Summer Solstice

Autumnal

Equinox

Winter Solstice

Spring Equinox

Summer WinterSolstice Solstice

• At Equinox March 21st & September 23rd

all places have equal Day and Night.

Moon

High / Low Tides

• As Earth & Moon attract each other toward themselves like two magnets.

• The moon tries to pull at anything on the Earth to bring it closer.

• But, the Earth is able to hold onto everything except the water. Because it is constantly moving and that allows moon to attract it

• This gravitation results in high and low tides each day. And Ocean moves from high tide to low tide and vice versa.

• As the moon travels around the earth and as they, together, travel around the sun, the combined gravitational forces cause the world's oceans to rise and fall.

Eclipse

• Definition– An obscuring of the light from one celestial

body by the passage of another between it

• There are two kinds of Eclipse but both occur as a result of relative positions of earth moon and sun

- Solar Eclipse

- Lunar Eclipse

Solar Eclipse

• When Moon comes between Sun & Earth.

• An eclipse of the sun occurs when the moon revolving in its orbit around the earth comes between the sun and the earth. The moon blocks the light of the sun and a shadow of the moon is cast over the earth's surface.

Types of Solar Eclipse

• There are two types of solar eclipse:

– Total solar eclipse– Annular solar eclipse– Partial solar eclipse

• Total Solar Eclipse– When the moon completely obscures the sun

• Partial Solar Eclipse– When the Sun and Moon are not exactly in line and

the Moon only partially obscures the Sun

• Annular Solar Eclipse– When the Sun and Moon are exactly in line, but the

apparent size of the Moon is smaller than that of the Sun. Hence the Sun appears as a very bright ring surrounding the outline of the Moon

Type Date Region

Annular May 20 China, Japan, Pacific, West U.S.

Total Nov 13 North Australia, South Pacific

Solar Eclipses in 2012

Lunar Eclipse

• When Earth comes between Sun and Moon

• A lunar eclipse is when the Earth comes between the Sun and the Moon causing a shadow of Earth on the Moon.

Can be viewed with naked eye

Types of Lunar Eclipse

• There are two types of solar eclipse:

– Total lunar eclipse– Partial lunar eclipse

• Total Lunar Eclipse– When the Moon travels completely into the

Earth’s umbra

• Partial Lunar Eclipse– When only a portion of the Moon enters the

umbra

Type Date Region

Partial Jun 04 Asia, Aus., Pacific, Americas

Lunar Eclipses in 2012