The earth in the solar system
The sun moon and all those objects shining in the night sky called celestial body.
Sun is a star.
Various patterns formed by different groups of stars called constellations
Northstar indicates North direction also called pole star
Celestial bodies do not have their own heat and light, Lit by the Light of the Stars Called planets (Greek word Planetai Means Wanderers)
The solar system
Sun, eight planets, satellites And some other Celestial bodies(Asteroids and meteoroids)
Sol In Roman mythology- It's Sun God.
Geography(Greek word Geo meaning Earth and graphia meaning writing)
The sun-
Center of solar system
Made up of extremely hot gases
Provides pulling force that binds the solar system
Ultimate source of heat and light
About 150 million kilometers away from Earth.
Planets
Eight planets -
Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune
All planets move around the Sun in fixed path Called orbits
Nearest Mercury Takes 88 days to complete one round.
Venus considered Earth's twin because of its size and shape.
Till 2006 Pluto was considered a planet.
The Earth
Third nearest
Fifth largest
Flattened at the poles
Geoid shape(Earth like shape)
Conditions favorable to support life
Outer space appears blue because 2/3 surface is covered by water - Called Blue Planet
Moon
Earth has only one Natural satellite
About 3,84,000 km away
Moves around Earth in 27 days- Eastward
Neil Armstrong first man 21 July 1969
Satellite is a Celestial body moves around planet.
Human made satellite- artificial body Some Indian satellite INSAT IRS EDUSAT
Asteroids-
Numerous tiny bodies which move around the sun called asteroids
Found between the orbits of Mars and Jupiter.
Meteoroids -
Small pieces of rocks which moves around the Sun Called meteoroids
Sometimes come near the Earth and tend to drop upon it.
Solar system- Galaxy- Universe
Our solar system is a part of galaxies called milky way galaxy (akash ganga)
Chapter 2
Globe latitudes and longitudes
Imaginary line running on Globe divides it into two equal parts called equator.
Northern Hemisphere and southern hemisphere
All parallel circles from equator Called latitudes
Northern latitudes and Southern latitudes
Important parallels of latitude
Equator- 0 degree
North Pole- 90° North
South Pole- 90° south
Tropic of Cancer- 23 1/2° North
Tropic of Capricorn- 231/2° South
Arctic Circle 66 1/2° North
Antarctic circle 66 1/2° south
Heat zones of the Earth
The area that receives the maximum heat called Torrid Zone.
Areas bounded by Tropic of Cancer and Arctic Circle in northern hemisphere
And Tropic of Capricorn and Antarctic Circle in the southern hemisphere Called temperate zones
Area between Arctic Circle and North Pole in Northern Hemisphere and Antarctic Circle and South Pole in southern hemisphere called frigid zones.
What are longitudes?
Lines of references
Distances between them measured in degrees each degree is further divided into minutes minutes into seconds.
Decreases steadily pole wards until it becomes zero at poles.
All meridians are of equal length.
Prime meridian Meridian which passed through Greenwich where British Royal Observatory is located- Zero degree longitude
Prime meridian 180 degree divide the earth into equal halves
Eastern Hemisphere and western hemisphere
Longitude and time
Earth rotates from west to east
East of Greenwich will be ahead.
Earth rotates 360 degrees in 24 hours
15 degree per hour or
1 degree in four minutes
Eastern countries- add
Western countries - minus
Why do we have Standard Time?
India's longitudinal extent 68°7' E and 97°25'E
In India the longitude 82 1/2° East is treated as standard Meridian.
It is known as Indian Standard Time.
Countries have great longitudinal extend have more than one Standard Time.
Example Russia 11
Chapter 3
motions of the Earth
Two types of motions rotation and revolution
Rotation Movement of Earth on its axis
Revolution movement of Earth around the Sun in fixed path or orbit
Axis of earth makes an angle of 66 1/2° with its orbital plane.
Portion facing Sun day other half night
Circle that divides the day from night called circle of Illumination
Earth completes one revolution takes 365 1/4 days
Consider year as consisting of 365 days and ignore six hours.
Six hours saved added to make one day.
Span of four years- Add it to month of February - called leap year.
Earth moves around the Sun in an elliptical Orbit
Note- Earth is inclined in the same direction.
Year divided into summer winter spring and Autumn seasons.
Seasons change is due to change in the position of the Earth around the Sun.
1) Northern Hemisphere tilted towards the Sun
Rays directly falls on the Tropic of Cancer
Receive more heat
Near poles receive less Heat
North Pole inclined towards the Sun
Arctic Circle experience continuous daylight for about 6 month.
It is summer in the region north of the equator.
Longest day on 21st June - Summer solstice
In southern hemisphere All these conditions are reversed
Winter season Nights are shorter.
2) Southern hemisphere tilted towards sun
Tropic of Capricorn receives direct rays
Summer in the southern hemisphere with longer days and shorter nights
Reverse happens in northern hemisphere
winter solstice- 22nd December
Christmas is celebrated in Australia in summer season.
21st March and September 23rd
Direct rays of sun fall on equator
Neither of poles tilted towards the Sun
Whole earth experiences equal days and equal Nights- This is called Equinox.
23rd September Autumn season in Northern Hemisphere and spring season in southern hemisphere.
21st march spring in Northern Hemisphere and autumn in southern hemisphere
Days and nights and changes in Seasons because of rotation and revolution of Earth's respectively.
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