The Earth and the Solar System - KCSE GEOGRAPHY NOTES, AUDIOVISUALS, Q & A, OTHER RESOURCES

THE EARTH AND THE SOLAR SYSTEM - KCSE GEOGRAPHY NOTES, AUDIOVISUALS, Q & A, OTHER RESOURCES

• OBJECTIVES
• NOTES
• QUESTIONS & AUDIOVISUALS

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The Earth and the Solar System TOPIC OBJECTIVES

By the end of the topic, the learner should be able to:

1. define the solar system
2. explain the origin of the earth
3. explain the effects of rotation and revolution of the earth
4. Describe the structure of the earth.

​The Earth and the Solar System COURSE OUTLINE

1. Definition and composition of the solar system
2. Origin, shape, size and position of the earth in the solar system
3. Rotation and revolution of the earth and their effects
4. Structure of the earth
   1. The atmosphere
   2. The hydrosphere
   3. The lithosphere/crust
   4. The asthenosphere/mantle
   5. The barysphere/centrosphere (outer and inner core)

​The Earth and the Solar System

Solar system is the group of heavenly bodies comprising the sun and the nine planets.
The origin of the Solar System
Theories
A theory is a set of reasoned ideas intended to explain facts or events
1. Passing Star Theory
A star with a greater gravitational pull passed near the sun, it attracted large quantities of gaseous materials from the sun, and the materials split, cooled and condensed to form planets, the planets were set in orbit by the passing star
Weaknesses

1. Doesn’t explain the origin of the sun and star.
2. Minimal chance of a star approaching another
3. High temperature, gaseous material drawn from the sun would disperse than condense
4. The gases should have followed the star since it had a greater gravitational pull

2. Nebula Cloud Theory
There was a slowly rotating cloud of dust and gas called Nebula, As the nebula rotated it flattened into a disc with high concentration of materials at the centre, The high concentration of material at the centre condensed to form the sun. Gases such as ammonia and methane condense to form larger planets that is Jupiter, Saturn, uranius and Neptune. Closer to the centre of Nebula, particles of dust and gas bumping into each other formed the inner smaller planets.
Evidence
Rotation and revolution of planets in anticlockwise direction
Weakness

1. The origin of nebular is not explained.
2. Cause of rotation is not mentioned.
3. All planet should rotate in the direction of the rotation of the nebula that is west to east but Venus and uranius rotates from west to east.

3. Collision Theory
Star with greater gravitational pull passed near the sun. It attracted large quantities of gaseous materials. The materials split into portions. Large portions collided with smaller ones and swept them to form planets. The weaknesses are the same as the passing star’s Theory.
4. Supernova/explosion Theory
There was a violent explosion of a star. A cloud of dust (nebular) remained from the star. There was fast movement of the cloud due to the force of explosion. Rotation speed increased due to gravitational attraction. The cloud flattened into a disc. The matter began to accumulate towards the centre to form a proto-sun which later began to shine. The rest of the cloud collapsed to form planets.
Weaknesses

1. Doesn’t explain the origin of the star
2. Doesn’t explain the cause of explosion

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Composition of the Solar System

1.   The Sun
It’s the centre of the universe.
Characteristics

• It’s a star - A star is a heavenly possessing its own light which it transmits.
• Nebula/galaxy is a cluster of stars.
• The earth is in a galaxy called The Milky Way.
• It’s made of very hot gases mainly hydrogen (70%) and helium (30%).
• Has a diameter of 1,392,000km.
• Surrounded by a layer of gas which has boiled from its surface which is called corona.
• Rotates on its own axis in anticlockwise direction.
• Has gravitational pull which holds all the planets in orbit around it.
• An orbit is a path which a planet or a satellite follows around a star or a planet.
• Temperature at its centre is 15m◦c and at the surface is 5500◦c.
• Radiates solar energy which is very important for all forms of life on the earth.

2.   The Planets
Planets are large spherical celestial/heavenly bodies in space.
There are 9 planets in our solar system.
Characteristics

• Spherical in shape
• Don’t have their own light but reflect it from the sun.
• Revolve around the sun in anticlockwise direction.
• Have their own force of gravity
• Only one is known to support life.
• The following are the planets arranged in order from the one nearest to the sun.

a) Mercury

• Nearest from the sun
• Its 58m km from the sun
• Has no satellites
• Takes approximately 88 earth days to revolve around the sun

b) Venus

• 2nd planet from the sun
• It’s 108m km from the sun
• One of the brightest planets
• Can be seen clearly with naked eyes
• Takes approximately 225 earth days to revolve around the sun
• Slightly smaller than the earth
• Has no satellites
• Together with the earth they are called twin planets due to having many similarities

c) Earth

• The 3rd planet from the sun
• The earth and the heavenly bodies make the universe
• The only planet that supports life
• The home of man
• Approximately 149m km from the sun
• Takes 365 ¼ days to revolve around the sun
• Has one satellite, the moon

"​I like science fiction and physics, things like that. Planets being sucked into black holes, and the various vortexes that create possibility, and what happens on the other side of the black hole. To me it's the microcosmic study of the macrocosmic universe in man, and that's why I'm attracted to it." ~Wesley Snipes

a) Mars

• Also called The Red Planet because when it’s observed through a telescope it appears reddish.
• The 4th from the sun
• Slightly smaller than the earth
• Approximately 228m km from the sun
• Takes 687 earth days to revolve around the sun
• Between Mass and Jupiter there are small celestial bodies called planetoids.
• Has no satellite.

b) Jupiter

• 5th planet from the sun
• Approximately 778m km from the sun
• Largest in the universe
• Rotates on its own axis at very fast speed
• Has flattened poles due to its fast speed of rotation
• Has very thick layers of ice on its surface takes 12 earth years to revolve around the sun
• Has 16 satellites

c) Saturn

• 6th planet from the sun
• Second largest planet
• Approximately 1427m km from the sun
• Takes 29 ½ earth years to revolve around the sun
• Has a ring around it
• Has 18 satellites

d) Uranus

• 7th planet from the sun
• About 4 times bigger than the earth
• Approximately 2870m km from the sun
• Also rotates very fast
• Also has flattened poles due to fast speed of rotation
• It appears greenish foe being surrounded by methane gas
• Has 8 satellites
• Takes 84 earth years to revolve around the sun

 e) Neptune

• One of the farthest from the sun
• 8th planet from the sun
• Approximately 4497m km from the sun
• Has 8 satellites
• Takes 165 earth years to revolve around the sun
• Very similar in size, colour and character with Uranus

f) Pluto

• 9th planet from the earth
• Farthest from the sun
• The smallest
• 1/6 the size of the earth
• Approximately 5900m km from
• Takes 248 earth years to revolve
• Has one satellite
• Very little is known about it

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