THE EARTH AND THE UNIVERSE

THE EARTH AND THE UNIVERSE

 Ø The Solar System

• The Sun

A star in the center of the Solar System

• Planets

Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto

• Natural satellites

Objects around the planets, the Moon is the natural satellite of the Earth

• Comets

 Ice and dust that orbit around the Sun

• Meteoroids

Rocks or metal that orbit around the Sun

• Asteroids

Rock and mental which lie between the orbit of Mars and Jupiter

Ø Relative Size and Distance

•   Distance

       

        Distance from        the Earth to the Moon     the Earth to the Sun

        Ratio                                      1                            400

• Size

       Size          Moon       Earth      Sun

       Ratio            1             4         400

THE SOLAR SYSTEM

The Constituents of the Solar system

1. The Solar System consist of nine planets and the Sun.
2. The other members of the Solar System are natural satellites, asteroids, comets and meteoroids.
3. The nine planets in the solar system beginning with the nearest to the Sun are Mercury, Venus, Earth, Mars, Jupiter, Satum,   Uranus, Neptune, and Pluto.
4. The relative of the Sun and its nine planets are shown in Diagram 6.1.
5. All the nine planets are moving around the Sun each following its own oval path called orbit.
6. The time taken for a planet to complete one revolution around the Sun is different from the time taken for another planet to do so.
7. Mercury takes the shortest time to complete one orbit, while Pluto takes the longest.
8. This is due to the fact that Mercury is the nearest planet to the Sun as shown in Table 6.1  
9. The relative sizes of the planets are shown in Diagram 6.2

  

     Planet             Time to complete 

                             one revolution

     Mercury                          88 days
     Venus                             225 days
     Earth                              365 days
     Mars                              687 days

    Jupiter                            12 years
    Saturn                             29 years
    Uranus                            84 years
    Neptune                         165 years
    Pluto                              247.7 years 

   Diagram 6.1 The Solar System

 Diagram 6.2 Relative size of the planets in our  Solar System

                      Diagram 6.3 Mercury 



A. Mercury

1. Mercury is the closest planet to the Sun.
2. Since Mercury is closest to the Sun, its temperature can be over 300`c in the daytime.
3. Mercury rotates on its own axis very slowly, making one full rotation every 59 Earth days.

   Diagram 6.4  Venus

   B. Venus

1.    Venus is the second planet from the Sun.
2.    The size of Venus is about the same as that of the Earth.
3.    The planet is always covered by a very thick cloud of carbon dioxide and acid vapor. 
4.    Thus, the temperature of Venus is extremely high, even though Venus is twice as far from the Sun as Mercury and receives only a quarter as much light.
5.   As a result, the surface temperature can be above 450*C.
6. Venus takes about 255 days to revolve around the Sun.
7. Venus rotates on its own axis once every 243 days.
8. Its gravity is the same as that of the Earth.

  Diagram 6.5 Earth

       C. Earth

1. Earth is the third planet from the Sun.
2. It is the fifty largest planet.
3. It is the only planet with oxygen and water. Thus, it is the only planet on which living things can survive and grow.
4. Earth takes about 365 days to revolve around the Sun and rotates on its own axis once every 24 hours.
5. Earth has a natural satellite (the Moon) revolving around it.

Diagram 6.6 Mars

D. Mars

1. Mars is the fourth planet from the Sun.
2. It also known as the Red Planet because its surface is being covered with red dust.
3. Mars is a cold and lifeless planet.
4. One revolution of Mars around the Sun takes 687 days.

Diagram 6.7 Jupiter

E. Jupiter

1. Jupiter is the largest planet in the Solar System.
2. It is the fifth planet from from the Sun.
3. Most of Jupiter's volume is made up of gases and ice with only a small rocky core.
4. The atmosphere is composed of  mainly hydrogen in gaseous and liquid forms together with helium, methane and ammonia.
5. Jupiter has sixteen natural satellites or moons and takes about 12 years to revolve once around the Sun.
6. Jupiter rotates so fast, once every ten hours, that it creates strong winds and great storms which persist over most of the planet.
7. Therefore, Jupiter is the planet which has the shortest day in the Solar System.

Diagram 6.8 Saturn

F. Saturn

1. Saturn is the sixth planet from the Sun.
2. It is surrounded by a system of rings which make it the most striking and beautiful planet when viewed through a telescope.
3. Saturn is the second-largest planet in the Solar System.
4. However, it is lighter than body of water of the same size.
5. Saturn is thought to have a small, rocky high-temperature core surrounded by ice and ammonia, mixed with grit and gases.
6. The time taken for Saturn to revolve around the Sun is around 29 years.
7. Saturn rotates on its own axis once every 10.7 hours.

Diagram 6.9 Uranus

G. Uranus

1. Uranus is the seventh planet from the Sun in the Solar System.
2. This planet is blue because it has cold gases, mainly made up of hydrogen and helium. 
3. Uranus also has a ring around it but the cannot be seen clearly because it is too thin and dim.
4. it has five moons, and it rotates on its own axis slightly more slowly than Saturn.
5. The time taken for Uranus to revolve around the Sun is around 84 years.

 Diagram 6.10 Neptune

H. Neptune

1. Neptune, the eighth planet from the Sun is almost the twin of Uranus. 
2. It is a little heavier than Uranus  and is very slightly bigger. it is bluish-green.
3. Neptune consists mainly of ice with some rocks and gases, and has less atmosphere.
4. Neptune  has two moons and takes about 165 years to revolve once around the Sun.

Diagram 6.11 Pluto

F. Pluto

1. Pluto is the ninth planets from the Sun.
2. it is the smallest planet in the Solar System  and is made of rock and thin ice.
3. Pluto is a dark and cold planet. its surface temperature can be as low as - 230*C.
4. This planet can be seen only through a telescope because it is so far away from Earth.
5. Pluto takes about 247.7 years to revolve once around the Sun.

Diagram 6.12  The asteroid belt

A. Natural Satellites

1. Natural satellites are the natural object which orbit around planets.
2. The moon is the Earth's only natural satellite.
3. All the planets in the Solar System have natural satellites except Mercury and Venus.
4. The number of natural satellites is shown in Table 6.2.

  

 Planet                                    Numbers of the natural satellites

   Mercury                                                        0

   

   Venus                                                             0

  

   Earth                                                              1

   Mars                                                               2

   Jupiter                                                           63

   Saturn                                                            61

  Uranus                                                            27 

  Neptune                                                          13

  Pluto                                                                3

Table 6.2

B. Asteroids

1. Besides the nine planets there is also an asteroid belt.
2. The asteroid belt lies between the orbits of mars and Jupiter.
3. Asteroids are small pieces of rocks mixed with metals orbiting round the Sun.
4. Asteroid vary in size. Some can be as small as dust particles while some can be a few hundred kilometers in diameter

C. Comets

1. Comets are small pieces of ice and dust that orbit around the Sun, but their paths are not like those of the planets.