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 The Solar system is the arrangement of sun, planets and other solid objects in the space in relation to the position of the sun. Or

 Is the group of heavenly bodies made up of the sun, the planets, the moons, natural satellites, asteroids, comets, the stars, meteors and meteorites that surround it.




 Components of the solar system includes the sun, planets, asteroids, meteors, comets and inter planetary dust and gases  



Is a heavenly body that possesses and transmits its own light. A group of stars is known as galaxy. To the sky there are millions of stars. 



Sun is the big star. It is one among the millions of stars that one sees at night except that it looks much bigger because it is closer to the earth than other distant stars.  

The sun is the main source of all light and heat that the planets receive. 

The sun is much larger than other distant stars from the earth, in fact much larger than all the planets put together. The elements that form the material of the sun are different proportion from those of the earth.  

The sun is composed of approximately; 75% hydrogen, 23% helium, and 3% of other elements The earth is relatively cold body but the sun is so hot that nearly all molecules are broken into their separate atoms and all are mixed together into a single hot gas. Its average surface temperature is about 6000 0c, it is much hotter in the interior where it is about 14,000,000 0c.  



 Solar energy is the heat and light produced from the sun. Or  

Is the energy produced by the sun. Solar energy has power that helps to perform an activity. This capacity exists in form of light and heat. 



 Solar energy is used in many ways: - 1. In drying clothes, grains, fruits and meat. 

2. Used by plants to manufacture their food through the process known as photosynthesis. 

3. Solar energy captured in solar panels and stored in batteries provides electricity used in generating industrial and home Appliances like television, refrigerator, Oven, electric iron and cooker. 

4. Many everyday items such as calculators and other low power consuming devices can be powered by solar energy effectively. 

5. Is used as a source of vitamin D for human being 

6. It is used for evaporation of water from water bodies which is necessary for rain formation. 



The planets are the large celestial bodies that revolve around the sun.  

There are eight known planets in our solar system, these includes Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune..  

All planets revolve around the sun in the same orbit that are elliptical and nearly the same plane. 

 The time taken to complete an orbit round the sun depends on the distance of the planet from the sun. All the light and heat of the planets come from the sun. Hence the temperatures on the planet depend on their relative distances from the sun.  

However, Pluto is not a planet because an object to be a planet, it needs to meet these requirements (criteria) defined by the International Astronomical Union (IAU) as follows:      i) It needs to be in orbit around the sun      ii) It needs to have enough to pull itself in a spherical shape     iii) It needs to have "Cleared neighborhood of its orbit" 

Note: Any object that doesn't meet the 3rd criteria is considered a dwarf planet. And so, Pluto is a dwarf planet is not a planet. 






  Are objects with leading heads and bright tail at the sky at night one .  

These are called comets. At present many scientists believe that comets are composed of ice crystals and fragment matters. Comets revolve around the sun far beyond the limits of Pluto. They can be seen from the earth only when they come close to the sun. 



 Asteroids are solid heavenly bodies revolving around the sun mostly between the orbits of Mars and Jupiter.  There are thousands of these, the largest having diameter of less than 800km. These bodies cannot be seen without a telescope because they are very far away. 




 Meteors refers to the hard matter falling from outer space, they become visible between 110 and 145 km above the earth‘s surface, where as a result of friction with the atmosphere become hot and usually disintegrate. 

 When they do completely disintegrate as they pass through the atmosphere reach the earth‘s surface and are known as meteorites. Meteorites are usually made of nickel, iron or silica fragments of disintegrated comets. There are two known meteorites in Tanzania one is found in Mbozi District and the other fell at Malampaka in Kwimba District in 1930. 





Natural satellite is anybody that moves around the planet or any other body larger than itself. There are 60 known satellite in the solar system. The largest know satellite is the earth‘s moon.  

The earth‘s moon has the diameter of 3456  km  and the distance from the earth to the moon is 375,000 km and it takes 291/2 to make a complete revolution round the earth.  


                 THE EARTH 

The earth  is the third planet from the solar system that support life. The Earth is made of the Atmosphere (air), Hydrosphere (water bodies), The crust solid, Molten material, Biosphere (living things). About ¾ of the earth‘s surface is covered by water. 

 In fact no other planet in the solar system is known to have water bodies; the shape of the earth is a flattened sphere.      This flattening is very slight as indicated by measurements in diameters through poles and at the equator. The diameter through the poles is 12,713 km while at the equator it is 12,757 km. 



 There are some several evidences which are used to prove that the earth is sphere like structure, some of them are shown in the following: - 

 (i) Sunrise and sunset  

 The sunrise and sunset at different places of the earth, people in the east see the sun earlier than the people in the west due to earth‘s rotation from west to east. if the earth was flat the whole world would have sunrise and sunset at the same time. 


(ii) Circumnavigation of the earth 

 If traveling from a certain point of the earth and you go straight around the earth you will come to the point of origin. the first traveler around the world named Magellan in 1519-1522 proved this, image did not encounter abrupt edge over the world in his voyage. 


(iii) Aerial photographs 

Photograph taken by satellites or aero plane from the air show that the earth has a curved or round shape. 


(iv) Ship‘s visibility;  If you are in the coast viewing a ship which is very far you will see the smokes, then the pipe and eventually the ship  


(v) Lunar eclipse 

The shadow of the earth thrown to the moon during lunar eclipse is always round. only a spherical object can give a circular shadow. 



The earth is in motion all the time. One does not feel this motion because one moves with it, like all other planets, the earth has two motions known as: -     (a) Rotation and 

    (b) Revolution 



Rotation is the spinning of a body on its axis.  

Earth‘s rotation – is a spinning of the earth on its axis.  

Axis – is an imaginary line joining the north and south poles through the center of the earth. The earth rotates on its axis from west to east. The earth‘s axis makes an angle of 661/20 from the perpendicular.  It makes one complete rotation after every twenty four hours or one day,  


The following observations illustrates the earth‘s rotation from west to east; 

1. When traveling in a fast moving vehicle we notice trees and other objects on both sides of the road moving in the opposite direction. This observation is similar to the movement of the earth‘s rotation to the sun. 

2. In the morning the sun appears to rise over the eastern horizon but due to the fact that the sun is the center of the solar system we know that it does not move in relation to the solar system. This shows that the earth is moving from west to east. 

3. At night most of the stars appear to move across the sky from east to west. This shows that the earth is moving from west to east. 


The results of Earths Rotation/Evidence to prove that the Earth Rotates 

(a) Day and night While the earth is rotating, the region of the earth facing the sun experience daylight. The region facing away from the sun experience darkness (night). 

(b) Different hours (time difference between longitudes)As the earth rotate from west to east it takes 24 hours for the earth to make full rotation through 3600 . Therefore as the earth rotate it causes a difference of 4 minutes for every 10 in turn. This is in turn means that it causes a difference of 1 hour for every 150 it turns. 

(c) Deflection of winds and ocean currents. As the earth rotate from west to east winds are deflected because they are not flowing in their intended direction. 

(d) Daily rising and falling of tides. The rise and fall of tides are caused by gravitational forces of the moon and the sun acting on the earth. 



Revolution is the movement of one body around another.  

Earth‘s revolution: -Is the movement of the earth around the sun 

- The earth takes 365 ¼ days for a complete revolution 

- When the earth takes 366 days to accomplish one revolution is called a Leap year 

- The earth revolution revolve around the sun in an elliptical 

- Due to the shape of the earth‘s orbit, the earth is very closer to the sun at one point of the year than at another. 



Aphelion is the furthest position of the earth‘s orbit from the sun. 

- The earth is at Aphelion each year on 4th July when it is in 152 million kilometers from the sun. 


Perihelion is the nearest position of the earth from the sun. 

- The earth is at perihelion each year on 3rd January when it is 147.3 million kilometers from the sun. Therefore the speed of revolution is about 29.66 km per second. 



Note   Apogee is the furthest position of the moon from the earth Perigee is the nearest position of the moon from the earth .  



When the earth revolves around the sun it causes: - 

(a) Seasons of the year 

(b) Eclipse(both solar eclipse and lunar eclipse)  (c) Difference in the length of day and night  (d) Change of midday sun in the latitudes. 



Season is one of the four periods of the year separated from each other by different temperature conditions. The seasons are summer, autumn, winter and spring.  

     They are more pronounced between 23 0  and 66 0 of latitudes. At the equator the year is divided between hot and wet seasons while at the poles is very cold all the year around and the season cannot be identified easily.  

The Northern hemisphere   -Summer months are May, June and July.  

                                                        -Autumn months are August, September and October,                                                          - Winter Months are November, December and January                                                          -Spring months are February, March and April. 


 In the Southern Hemisphere   -Summer months are November, December and January, 

- Autumn months are February, March and April  

                                                           -Winter has May, June and July while 

- Spring months are August , September and October. 



Seasons are caused by inclination of the earth‘s axis and the earth‘s revolution around the sun. The earth‘s axis is tilted at an angle of 66 0 to the earth‘s orbital plane and it is always pointing to the same direction in space. In its revolution around the sun one of the hemispheres is inclined towards the sun to one period of the year and away from it at another period of the year. 



Eclipse this is the movement of one heavily body between the two others, such that it casts shadow over the other. Or  Is the total or partial cut off of light received by one space body from another by interception of the third space in passing between the other two.  


The eclipse involves three heavily bodies namely; the Sun, the Earth and the Moon.  

So long as the sun is the central body of the solar system, it never moves, only the earth and the moon are in the motion all the time.  

An eclipse is said to be total eclipse when the whole body is obscured i.e completely blocked from the sun light and  it is described as a partial eclipse when the only part of the body becomes obscured.  

At any place an eclipse will last short time, hardly seven minutes because both the earth and the moon are in motion. 


           TYPES OF ECLIPSE 

 There are two types of eclipse i.e Lunar eclipse and solar eclipse 


This occurs when the earth moves between the sun and the moon, this casting its shadow over the moon. Image of the diagram showing lunar eclipse 




The solar eclipse also known as the sun eclipse This occurs when the moon passes between the earth and the sun casting its shadow over the earth.  

This can be partial solar eclipse or total solar eclipse depending on the position of the moon or the earth, in Tanzania 16th February 1980 was the a total solar eclipse and partial solar eclipse in Mbeya Tanzania at Wanging‘ombe was 1st September 2016. 

      Umbra or total eclipse it occurs when whole body obscured or completely blocked from the suns light,        Penumbra or partial eclipse is when the only part of the body becomes obscured. 

 NB; At any place eclipse last for short time up to seven minutes 




 The apparent movement of overhead sun is related to the different positions of the earth on its movements it revolve around the sun. The overhead sun appears to move northwards and southward in an osculating (swinging) manner. However the overhead suns northward limit is latitude 00 N People beyond this latitude never see the sun vertically above their head. The latitude of 231/20 N is known as Tropic of cancer. Similarly the overhead sun ends 231/20 N is apparent southward movement. This latitude is known as Tropic of Capricorn.  on 21st June the sun is vertically overhead on the tropical of cancer this known as summer solstice in the Northern hemisphere. On the 22nd December the sun is vertically overhead on the Tropic of Capricorn this is the winter solstice in the northern hemisphere. The word solstice suggest that the sun on these days appears to stand still between its north ward and south ward journeys. 



The sun is overhead twice a year at the equators 21st march and 23rd September.  

The 21st march is known as the spring equinox and 23rd September is known as autumn equinox in the northern hemisphere.  

Equinox means equal nights, at equinox the length of the day and night is equal over all places on the earth‘s surface. Viewed from the southern hemisphere the solstices and equinoxes are reversed. 



Places along the equator experience equal day and night all the year, but northwards or southwards towards the poles, the length of the day and night vary with latitudes for instance in northern summer when the northern hemisphere is inclined towards the sun, days are longer than nights. 

        However at latitude 661/20 North known as the Arctic Cycle and beyond the appears around the sky without setting in the North Pole day light is experienced for six months before the sun set. Then this region remains in darkness for the next six months, 

       Latitude 661/20 south is known as Antarctic cycle. The Polar Regions south of the Antarctic cycle experience the long six months night from March to September and the six months day light from October to February. 



Parallels are more commonly known as Latitudes.  

Latitude/Parallel Is an imaginary line drawn on map from west to east and forms a circle. It measured in degree minute and seconds of a point on the earth‘s surface north or south of the earth from the equator.  


Meridians Are commonly known as longitude.  

Longitude/Meridian, Is angular distance measured in degrees East or west of the prime meridian, they run from north to south. 


The equator is the latitude which divides the earth into two equal hemispheres, one in the north and other in the south. 


      Importance of Parallel and Meridian 

a) Longitude (Meridian) enable us to calculate local and international times of different places on the earth‘s surface. 

b) Latitudes (Parallel) helps us to explain and understand the variation in climate on the surface of the earth. 

c) Parallel and meridian are used by pilots and sailors to guide their path. 

d) They enables us to locate places on maps, for example Tanzania is found at the latitude of 6degree and 00 south of the equator and longitude 35degree and 00 east of Greenwich meridian. 



Latitude: Is the angular distance north or south of the equator measured in degrees, minutes and seconds. OR  Are lines drawn on map from east to west.  

The equator is latitude of zero (0) degree The equator divides the earth into equal parts (Hemisphere), called northern hemisphere and the southern hemisphere. Latitudes are also known as parallel lines because the equator  never meet. The lines of latitude are measured from zero degree to 90 degree north and south. 

                 The main lines of latitude are 

  The equator( latitude 0 0 ), The tropical of cancer(latitude  23 ½ 0N), The tropical of Capricorn (latitude 231/20S), The arctic cycle(latitude  661/20N), and Antarctic cycle (latitude 661/20S ).  


Longitude Is an angular distance measured in degrees east or west of the prime meridian, they run from north to south.  Greenwich is the longitude of zero degree(00), it‘s also known as prime meridian. The prime meridian the line running through the poles (North and South) and is known as Greenwich. 

 Longitude are measured from 00 to 1800 East or West of the Greenwich, all meridians are passing through the north and south poles. 




 The earth rotates on its own axis from west to east once on every twenty four hours (one day). This means that the earth turns through 360 degree in twenty four hours.  

All place along the given meridian will experience midday along the same meridian, it is known as Local mean, on the Greenwich meridian is known as Local Mean Time (LMT) When it is 12:00 noon, on the Greenwich meridian it will be 1:00 at a place of 15 degree E or 11:00 at a place of 15 degree W. 



The intersection of the surface of the sphere and a plane through its center for example meridian of longitude and equator are great circle in the earth‘s surface. There for is no limit to the number of great circle that can be drawn. The great circle is drawn on a globe (or other sphere) with a center that includes the center of the globe. Thus a great circle divides the globe into two equal halves. 

The following are the great circle 


Greenwich (prime meridian) 

All longitudes  

Importance of Great Circle 

1. The great circles are important for aero planes which use them as route ways to guide their path. 

2. Great circle are important for ship to follow routes along great circles. 



 Refers to a period that is used for event or activity. It is measured in seconds, hours, days, months or years. 



 Time zone is the region having the same standard time. Standard time is common on time for all countries belonging to the same time zone for example Tanzania, Kenya, Uganda, Ethiopia, Djibouti and Somalia use the same standard time. 

This commonly referred to the East African Standard time.  

Local mean time is the time recorded along the same meridian  

There would be problems of telling time if every place had its own time set according to local mean time. For example, there would be great confusion in railway airway time table or in radio programs if they had to show difference time each one place within a small area. To avoid this problem difference stretches on earth takes their time from great meridian. The time adopted is known as STANDARD TIME. 

 In East Africa Standard time is taken from meridian of 45 degree E when a whole stretch of land keeps to the same standard time that stretches from a time zone.  

There for time zone refers to a stretch of land where standard time is accepted through out a longitudinal zone 15 degree width.  

Countries with large stretches of land have several standard zones. There are 24 time zones in the World. The Greenwich meridian is the starting point for dividing the globe into 24 time zones, The standard time for Greenwich is known as Greenwich Mean Time (GMT). The above confusion was avoid when it was internationally agreed to split the World into 24 time zone according to longitudes The longitudinal division across the earth with an approximates with of 15 degree of longitude which is regular across the oceans.  


The earth rotates on its axis from west to east once every twenty four hours (one day). This means that the earth 

turns through 3600 in 24 hours or it turns 10 in every 4 minutes.  




International Date Line  is the line where date changed or where the calendar day begins.

This line roughly follows the 1800 meridian. If one travel Eastward and cross the International Date Line one will gain a day. If one travel westwards across the International Date Line one will lose a day, 


Why international Date Line is Zigzag  The International Date Line is Zigzag at certain places to enable different parts of the country to keep the same date. 

Or international date line is Zigzag to avoid the same area to have two different date that will bring confusion  


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