Mawasiliano ni mchakato wa kuhawilisha taarifa kwa njia ya ubadilishanaji wa mawazo, hisia, malengo, tabia, matarajio, mitazamo kupitia mazungumzo, ishara na maandishi.
MAWASILIANO (Lugha kama Chombo cha Mawasiliano)
Sources of History
Identify sources of History
Sources of history refers to the avenues that can be used to get historical information.
Sources of History
A Nation can be defined as a large group or community of people living in a defined geographical area and sharing a common history, culture and language under one government.
Our Nation
Physics is often described as the study of matter and energy. It is concerned with how matter and energy relate to each other, and how they affect each other over time and through space.
INTRODUCTION TO PHYSICS
The Importance of the Parallels and Meridians
The Planets
Planets in the Solar System
Locate the planets in the solar system
Revolving around the sun are bodies called planets (mentioned in the previous section). Planets revolve around the sun in anticlockwise direction following paths called orbits. As they revolve around the sun, they appear to move among the stars. This is the reason why the Greeks called them the planets, which in their language means “wandering stars”.
All the light and the heat of the planets come from the sun. Hence, the temperatures on the planets depend on their relative distances from the sun. All planets revolve around the sun in the same direction in orbits that are elliptical and nearly in the same plane.
Relative Distance of Planets from the Earth
Show relative distance of planets from the earth
Each planet has its own orbit and takes a different length of time to complete one revolution around the sun. Being close to the sun, Mercury takes the shortest period of time to complete one revolution. On the contrary, Neptune which is furthest from the sun takes the longest time. The table below shows the relative distances of planets from the Earth.
Table 1.1 Relative distances of planets from the Earth
| Planet | Distance from the sun (million kilometres) | Average temperature (degree Centigrade) | Period per orbit (or revolution) |
| Mercury | 58 | 340 ** | 88 days |
| Venus | 108 | -40 | 225 days |
| Earth | 150 | - | 365 ¼ days |
| Mars | 228 | -100 | 1 year and 322 days |
| Jupiter | 777 | -138 | 11 years and 315 days |
| Saturn | 1426 | -247 | 29 years and 167 days |
| Uranus | 2869 | -200 | 84 years and 6 days |
| Neptune | 4495 | -265 | 164 years and 288 days |
** +340 degrees Centigrade is the average temperature for sunlit side. The dark side has a temperature of -253 degrees Centigred
Apart from planets, there are other heavenly bodies that are found in the solar system. Most of these bodies are much smaller than the planets and some of them revolve around the planets. They include comets, asteroids, meteors, and natural satellites.
Characteristics of Comets, Asteroids, Meteors and Satellites
Describe the characteristics of comets, asteroids, meteors and satellites
Comets
Comets are objects with leading heads and bright tails in the sky. Sometimes they can be seen at night. They are composed mainly of rock, ice, dust, and frozen gases. A combination of all of these components gives the comet a shiny appearance. As the comet passes near the sun, it leaves a tail of dust. Comets orbit around the sun far beyond the limits of Pluto (Fig 1.4). They can be seen from the Earth only when their orbits overlap that of the Earth. This is because other times their orbits are very far away.
Fig 1.9 A typical comet
Asteroids
Asteroids are solid heavenly bodies revolving around the sun, but are too small to be called planets. Tens of thousands of these minor planets are gathered between the orbits of Mars and Jupiter. The largest asteroid has a diameter of just less than 800 kilometres. These bodies can only be seen with a telescope because they are very far away from the Earth.
Asteroids are found in a portion of the solar system called asteroid belt. As the name suggests, this is a belt where asteroids are most likely to occur. The section is found between Mars and Jupiter. The largest of the existing asteroids is called Ceres, with a diameter of approximately 930 kilometres.
Meteors
Meteors are pieces of hard matter falling from outer space. They can be seen when they come close to the Earth, at about 110-145 kilometres above the Earth’s surface, whereas as a result of friction with the atmosphere, they become hot and usually disintegrate. But when they don’t disintegrate completely in passing through the atmosphere, they teach the Earth's surface as large boulders known as meteorites. These bodies are usually made of nickel, iron and silica. Sometimes meteors reach the Earth’s surface with such a force that they make large holes or craters called meteor craters.
Natural satellites
A natural satellite or moon (in the most common usage) is an astronomical body that orbits a planet or minor planet (or sometimes another small solar system body).
The largest known satellite is the moon. Other planets also have large moons, e.g., Jupiter’s Galilean moons (Ganymede, Callisto, Io, and Europa), Saturn’s moon (Titan) and Neptune’s moon (Triton).
Four dwarf planets are also known to have natural satellites: Pluto (Charon, Hydra, Nix, Kerberos, and Styx); Haumea (Hiʻiaka and Namaka), Makemake [S/2015 (136472) 1]; and Eris (Dysnomia). As of January 2012, over 200 minor-planet moons have been discovered.
Most of the 178 known natural satellites are irregular moons, while only 19 are large enough to be round. Ganymede, followed by Titan, Callisto, Io and Earth's Moon are the largest natural satellites in the solar system.
Fig 1.10 Some natural satellites (moons) in the solar system
Local Incidents Linked to Meteorites
Narrate local incidents linked to meteorites
There are two known meteorites in Tanzania. One is found in Mbozi district in Mbeya region and another is in Malampaka in Kwimba district of Mwanza region. These meteorites fell from space and reached the Earth in 1930 and they formed large holes on the Earth’s surface.
The Planets and Other bodies in the Solar System
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