Geography

Key unit competency:

 By the end of this unit, I should be able to distinguish between the components of

the universe and the solar system.

Introductory activity:

One of the students in senior one moved outside one evening and all of sudden

saw a running star that disappeared. The moon was fading, being covered by dark

clouds. He wondered whether there are moons elsewhere and went back to bed. In

the morning, the sunrise with golden rays replaced the dark and starry night.

a. Identify the heavenly bodies mentioned in the passage.

b. Using your experience and the passage above, identify other

components of the universe not mentioned in (a) above.

4.1. The universe

4.1.1. Definition of the universe and Components of the universe.

The universe refers to all of space and everything in it. It contains everything that exists, from the smallest particles to the largest structures known. The exact size of the universe is not known. Astronomers estimate that it contains about 100 billion galaxies. Astronomers are experts who study bodies in the sky or outer space. A galaxy is a system of stars, together with gas and dust. These are held together by forces of gravity. Each of the galaxies has an average of 100 billion stars. The origin of the universe is explained through the Big Bang Theory, which happened about 13 billion years ago.

4.1.2. The components of the universe 

The Universe contains many components, which vary considerably in size. The smallest components are atomic particles followed by atoms (mostly free hydrogen and helium), molecules, dust, space rocks, comets, asteroids, moons, dwarf planets, planets, solar systems, stars, black holes, nebulae, and galaxies. Among these components the solar system is the most known with certainty.

The table below shows the components associated with the universe.

4.2. Solar system: sun and planets

Activity 4.2.

1. Using the previous knowledge that you have in Geography, explain the

meaning of solar system and identify the elements or components that

form it, and share your finding in class.

2. Using internet, text books and other sources of geographical

information, research on the characteristics of sun and planets.

The term solar system is defined as the arrangement of the sun and planets that revolve around it (Sun). The solar system is therefore made up of the following: the sun, planets including the earth, the moon and other heavenly bodies such as asteroids, comets, meteorites, meteors, etc.

4.2.1. The sun

 The sun as earlier studied, is one of the billions of stars that make up the Milky Way galaxy. It is one of the smallest stars in our universe. However, it is 109 times bigger than Planet earth. It forms the center of the solar system. Its gravitational force keeps planets in their orbital position. All the 8 planets revolve around.

1. Characteristics of the Sun

The sun as any other heavenly body, has characteristics that distinguish it from the

rest of other components of the solar system. These are explained hereunder:

– It makes or emits its own light/heat.

– It has the diameter of 139,200 km.

– Its temperature ranges from 4000-9000 degrees Celsius.

– Its mass stands at 1.98892 x 1030 kilograms.

– It has a density of 1.4 grams per cubic centimeters.

– The sun is made up of hydrogen and helium.

– Its radius is estimated to be at 695,500 kilometers.

– It takes 25 days to turn once on its axis.

2) The influence of the sun on the Earth

– It holds the earth in its orbital position.

– It contributes greatly in the balancing of the tidal bulge caused by the moon’s

gravitational pull and the inertia.

– The sun is the source of the energy that is used by the earth and all that is

therein.

– It engines the hydrological cycle.

– Supports life on earth through many ways such as creation of suitable and

favourable temperatures.

– The sun influences the general climate at the hand of the solar radiation

received.

– Contributes to the formation of tides that support in one way or the other

support ecosystem and man’s activities. 

4.2.2. Characteristics of different planets and their positions 

The term planet means the rock solids that are in oval or spherical shape floating in space and rotating on its axis and revolving round the sun. Planets are grouped into categories as shown below:

Pluto is known as a dwarf planet. It never developed fully. It is very important

to know that Pluto was removed from the list of planets in 2006, because of the

following reasons:

c. Its size is too small to be classified as a planet.

a. It has no uniform revolution round the sun.

b. Its revolution is not circular but spherical in nature.

c. Its movement is too slow when compared with the rest of the planets

of our solar system.

Application Activity 4.2

1. You are asked to address the senior fives from other schools, explain

what you would tell them about the positioning and characteristics of

the planets found in our solar system.

2. “The earth is the only planet that supports life” Explain why it is so and

show how you would ensure that it continues supporting flora and

fauna.

4.3. Earth: Peculiar elements of the earth

The peculiar elements of the earth are outer parts of the eath. They include the

following:

1. Hydrosphere or water bodies

2. Lithosphere or Land and rocks

3. Atmosphere or Gasses

4. Biosphere or flora and fauna

– Hydrosphere: This stands for all the waters found on the earth surface.It

covers 71% of the earth’s surface.It includes: Lakes, Seas,Oceans,Wetlands ,

Rivers,Wells,Streams,Clouds.

– Biosphere: This is known as ecosphere. It is a part of the earth that includes

the totality of life on the earth (Animals,Plants and Man).

– Lithosphere: This is the solid part of the exterior area of the earth.It is made

up of the crust and a small percentage of the upper mantle (Land ,Rocks, Soils

and Minerals).

– Atmosphere: It describes the zone occupied by air or gasses that surround

the earth.This zone is composed of gasses such as: Nitrogen,Oxygen, Argon

,Water vapour, Carbon dioxide, Helium and Methane.

4.4. Earth’s movements

Learning activity 4.4

 Read the following passage and answer the questions provided.

 Every day the sun rises in the east and sets in the west. This process led many people in the past to think that the sun is moving, and the earth is fixed. The sun moves around the earth. But with the advancement of science, this has been proved that the sun itself is moving and the earth has also motion. Later it has been revealed that the sun does not move around the earth, rather the earth moves around the sun.

With the help of your knowledge and skills acquired in previous studies answer

the following questions?

a. How many movements does the earth make?

b. Identify proof for the earth rotation and revolution

c. Describe effects caused by the above movements

4.4.1. Rotation of the Earth 

Rotation of the Earth is defined as the movement of the Earth spinning on its own axis. This movement of the Earth on its own axis is in an anticlockwise direction. The earth takes 24 hours to complete 360˚. At the equator the earth rotates at a speed of 1676 km and zero km at the poles per hour.

The effects of rotation of the earth

 As the Earth turns around its axis, it affects some processes on the earth’s surface and other associated celestial phenomenon. Some effects of the earth rotation are:

i. Rotation causes day and night

 Earth’s rotation on its axis creates day and night. The one half of the Earth that faces the sun has day time, while the opposite half facing away from the Sun has night time.

ii. Rising and falling of ocean water (tides)

During the rotation of the earth, gravitation force pull of the sun and the moon acts

on the ocean water to produce tides which may be high or low.

iii. Deflection of wind and ocean current (Coriolis Effect)

Rotation causes winds to be deflected to the right in the Northern or to the left

in southern whenever they cross the Equator. This deflection is called the Coriolis

Effect.

iv. Time difference between longitudes

One round of the Earth is completed after turning 360 .

This implies that the earth takes 24 hours to complete rotation. Therefore, for the

earth to cover 15o it is calculated as follows:

v. Temperature difference 

Due to the spherical shape, the parts of the Earth located in the tropical areas between 23.5˚ North and South of Equator, get direct sunlight all the year round. Regions located in higher latitude get less rays during the year.

4.4.2. Revolution of the Earth 

The revolution of the earth is the movement of the earth around the sun. Earth revolves around the Sun along an oval-shaped path called an orbit. The area of the oval-shaped path is called Plane of the ecliptic, in which the axis of the Earth is tilted at an angle of 23 27’. Earth takes 365 days and 6 hours or one year to complete one revolution, at a speed of 106,260 km/h around the Sun (30 kilometres per second).

The Leap year is the year with 366 days which come after four years where February has 29 days instead 28 days. This results from adding 6 hours of rotation of each year to make one year after 4 ordinary years.

The consequences of the revolution

i. Determination of seasonal variation

The whole year has been divided into four divisions. Each of such division is known as a season. There are four seasons namely summer, autumn, winter, and spring. The earth’s revolution leads to change in the sun’s overhead positioning. This comes along with the occurrence of solstices (winter solstice, summer solstice) and equinox.

– Solstice is either of two times of the year at which the sun reaches its highest

or lowest point in the sky at midday, marked by the longest and shortest days

over the tropics. Solstice occurs on 21st June and 22nd December when the

sun’s overhead position is either at the tropical of Cancer or Capricorn.

– Equinox occurs two times in the year (around 21st March and 23rd September)

when the sun is above the Equator, day and night have equal length. 

The four seasons:

Summer is the hottest of the four temperate seasons. This occurs immediately after the spring season and before autumn. When it is the summer solstice, the days are the longest and the nights are the shortest. The day length begins to decrease as the season progresses towards autumn. When it is summer in the Northern Hemisphere, it is winter in the Southern Hemisphere, and vice-versa.

Winter is the coldest season of the year in the polar and temperate zones. It occurs after autumn and before spring in each year. Winter is caused by the axis of the Earth in that hemisphere being oriented away from the Sun. when it is winter in the Northern Hemisphere, it is summer in the Southern Hemisphere, and vice versa. During winter the days are short and nights have longer hours. However, this changes as the season progresses towards spring.

Spring is one of the four conventional temperate seasons, following winter and preceding summer. Days become longer, and weather gets warmer in the temperate zone because the Earth tilts towards the Sun. In many parts of the World plants grow and flowers bloom.

Autumn, this is a season of the year between summer and winter during which temperatures gradually decrease. The fall in temperatures brings direct impact on the growth of vegetation. Therefore, the vegetation begins to decrease. It’s the season when the days get shorter and colder, and everything turns brown and the plants begin to shed leaves.

ii. Varying length of day and night at different times of the year 

The revolution causes variations in the length of the day and night over different latitudes. When the sun is in the Southern hemisphere i.e. overhead the tropic of Capricorn, the latitudes in the northern hemisphere receive less hours of the sunlight (daytime) but more hours of night time; while the Southern hemisphere receives more hours of heating hence more hours of daytime.

During the summer solstice, day time is longer than night time in areas found in higher latitudes. This implies that, latitudes beyond equator will experience increase in hours of day time towards the poles (from 12hrs to 24hrs at the arctic circle and beyond). During the winter solstice, night time is longer than day time at latitude beyond equator. Norway is known as the land of the midnight sun because the sun does not go below the horizon or comes above it on 21st June

iii. Climatic zone. 

These are divisions of the Earth’s climate into general climate zones according to average temperatures and rainfall. The three major climate zones on the Earth are: the Polar, Temperate, and Tropical climatic zones. Temperatures in these three

climate zones are determined mainly by the location, or latitude. The reason why the equatorial zone is hotter than the poles is that sun’s rays fall vertically at the equator and obliquely at the poles. Example, the stations around the equator such as Kisangani, Masaka, Libreville, and Manaus experience hot temperatures while areas such as Alaska, Greenland and Siberia near the poles experience cold temperature.

iv. A light year

 A light year is a unit of distance. It is the distance that light can travel in one year. Light moves at a velocity of about 300,000 kilometers (km) each second. More precisely, one light-year is equal to 9,500,000,000,000 km.

Why such a big unit of distance?

 Well, on Earth, a kilometer may be just fine. It is few hundred kilometers from Kigali city to Rwamagana; it is a few hundred kilometers from Rusizi to Ngoma. In the Universe, the kilometer is just too small to be useful.

For example, the distance to the next nearest big galaxy, the Andromeda Galaxy, is 21quintillion km. That’s 21,000,000,000,000,000,000 km. Astronomers use other units of distances in terms of the Astronomical Unit (UA). The AU is defined as the average distance between the Earth and the Sun. It is approximately 150 million km.

4.5. The Moon

Activity 4.5.1

With the help of geographical documents and other relevant sources of

information, search for the following information:

a. The natural satellite of the earth.

b. The characteristics of the moon.

c. How moon influence the earth.

d. Types of eclipses.

e. Identify the effects tides may cause.

The moon is a natural satellite that moves around the planet (larger natural body) in space. It is the only satellite of the earth which is about 4.5 billion years old. The moon is the natural satellite that goes around the earth and that people can see shinning in the sky at night.

4.5.1. Characteristics of the moon

4.5.2. Phases of the moon 

As the Moon orbits Earth, it reflects light from different angles, which change shape of the moon. These change shapes of the moon are called the phases of the Moon.

The phases of the Moon are divided into Primary phases and Intermediate phases.

Primary phase includes the following:

– The New moon phase: This is a period when the moon is between the Sun

and the Earth. Its sunlight side is turned away from Earth (it is not visible).

– The first quarter phase: Is a phase that occurs 7 days after new moon phase

when half shape of the Moon appears to be receiving sunlight.

– The full moon phase: The whole side of the Moon receiving sunlight faces the

Earth, 14 days after new moon. This implies that the Earth, Sun, and Moon are

almost aligned in a straight line, with the moon in the middle.

– Last quarter phase: A half of the moon appears to be lit by sunlight. The left

part of the moon is facing the direction of the rising sun. This is because the

moon is in front of the sun but between the Earth and the sun.

Intermediate phases

– Waxing crescent is a small part of the moon that receiving sunlight seen from

the Earth just as a bright crescent in the direction of the setting sun.

– Waxing Gibbous: This is when the moon appears to be having a small part

that receives sunlight as seen from the Earth. It is just as a bright crescent in

the direction of the rising sun.

– Waning Crescent: The Moon appears to be partly but less than one-half

illuminated by direct sunlight. The fraction of the Moon’s disk that is illuminated

is decreasing. 

– Waning Gibbous: This occurs when more than a half of the lit portion of the moon can be seen and the shape decreases in size from one day to the next. It occurs between the full moon and the third quarter phases.

4.5.3. Influence of the moon on the earth

1) Eclipses of the moon

Eclipse is the obscuring of one celestial body by another, particularly that of the sun

or a planetary satellite.

Types of eclipses

 – A lunar eclipse: A lunar eclipse occurs when the moon passes directly behind the earth into its umbra (shadow). This can occur when the sun, earth and the moon are aligned exactly or very closed with the earth in the middle. A lunar eclipse occurs only during night. A lunar eclipse may be total lunar eclipse: that happens only when the sun, earth and moon are perfectly aligned. When its alignment is less than perfection, therefore a partial lunar eclipse occurs.

– Solar eclipse: This is a type of eclipse that occurs when the moon passes between the sun and earth, and the moon fully or partially blocks rays of the sun from reaching the earth. This occurs during daytime.

(2) Tides 

The word “tide” is a term used to define the alternating rise and fall in sea level, produced by gravitational attraction of the moon and the sun. The moon tries to pull anything on the earth to bring it closer, but the earth is able to hold onto everything except water. Since the water is always moving, the earth cannot hold onto it, and the moon is able to pull it. Each day, there are two high tides and two low tides. The ocean is constantly moving from high tide to low and then back to high tide. The high tide is called spring and the low tide is named neap.

Application activity.

Using specific examples answer the following questions.

1. Explain why the moon shows one side from the earth.

2. Explain what happens when the moon is placed between Earth and the

sun.

4.6. Other heavenly bodies

It is important to note that there are other heavenly bodies. These include the ones

shown below:

-Asteroids - Meteoroids - Meteorite - Meteors

-Comet - Constellations - Galaxies

Application activity

Search on internet and use other geographical documents and answer the

following questions:

1. Discuss conditions that make our planet habitable.

2. What are the benefits people gain from some heavenly bodies that land

on the earth’s surface?

a. Identify the heavenly bodies shown in the two photographs.

b. Mention and describe the heavenly bodies found in the universe that

are not shown in the two photographs.

c. Explain why the areas shown in the two photographs are all found on

planet earth yet having different habitable conditions.

d. Draw a program that can enable man to live in harmony with the

universe and the earth.

2. Read the story below and use it to answer the questions that follow:

Recently John and Mary went to visit their uncle in Rubavu. In the afternoon of their second day, they were taken by their cousins to visit the lake shores. Evening came, and the moonlight was so intense that one could pick the smallest thing at that time. Suddenly, they saw water extending in a rhythmic manner to the place they had made a camp fire.”

a. How could you use your knowledge to convince John and her sister

Mary that what happened was connected to the moon, sun and

earth’s rotation.

b. Suppose you want to build near the coastline, explain how the

knowledge and the skills acquired from the lesson on tides can guide

you.

c. The Indian Ocean experiences many tides, design a project that you

would sell to the Kenyan government to address the effects of tides

on the coastal biodiversity.