New Creative Science Book 9

lake as a result of the breaking down of glacier lakes is called a glacier lake outburst.
Near the area of Glacier Lakes, the temperature has been increasing day by day. It
increases the risk of the outburst of Glacier Lakes. As the glacier lake outbursts, the
water in river increases. It may cause glacier floods in the rivers which are originated
from the mountains. Such floods may cause loss of life and property.

Glacier Lakes are like other lakes but water of these lakes is covered with snow.
Due to the bursting of such glacier lakes, there may be chances of glacier floods
in Glacier rivers. Sometimes earthquakes may also cause glacier lakes burst and
sometimes huge increase in water in such lakes may also cause the outburst of such
glacier lakes.

14. Effects of glacier lake outburst
i) Floods in glacier rivers
ii) Loss of life and property
iii) Destruction of the infrastructure
iv) Destruction of human settlement areas
v) Destruction of crops and other agricultural products

Cyclone

It is an atmospheric disturbance
which involves a closed circulation
around a low pressure region. Thus, the
close circulation of a storm around the
low pressure region is called a cyclone.
A cyclone moves in an anti-clockwise
direction in the Northern Hemisphere
and in the clockwise direction in the
southern hemisphere.

Tropical cyclones are originated in
the tropical zone of 5° to 25° and latitude in both the hemispheres. This cyclone is
formed in the ocean only because the ocean can supply sufficient amount of energy
for its formation. For the formation of a cyclone, the temperature of the water surface
should be higher than 26°C . This is the main reason why Nepal doesn’t experience
tropical cyclones.

Extra tropical cyclones develop in the regions lying between place with 30° to
65° latitudes in both the hemispheres. It has size of 160 km to 3200 km in direction.

Causes of cyclones

When the temperature of the sea water is below 50 meter depth rises to 26.50°C
or more, a cyclone develops in the sea. The process of developing a cyclone starts

New Creative Science, Class 9 | 347

in areas from 50 to 250 north and south latitude where air pressure is less. Water
vapour and hot air slowly rise and the air from the surrounding areas comes to fulfill
the vacuum. As a result, a cyclone develops and takes the form of a cyclone which is
called tropical disturbance. As air pressure decreases, the cyclone becomes stronger
and its velocity is about 119 km/hr.

Rise in temperature is mainly responsible for a cyclone. The rise in the water
level in the sea as a result of a cyclone is called a storm surge. A storm surge causes
the destruction of lives, property and human settlements near the sea bank.

Effects of cyclone
i) During a cyclone, there occurs a strong storm. It causes the destruction of
lives, property and human settlements near the sea bank.
ii) A tropical cyclone causes heavy rainfall.
iii) It causes a lot of harm to human settlement areas in towns and villages.
iv) It may cause the disturbance in the ecosystem of the surrounding region.
v) Agricultural land is severely affected.
vi) It causes harm to human beings, plants and animal life.
vii) Communication system may be affected by a cyclone.

Controlling measures of cyclones
i) Coastal areas should be well-prepared to face a cyclone.
ii) Houses in coastal areas should be built in such a way that it can withstand
heavy rainfall and forceful winds.
iii) Shelter beds should be made to check soil erosion and the speed of the wind.
iv) Sensitivity techniques should be used to forecast a cyclone appropriately.
v) When a cyclone comes, rescue and relief operations should be carried out as
soon as possible in the affected area.

ANSWER WRITING SKILLS

1. What is a storm surge?
Ü During a cyclone, the water level in the sea and ocean increases. It is called a

storm surge.

2. What types of countries are prone to cyclones?
Ü Those countries which are near the sea and the ocean are mainly prone to cyclones.

Generally, land-locked countries are not affected by cyclones.

3. List out the some names of cyclones which have the name of human beings.
Ü Bhola cyclone in Bangladesh, Mitch cyclone in Honduras, Katrina cyclone in the

USA, Nargis cyclone in Myanmar are some of the common cyclones, which are
given the names of human beings.

348 | Natural Hazards

4. What are ever green rivers?
Ü Those rivers which are originated from the Himalaya region especially from

Glacier Lake and run throughout the year are called ever green rivers. They have
more or less the same amount of water throughout the year.

5. What are Glacier rivers? How many glacier rivers and glacier lakes are present
in Nepal?

Ü Those rivers which are originated from the Himalaya region especially from
Glacier lakes and run throughout the year are called Glacier rivers. In Nepal,
about 3232 Glacier rivers and about 2323 glacier lakes are found.

SUMMARY
” Those incidents which cause the destruction of lives and property are called

hazards.
” Those incidents which occur randomly by the nature itself and cause huge

destruction of lives and property are called natural hazards.
” Natural disasters are floods, landslides, earthquakes, volcanic eruptions,

cyclones, etc.
” Some hazards do not occur naturally but human beings are responsible for

such hazards, which are called man-made hazards.
” Examples of man-made disasters are road accidents, epidemics, droughts,

nuclear radiations, chemical effects, etc.
” The overflow of water due to the glacier outburst is called a glacier flood.
” The overflow of water from the glacier lake as a result of the breaking down of

Glacier lakes is called a glacier lake outburst.
” The close circulation of a storm around the low pressure region is called a

cyclone.

EXERCISE

A) Multiple choice questions.

1. Which of the following is not a natural disaster?

(a) Flood (b) Earthquake
(c) Road accident (d) Glacier lake outburst

2. Which of the following methods is useful during earthquake?

(a) Run towards house (b) Search the food

New Creative Science, Class 9 | 349

(c) Stay safely at the same place until an earthquake stops

(d) Call for the police

3. How many glacier lakes are found in Nepal?

(a) 3252 (b) 2323
(c) 2300 (d) 3423

4. How many glacier rivers are there in Nepal?

(a) 2323 (b) 3423
(c) 3232 (d) 2345

5. What is the main cause of a glacier flood?

(a) Heavy rain-fall (b) Snow storm
(c) Bursting of a glacier lake (d) Earthquake

B) Answer the following questions.

1. What are Natural hazards? How can they be controlled?
2. Write down the differences between man-made hazards and natural hazards with

examples.
3. How are human beings responsible for natural disasters?
4. What is a glacier flood? Write its causes and effects.
5. Write down the names of major glacier lakes found in Nepal.
6. Write a short note on GLOF.
7. Human beings are responsible for the GLOF. Give reasons.
8. What is a cyclone? How does it occurred?
9. What are the effects of a cyclone? How can it be controlled?
10. How can we minimize the risk of hazards? Write five points.

A

B GLOSSARY
C

Natural disaster : the sudden occurring of the natural hazards which destroy land, property

and life

Glacier River : the rivers which are originated form glaciers

Glacier ood : the over ow of water and ice from the glacier lake

Cyclone : the high speed spiral storm

Volcanic eruption : the outpouring of magma in the form of lava



350 | Natural Hazards

UNIT

23 GREENHOUSE

About the Artificial Atmosphere
Greenhouse Effect
The earth is surrounded with the mixture of different
Have you seen a plastic types of gases. It is known as the atmosphere. The
house or a glass house in a atmosphere contains different gases like nitrogen, oxygen,
nursery? Do you know its carbon dioxide, water vapour, CFC (chlorofluoro carbon),
importance? It is called an etc. The earth receives heat and light from the sun. This
artificial greenhouse. Thus, heat and light make the earth warm during the day time.
an artificial greenhouse is a
structure with walls and a Greenhouse effect (Global warming)
roof made up of plastic or
glass in which temperature Why does the earth become cold at night? Does heat
is maintained according to received by the earth remain on the earth’s surface or it
the requirement. reflects back? We have experienced that we feel warmer
during a cloudy night than in a clear night. Why? Do you
have answer to these questions?

The world is growing industrialized to very fast. Due
to industrialization, the production of carbon dioxide gas is
increasing day by day. Most of the solar radiations coming
from the sun reflect back but some radiations are trapped
in the earth’s atmosphere.

The atmosphere of the earth plays a vital role to
maintain the temperature of the earth. The gases like carbon
dioxide, water vapour, CFC, etc. present in the atmosphere
trap the solar heat and do not allow at escape out. As a
result, the atmosphere of the earth becomes warmer. This
natural phenomenon is called a greenhouse effect. Thus,
the phenomenon of increasing temperature of the earth
due to different greenhouse gases like carbon dioxide,
water vapour, CFC, etc. is called a greenhouse effect or
global warming. If there is no greenhouse gas in the earth’s

New Creative Science, Class 9 | 351

atmosphere, the earth’s temperature falls below the freezing point. It makes enough
ice on the earth’s surface. In this condition, no living beings can survive on this earth’s
surface. So, the greenhouse effect plays a vital role to maintain the temperature of the
earth. Greenhouse gases make the earth suitable for living beings.

Disadvantages of the greenhouse effect

In spite of some advantages of the greenhouse effect, it has many disadvantages.
Some disadvantages of the greenhouse effect are listed below.

i) It increases the temperature of the earth every year.
ii) It changes the pattern of the water cycle.
iii) It causes the melting of ice from the Himalayan region.
iv) It increases the sea level because of which human settlement near the sea areas

are very risky.
v) It causes climatic change due to global warming.
vi) It affects human health.
vii) It destroys biodiversity.
viii) It imbalances the ecosystem.
ix) It reduces agricultural products.
x) It increases desert areas.
xi) It imbalances the geochemical cycle of the earth.

Artificial greenhouse

Have you seen a plastic house or a glass house in a nursery? Do you know its
importance? It is called an artificial greenhouse. Thus, an artificial greenhouse is a
structure with walls and a roof made of plastic or glass in which temperature is
maintained according to the requirement.

How of artificial greenhouse works?

The sun emits all kinds of solar radiations.
The short wavelength solar radiations coming
from the sun enter the artificial greenhouse. Some
of the energy of these short wavelength radiations
gets absorbed by the greenhouse. As a result, short
wavelength solar radiations are converted into
long wavelength radiations. The long wavelength
solar radiations cannot pass through the artificial
greenhouse. They are trapped inside the artificial

352 | Greenhouse

greenhouse and increase the temperature. This phenomenon of the increasing
temperature inside the artificial greenhouse is called a greenhouse effect.

Importance and utility of an artificial greenhouse

An artificial greenhouse has higher temperature compared to the temperature
outside. To grow summer plants, they need more heat compared to the winter plants.
If we want to grow these summer plants in winter season, it becomes very difficult.
Because, they cannot get sufficient heat form the atmosphere. Inside the artificial
greenhouse there is more temperature where summer plants can be grown easily.
Some useful effects of an artificial greenhouse are listed below.

i) We can grow many crops in all seasons and plants according to our
requirement.

ii) We can maintain temperature in the winter season for various crops.
iii) We can grow various corps in the mountain and Himalaya regions which

are mainly grown in hot and temperate regions.
iv) We can grow certain species of plants throughout the year.
v) By growing the off seasonal crops, we can improve our economic condition.

Climatic change

Climate refers to an average state of weather for a long time. Nepal has different
types of land topography. It has large geographical variation. Its land topography can
be divided into mountain, hilly and terai regions. It has large variation in climate due to
its land topography. In Nepal, there is high temperature in the terai region and a lower
temperature in the Himalayan region. So, our country is popularly known as a sensitive
country from the perspective of climate change.

Causes of climatic change

There are many causes which are responsible for climatic change. Some causes of
climatic change are discussed below.

1. Increase in Temperature

Increase in temperature is one of the main responsible factors for climatic
change. Due to increase in temperature, some parts of the earth get heated very fast
and some parts cool very fast. Such kind of variation in temperature brings climatic
change.

New Creative Science, Class 9 | 353

2. Release of greenhouse gases
Fossil fuels are the main sources of energy in the present world. We derive

around 70% energy from fossil fuels. As we burn fossil fuels, a large amount of carbon
dioxide is released in the atmosphere. It is mainly responsible for greenhouse effects.
The greenhouse effect is responsible to increase the temperature of the earth. So, it
brings climatic change.

3. Deforestation
People are cutting trees for different purposes. Due to this forest areas are

decreasing day by day. Decrease in the number trees or forest areas increases the
carbon dioxide in the atmosphere. More carbon dioxide in atmosphere causes global
warming, which brings climatic change.

4. Over use of chemical fertilizers
People use different kinds of chemical fertilizers to increase the productivity

of crops. Overuse of such chemical fertilizers decreases the fertility and increases
the dryness of soil. Overuse of nitrogenous chemical fertilizers also affects aquatic
animals. This may promote the greenhouse effect and climatic change.

5. Industrialization
The production of harmful gases like carbon dioxide, carbon monoxide, sulphur

dioxide, oxides of nitrogen, etc. is mainly due to industrialization. These harmful
gases and chemicals directly mix into the atmosphere and cause acid rain. So,
industrialization is also one of the causes of climatic change.

6. Volcanic eruption
Due to volcanic eruptions, different compounds of sulphur release into the

atmosphere. These compounds of sulphur and dust particles present solar radiations
from reach up the earth’s surface. It results in the decrease of the earth’s temperature.
This also brings climatic change.

Effects of climatic change

Human beings and other living organisms are directly and indirectly affected by
the climatic change. Some major effects are discussed below.

354 | Greenhouse

1. Change in the temperature of the atmosphere

The temperature of the atmosphere rises every year due to climatic change. Every
year, the rise in temperature is about 0.04°C . Due to the increase in temperature, ice is
melting from the Himalaya region. It increases the sea level and sinks low land areas
of the earth's surface.

2. Impact on biodiversity and ecosystem

There are different types of plants and animals on the earth. They survive in
areas with suitable temperature and climate. All animals and plants cannot survive in
fluctuating climate and they become extinct from the earth’s surface. Due to increase
in temperature of the earth, there is always danger of different types of disasters
like glacier outbursts, glacier floods, cyclones, etc. So, biodiversity and ecosystem are
badly affected from these disasters.

3. Effects on agricultural products

Due to climatic change, there occurs partial or least rain, untimely rain, droughts,
etc. It has a direct effect on agricultural products. In our country, most of the people
depend upon seasonal rain for agriculture. So, due to less rainfall, there is decrease in
agricultural products.

4. Natural Disasters due to climatic change

Due to climatic change there occurs some natural disasters like glacier outbursts,
glacier floods, cyclones, floods, landslides, etc.

5. Negative effect on water resources

Climatic change has a direct effect on water resources. Due to increasing
temperature, the melting of glacier lakes take place. It increases the size of glacier
lakes and may cause glacier floods. Floods bring negative effects on land and the
pond ecosystem.

6. Energy crisis

Hydroelectricity depends upon the flow of water. Due to climatic change, there
is less flow of water in rivers. It directly affects hydroelectricity. We are facing a
problem of power cut in our country due to the energy crisis. So, the climatic change
promotes the energy crisis.

New Creative Science, Class 9 | 355

7. Impact on human settlement

Climatic change brings different types of natural calamities like flood, landslides,
GLOF, etc. which cause huge damage to human settlement areas. Many people can be
displaced from their settlement areas due to such natural calamities.

8. Effects on physical Infrastructure

The infrastructure like roads, bridges, etc. may be damaged due to the natural
disasters like heavy rain, landslides, floods, etc. Many people will be affected due to
the damage of such physical infrastructure.

Controlling measures of climate change

i) It is necessary to decrease the production of greenhouse gases.
ii) Afforestation program should be launched in bare land.
iii) Public transportation should be encouraged more than private vehicles.
iv) Alternative sources of energy like solar , hydropower, etc. should be used

more than fossils fuel.
v) Water should be conserved.
vi) Excessive emission of greenhouse gases from industries and factories should

be controlled.
vii) Use of fossil fuels should be minimized.
viii) People should be aware of climatic change and its effects.
ix) Use of artificial greenhouse should be decreased.

ANSWER WRITING SKILLS

1. What are cold frames?
Ü Artificial greenhouses which made in a small scale are called cold frames. They

are made from plastics or glass. They are used to grow off seasonal plants and to
develop small nursery plants.

2. What is the value of increased temperature in the last 100 years?
Ü The value of increased temperature in the last 100 years is about 1.4 °F . Every

year the rise in temperature In Nepal is about 0.06°C .

3. What will happen if there is no greenhouse effect on the earth?
Ü If there is no greenhouse effect on the earth, the average temperature of the

earth will be very less. At that temperature, the survival of living beings will be
impossible.
356 | Greenhouse

4. How does a volcanic eruption decrease the earth’s temperature?
Ü In a volcanic eruption, different kinds of sulphur compounds are released. These

sulphur compounds along with dust particles protect solar radiations to enter the
earth's surface. Therefore, a volcanic eruption decreases the earth’s temperature.

SUMMARY
” The earth is surrounded by the mixture of different types of gases, which is

known as atmosphere.
” The phenomenon of increasing temperature of the earth due to different

greenhouse gases like carbon dioxide, water vapour, CFC, etc. is called the
greenhouse effect or global warming.
” An artificial greenhouse is a structure with walls and a roof made of plastic or
glass in which temperature is maintained according to the requirement.
” Climate refers to an average state of weather for a long time.

EXERCISE

A. Multiple choice questions

1. An artificial greenhouse is made by

(a) Rubber (b) Plastic or glass
(c) Wood (d) glass

2. Which is the main greenhouse gas? (b) Carbon dioxide
(d) Chlorofluorocarbon
(a) Oxygen
(c) Nitrogen

3. Why is an artificial greenhouse made?

(a) To maintain earth’s temperature (b) To decorate gardens
(c) To grow off-seasonal plants (d) All of the above

4. In an artificial greenhouse which phenomenon occurs?
(a) Short wave radiations change into long wave solar radiations
(b) Long wave radiations change into short wave radiations
(c) Carbon dioxide gas is filled inside the greenhouse
(d) All the above

5. What is the major cause of the greenhouse effect?
(a) Over production of greenhouse gases
(b) Maximum number of artificial greenhouses

New Creative Science, Class 9 | 357

(c) More use of bio-gas
(d) None of the above

6. What type of energy is stored in a greenhouse?

(a) Heat (b) Nuclear

(c) Light (d) Kinetic

7. What type of problem is seen due to climatic change?

(a) Global warming (b) GLOF

(c) Flood (d) All of the above

B. Answer the following questions.

1. What is the greenhouse effect or global warming?
2. What are the greenhouse gases? Write down their names.
3. What do you mean by an artificial greenhouse? Write its importance.
4. List out the causes of climatic change and discuss any two in detail.
5. What are the effects of greenhouse gases?
6. List out the preventative measures of the greenhouse effect?
7. How are human beings affected by the greenhouse effect?
8. What is the advantage of greenhouse gases?
9. Why is the roof of an artificial greenhouse made slanted?
10. How can we decrease the climatic change?

A

B GLOSSARY
C

Deforestation : cutting down of forest in a large scale

Greenhouse gases : the gasses which are responsible for the greenhouse e ect

Greenhouse e ect : the increase in temperature due to the greenhouse gases

Cold frame : small scale greenhouse

Global warming : increasing temperature of the earth

358 | Greenhouse

UNIT

24 THE EARTH IN THE UNIVERSE

About the Scientist The universe

Stephen William Hawking Everything what we see, hear and feel, are the members
of the universe. The universe is the vast surrounding space.
Stephen William Hawking It includes everything including all the celestial bodies,
is a British theoretical galaxies, vast space and the whole world. It is infinite and
physicist, whose world- unbelievable. The Milky Way is a medium-sized galaxy
renowned scientific career consisting of about one hundred sixty billions of stars.
spans over 40 years. Among them, the sun is the only the medium-sized star,
His books and public which is also a middle-aged star. The sun is the main
appearances have made him member of the solar system, around which eight planets,
an academic celebrity and asteroids, satellites and comets revolve.
he is an Honorary Fellow of
the Royal Society of Arts. Some units to measure the distance in the
He is lifetime member of universe
the Pontifical Academy of
Sciences, and in 2009 he was It is very difficult to measure the distance in the
awarded the Presidential universe in the units like metres, kilometres, etc. as the
Medal of Freedom, the distance between two heavenly bodies is very large. So,
highest civilian award in the special units must be used to measure the distance between
United States. the heavenly bodies. Some of the units used to measure the
distances in the universe are:
Hawking has a neuro-
muscular dystrophy that (a) Astronomical unit (AU)
is related to amyotrophic (b) Light Year
lateral sclerosis (ALS), a (c) Parsec
condition that has progressed
over the years and has left (a) Astronomical unit (AU)
him almost completely
paralysed. It is defined as the mean distance between the sun and
the earth. Its value is 1.5 × 1011 m. It is used to measure
the distances between the members in the solar system i.e.
smaller distances in the universe.

(b) Light year

The distance traveled by light in one year passing
through a vacuum is known as one light year. Its value is
9.46 × 1012 km.

Methods to calculate the value of one light year
We know that,
Velocity of light in vacuum (v) = 3 × 108 m/s
Time taken (t) = 1 year

New Creative Science, Class 9 | 359

We have,
Distance travelled = v × t

= 3 × 108 m/s × 1 yr
= 3 × 108 × (1 × 365 × 24 × 60 ×60)s
= 9.46 × 1015 m
= 9.46 × 1012 km
\1 light year = 9.46 × 1012 km

(c) 1 Parsec

The distance which is equal to 3.26 light years is called 1 parsec.

\ 1 Parsec = 3.26 light years

MEMORY TIPS

 Proxima Century, the second nearest star from our solar system lies 4.3

light years away. Sirius is 8.6 light years and Vega is 26.5 light years away.

(First nearest star is the sun itself)

 Parsec = The parallax angle having the value of 1 second.

10 = 1 minute, 1 min = 1 second
60 60

Parallex angle means the angle which is obtained by bisecting the vertex of

an isosceles triangle by a perpendicular on its base.

If an angle of 1° is equally divided into 3600 fragments, then a single

fragment of the angle is called 1 second (1’’).

Parsec is the vertical distance of the triangle (height of the perpendicular

drawn from the vertex to base) of the isosceles triangle, whose base is

taken the longest diameter of earth’s orbit. See the figure:

Solar System
The system of eight planets, satellites, comets, asteroids, meteors, etc. which

360 | The Earth in the Universe

revolve around the sun is called the solar system. The sun is the main member of
the solar system. The eight planets Mercury, Venus, Earth, mars, Jupiter, Saturn,
Uranus and Neptune revolve around the sun in their own orbit. Along with them,
their satellites, asteroids, meteors, meteorites, comets also revolve around the sun.
Among these eight planets, only our earth has life on it. The summary of eight planets
is given in the following table.

The brief about the Planets (From the source)

S. N. Planet’s Mean Diameter Approx. Planet’s Planet’s Satellite Atmosphere
name distance (km) Temperature day year number
from the Nil
sun (km) (°C) 59 days 88 days 1 (Moon)
2 [Phobos 90–95%, CO2,
1. Mercury 5.8 × 107 4880 427°C at day 243 days 225 days and Diemos] clouds of H2SO4
2. Venus and -170°C at
3. Earth 1.08 × 108 39 N2 (78%), O2
night 32 (21%) CO2, H2O,
1.5 × 108 21
1204 About 480°C 8 etc.
2.26 × 108 Thin CO2, little
12756 About 22°C About 24 hrs About 365 water, and little
7.78 × 108 days
1.5 × 109 O2
4. March 6720 25°C at day 24 hrs 37 687 days H2 , He
5. Jupiter 2.87 × 109 140800 -120°C at night minutes H2 , He
6. Saturn 4.48 × 109 120585
7. Uranus 51200 -150°C About 10 hrs. About 12 yr H2 , He, CH4
8. Neptune 48000 -180°C 29.5 yr H2 , He, CH4
10 hrs and 14
- 216°C minutes 84 yr
-220°C 164 yrs
17 hrs and 8
minutes

16 hrs

Phases of the moon

The moon is the only natural
satellite of the earth. It revolves
around the earth in its own elliptical
path. Due to its revolution around the
earth, we see the different changing
shapes of the moon every day in the
sky. Here, we will discuss about the
different phases of the moon.

The moon changes its shape daily
because of the following reasons.

i) The moon does not have its
own light and it reflects the
sunlight.

ii) The moon revolves around the earth in its elliptical path.

New Creative Science, Class 9 | 361

Due to this, on different days, different bright or dark parts of the moon face
towards the earth and we see the changing shape of the moon every day.

When the moon is between the sun and earth in a straight line, only the dark part
of the moon faces us and we do not see any moon on the sky. This day is called no
moon day or the new moon.

When the moon makes an angle of 12°, only a little bright part of it faces the
earth. This structure of the moon is called the waxing crescent.

The bright part goes on increasing to make an angle of 90°, the bright part of
moon is seen in the form of hemisphere. This is called the first quarter.

When the moon reaches an angle of 168°, only a little part remains dark. It is
called the waxing gibbous.

Ultimately, when the moon makes an angle of 180° the moon is seen completely
round, which is called the full moon.

This period in which the bright part of moon goes on increasing is called the
bright half or the waxing moon. It completes in about 15 days.

Now, in the course of revolution, when the moon makes an angle of 192°, its dark
part covers the moon slightly, which is called the waning gibbous.

When the moon reaches at an angle of 270° the moon is seen at hemisphere again.
It is called last quarter.

When only a very little amount of bright part of the moon is seen it is called the
waning crescent. At this condition the moon forms an angle of 348°.

Finally, after making an angle of 360°, again the moon is not seen in the sky,
which is called the new moon.

The time period in which the dark part of moon increases is called the dark half
or the waning moon.

Sidereal month and synodic month

It is a known fact that the earth revolves around the sun, and the moon revolves
around the earth and at the same time the moon also revolves around the sun.

The time taken by the moon to complete one revolution around the earth is called
the sidereal month. Its time period is about 27.33 days. It is widely used in astrology.

The time taken by the moon to reach the full moon from the full moon or new
the moon from new moon is called the synodic month or, the time between two
consecutive new moons and two consecutive full moons is called the synodic month
or the lunar month. Its time period is 29.5 days.

QUESTIONS >>
# What do you mean by the phases of the moon?
# What do you mean by the synodic month and sidereal month?

362 | The Earth in the Universe

Relationship between the sun, the earth and the moon

The sun is a medium-sized star. It is the centre of the solar system. It is the nearest
star from the earth. It has more than 70 percent of hydrogen. The hydrogen atoms
combine together to give helium and large amount of heat and light. This heat and
light is the main source of energy on the earth's surface as well as in all the planets
and satellites. The sun rises in the east and sets in the west. It is due to the fact that the
earth revolves the sun from west to the east.

There are 8 planets in the solar system. Among them, the earth is a living
planet as it has living beings. On the earth's surface, there is air, water and suitable
temperature for the survival of the living beings. The earth revolves around the sun
in an elliptical orbit. During its revolution, sometimes it comes close to the sun and
sometimes it goes far away from the sun. The earth is a non-luminous body. It gets
heat and light from the sun.

The heavenly bodies which revolve around the planets in their own orbits are
called satellites. There are about 152 natural satellites in our solar system revolving
around the planets. The short description and the no. of satellites are each planet is
given in the following table.

S.N. Planet’s name Satellite’s number
1. Mercury 0
2. Venus 0
3. Earth 1 [moon]
4. Mars 2 [Phobos and Deimos]
5. Jupiter 63: [Europa, Io, Callisto, Ganymede
etc.]
6. Saturn 46 [Titan]
7. Uranus 27 [Miranda, Ariel, Umbrial etc.]
8. Neptune 13 [Trition, Nereid etc.]

Source: Encarta - 2006

Artificial satellites are the man-made machines revolving around a planet. They
are launched for various purposes like research and investigation, weather studies,
communication, military purposes, navigation, etc. The moon is a natural satellite of
the earth. It revolves around the earth.

The comparative study of the sun, the earth and the moon

Basis The sun The earth The moon
Mass 2×1030 kg 6×1024 kg 7.35×1022 kg
Average radius 695508 km 6371 km 1737 km

New Creative Science, Class 9 | 363

Equatorial 4370005 km 40075 km 10921 km
perimeter
Area 11990 times more 510072000 sq.km 37930000 sq. km
than the earth
Temperature 570000C 150C -1250C to 1300C
Acceleration due – 9.8 m/s2 1.6 m/s2
to gravity
Escape velocity 617 km/s2 11.2 km/s 2.38 km/s
Time for rotation 300000000 days 24 days 27 days
Rotation velocity 221 km /s 29.8 km /s –
Density 1.4 g/m3 5.51 g/m3 3.34 g/m3
Atmosphere H2, He, etc. N2, O2, CO2, Argon, Ar, He, Rn, etc.
etc.

Diurnal and annual motion of the earth

The earth has two types of motion
diurnal and annual. The earth moves
around on its own axis. It is called diurnal
motion or rotation. The earth takes about 23
hours, 56 minutes and 4 seconds to make a
complete rotation.

The earth moves around the sun in
its own orbit. It is called annual motion or
revolution. The earth takes about 365 days and 6 hours to complete one revolution
around the sun. The axis of the earth is inclined to the plane of the orbit at an angle of
66½ which causes the change in the length of day and night.

The earth rotates from west to east. When the earth rotates, the part which faces
the sun experience the day and the part which goes away from the sun experience
the night.

When the earth is at E1 the condition during its rotation i.e. on 21st June, the
northern hemisphere of the earth experiences sunlight for more time, and hence in
the northern hemisphere has the longest day. This day is called the summer solstice.
In this condition, there is summer season in the northern hemisphere.

When the earth reaches to E2 condition on 23rd September, both the hemispheres
have the sunlight for equally so, days and night are equal on this day, and it is called
the autumn equinox.

364 | The Earth in the Universe

When the earth reaches E3 condition, 22nd December, the northern hemisphere
tilts away from the sun, and hence it experiences the winter season and this day is the
shortest day in the northern hemisphere. It is called the winter solstice.

When the earth reaches E4 on 22nd March again both the hemispheres receive
the equal amount of sunlight for the same time. Hence, both the day and night are
equal and this day is called the spring equinox.

At the Polar Regions, the darkness or brightness lasts for 6 months and there is
extreme cold in this region.

MEMORY TIPS
In 500 AD, Philolaus, a Greek Philosopher, stated that the earth was moving around
a central fire in the west to east direction.
Later, a Greek astronomer Aristarchus of Samos, stated that the earth rotates and
moves in an orbit around the sun.

Eclipse

The eclipse is a shadow of a heavenly body which falls on another body in the
space. Eclipses are seen because:

i) Only the sun is a luminous body and other celestial bodies reflect its light.
ii) During the course of their rotation and revolution, the sun and the other

two heavenly bodies may lie in a straight line, and the shadow of one body
falls on the another body forming an eclipse.
iii) Light travels only in a straight line.

There are two types of eclipses seen from the earth i.e. (a) Solar eclipse (b) Lunar
eclipse

New Creative Science, Class 9 | 365

(a) Solar eclipse
When the moon comes between the earth and the sun and they lie in a straight

line, the shadow of the moon falls on the earth. It is called the solar eclipse. In this
condition, some or the total part of the sun is blocked by the moon and we cannot see
it. It occurs on the new moon day.

i) Total solar eclipse
When the sun is totally blocked by the moon, then it is called total the solar

eclipse. It is for a short duration of about 8 minutes. This type of eclipse is very rare
and repeats after 360 years at any particular place. It is very important for scientists
because they can study about the corona of the sun in this condition.
ii) Partial solar eclipse

It is the condition in which the sun is partially blocked by the moon.
iii) Annular solar eclipse

When the moon is the farthest from the earth, then it blocks the central part of
the sun and the bright part of the sun is seen as a ring called the annular eclipse. It is
very rare and repeats after a thousand years only.

366 | The Earth in the Universe

The solar eclipse begins from the western part and escapes from the eastern part
of the sun. It is shorter than a lunar eclipse.

Lunar eclipse

When the earth comes between the sun and moon and they lie in a straight line,
the shadow of the earth falls on moon. We cannot see the moon partially or totally it
is called lunar eclipse. It occurs on the full moon day. The total lunar eclipse stays for
a long time i.e. 1 hr 40 minutes as the size of the earth is greater than the moon.

During the total lunar eclipse, the moon does not dark completely but appears
red due to the refraction of light from the earth’s atmosphere.

The lunar eclipse begins from the eastern part and escapes from the western part
of the moon.

QUESTIONS >>
# Why a lunar eclipse stays for a long time?

The Nodes; RAHU and KETU

The points at which the orbits of the moon and the earth cut are called nodes i.e.
RAHU and KETU.
ANSWER WRITING SKILLS
1. Pluto has been taken out from the category of planets. Why?
Ü The international convention of astronomers held on 2006 in Prague of Czech

Republic has removed Pluto from the list of planets because,
(a) It is much smaller than the size of other planets.
(b) Its orbit crosses with the orbit of Neptune.

New Creative Science, Class 9 | 367

2. The solar eclipse is shorter than the lunar eclipse. Why?
Ü It is because, during the solar eclipse, the sun and moon move in the opposite

direction and the size of the moon is smaller so it casts a shadow of smaller
area. But in the case of the lunar eclipse, the moon and earth move in the same
direction and area of the earth’s shadow is more than that of the moon’s shadow.

3. Why is total a solar eclipse very important for scientists?
Ü During a total solar eclipse, they can learn about the corona of the sun and it is

very rare. So, it is important.

4. A lunar eclipse is never annular. Why?
Ü The earth is bigger than the moon, and it is impossible for it to come to the centre

of the moon. So, it is impossible for the lunar eclipse to be annular.

5. During total lunar eclipse, the moon is not darkened completely but it appears
coppery red. Why?

Ü It is due to the refraction of the sun rays through the earth’s atmosphere.

6. The northern hemisphere has the longest day on 21 June. Why?
Ü On 21st June, the northern hemisphere tilts towards the sun. Thus, it receives the

direct sun-rays for a longer time. So, it has the longest day.

7. There is no eclipse on every full moon and new moon day. Why?
Ü The orbital plane of the earth does not coincide but is at a angle of 5.15°. Hence,

the three heavenly bodies i.e. the sun, the moon and the earth do not come to
the same straight line on every full moon or new moon day. Hence, there is no
eclipse on every full moon and new moon day.

SUMMARY
” The universe is the vast unmeasurable and unimaginative.
” The earth rotates in its own axis which is called the diurnal motion and the

earth moves round the sun, which is called the annual motion.
” The shadow of the earth falling on the moon is called the lunar eclipse. It lasts

for about 1 hour and 40 minutes.
” The shadow of the moon falling on the earth is called the solar eclipse. It lasts

for about 8 minutes.
” The time taken by the moon to complete one revolution around the earth is

called the sidereal month. Its time period is 27.33 days.
” The time between two consecutive new moons and full moons is called synodic

month. Its time period is 29.5 days.

368 | The Earth in the Universe

” The heavenly bodies which revolve around the planets are called satellites.
” There are 152 natural satellites in our solar system.
” A total solar eclipse is very important for scientists.

EXERCISE

1. Define the solar system. Why is Pluto taken out from the list of planets?

2. What are diurnal and annual motions of the earth? What are their effects?

3. Explain how the changes of seasons take place on the earth.

4. What are the phases of the moon? How are they caused?

5. Define:

(a) waxing crescent (b) waning crescent (c) waxing gibbous
(d) waning gibbous (e) sidereal month (f) synodic month

6. Give reasons:

(a) The duration of the day and the night varies in different seasons.

(b) An eclipse does not occur on every new moon and full moon day.

(c) An eclipse only occurs on a new moon and full moon day.

(d) A total solar eclipse is very important for scientists.

(e) A lunar eclipse stay longer than a solar eclipse.

7. Draw a well-labeled diagram of the solar eclipse.

8. Draw the well-labeled diagram of the lunar eclipse.

A

B GLOSSARY
C

Vast : very big
Diurnal : motion for day and night
Arti cial : man-made
Annual : which occurs yearly
Eclipse : the shadow of one object on the other



New Creative Science, Class 9 | 369

Specification Grid

Subject : Science Full Marks: 75
Class : Nine Time: 2:15 Hours

AREA Topics K U A H.A Total
42 Marks

Physics 1 Measurement 5×1 4×2 2×3 1×4 23
2 Force
Chemistry 3 Machine 4×1 4×2 2×3 1×4 22
4 Work, energy and power 1×2
Biology 5 Light 5×1 13 2×3 1×4 23
6 Sound 1×1 26
Geology 7 Electricity and magnetism 15 …….. 1×4 7
and 8 Classification of elements 15
9 Chemical reaction 64 38
Astrology 10 Solubility 18 16 75
11 Some gasses
12 Metals
13 Carbon and its compounds
14 Water
15 Fertilizers
16 Classification of plants and animals
17 Adaptation of the organisms
18 Systems
19 Sense organs
20 Evolution
21 Nature and environment
22 Natural hazards
23 Greenhouse
24 The earth in the universe

Total questions
Total Marks

Note : Questions will be asked from each unit.
K = Knowledge
U = Understanding
A = Application
H.A = Higher ability

370 | The Earth in the Universe

A sample set of model question

Group 'A' 15 × 1 = 15
1. Define fundamental units with an example.
2. State Newton’s third law of motion.
3. What is efficiency? Write down its formula.
4. Define refractive index.
5. State Ohm’s law.
6. What are fundamental particles of an atom?
7. Define reactant and products.
8. The solubility of potassium nitrate is 96. What does it mean?
9. Define malleability and ductility.
10. Write down the phylum of hydra and crocodile.
11. Name any two excretory organs of the human body.
12. Write down the main function of the optic nerve in the eye.
13. What is embryo?
14. What are abiotic factors of the ecosystem?
15. Write down the full name of GLOF.

Group 'B' 13 × 2 = 26

16. Write down any two differences between pendulum watch and quartz watch.
17. A gun recoils while firing a bullet, why?
18. Wheel and axle is a continuous lever, why?
19. The critical angle of diamond is 24 degree. What does it mean?

20. Write down any four information which are obtained from a balanced chemical reaction.

21. Write down any two chemical reactions where we use positive and negative catalyst
each.

22. Write down any four roles of zinc in the human body.

23. Diamond is a bad conductor of electricity but graphite is a good conductor of electricity, why?

24. Write two differences between bryophytes and pteridophytes.

25. Write down the name in the life cycle of culex
mosquito.

26. Write down any two adaptational characteristics
of aloe.

27. Viruses are called obligatory parasites, why?
28. Write any four causes of glacier flood.

New Creative Science, Class 9 | 371

Group 'C' 6 × 3 = 18
29. Study the given graph and answer the following questions.

i. Name the type of motion in OA and AB.
ii. In which portion of the graph, there is

acceleration and retardation.
iii. In which portion of the graph there is zero

acceleration. Figure of the graph
30. A load of 600 N is lifted by a machine applying 400 N

effort. If effort distance and load distance are 60 cm and
30 cm respectively, calculate MA, VR and efficiency.
31. Write down any three uses oxygen gas.
32. Write down any three uses of water.
33. Write down any three important characteristics of bacteria.
34. Write down three importance of excretory system in human body.

Group ‘D’ 4 × 4 = 16

35. Observe the given diagram and answer the following questions. Figure of dispersion of light
A
a. What type of process is shown in

the diagram?

b. Why does this process not occur in Q Least deviation S
c. glass slab? P A(Sbuenalimghotfowr hbiutelblilBgighhtt) Glass prism CMaximum deviation
Write down the colour spectrum
from bottom to the top.

d. Why does red colour lie at the top

and violet colour at the bottom?

36. Observe the given diagram and answer the following questions.
a. Which gas is going to prepare according to the given figure?
b. Name the chemicals required to prepare this gas
c. We take impure granulated zinc in this
process, why?
d. Why is this gas collected by downward
displacement of water?

37. Identify the given organisms and write down any two

characteristics of each.

38. Describe the different phases of the moon with the help of diagram.

372 | The Earth in the Universe