This document provides information about the Earth and its motion in the universe. It describes the Earth's daily rotation and yearly revolution around the Sun, which causes seasons and varying day and night lengths. It also explains the phases of the Moon and lunar and solar eclipses, noting that eclipses occur when the Sun, Moon, and Earth are aligned. Diagrams are included to illustrate these concepts.

1. The Earth in the Space
OMENDRA
SHAH

2. The Earth in the Universe
After completion of this lesson, student must be able to:
Describe diurnal and annual motion of the earth.
Explain the phases of the moon.
Determine the relation of the position of the moon,
the earth and the sun.
Explain with a diagram, umbra and penumbra of a
shadow.
Explain lunar and solar eclipses with reason and
diagram.

3. Universe is a huge space which contains everything that exists
including solar system, constellations, Galaxies etc.
Constellations are the group of stars having fixed shapes.
Examples: Aries, Cancer, Aquarius, Leo, Libra etc.
Galaxy is the system of stars that consists star, star clusters, dust
and gases held together by gravity.
Solar system is composed of the sun, eight planets including
the earth, satellites, asteroids, comets, meteorites etc. The
distance in the space is measured in the term of light year.
Planets are the heavenly bodies which revolve around the sun in
elliptical path without being intersected by path of other
planets.
In Greek, the meaning of planet is 'wanderer'.
There are major eight planets in the solar system. They are:
Mercury Venus Earth Mars Jupiter, Saturn, Uranus and Neptune.
The closest planet and the farthest planet from the sun is
mercury and Neptune respectively
Mercury is the fast rotating planet. Venus is the brightest
planet. Mars is red planet. Jupiter is the largest planet. Earth is
the only one planet where the life is possible.

5. The universe has unlimited size and unknown shape.
All the existing things include galaxies, planets,
satellites, comets, and meteors.
The solar system is located in Milky Way galaxy. The
Milky Way galaxy is a medium sized galaxy, which
consists of about 150 billion of stars. Astronomers
believe that there are 10^12 such galaxies in the
universe. Astronomical unit (AU), Lightyear (LY) and
parsec are used to measure the distance in the
universe.
1 AU = 1.5 × 1011 m
1 LY = 9.46 × 1015 m
1 parsec = 3.26 LY

6. Planets Asteroids
The heavenly bodies which
revolve around the sun are
planets.
The heavenly bodies which
revolve round the sun mainly
between mars and jupiter are
called asteroids.
They are bigger. They are smaller.
The differences between planets and asteroids are as follows:

7. Synodic month Sidereal month
The time period between any
two consecutive full moon is
called synodic month.
The time required for one
complete revolution around
the earth by the moon is
called sidereal month.
It has 29days. It has 27 days.
The differences between synodic month and sidereal month are as follows:

9. Galaxy Constellation
It is the collection of billions
of stars.
It is the collection of limited
number of stars.
It has no regular pattern. It has regular pattern
There are about 1010 galaxies
in the universe.
There are about 88
constellations known.
The differences between galaxy and constellation are as follows:

10. Stars Planets
The heavenly bodies which
have their own source of
light are called stars.
The heavenly bodies which
revolve round the sun and do
not have their own source of
light are called planets.
Stars are luminous objects
Planets are non-luminous
objects
They are bigger in size. They are smaller
The differences between stars and planets are as follows:

11. Only the sun is known star, which has a group, like solar family
and only one planet the earth of it has suitable conditions for
organisms to survive on it.
The eight planets of the solar system are Mercury, Venus, Earth,
Mars, Jupiter, Saturn, Uranus and Neptune. Countless meteors,
meteorites, and comets also revolve around the sun beside
planet. Drifting particles called interplanetary dust and an
electrically charged gas known as plasma exist in the space of
the solar system.

12. TERRESTRIAL PLANETS (INNER PLANETS)
Mercury, Venus, Earth, and Mars. These planets
are those closest to the Sun. They are
characterized by their dense, rocky composition.
GAS GIANTS (OUTER PLANETS)
There are also four gas giant
planets: Jupiter, Saturn, Uranus, Neptune. These
planets are found in the outer solar system. They are
characterized by their massiveness and gaseous
composition.

13. According to international convention of
astronomers held on 2005 AD following criteria
should be fulfilled by revolving planets:
A planet should have its own orbit around the sun.
Its shape must be round.
Its orbit must not cross the orbit of other planets.
Pluto was removed from the planet as it crosses
the orbit of Neptune.

14. Planet FAQ
How many planets are there in our solar system? There are 8 planets in
our solar system.
What is the smallest planet? Mercury is the smallest planet.
What is the largest planet? Jupiter is the largest planet.
Which planet is closest to the Sun? Mercury is the closest planet to the
Sun.
Which planet is farthest from the Sun? Neptune is the farthest planet
from the Sun.
What is the coldest planet? On average Neptune is the coldest planet
What is the hottest planet? Venus is the hottest planet.
What are the inner planets? Mercury, Venus, Earth and Mars are the inner
planets.
What are the outer planets? Jupiter, Saturn, Uranus and Neptune are the
outer planets.
Which planets have rings? Jupiter, Saturn, Uranus and Neptune have rings.
Is there life on other planets? Not that has been encountered so far!

16. The Earth
Our Earth is the only planet in our solar system which supports the life of
living organisms. Earth is also known as the green planet.
It is the third planet from the sun at a distance of about 150 million
kilometers.
 It is the fifth largest planet. It takes 365.256 days for the Earth to travel around
the Sun and 23.9345 hours for the Earth rotate a complete revolution.
The diameter of Earth is 12,756 kilometers.
The atmosphere of earth is very suitable for the life of living organisms. The
atmosphere of earth is composed of various types of gasses. The majority of the
atmosphere is composed of nitrogen (78%), then oxygen (21%) and other
constituents (1%).
Earth is believed to be existent for 450 million years & evidence are from 225
million years.
The structure of earth is divided into mainly four layers namely Crust, Mantle,
Inner Core and Outer Core.

18. Equatorial Diameter: 12,756 km
Polar Diameter: 12,714 km
Mass: 5.97 x 10^24 kg
Moons: 1 (The Moon)
Orbit Distance: 149,598,262 km (1 AU)
Orbit Period: 365.24 days
Surface Temperature: -88 to 58°C
Earth is the third planet from the Sun and is the largest of
the terrestrial planets. The Earth is the only planet in our solar
system not to be named after a Greek or Roman deity. The Earth
was formed approximately 4.54 billion years ago and is the only
known planet to support life.
Earth Planet Profile

19. Diurnal and annual motion of earth
The earth moves round on its axis as well as in its orbit around the sun. The
motion of the earth on its axis is called diurnal motion and a complete round
on its axis is called a rotation. The earth takes about 24 hours (23 hours, 56
minutes and 4.09 seconds) to complete one rotation.
A complete round around the sun is called revolution. The earth takes about
365 days (365 days, 6 hours, 9 minutes and 9.4 seconds) to complete one
revolution.
The axis of the earth is inclined to the plane of the ecliptic at an angle of 66.5o.
So due to this, the receives different season and varying lengths of day and
night.

20. An effect of rotation on the earth
When the earth rotates on its axis, only one
portion of the earth faces the rays of the sun and
experiences the day. The other portion of the
earth is away from the sun’s rays which
experience the night. When the earth rotates
eastwards, every part of the earth is exposed to
the sun at a different time. The part of the earth
that comes from the darkness into the sun's rays
experiences sunrise and the part of the earth that
comes from the brightness (facing sun) into the
darkness experiences the sunset.

23. •A normal year is taken to have 365 days and an extra day is added every four years
to the leap year.
•In E1 condition of the earth in the given diagram, on June 21, the earth comes in
the position when the northern hemisphere is tilted towards the sun is called
summer solstice in that hemisphere. In this condition, the northern hemisphere
has the longest day and the shortest night but shortest day and longest night in
the southern hemisphere. During this period, the southern hemisphere has
winter.
•In E3 (December 22) condition, the hemisphere is tilted away from the sun; it is
called winter solstice. In this period, the northern hemisphere has the shortest
day and the longest night but southern hemisphere has the longest day and
shortest night. Here, the southern hemisphere has summer.
•In E4 (22 march) and E2 (23 September), the sun is vertically overhead. These
two days are termed equinoxes, meaning equal nights. 22 March is called spring
equinox and 23 September is called autumn equinox.
•The darkness and daylight lasts for half of the year respectively beyond arctic
circle and antarctic circle. In this region, the sun is never high in the sky. So, this
region faces the extreme coldness.

26. When we observe the sky daily for some
days, we find that the moon changes its
shape every day. It is called phases of the
moon.
Phases of the moon occur because of
following reasons:
oThe moon is a non-luminous body and
reflects the sunlight.
oThe moon is revolving around the earth
in its elliptical orbit.

28. A. When the moon forms an angle of 00 from the plane of earth’s orbit, the
whole dark part of the moon faces towards the earth and hence any part of
the moon is not seen i.e. is a new moon(m1).
B. After 24 hours, when the moon forms an angle 120 from the plane of its
orbit, a little bright part of the moon faces towards the earth and a
minimum part of the moon is seen bright. It is called waxing crescent
(m2).
C. When the moon forms an angle of 900, the bright part of the moon is seen
in the form of the hemisphere which is called a first quarter (m3).
D. When the moon forms an angle of 1680, very little part of the moon
remains in the dark which is called waxing gibbous (m4).
E. When the moon forms an angle of 1800 from the plane , the moon is seen
completely round, which is called full moon. When the moon forms an
angle of 192o from the plane very little part is covered by the darkness and
it is called waning gibbous (m6).
F. When the moon forms an angle of 2700, the moon is seen in the form of
hemisphere again, which is called last quarter (m7).
G. When the moon forms an angle of 3840, very little part of the moon is seen
in the sky and it is called waning crescent (m8) .
H. After completing an angle of 3600 by the moon in its orbit again new moon
occurs.

29. Some interesting facts about the moon:
I. The moon rises about 50 minutes late daily.
II. The time of sunrise and moonrise is same on the new moon.
III. On the full moon, the moon rises, at the time of the sunset.
IV. Moon rises at the mid-day on the first quarter.
V. The moon rises at the midnight on the last quarter.
VI. The moon rises about 50 minutes after the sunrise on the waxing crescent.
VII.The moon rises about 50 minutes before the sunset on the waxing gibbous.
The moon completes one revolution around the earth in about 27.33 days (27
days, 73 hours, 43 minutes and 11.5 seconds). This period is called sidereal
month. The time taken by the moon to move from ‘m1’ to ‘m2’ condition is the
sidereal month.
The time taken by the moon to come from m1 to m3 condition is called a
synodic month or a lunar month. Thus, the duration between two consecutive
new moons is a synodic month. Its duration is 29 days, 12 hours, 44 minutes
and 3 seconds i.e. about 29.5 days.

30. Eclipse
The revolution of the earth around the sun and the moon
around the earth sometimes cause the three heavenly
bodies in the same line. It causes some or total parts of the
moon or the sun invisible, that is called the eclipse.
Causes of the eclipse
a. The sun is luminous body whereas the moon and the
earth are non-luminous.
b. The moon and the earth are opaque.
c. While the earth revolves around the sun and the moon
around the earth, sometimes, all three masses lie in a
straight line.
Umbra and penumbra
When a shadow is formed then the dark shadow is umbra
and the light shadow is penumbra. The umbra causes total
eclipse and penumbra causes the partial eclipse.

31. Solar Eclipse

32. Solar eclipse
When the moon passes directly between the earth and the sun, it
blocks the sun. It casts the shadow some part or all the part of the
sun is not seen. It is called solar eclipse.
A total solar eclipse occur when the sun is completely covered by
the moon. It remains for 10 minutes. Total solar eclipse is
important for scientist because they can study about corona of the
sun in this condition.
A solar eclipse stays for short period and it occurs on the new
moon.

34. Lunar Eclipse

35. Lunar eclipse
When the earth passes directly between the moon and the
sun. It obstructs the light of the sun. The earth casts its
shadow on the moon and the moon darkens partially or
completely. It is called lunar eclipse.
During a Total Lunar Eclipse, the Sun, Earth and Moon form a
straight line. A total solar eclipse stays for longer period of
time i.e. 1 hour and 40 minutes.
A lunar eclipse occurs on the full moon only and it begins
from the eastern region of the moon.

36. The nodes: RAHU and KETU.
When we study the above diagram, we find that the
plane of the moon’s orbit cuts the plane of the earth’s
orbit at two points. The two points are called nodes
RAHU and KETU.

37. Earth revolves around the sun in 365 days. Orbit in which
earth revolves around is in an ellipse-shaped. So,
sometimes earth goes nearer and sometimes further to the
sun. When the earth moves nearer to the sun-earth
becomes hotter and when the earth moves farther to the
sun-earth becomes cooler. Due to this phenomena, earth
experiences the different season.
There are four seasons. They are:
Summer
Winter
Autumn
Spring