CHAPTER NO.1 SOLAR SYSTEM
CHAPTER NO.1 SOLAR SYSTEM
As a student of Geography, our relation with
Universe begins with the query that what is the position of Earth in the
Universe because definition of Geography itself is related to the Earth. Earth
is one of the eight planets of this universe where life is possible. These
eight planets have around 150 satellites also which revolve round their
respective planets.
ago. This condensation caused revolution of Nebula
and it further cooled down due to convectional activity. As it condensed and
shrank,bulges got created init and they got separated in shape of rings which
are found as planets. Sun is also one of such rings. All the planets now
revolve round the sun while rings separated from planets which are
known as satellites revolve round their respective
planets. Nebula theory was presented by French mathematician, Marquis de
Laplace (23 March 1749— 5 March 1827) in 1796 A.D. According to which
sun,planets and satellites have come into form out of Nebula only.
The thinkers other than Laplace who gave their own
theories about formation of
Universe are; Emmanuel Kant,Chamberlane &
Molten. James Jeans and Harold Jaffery supported Chamberlane’s theory. By 1950
Otto Schmidt of Russia and Carl
Friedrich von Weizsicker of Germany made some
changes in Nebula Hypothesis and gave an idea that sun was surrounded by
Nebula which was constituted by
Hydrogen, Helium and Dust particles principally.
These particles gradually formed a saucer shaped cloud. But most recognised
theory about evolution of Earth remains Big Bang Theory only.
Edwin Powell Hubble (November 20, 1889 — September
28,1953) gave proofs of continuous expansion of Universe in 1920. By 1950 to
1960 this theory was
recognised and it was proved by 1972.
The Cosmic Background Explorer
(CoBE) gave evidences that all the
constituents of Universe’ were
stationery in form of tiny ball type dots and a
great explosion occurred around
13.7 Billion (Around 1375 crore) years ago. It was
with in three minutes
of first Big Bang that first ever cell was formed.
Great explosion gave
birth to Galaxies, Stars and Planets. As universe
expanded, galaxies (ike Milky Way), stars and planets withered away from one
another. All these celestial bodies owe their birth to single ball of
fire.Statistical data of the Earth :
Our Earth is fifth largest planet in the solar
system.
1. Diameter
Equatorial Diameter — 12,756 km
Polar Diameter — 12,714 km
2. Circumference
Equatorial Circumference — 40,077 km
Polar Circumference — 40,009 km
3. Surface Area
Total —510 million (51 crore) sq. Km
— 29% covered by continents
— 71% covered by oceans
4. Volume — 10,00,000 millioncu. Km
5. Mass — 5.98 x 10?! metric ton
6. Density —5.52g/cm3
7. Rotation Period — 23 hours, 56 minutes & 4.09
seconds
8. Orbit Period — 365 days & 6 hours
Solar system consists of Sun and those celestial
bodies which form common family because of gravitational force. This family
however includes eight planets, 166 satellites, 5 dwarf planets,billions of
small celestial bodies and various comets, shooting stars,asteroids and other
particles etc.
Early thinkers were of the view that not only Earth
but all the planets owe their origin to Sun. There are various stars resembling
to Sun in the Universe. All these stars have their respective planets revolving
round them. On same pattern Sun also has various planets.
The early thinkers named these celestial bodies as
‘wanderers’. They named these wandering planets after various Roman gods and
goddesses.
Jupiter — King of gods
Mars — God of war
Mercury — Messenger of the gods
Venus — Goddess of love and beauty
Saturn — Father of Jupiter & God of Agriculture
(Planets mentioned above are easily visible from
earth while those mentioned next may be seen with telescopic help only)
Uranus — Located in 1781, God of Heavens
Neptune — Located in 1846, God of Seas
Pluto — Located in 1930, now declared dwarf planet
D= Mass per Unit / Volume
Our Universe contains 176 billion (one billion = 100
crores)constellations (group of stars) and each constellation includes hundreds
of billion stars. The constellation in which Sun exists, is so big that from
the core of constellation, light takes around 27 thousand years to reach up to
sun. The solar system which is part of Milky Way galaxy is in
disc-shaped spiral form.
Light Year :Light Year is a distance that light
travels in one year at velocity of 3,00,000 km/sec.
Thus a light year means; 3,00,000 x 365 (days) x 24
(hours) x 60(minutesO x 60 (seconds) = 94,60,80,00,000 km.
Sun : Sun rotates round its axis from West to East.
About 99.85% mass
of solar system lies with sun only whereas planets
constitute — 0.135%,
comets — 0.01%, satellites —0.00005%, dwarf planets
— 0.000002%,shooting stars — 0.0000001 % and inter planetary medium consists of
0.0000001 % of the rest of mass.
As already mentioned sun is not stationery and
completes one rotation round its own axis in 25 days. One rotation of sun takes
25 days (of Earth) if observed from the equator while if we observe it from its
poles, each rotation of sun takes 36 days. The rotation of sun was observed by
Galileo first of all.
tar Profile o un Age = 4.6 billion years
Type = Yellow dwarf Diameter = 13,92,684 km
Circumference at its Equator = 43,70,005.6 km Mass = 3,33,060 x Earth
Surface temp = 5500°C One million Earths may fit
inside a sun.
Sun is source of light, heat, energy and hfe on our
Earth.Normally looking pale, this spherical ball of fire has 13 lakh multiples
more volume than that of Earth and 3.25 lakh times more weight.Pressure of
gaseous material on its centre is 200 billion multiples more than the pressure
of air, Earth experiences while density of gases is 150 times more than that of
water. Temperature of sun is 50 lakh degrees Kelvin (one Kelvin is equal to one
degree on Celsius scale).
Do you know ?
Each black spot on sun is 25 to 30 mes bigger thn
the size of Earth and 10 thousand times more powerful magnet than that of
Earth.
Hydrogen in form of Plasma turns into Helium at this
temperature. This fusion gives birth to energy. The quantum of such produced
energy may be imagined from the fact that fusion produced
energy in one second is more than as much mankind
has used on Earth
till date. This fusion is continuous process on the
surface of Sun.Gravity of Sun is 28 times more than that of earth and black
spots visible on sun are actually very powerful magnetic regions. Each magnetic
regions of sun is more than 10 thousand times more powerful
than magnetic power of Earth. Actual size of each black
spot may be lakhs of square kilometers. Temperature at photosphere of sun is
only 6000° Kelvin while ends of chromospheres experience it 10 thousand degree.
At corona this temperature varies from 10 lakh Kelvin to SO lakh Kelvin.
Continuous winds blow at the surface of sun at speed of
800 to 900 kilometer per second and these may prove
dangerous for Earth at times. These winds have their fatal affect on
Ionosphere. Solar storms disturb communication system on Earth. Many a times,
power grids get destroyed or seized because of disturbance at the surface of
Sun.
Planets :Planet is a Greek word which means,
Wanderer. All the planets
are spherical and are total eight in number. We can
group these planets
in two, that is:-
Inner planets are those planets which are nearer to
sun as compared to others. Secondly their relief constitution includes rocks
and metals. These planets are known as terrestrial planets
also. Namely these planets are; Mercury, Venus,
Earth & Mars.
Outer planets are beyond asteroids and are
constituted of gases,popularly known as Gas Giants. These are; Jupiter,
Saturn,Uranus and Neptune.
Mercury
Venus
Earth Inner Planets
Mars
The Asteroids
Jupiter
Saturn Outer Planets
Uranus
Neptune
The planets do not have any light of their own but these
illuminate by reflecting sunlight and are visible at nght. In the sequence of
their distance from sun, these may be retented from initial alphabets of words
in this sentence; My Very Efficient Mother Just Served Us Nuts.
1. Mercury :
This planet is not only smallest one but also lies closest
to Sun. It does not have atmosphere of its own and
is engulfed by blasts taking place because of Sun. Its core is made of iron and
has this part larger than crust. It is presumed that this crust reduced due to
some comet accident. Mercury lies some 579 million (57crore 90 lakh) kilometer
away from Sun and its average temperature varies between 420°C during day to
-180°C at night. It completes its revolution around Sun in 88 days while takes
58 days and 16 hours
to complete its one rotation on its axis. Galileo
founded Mercury in
1631 which has no satellite.
2. Venus :
This is arocky celestial body like Earth and second planet if
counted serial vise from Sun. It completes its
revolution round sun is
224.7 days while takes 243 long days to complete its
rotation round its own axts from East to West. All the other planets rotate
around their axis from West to East. This hottest planet is second most
glittering celestial body, first being the Moon.
Also known as sister
planet of Earth, Venus resembles to it in shape,
size and gravity. It
has a number of volcanoes just like Earth and its
surface has been
formed because of volcanic eruptions. Its atmosphere
consists of Carbon dioxide (96.5%) and Nitrogen. That is why it is called
“Veiled planet’ also. Venus lies nearly 1082 million kilometers away from Sun.
3. Earth :
Our mother planet's name has not been derived from Greek or Roman language but
from old English and Germanic. According to International Astronomical Union ([AU)
biggest among Inner planets, Earth is only planet which has Geological activity
taking
place in its core. Its atmosphere is also quite
different to that of other
planets as it consists of 77% Nitrogen and 21%
Oxygen which gives it a name of “blue planet’. Earth is only planet where life
exists.Situated nearly 14.96 crore kilometers away from sun. The earth
completes a rotation round its axis in 23 hours, 56 minutes and 4.09
seconds (approximately 24 hours) while to revolve
around the sun, it takes 365 days 5 hours and 48 minutes. It has a satellite
named Moon.
4. Mars :
Known as the Red Planet, Mars is fourth planet of our solar system as counted
from Sun. Its soil has very rich iron content and because of Ferrus content it
looks red. As far its rotation on axis is concerned, it has similarity with
Earth and it supports various seasons also. Mars is a cold planet which has
thin atmosphere. Its
one rotation on its axis is completed in 24 hours,
37 minutes and 23 seconds while its revolution against sun takes 687 days.
Having two satellites, Mars is pleaced around 2279 lakh kilometer away from
sun.
Do you know?
ISRO’s Mars Orbiter Mission got rare success on 24th day of September, 2014 when its Orbiter set itself as artificial satellite of Mars. India spent just 450 crores on the mission which is 10th part of what U.S. spent on its first Mars mission.
The success of India to plant its Orbiter
in orbit of Mars in its just first attempt has made it a proneer and an
exceptional one. Mars is only planet other than Earth which has tce-caps on its
poles which have been named as Planum Boreum (North Pole) and Planum Australe
(South
Pole) or Southern Cap. The spacecraft that reached
in the orbit of Mars
is named 440 Newton Liquid Apogee Motor (LAM).
5. Jupiter : First beyond the
Asteroids, Jupiter is fifth planet of our solar system and is the biggest
planet. This planet is one of the Gas Giants and has 1280 kilometer wide
atmosphere composed of gases hike Methane, Ammonia, Hydrogen and Helium. It
revolves a round the sun in anti-clockwise direction and completes one
revolution in 12 years. Its rotation on its axis is very fast and completes one
in just 10 hours causing severely blowing winds. These winds look like
multi-coloured cloud belts. Jupiter is tilted on its axis at 3.1° and has more
than 60 satellites. Most of the satellites are unknown for
mankind as far information about them is concerned.
6. Saturn :
The sixth from sun and second largest planet in solar system is Saturn.
Situated some 1,431 million kilometers (More than 143 crore km) away from Sun,
it is constituted of iron and nickel principally. Completing its rotation on
its axis in 10 hours and 41
minutes, it makes one revolution around Sun in 29.5
years. Its swift rotation gives rise to winds at the speed of 1800 kilometers
per hour.Speed of winds on Saturn is higher than that on Jupiter but lesser
than that on Neptune. There are nine rings around Saturn which
from three arcs around it. These rings are made of
frozen ice and rocks. It has around 62 satellites and biggest among them 1s
Titan which is almost double the size of Moon. The atmosphere of Titan is
thicker than that of Earth.
7. Uranus :
This is seventh planet of our Solar System and third largest planet. Its size
is 63 multiples bigger than earth but in weight itis only 14.5 multiples than
that of Earth. Constituted of gases,Uranus has coldest atmosphere as compared
to all the planets and has an average temperature of —223°C. Many layers of
clouds are
found on Uranus. Higher cloud formation consists of
Methane gas while lower formation consists of water. Speed of winds on this
planet is 250 meters per second while it is tilted at 97.77° on its axis.
Revolving round sun in anti-clockwise direction, it completes one
revolution in 84 years while for completing one
rotation around its
axis, it takes 10 hours and 48 minutes.
8. Neptune :
Neptune resembles to Uranus as seen in the Solar System. But it 1s smaller than
Uranus and its surface is more condense. Presence of Methane gas makes it look
green. Winds blow
at speed of 2100 kilometers per hour in the
atmosphere of this planet. The planet consists of around 900 full circles and
various incomplete arcs. Situated approximately 4,498 million kilometer away
from Sun, it completes one rotation its axis in 16 hours and a
revolution around sun in 164.8 years. Neptune has 13
satellites while Triton and Neried are two main satellites.
Do you know ?
When Hydrogen gas turns into heavier atoms of helium as constituent of a star, its density increases to the extent that it blasts,turns into ash and vanishes.
There are various dwarf planets in our solar system, out of which only five have been recognised.
1. Pluto (Earlier know as ninth planet, was declared
dwarf in August, 2006)
2. Ceres
3. Eris
4, Make make
5. Heumea
Satellites :Satellites
are of two types, manmade and natural. Satellites are actually celestial
objects that revolve around some other celestial object. Natural satellites
rotate on their axis also. They neither have atmosphere nor light of their own
but due to reflection of sunlight, they
look illuminated.
Manmade satellites are made of aluminium or plastic
and are hardened with help of carbonic sheets. They travel at the speed which
is 10 to 30 multiples more than that of an aircraft. Humankind has been
benefitted extremely by manmade satellites in fields of telecommunications,
weather forecasting, geological activities and atmospheric activities among
other fields. India fired its first satellite named Arya Bhat in 1975 and since
than, we have sent more than 75 satellites into the orbit.
Moon is natural satellite of our Earth. It is around
3,84,403 kilometers away from Earth and takes 27.3 days to complete its
revolution around Earth. As yet mankind has touched only this celestial body i.e.
Moon on 21st July 1969. Atmosphere of Moonis so thin that it weighs only104
kilograms and gravity is only one sixth part of the gravity of Earth.
Do you know?
Lunar eclipse is a state of Sun, Earth and Moon,
when shadow of earth falls on Moon. This condition happens on full moon days
only. We ad an important full moon day and total eclipse on 8th October, 2014
oon looked red (Blood Moon) on that day but this characteristic was isible in
North and North-East India, North America and Australi only. This celestial
fete shall again be visible in 2018.
Asteroids or Planetoids :These are small planets,
too smaller than planets of Solar System but bigger than Asteroids. These
celestial bodies revolve round the sun in anti-clockwise direction. These rocky
bodies are numerous and most
of these are concentrated between Mars and Jupiter.
Five of them namely Ceres, Pallas, Vesta, Hypiea and Euphrosyne have been
recognised. European Space Agency has found water vapour on Ceres
on 22nd January, 2014.
Comets :The
word comet is derived from Latin word ‘Stella Cometa’which means “hairy star’.
These celestial bodies were part of sun earlier and are made of frozen gases,
ice and small rocky substances. Head of cometis 16 million kilometers in
diameter and is followed by cloud of misty substance looking like a tail. This
tail is also lakhs of kilometer long. Tail is never towards sun facing side of
comet and shines with
rays from Sun. Comet which passed through Solar
System was first seen in 1705 and it passes close to sun after every 75.5
years. English scientist Edmond Halley founded it and it was therefore named
Halley’s Comet. Comets are being traced regularly. Their total number was 5,186
in August, 2014. Halley’s Comet was seenin 1910, then in 1986 and next it shall
be sighted in 2062. Nucleus of Halley’s Comet is 16 x
8x 8 kilometers and it is the darkest object in
solar system. This comet
is periodical one and may be sighted at specific
intervals but all the comets are not periodical.
Meteors or Meteorites :One can see a streak of star
light in the sky sometimes, it gives an impression that any part of star has
broken away. These are actually meteorites. Parts of meteontes that remain
unburnt and reach our Earth in small parts are named as meteorites. When these
enter the
atmosphere of Earth, burn out immediately and vanish
in shape of ash
most of times. A part of Arizona desert in U.S. is
known to have come into form due to striking of some meteor. There are,
however, various principles about formation of meteors. Some thinkers part them
parts of planet which has vanished while others say these are parts of Sun,
Earth and Moon only.
Indian Museum at Kolkatais known for preserving
remains of meteors. Biggest such museum in Asia, it has 468 meteor parts. Their
study has concluded that meteors are made of metals like iron,
nickel,aluminium, oxygen and tin. These get attracted towards Earth because
of gravity of Earth. On April 21, 2013 a meteor
shower was observed in many parts of the world in which more than 20 shooting stars
were seen within an hour. This shower is known as Orionid Meteor Shower. Such
wonderful sights are very common in our solar system.
et us do something :Gather information about UFOs
(Unidentified Flying Objects
prepare a report about them.
(ii) SHAPE AND SIZE OF EARTH
Our Earth is fifth biggest planet and is placed
third as counted from sun. Ours is only planet where life is possible. Itis
spherical object with a diameter of around 13,000 kilometers. As compared to
other celestial bodies, Earth has a smaller entity while for mankind it is far
much bigger. It may be divided in various physiographic units. Highest
point on the Earth is Mount Everest (8,848 meters)
while deepest point
is Mariana Trench (11,030 meters) in Pacific Ocean.
Do you know ?
“Geodesy” is a branch of science, responsible for
measuring the Earth’s size & shape with the help of surveys and
mathematical calculations etc.
Some 2600 years back, Greek thinkers gave an idea
for the first time that Earth ts spherical. Earlier Babylonian thought put its
shape as crescent while Thales gave an idea in 600 B.C. as if earth was like
round table top and floating over water. Eingremendore condemned table top idea
and put it as cylindrical object which is rotating on its axis. Philnolsh was first
philosopher who gave an idea that Earth is round while Eratosthenes, the
Director of Greek Library measured the
circumference of Earth with the help of Sun rays. He
checked the angle of Sunrays at city of Alexandria in the noon and then angle
of Sunrays at city of Syene which is 960 kilometers away. From these readings
he came to the conclusion that circumference of Earth is around 43,000
kilometers. This measurement is quite close to the exact measurement of 40,000
kilometers.
Earth is not exact sphere. Its cross section at
equator divides it exactly but cross section from poles does not bring same
results which prove that itis a bit flat at poles. Therefore it is oblate
spheroid and is known as Geoid. Indian mathematician Arya Bhat (476 A.D. to 556
A.D.) also was of the view that Earth is spherical and its circumference
is 4,967 yajnas, which of calculated at present
measures to 39,968 kilometers and more exact to present day calculations.
Shape of earth proves more clear by some other ways
and simple experiments also which are given as:-
1. Experiment of sailing ship :
As we observe an approaching ship in some sea, we cannot see whole of it at
first sight, rather we see its top first of alli.e. chimney portion then
central portion and gradually whole of the ship appears. It happens so because
Earth is round and not flat. Had our Earth been flat, we could have seen whole
of
approaching ship at first sight itself.
2. Shadow of Earth during Lunar eclipse
: Lunar
eclipse is a celestial stage when shadow of Earth covers moon. This shadow is
visibly round, proving that earth is spherically round. It was Greek
thinkers who draw attention of the world towards
this fact.
3. Time of Sunrise :
Time of sun rise varies with the change of place,
means sunrise in eastern nations is earlier than
that of western nations. Had our Earth been flat, Sun would have risen at same
time at all the places. This proves that Earth ts round.
4. Size of shadows:
If we install two or various poles in right angled position, we find that sizes
of their shadows differ as compared to the distance of poles itself. This
proves that Earth is geoid as had been flat, size of shadows would have been
same.
5. Times Zones:
We have 24 different time zones on our Earth. When there is noon in Hawaii
islands, Middle East nations experience midnight at that moment, proving the
shape of Earth.
6. Pictures from space:
We have various pictures of Earth which have been taken from the space,
directly proving that Earth is geoid.
7. Going round the Earth:
If a person starts going round the Earth from a point, having not changed his
direction reaches the same place on completing his journey. Had the Earth flat,
one would have needed to change his directions many a times. It proves that
Earth is
geoid.
8. Size of horizon: While standing
in an open ground, we can observe horizon where Earth and sky seem to meet.
When we look at same horizon from some height, it looks broader and farther also.
It proves that Earth is geoid, had it been flat size of horizon would not
have changed.
9. Positioning of Sun rays :
According to a simple observation,persons living near the Equator find high
temperature of sunrays while those living near poles find lesser temperature as
sunrays lie
slanting for Polar Regions. This happens only in
geoid shapes and cannot happen so in case of flat shapes.
Earth had its 71% portion covered with water and
therefore when observed from the space, it looks blue. This fact makes it
unique and it is known as “Blue Planet’? which is only planet known till
date,supporting life, vegetation and temperature.
MOTIONS OF THE EARTH
Life exists on Earth due to rays of Sun only. The
solar energy has very deep connection with life on the Earth which does not
have its position permanent in the solar system due to its motion rather its
motions are permanent. Earth rotates on its axis while revolving round the Sun.
Hence there are two motions of the Earth :
1 Rotation
2. Revolution
Earth completes its one rotation in 24 hours while
one revolution takes place in whole of a year.
1. Rotation of the Earth Our Earth rotates on its
axis from west to east direction,completing one rotation in 24 hours.Process of
day and night happens
only due to this motion of Earth.Axis of Earth is
that imaginary line which joins North and South poles.Speed of Earth while
rotating is quite high i.e. 1600 km/hr. It completes its voyage of 40,000
kilometers in 24 hours. While rotating on axis, the
portion which faces sun, experiences day and the portion which ts away from sun
experiences night. Speed of Earth rotation varies with difference in latitudes
but as the speed is constant,we cannot feel it moving. It happens in same way
as we cannot feel
speed of train when it moves constantly but we
certainly feel its movement when it starts or stops.
Earth makes an angle of 6612° while moving in its
orbit while 23° angle from its right angled axis. Had there been no rotation,
Earth would have remained in one position constantly and it would have affected
life quite severely. The axis of Earth is an imaginary line
around which the planets spins.
Effects of Earth’s rotation Rotation of Earth has
various effects over it, like following :-
1. Forming day & night : Formation of
days and nights is possible only due to rotation of Earth. This also has effect
over local temperature, moisture and direction of winds. These factors have
great effect over existence of life on this planet.
Our agriculture also
depends upon these factors.
2. Constant direction or circulations :
Earth rotates constantly from West to East which has its impact not only over
winds but over ocean currents also. According to Farrel’s law, all independent
moving bodies tend to deflect towards their right in Northern
Hemisphere and towards their left in Southern
Hemisphere because of rotation of Earth. This is also known as Coriolis Effect.
3. Formation of tides :
It is due to rotation that gravitation force varies on different parts of Earth
at various moments. This variation causes tidal activity known as high tide and
neap tide in oceans,twice a day.
4. West to East movement :
Earth rotates from west to east which gives animpression as if Sunis moving
from east to west. This is due to rotation of our Earth. Had it not happened,
what would have been the effect ?acing East while West shall be at our back.
What directions shall be at our night and left ?
5. Knowledge about directions and
situation : Sun rises in the East.
Eastern places receive sun rays earlier than Western
places. The difference in timing gives us an idea about situation of various
places. For example, Sun rises earlier in Arunachal Pradesh as
compared to Gujarat. Can you calculate the time
diffrence ?
2. Revolution of the Earth:Second
motion of Earth is its movement around sun, called revolution of Earth. This
movement is on elliptical orbit which
completes in 36514 days. Our calendar year is of 365
days generally leaving 6 hours each for three years but we add a day in our
calendars each fourth year, making it a leap year. This day is added in the
month of February. Each fourth year when year has 366 days, its February has 29
days.
During its revolution, Earth keeps its bent at 6612°
angle and covers its
path of 93,98,86,400 kilometers annually in
elliptical voyage. This shape and angle bring different effects. On January 3,
the Earth reaches closest to Sun and this position is called ‘perihelion’.
During its revolution, when the Earth is farthest from Sun, that state is known
as ‘aphelion’ and it happens on July 4 every year. Distance of Earth and Sun at
aphelion stage is 15,21,71,500 kilometers while distance at perihelion stage is
14,71,66,480 kilometers where as average distance
of Earth from Sun may be put at 14,95,97,892
kilometers. TAU)
Revolution of Earth brings following effects:-Effect
of tilted axis on Day & Night Earth is tilted on its axis at an angle of
662° and during its revolution around sun, it remains tilted towards one side.
This characteristic is known as Polarity of Earth’s axis also. Had it not been
so, length of day and night would have remained constant throughout a year but
it is not so as Northern Hemisphere keeps tilted towards sun for
six months, resulting into longer span of day as it
receives longer sunlight during 24 hours. In those days as Southern Hemisphere
is away from sun, it receives shorter span of sunlight during same 24 hours and
has longer nights. While this process of varying spans of day and night goes on
in both hemispheres, span of day and night is almost constant at Equator. As we
move away from Equator variation goes on increasing and at poles, we find six
months of day and six months of night ina year. Whole of this process is due to
Earth’s tlt which takes place
during its revolution.
Tilt of the Earth along with its revolution causes
various temperature zones also. Sun rays fall straight from 2342°N to 2342°S
latitudes whole the year long. These latitudes known as Tropic of Cancer and
Tropic of Capricorn respectively, give a name, Tropical
Zone, to the region falling between these two
tropics. Equator passes
through the centre of these tropics. The regions
lying between 2342°N (Tropic of Cancer) to 661%2°N (Arctic Circle) and between
23'2°S (Tropic of Capricorn) to 6642°S (Antarctic Circle) never got straight
sun rays, nor these regions get away from sun during any part of year.
Slanting sunrays make these regions neither very hot
not very cold and
hence known as Temperate Zones. Regions above Arctic
Circle and up to North Pole and below Antarctic Circle and up to South Pole
remain away from sun fairly for months during a year and whenever these regions
receive sunrays that also are so slanting that hardly these may
be called warm. Therefore these regions are better
known as Frigid Zones.\
Change of Seasons :Change of seasons on our Earth
takes place due to following
seasons:-
i) Revolution of Earth
ii)Tilt of Earth at 66° onits axis
What are the situations and positions in which Earth
reaches while its revolution and what results come out of these, is to be
studiedn in detail:-
Position on June 21 :
Northern Hemisphere lies tilted towards Sun on
June 21, while Southern Hemisphere ts away from it.
Sun rays fall straight on tropic of Cancer and hence days are longer in
Northern Hemisphere. There is summer season in Northern Hemisphere which is
quite hot near Equator. June 21 is particularly longest day and shortest
night in Northern Hemisphere. This is also known as
June solstice or summer solstice for Northern Hemisphere and winter solstice
for Southern Hemisphere.
Position on September 23 : Three months after June
solstice, Sunrays fall straight on Equator. This is the position when despite
tilt of Earth on
its axis position is so that no hemisphere is
comparatively tilted towards sun which results into equal spam of day and night
i.e. of 12 hours each,known as Equinox. (Equinox is a Latin word which means
equal day
and night). Equator is a place on Earth where span
of day and night does
not change much whole the year long. In September
when this situation happens on 23rd day, it is known as Autumn Equinox in
Northern Hemisphere and Vernal Equinox in Southern Hemisphere.Position on
December 22 : In this position Southern Hemisphere is tilted towards sun while
Northern Hemisphere is away from it. Sunrays fall straight on 2344°S that is
Tropic of Capricorn and days are longer in Southern Hemisphere while nights are
shorter. Situation of day and
night is exactly opposite in Northern Hemisphere
where nights are longer than days. This position is known as December solstice
or summer solstice in Southern Hemisphere and winter solstice in
Northern Hemisphere.
Position on March 21 : Three months
after, on March 21, Sunrays again fall straight on Equator and this situation
is known as March Equinox. This situation is exactly opposite to that on
September 23.Days and nights are equal at Equator. This position is known as
Autumn Equinox in Southern Hemisphere and Spring Equinox in Northern
Hemisphere.Generally speaking March 21 and September
23 have equal span
of days and nights.
(ii) LATITUDES AND LONGITUDES
Literary meaning of the word *Geography’ is to know
the details of some location, distribution of facts, populations etc. Details
of some location from the climatic aspect and time cannot be explained if we do
not take help of latitudinal and longitudinal measures of particular place. In
other words, distance from Equator is most important fact for some place while
seeking its details. Earth continues two motions all
the time i.e. rotation and revolution. The imaginary
line drawn on the earth which divides it into two parts known as northern and
southern hemispheres is known as Equator. Physical location, climate,vegetation
etc. may be known more thoroughly depending upon the
factual distance of some region from the Equator.
The cartography of longitudes has made things more easy for marine explorers
during their oceanic navigation.
Various experiments have been carried out to settle longitudinal cartography :-
Amerigo Vespucci faced a lot of problems when he tried to measure expansion of Earth, east to west i.e. horizontally on 23rd August 1499. He sought help of Almanac measurements to find relation with various other celestial bodies and concluded that position of Moon is at 314° East of Mars.
This conclusion of his has made basis for drawing longitudes. His
experimentation and results however could not find favour with various thinkers
of his times. It did not suit according to Almanac Calender even as there was
no stable platform on which his theory could be raised.Galileo Galilei gave a
theory in 1612 A.D. that orbits of Moon and Jupiter may be used as clock.He
proved it by experimentation
but in 18th century a lot of incidents happened on
earth in which exact location in the oceans could not be found. In this
situation, the British Government set up a Board of Longitudes in 1714 A.D. and
motivated experimentation and research on the issue by announcing various
prizes for it.
Important Meridians
John Harrison, an English clockmaker brought out a
marine Chronometer which could study longitudinal positions in Oceans. This
instrument however, was very costly and beyond reach of many,
financially. Therefore Lunar Distance Method of
Amerigo Vespucci remained popular for many decades. It was in 20th century,
wireless telegraph went more popular than lunar distance method. Starting point
for latitudes was equator uncontestedly but emergence of longitudes saw various
experiments.
Hipparcus brought out a grid of latitudes and
longitudes in 300
B.C. and various maps were drawn with the help of
local time and absolute time. He contributed in setting up of starting
longitude. His measurements were however more clarified 75 years later 1.e. in
225 B.C., Eratostheres, a Greek Mathematician and Space scientist,
measured circumference of Earth and prepared maps of
the world.Another explorer Al-Birunie gave theory that Earth rotates round its
axis which results into direct relation between longitudes and time.After all
this experimentation, the International Community proposed Greenwich longitude
as starting longitude in 1884 A.D. and it was accepted world over.
1. Latitudes or Parallels :The angular distance of
any place falling in north or south of Equator is known as its latitude. These
latitudes or parallels are measured in degrees, minutes and seconds.
Geometrically, a circle is
measured at 360 degrees (°) and same ts for equator.
Each degree is divide in 60 minutes (’) and each minute is further divided in
60 seconds (’). Animaginery straight line joining North and South poles when
intersects Equator, it divides circle in four parts, each of 90°. Hence earth
ts divided in 90° parallels in Northern Hemisphere and 90°
parallels in Southern Hemisphere. The places in the
north of Equator are represented with latitudinal degrees followed by “N’ and
those in south, with latitudinal degree, followed by *S’ while equator remains
O°.As itis very clear that a place situated at 1° angle from Equator shall be
at 1° parallel, in kilometers each degree in 111 kilometers away from the
other.
Latitudinal lines are those imaginary lines which
join all the places on globe which are at same angular distance from
equator.Equator is known as “Great Circle’ also which divides the earth in two
equal parts. Parallels or Latitudes are not straight lines but circular lines
drawn parallel to equator horizontally. These circles have same centre i.e.
axis and 90° N and 90° S are more points.
Some important latitudes or parallels are as under
:-
(i) Equator - 0°
(ii) Tropic of Cancer — 23'12°N
(iii) Tropic of Capricorn - 2344°S
(iv) Arctic Circle - 6644°N
(v) Antarctic Circle - 6612°S
(vi) North Pole - 90°N
(vii) South Pole - 90°S
Latitudes or parallels have very important and close
relation with
sunlight, revolution, tilt at 232° angle and so on.
Sun shines straight over Tropic of Cancer (2342°N) on 21st June and over Tropic
of Capri-corn (23'2°S) on 22nd December. It results in making June 21 the
long-est day in Northern Hemisphere while December 22 the longest day in
Southern Hemisphere. Arctic Circle (6642°N) region does not experi-
ence high temperature in June while sunrays reach
across North Pole in
this period of the yearly voyage. Same way in
December when South-ern Hemisphere is tilted towards Sun, the sunrays cross
South Pole to reach 6612°S latitude i.e. Antarctic Circle. Hence Polar Regions
have continuous days and nights whole the year tong.
The tilts of Earth and approach of sunrays allows us
to divide the
Earth into various temperature zones also. Regions
lying O° to 2344°N
and 0° to 2342°S are known as Tropical regions while
regions lying between 2342°N to 6642°N and 2342°S to 66%°S are known as
Temperate regions. Regions falling above 6642°N to North Pole or
6614°S to South Pole, are known as Polar Regions or
Polar Regions or Frigid Zones.
Distance from Equator i.e. latitudinal situation and
distance above sea level are two major factors which have their effect over
climate of some place. Any place situated near the Equator shall remain hot as
such region shal] remain under direct sunlight whole the year
long where as places near poles which never recetve
straight sunrays
shall remain cold in control to equatorial
regions.Measuring latitudinal position of some place : It is necessary to know
declination of the sun if we want to know latitudinal positioning.
Zenith is a place exactly overhead in space. The
zenith distance and
declination of sun or angular distance from Equator
at a particular place
and time, if calculated, tells us our Latitudinal
position. When a person
moves from a place, his/her zenith distance also
changes and that
changes latitudinal positioning.
North Pole lies exactly beneath North Star which we
may find with the help of pointers of Great Bear. At night, angular distance
from North Star can conclude of our latitudinal position. Chandigarh is at
30°.42'N latitude.
2. Longitudes or Meridians :Geographical
location its not very feasible to find with a single geographical factor.
Location and time surely need latitudinal measurement to conclude measurement
while what needs more or in
addition to it, is longitudinal position. More
precisely we can say that
location and time may be found out not only by
knowing north-south position but east-west position also. Longitudes are those
imaginary lines drawn on a globe which join North and South poles. These lines
are also circular actually, intersecting at North and South poles but at first
sight these look like arcs. We take 0° longitude as Prime Meridian,
which passes through a place known as Greenwich near
London. There are 180° longitudes towards east of Prime Meridian and same
number is there towards west of Prime Meridian. 180° Meridian which falls
exactly opposite to Prime Meridian is again acommon Meridian from east or west
and technically known as International Date Line. The full
circle of O° & 180° longitudes divides the Earth
in two parts known as
Eastern Hemisphere and Western Hemisphere
respectively. Distance of
a place east or west of Prime Meridian are measured
as an angle and this angular distance is called the longitude of that
particular place.
India is situated in Eastern Hemisphere. Longitudes
are always of equal size and are around 69 miles away from each other at the
Equator. Longitudes or Meridians are also measured in degrees,minutes and
seconds.
In simple language the Zenith refers to an imaginery point directly "above" a particular location on the imaginery celestial sphere.The Zenith is the highest point on the celestial's sphere.
The North Pole also known as
the Geographic North Pole is defined as the point in the Northern Hemisphere
where the Earth's axis of rotation meets its surface. North Pole is the
northern most point on the Earth,
lying diametrically opposite the south pole. It is
also called true North.
A Pole star is a visible star, preferably a
prominent one, that is
approximately alignes with the Earth's axis of
rotation, that is a star
whose apparent position is close to one of the
celestial poles, and which
lies approximately directly overhead when viewed
from the Earth's North Pole or South Pole and Geoid is the shape that the
surface of the oceans would take under the influence of Earth's gravitation and
ratation alone, in the absence of other influences such as winds and tides. All
points on the Geoid have the same gravity, potential energy.
The force of gravity acts everywhere perpendicular
to the Geoid,meaning that plumb lines points perpendicular in water levels
parellel to the Geoid.
Grid system of Latitudes and Longitudes : As we draw
longitudes and latitudes on a globe, it looks like a full fledged net or grid,
therefore drawing of longitudes and latitudes is known as Grid System. If we
are to find location of some place on globe or map and we have its longitudinal
and latitudinal position. For example Patiala (Punjab) is located at 30°.23'
North latitude and 76°.21' East longitude. While trying to find it on a map, it
shall lie at the place where these two latitudinal and longitudinal lines
intersect one another.
Longitude and Time : Longitudes help us calculate
local time of a place which in turn helps us about timing of sun rise and sun
set.Greenwich Meridian is first longitude and it is presumed universally that
when sun is shining above this longitude, that is to be called noon
12:00 GMT (Greenwich Mean Time). The
Earth rotates round its axis one full circle in 24
hours means 360° cross in that span of a day. On calculating it further, we
conclude that 15 degrees face sun in an hour and one degree in 4 minutes. As we
proceed eastwards
from Greenwich Meridian, we add up time at rate of 4
minutes per degree while proceeding westwards we have to deduct time at same
rate. India and U.S. have a difference of 9 hours 30 minutes as India falls in
Eastern Hemisphere while U.S. falls in Western Hemisphere.
In other words, when Greenwich has noon, means when
clocks strike 12 at Greenwich, clocks at 15°E shall strike I p.m. while clocks
at 15°W shall strike 11 a.m. At the same rate clocks at places 30°E shall strike
2 p.m. while at 30°W shall strike 10 a.m. It shows that if we know longitudinal
location of a place, we can find time easily. For example;India has set its
standard time at 8212°E longitude which passes near
Allahabad. The time at Allahabad or 8242°E shall be
calculated like
this:-
Greenwich longitude = 0°
Allahabad longitude = 82°.30'
Difference of longitudes = 82°.30' - 0° = 82°.30'
Difference of time = 82.5 x 4 minutes = 330 minutes
or
5 hours 30 minutes
As Allahabad falls in east of Greenwich, 5.30 hours
shall be added to the time at Greenwich or popularly we say that time in
Indiais +5.30 hours to Greenwich Time.
Indian Standard Time :Each place has its own local
time which is due to longitudinal difference of each place. Recognition of
local time of each place brings variation of time to the extent that it cannot
be cured for setting time for various systems such as transport, offices and so
on. To overcome this
problem, each nation has set its time according to
some standard longitude. Such a time is known as ‘standard time’ which is based
upon some Central Mendian of each nation.
India has set 82!2°E longitude as its Standard
Meridian which passes close to Allahabad. This longitude divides India in two
parts vertically. Standard time for whole the world is calculated from
Greenwich Meridian and time is known as Greenwich
Mean Time i.e.GM.T. whereas that of India, it is known as Indian Standard Time
i.e. IST.
Time difference of local mes of Dwarka (Gujarat) in
west of India and
Dibrugarh (Assam) in east is of 1 hour and 45
minutes. Farthest extent
of India towards East lies in Andaman and Nicobar
islands.
Some big nations i.e. with broad East-West extent,
have more than one standard times. Russia has 11 standard times while U.S.A.
and Canada have 9 and 6 respectively and as many time zones of their own.
International Date-Line :Emergence of longitudes and
distribution of time on the Earth according to longitudes left one problem
unsolved that at which
longitude, date shall change. To table with the
issue, International Meridian Conference was held at Washington in 1884 A.D.
and 180°longitude was finalised as International Date Line (IDL) which passes
through Pacific Ocean and separates two dates. Tango and American Samoa are two
islands places located quite close in Pacific Ocean but
Tango lies in Eastern Hemisphere and American Samoa
in Western Hemisphere and therefore there is a difference of full one day in
dates of these two islands. Fiji lies in the East of Tongo and its time trails
for an hour as compared to Tongo. On the other hand Hawaii islands are in the
west of Samoa and its time in one hour ahead of Samoa. There are
many island nations or places in Pacific which have
to tinker with time.
We divide the world in 24 standard time zones. Each
time zone contains 15 Meridians. As 180° Meridian of International Date Line
falls exactly opposite to Greenwich Meridian (0°), the time difference between
these two longitudes is of 12 hours. Immediately to the left of the
International Date Line, the date is always one day ahead of the date (or day)
to the nght of the International Date Line in Western
Hemisphere.
What is Globe Positioning System (GPS) ? Try to find
out.In simple words, date changes at International Date Line. As we proceed
towards east, a day is deducted but as we travel towards west, a day is added.
For example if a traveller crosses International Date Line while travelling
towards east, a day needs to be deducted but when that
traveller crosses back International Date Line towards
west, aday needs
to be added. International Date Line passes through
Pacific Ocean that
saves many people from changing calendars frequently
because had it
been passing through land area, people would have
faced trouble of frequent change in calendars.
EXERCISE
1. Answer the following questions in
few words :
(a) Which thinker gave the theory of Nabula first of
all ?
(b) What is the difference between East-West and
North-South diameter of Earth ?
(c) Which planets represent gods of war, love and heavens
according to Roman Study ?
(d) Which planets of “Solar System’ are gas giants ?
(e) Write full form of ISRO.
(f) Which are the highest and lowest places on the
Earth ?
(g) Name first longitude and latitude.
(h) Great Meridian divides the Earth in which
hemispheres ?
G) Write full form of GMT and IST.
I) What is time difference between Fiji and Samoa ?
2. Answer the following questions in
few sentences :
(a) How many natural satellites each planet of Solar
System has ?
(b) Name the thinkers who gave theories about origin
of Earth.
(c) In how much time does Earth complete its motions
?
(d) Difference of time in Sunrise proves that Earth
is round, how ?
(e) Which scientists were involved in settling
Longitudes & Latitudes ?
(f) What is Zenith ?
(g) What do you understand by horizon ?
h) Longitudes are circles, how ?
3. Answer the following questions in a
paragraph :
(a) Earthis not flat but a sphere, give three
positive points of this shape.
(b) How can we find direction during day and night
with help of celestial bodies ?
(c) Put light upon temperature zones on basis of
important latitudes.
(d) Write a note on “Commets’.
(e) What is a Light year ? What is measured with its
help ?
(f) Write any three facts related to Statistics of
Earth.
(g) Draw a graphic showing four Stages of revolution
of Earth.
(h) Which planets are, ‘Blue, Red and Veiled’
planets ?
4. Answer the following in 150 to 250
words :
(a) Write graphical notes on both motions of Earth.
(b) Write note on planets in Solar System.
(c) Give examples and prove that Earth is round.
(d) How and Why do seasons change ? explain.
(e) Write notes on Northern, Southern, Eastern and
Western Hemispheres.
(f) Write in detail how Earth orignated.
