Latitude, Longitude and International Date Line

Latitudes

It can be defined as the angular distance measured at the centre of the Earth with espect to any point on the meridian. These are depicted in degrees, minutes and seconds. Equator is called the 0° latitude. These are imaginary circles, drawn on the surface of the earth, at an interrval of 1° on both the hemispheres making the total number of latitudes to 181. 23 l/2 ° latitude on the Northern hemisphere is called the Tropic of Cancer (23 l/2°N), whereas in the southern hemisphere the same latitude is called the Tropic of Capricorn (23 l/2 ° S). 66 l/2° latitude in the northern hemisphere is called the Sub-Arctic Circle (66 l/2° N) whereas 66 l/2° latitude in the southern hemisphere is called Sub-Antarctic Circle (66 l/2 ° S). The latitudinal distance of 1° is about 11 km.

Longitudes

Angular distance of any place from the Prime Meridian, is called longitude. It is also measured in degrees, minutes and seconds. The Prime Meridian is at 0° and is known as the Greenwich Line as it passes through Greenwich, in London. Part of the Earth on the eastern side of the Prime Meridian is called Eastern hemisphere and that on the western side of it is called Western hemisphere.
Since, the Earth is Geoid shape so it rotates by 360° in 24 hours. Therefore, the earth takes 4 minutes to move by 1° of longitude. Since the Sun rises in the east and the Earth moves from west to east, time on the eastern hemisphere is ahead of the Greenwich and that on the western hemisphere is behind it. This is the reason behind differences in local times at different places on the Earth. For every 15° of longitudes there is a difference of one hour in time. In this way The time on the 180° E longitude is 12 hours ahead of the Greenwich and that on the 0°-180°W longitude is 12 hours behind the time at Greenwich. Hence, there is a difference of 24 hours in the time in east and west of the 180° longitude.

International Date-Line

It is an imaginary line drawn at the 180° longitude, avoiding the continuous land parts. It is bent at 75° N latitude towards east to avoid division of Siberia and to separate Siberia and Alaska. There is a difference of 24 hours or one day in east and west of it. Therefore, one day is either gained or lost while crossing this line. While crossing it from east to west one day is gained and while going from west to east one day is lost.
Local Time: The time at a particular place on the Earth, as calculated by the position of the Sun, is termed as the Local Time of that place. In India there is a difference of 2 hours in the local time of the eastern most (Arunachal Prades) and the western most (Dwarka in Gujarat) parts.
Standard Time: This is the imaginary line passing through mid of the standard Meridian in the middle of the country. Standard Time of the country is followed all over the country to avoid the inconvenience caused by the difference in local times of different place in the country. For example, 82M>° E longitude, passing through Naini, near Allahabad (Uttar Pradesh), is the Standard Meridian of India. The time at this longitude is the Standard time of India, called Indian Standard Time (1ST).

Some helpful facts to calculate the Standard Time of a Place:

• To the left of the 0° longitude (the Prime Meridian) are the Western longitudes and to its right are eastern longitudes, whereas to the left of the 180° longitude (the International Date Line) are the eastern longitudes and to its right are the western longitudes.
• When we move towards the left of any longitude the time gets reduced by 4 minutes for every 1° of longitude whereas while moving towards the right of any longitude the time gets enhanced by 4 minutes for every 1° of longitude.
• We gain one day (24 hours) while crossing the International Date Line from its right and loosing one day while crossing it from its left.

The Motion of Earth

The Earth has two types of motions:

1. Rotational Motion
2. Revolutional or Orbital Motion

• Rotation : The Earth rotates on its axis, from west to east like a top. This motion is called Rotation of the Earth.
• Revolution : While rotating on its axis, the earth also goes around the sun in an elliptical path and completes one round in 365 days and 6 hours. The elliptical path traced by the earth is called its orbit. This motion of the earth is called revolution.
• Perihelion : When the earth is at the minimum distance from the sun, while in orbit, this position is known as perihelion. The earth is at this position on 4th July.

Change in Seasons

The earth moves not only on its axis but also in its orbit around the sun. Therefore, the earth changes its position continuously with respect to the sun. There are four major positions of the earth, while it revolves around the sun.

1. Position on 21st June : In this position the sun shines perpendicularly over the Tropic of Cancer. This position in called the Summer Solstice. It is the time of summer season in the northern hemisphere, while in the southern hemisphere, it is winter season. The day in the northern hemisphere is longest on 21st June.
2. Position on 22nd December : In this position the Sun shines perpendicularly over the Tropic of Capricorn. This position is called Winter Solstice. During this period, days are long and nights are short in the southern hemisphere. This positions marks the summers in the southern hemisphere and winters in the northern hemisphere.
3. Positions on 21st March and 23rd September : In these two positions the Sun shines directly overhead on the Equator. Therefore, half part of all latitudes receives the sun-light at these times. Hence, everywhere, the duration of day and night is equal.. Seasons are also similar in both the hemispheres. These two positions are referred to as Equinoxes. 21st March is called Spring or Vernal Equinox whereas 23rd September is called Autumn Equinox.

Eclipses

• Both the Earth and the Moon get hght form the Sun. Only one part of the Moon can be seen from the earth because of equal rotational speed of both the earth and the Moon. Illuminated face of the Moon is seen on the Earth once a month on the Full Moon. On the New Moon the Moon is not seen at all because on this night the completely dark Moon faces the Earth.
• When the Earth comes in between Sun and the Moon, the hght of the Sun is not able to reach the Moon, rather, the shadow of the Earth falls on the moon. This is called the Lunar Eclipse. Lunar Eclipse always occurs on a Full Moon. When the Moon comes in between the Sun and the Earth, the light of the Sun is interrupted and shadow of the Moon falls on the Earth. This is called the Solar Eclipse, which occurs on New Moon day.

The Solar System

The Sun and bodies revolving around it, which includes 8 planets, satellites, comets, meteors and asteroids, together constitute the solar system. The source of energy for the sun is the nuclear fusion reaction in which Hydrogen changes into Helium.

The Sun

The part of the sun that we can see in known as photosphere. The outer most part of the sun, which is visible only at the time of a solar eclipse, is known as corona. A storm of hot atoms which dissipates from the photosphere of the Sun, overcomes its gravity and goes into the outer space, is known as Solar Flares. When Solar Flares reach the Earth's atmosphere, after colliding with the air and dust particles, it produces a spectacular colourful effect. In the North-Pole region, this effect can be seen as Aurora Borealis and in the South-Pole region as Aurora Australis. The regions from where the solar flares originate, some dark spots are seen, these are called Sun Sport. ISRO (Indian Space Reserch Organisation) is planning to launch a satellite called Aditya to study the sun. Time taken by the light to reach the earth form sun is 8 min 18 sec.

The Planets

These are the celestial bodies, originating from the sun and are revolving around it. They do not have their own light and receive light and heat from the Sun. All the planets revolve round the sun from west of east. But, Venus and Uranus are the exceptions, which revolve around the sun from east to west. 'Terrestrial Planet' are Mercury, Venus, Earth and Mars because of their structure being similar to that of the Earth. 'Jovian Planets' are Jupiter, Saturn, Uranus and Neptune bacause their structures are similar to the Jupiter.

• Mercury : This is nearest to the Sun and it is the smallest planet of the solar-system. It takes 8 8 days to complete one revolution of the sun. Life is not possible on this planet because of the absence of atmosphere. This member of the solar family has no natural satellite. Mariner-10 was the only artificial satellite.
• Venus : It is the Second closest planet to the Sun. This planet, unlike other planets, goes around the Sun from east to west and is the nearest planet to the Earth, it is the brightest object seen in the sky, after the Sun and the Moon therefore it is called 'Morning star' is well as 'Evening star'. Being almost similar to the Earth in size and mass it is also called the sister planet of the Earth. Its atmosphare is mainly composed of C02 (90-95%), which produces a 'Pressure cooker condition' on this planet. Venus also has no natural satellite.
• Earth : it rotates on its axis from west to east. It is tilted on its axis by 23%. It takes about 365% days to complete one revolution around the sun. Its average distance from the sun is about 150 million km. It looks blue when seen from the outer space due to the presence of large amount of water, hence it is also called the 'Blue Planet'.
• Mars : It is called 'Red Planet' bacuse of its red appearance. It is the only planet, besides earth, where the possibility of life exists, because of the presence of atmosphere and glacial water as observed by the artificial satellite, 'Mars Odyssey'. Its rotation is like that the earth. It has two natural staellites-Phobos and Domos, the smallest satellites of the solar system. The highest point on this planet is Nicks Olympia which is three times as high as Mt. Everest.
• Jupiter : This is the largest planet of the solar system. It has 28 natural satellites going around it wherein Ganymede is the largest satellite of the planet as well as of the solar system. Ayo, Europa, Calisto, Almethia, etc are other satellites. The atmosphere of the planet is composed of Hydrogen, Helium, Methane and Ammonia. It possesses the quahties of both a planet and a star, as it has its own radio energy. Its most distinguish feature is the great red spot, which is believed to be a complex storm in the atmosphere of the planet.
• Saturn : Its most spectacular and mysterious characteristic is the presence of fully developed rings around it. These rings are composed of Small particles, which go around this planet collectively, due to its gravitational force. It is also called the 'Gaseous Globe' Galaxy like Planet. It appears yellow in the sky. Like Jupiter, the atmosphere os Saturn is also composed of Hydrogen, Helium, Methane. 30 Natural satellites of this planet have been discovered, till date, of which Titan is the largest, having the size.comparale to Mercury and its Own atmosphere and the gravitational force. Other satellites of Saturn inclued Mimansa, Ensiladu, Tethys, Phobe etc. Saturn is the last planet of the solar system that can be seen through the naked eyes.
• Uranus : Due to higher inclination of axis, it is also known as 'Lying Planet'. Uranus reloves the sun from east to west. Its atmosphere is composed of Hydrogen, Helium and Methane. When seen through the telescope, it appears green. Being very far from the Sun, it is very cold. It has 5 rings around it like Saturn (having 7 rings). These Delta and Epsilon. This planet has 21 natural satellites. The Sun rises in its west and sets in its east.
• Neptune : It was discovered by a German astronomer, Johan Galle. Its atmosphere is very dense, consisting of Hydrogen, Helium and Methane. It appears light yellow in colour. It has 8 natural satellites, of which Tritan and Mereed are important.
• Pluto: It was discovered in 1930 by Clyde Tombagh and was considered as the ninth and the smallest planet of our solar system. But at the summit of International Astronomical Union (IAU) held in Prague (Czech Republic) on 24 August 2006, scientists withdrew the status of planet form it.

Satellites

These are the celestial bodies which revolve their respective planets and around the sun as well. Like planets, satellites also do not have their own light and shine with the light of sun. Like planets, their orbits are also elliptical.

Asteroids

These are found between the orbits of Mars and Jupiter. These are celestial bodies with sizes ranging from a few meters to hundreds of the kilometres of diameter, revolving around the sun. They have originated by the disintegration of the planets.

Planets according to their decreasing size:

1. Jupiter 2. Saturn 3. Uranus 4. Neptune 5. Earth 6. Venus 7. Mars 8. Mercury

Planets according to their decreasing mass:

1. Jupiter 2. Saturn 3. Neptune 4. Uranus 5. Earth 6. Venus 7. Mars 8. Mercury

Planets according to their decreasing density:

1. Earth 2. Mercury 3. Venus 4. Mars 5. Neptune 6. Jupiter 7. Uranus 8. Saturn

Terrestrial Planets:

1. Mercury 2. Venus 3. Earth 4. Mars

Jovian Planets:

1. Jupiter 2. Saturn 3. Uranus 4. Neptune

Planets according to decreasing revolution period:

1. Mercury 2. Venus 3. Earth 4. Mars 5. Jupiter 6. Saturn 7. Uranus 8. Neptune

Meteors and Meteorites

Meteors are the celestial bodies composed of dust and gases. After coming under the influence of earth's gravity, they move with a great velocity towards the earth. But, due to collision with the particles of the atmosphere they burn and get converted into ash. Meteors which are large in size and do not burn completely and reach the surface of the earth are called meteorites.

Coments

There are the bodies composed of dust, ice and gases, which come from the colder and darker areas, away from the sun. They go around the sun in large and irregular orbits. While moving in their orbits, when they come very close to the sun, they start glowing with a bright gaseous tail always pointing away from the sun. Many a times, comets are visible to the naked eye and present a very spectacular sight. Comet Halley, discovered by Edmund Halley, returns after every 76 years.

The Universe

Copernicus in 1543 A.D. proposed the heliocentric view, which states that the Sun is the centre of the Universe instead of the Earth.

The Origin of the Universe

Big-Bang Theoery: By E. George lamantor. According to him, 15 billion years ago there was a big heavenly body, made up of heavy matters. Due to sudden explosion (Big Bang) of this heavenly body, normal matters came out of it. And many celestial bodies were created as a result of aggregation of these normal matters. Gradually their size increased due to continuous accumulation of normal matter around them. In this way, galaxies were created. Stars were formed due to re-explosion of these galaxies. In course of time, the planets were also formed in the same process.

Galaxy

A Galaxy is a large constellation of stars in which there is a central bulge and three rotating arms. Every galaxy is composed of about 100 billion stars. Our own galaxy is known as 'Mandakini' which has spiral shape. A group of stars known as 'Milky Way' seen in the night, is a part of our galaxy. Orian Nebula is the brightest and the coldest group ofstars of our galaxy.

Life Cycle of a Star

• Rotation of the galaxy causes the gaseous clouds present in the universe to become compact and due to the gravitation the process of nuclear fusion starts at the centre of this gaseous mass, converting hydrogen into helium. This process liberates an enormous amount of energy in the form of heat and light. At this stage the gaseous mass becomes a star. When star expands to a large size the temperature of the star at this stage also falls down, so it appears red. This is the Red Giant Star.
• Supernova : The helium starts converting into carbon and carbon into heavy metal like iron in the core. This results in a massive explosion in the which is known as supernova.
• Chandrasekhar Limit : If the initial mass of the star is less than 1.4 times the mass of the sun, then it ends its life as a white dwarf star, which is also known as a Fossil star. White dwarf ultimately turns into a Black dwarf. The limit 1.4 of solar mass has come to be known a Chandrasekhar Limit.
• Neutron Star: Unlike above, if the mass of the star is much more than the mass of the sun then it became Neutron Star.
• Black Hole: A Neutron Star remains contracting and, thus, mass in a large quantity, concentrates on one point. Such body with high density is called Black Hole. It does not allow anything to escape, including the light due to which it can be seen. It is John Wheeler who propounded the concept of Black Hole.

Neolithic Age in India

Neolithic Age in India

The Neolithic period began around 107 00 to 9400 BC in Tell Qaramel in Northern Syria. In South Asia the date assigned to Neolithic period is 7 000 BC and the earliest example is Mehrgarh Culture. Mehrgarh is the oldest agricultural settlement in the Indian subcontinent.

Mehrgarh: The site is located near the Bolan Pass, to the west of the Indus River valley and between the present-day Pakistani cities of Quetta, Kalat and Sibi. Mehrgarh was discovered in 197 4 by an archaeological team directed by French archaeologist Jean-François Jarrige, and was excavated continuously between 1974 and 1986. The earliest settlement at Mehrgarh—in the northeast corner of the 495-acre (2.00 km2) site—was a small farming village dated between 7000 BCE–5500 BC.
Early Mehrgarh residents lived in mud brick houses, stored their grain in granaries, fashioned tools with local copper ore, and lined their large basket containers with bitumen. They cultivated six-row barley, einkorn and emmer wheat, jujubes and dates, and herded sheep, goats and cattle. Residents of the later period put much effort into crafts, including flint knapping, tanning, bead production, and metal working. The site was occupied continuously until about 2600 BCE.
In April 2006, it was announced in the scientific journal Nature that the oldest (and first early Neolithic) evidence in human history for the drilling of teeth in a living person was found in Mehrgarh. Mehrgarh is now seen as a precursor to the Indus Valley Civilization.

"Discoveries at Mehrgarh changed the entire concept of the Indus civilization,"

Major features of Mesolithic Age:

• Cigar Snapped handmade Brick structures with fire places, stone blade industry using flint, composite stickle, grinding stones, bone tools, Pottery etc.

• The Neolithic settlers were cattle herders and agriculture was main occupation. The handmade pottery has been found from the Neolithic sites. The pottery is coarse in nature and not much polished.

Mesolithic Age in India

Mesolithic Age in India

The Pleistocene ended sometimes around 9000-8000 years ago and the climate changed. The climate became warmer and humid and there was expansion of flora and fauna contributed by increased rainfall. This led to availability of new resources to humans and thus the human beings moved to new areas. This period is marked with increased population. The first human colonization of the Ganga plains took place during Mesolithic period and this has been proved by presence of more than two hundred archaeological sites in Allahabad, Pratapgarh, Jaunpur, Mirzapur and Varanasi districts of Uttar PradeshThe other regions where effective human colonization occurred are deltaic region of West Bengal, West Coast near Mumbai, Coastal area of Kerala. The term Mesolithic was introduced by John Lubbock in 1865. The early period of Mesolithic age marks the hunting, fishing and food gathering which turn to hunting, fishing, food gathering as well as domesticating the animals. The tools are microliths which are smaller in size
and better in finishing (more geometric) than the Paleolithic age. Agriculture had not developed.

• The earliest evidence of domestication of animals has been provided by Adamagarh in Madhya Pradesh and Bagor in Rajasthan. A study has also suggested cultivation of plants around 7 000-6000 years back near Sambhar lake in Ajmer Rajasthan.

• The Pachpadra basin and Sojat Area of Rajasthan is a rich Mesolithic sites and lot of microliths have been discovered.

• Bagor in Rajasthan is the almost largest Mesolithic site in India.

• Another major Mesolithic site in Rajasthan is Tilwara.

• In Guajarat some places on the banks of river Sabarmati are Mesolithic sites which include the Akhaj, Valsana, Hirpur, Langhanj etc.

• Sarai Nahar Rai in Allahabad-Pratapgarh of Uttar Pradesh is a Mesolithic site. Other sites in Uttar Pradesh are Morhana Pahar and lekkahia.

• In Madhya Pradesh Bhimbetka along with Adamgarh are major Mesolithic sites.

• In Jharkhand Chhota nagpur plateau is a major Mesolithic site in India.

• In Orissa Mayurbhanj, Keonjhar, Sundergarh is a major Mesolithic site in India.

• In south India Godavari basin is rich in microliths.

The rock painting of Mesolithic period is found in Adamgarh, Bhimbetka of Madhya Pradesh and Pratapgarh, Mirzapur of Rajasthan. Apart from the animals, hunting scenes, the Mesolithic sites have also painting of social life, sexual activity, child birth, rearing of children and burial ceremony.

Microliths : These are tiny tools made from micro blades of one to five cm length, by blunting one or more sides with steep retouch. The main tool types are backed blades, obliquely truncated blades, points, crescents, triangles and trapezes. These microliths were used as components of spearheads, arrowheads, knives, sickles, harpoons and daggers. They were fitted into grooves in bone, wood and reed shafts and joined together by natural adhesives like gum and resin. (VN Misra) Hunting-gathering way of life was slowly replaced by food production from about 6000 B.C

Indian History

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The currently available sections include:

1. Paleolithic Age in India.....click here to read.
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