Introduction the Universe

Introduction Geography is made up of two Latin words geo and graphy. Techniques in Geography Geo means “Earth” and graphy means “to describe”. Thus the general meaning of geography is the branch of science Important techniques used for the geographic enquiry are which explains about the Earth. the following: Greek scholar Haecetus has been regarded as “father of 1. Cartography: It is the science and art of drawing maps geography”. Another Greek scholar Eratosthenes first coined and charts. the term geography. He wrote the book Geography. Alexander 2. Mathematical Geography: It is closely related to the Von Humboldt and Carl Ritter are known as “founders of making of maps and interpretation and analysis of modern geography”. statistical data. 3. Remote Sensing and Geographic Information System (GIS): Remote Sensing and GIS have emerged as the most important and powerful technique for the study of geographic problems. The Universe l The universe contains billions of stars, planets, asteroids, l The Moon, for example, is a satellite of the Earth. It moves comets, meteors, solid and gaseous particles, which are around the Earth and also around the Sun along with the called celestial bodies. Earth. l Meteors: Small pieces of space debris (usually parts of Celestial Bodies comets or asteroids) that are on a collision course with the l Nebula: It is a diffused mass of interstellar dust or gas or Earth are called meteoroids. When meteoroids enter the both, visible as luminous patches or areas of darkness Earth’s atmosphere they are called meteors or colloquially depending on the way the mass absorbs or reflects a shooting star or falling star. incident radiation. l Comets: Comets are the most exciting of the heavenly l Galaxy: The universe contains over 100 billion galaxies. A bodies. They are made up of loose collections of ice, galaxy is a group of billions of stars. Our own galaxy is dust, and small rocky particles. A well developed comet called the Milky Way, and it contains about 300 billion has a tail which is always turned away from the Sun. The stars (300,000,000,000) and one of these is our Sun. head forms the bright portion of the comet. Halley’s Comet (Markenian-348: Largest known galaxy. It is 13 times larger is one of the important comets. It visits the Earth regularly than Milky Way.) and is visible once in 76 years. It was last seen in 1986. l Constellation: Constellations are clusters of stars which l As comets approach the Sun, they develop enormous appear in a specific form. Centaurus, Gemini, Leo, Hercules tails of luminous material that extend for millions of and Virgo are major constellations. kilometres from the head, away from the Sun. l Stars: Some celestial bodies that have their own heat and l Asteroids: Between the orbits of Mars and Jupiter, there light are called stars. The Sun is also a star. is a swarm of small bodies which also revolve round the l The brightest star is Sirius, also called Dog Star, and the Sun. They are called asteroids. closest to the Earth is Proxima Centauri. l Stars are made up of vast clouds of hydrogen and helium Our Solar System gas and dust. Planets and other objects go round the Sun, and these make l Planets: Some celestial bodies do not have their own heat up the solar system, with the Sun at the centre. and light. These are called planets. The word planet means The solar system contains different types of objects ‘wanderer’. including: l Satellites: The word satellite means a smaller companion l a star — the Sun to anything. True to their meaning, these satellites revolve around their planets and also follow them in their revolution l planets, which go around the Sun around the Sun. l satellites, which go around the planets Geography l 1 l It rotates along its own axis in 24 hours. in a complete revolution, it comes closest to the Earth l It revolves around the Sun in 365 days 5 hours and 42 twice and goes the farthest twice. minutes. l The nearest position of the Moon to the Earth is known as l It is called the Blue Planet. perigee and the farthest position is known as apogee. l It is the only planet where life exists due to favourable When the Earth, the Sun and the Moon are collinear, it is atmosphere. known as syzgie. l Its diameter is 12,733.2 kilometres. Solar Eclipse and Lunar Eclipse l It has only one satellite — the moon. l When the Earth comes between the Sun and the Moon, l It is tilted at 23½ degrees on its axis and thus makes an the Moon is unable to get sunlight, i.e. the Moon is angle of 66½ degrees. partially or fully over-shadowed. This is called the lunar l It takes 23 hours, 56 minutes and 4 seconds to rotate once eclipse. on its axis and 365 days, 5 hours, 48 minutes and 46 seconds l When the Moon comes between the Sun and the Earth, (i.e. approx 365½ days) to revolve around the Sun. Rotation the Earth doesn’t get sunlight. This is known as the solar creates days and nights. The earth’s revolution around the eclipse. Sun is responsible for various seasons in a year. For the sake of convenience, the awkward one quarter of a day is ignored 4. Mars for three years and then an extra day is added to every fourth l It rotates along its own axis in 24.6 hours (almost equal to year to give us our ‘Leap years’ of 366 days. the time taken by the Earth). Statistical Data of the Earth l Due to presence of iron oxide, it appears red and is called the Red Planet. The Earth is the fifth largest planet in the solar system. l On Mars, Nix Olympica Mountain is situated, which is l Diameter three times loftier than Mount Everest. Equatorial Diameter 12,756 km l Mars has two satellites Phobos and Deimos. Polar Diameter 12,714 km l It is the only planet after Earth which has sign of water l Circumference and there is possibility of life. Equatorial Circumference 40,077 km l Various space missions so far have been sent to Mars, eg Polar Circumference 40,009 km Vikings, Pathfinder, Mars Odyssey and Curiosity. l Density 5.52 g/cu cm (5.2 times l It has thin atmosphere comprising nitrogen and argon. that of water) l Age 4.6 billion years 5. Jupiter l Highest Land Point (Mt Everest)8848 m l It is the largest planet of the Solar System. Its diameter is l Lowest Land Point (Dead Sea) -397 m 11 times and area 120 times that of the Earth. It is called the l Greatest Ocean Depth 11022 m Lord of Heavens. (Mariana Trench) l It has more gravity as compared to the Earth. l Temperature Highest: 58°C at Al- l It is the fastest rotating planet. Aziziyah, Libya l It rotates along its own axis only in 10 hours. Lowest: –89.6°C at l It revolves around the Sun in 11 years and 10 months. Antarctica l Its surface is not solid and its atmosphere, made of Average: 49°C hydrogen, helium, ammonia and methane, is very dense. l Escape Velocity: 11200 m/s l One special feature of this planet is the ‘Great Red Spot’. The Moon l Jupiter has 63 satellites. l Ganymede, the largest of these, is larger than the planet l Diameter – 3,475 km Mercury. l Gravitational force – 1/6 of the Earth l Average distance from the Sun – 3.85 lakh km 6. Saturn l It revolves around the Earth in 27 days 7.4 hours. l It is the second largest planet of the Solar System. It is l It has low albedo (the amount of sunlight which the planet 141.7 crore km away from the Sun. It revolves around the reflects). It reflects only 7% and the rest is absorbed. The Sun in 29 years and 6 months. speed of rotation and revolution of the Moon is almost l Its main feature is the presence of a circular ring around it the same. Therefore, we always see the same portion of which does not touch the surface of the Saturn. the Moon. l Saturn is made up of lighter gases, in which 63% is l Its light reaches the Earth after reflection in 1.3 seconds. hydrogen. l It has no atmosphere. l It has the largest number of satellites. It has 60 satellites. l It revolves around the Sun in an elliptical orbit. Therefore, l The largest satellite of Saturn is Titan. Geography l 3 Globe: Latitudes and Longitudes l Globe is a true model (miniature form) of the Earth. on all latitudes between the Tropic of Cancer and the l To locate any particular place on the globe we need certain Tropic of Capricorn. This area, therefore, receives the points of reference and lines. maximum heat and is called the Torrid Zone. l It can be noticed that a needle is fixed through the globe in l The mid-day Sun never shines overhead on any latitude a tilted manner which is called its axis. Two points on the beyond the Tropic of Cancer and the Tropic of Capricorn. globe through which the needle passes are two poles – l The angle of the Sun’s rays goes on decreasing towards North Pole and South Pole. the poles. As such, the areas bound by the Tropic of l The Earth moves around its axis, which is an imaginary Cancer and the Arctic Circle in the Northern Hemisphere, line.

Load more