The Universe and Our Earth

 The earth is our habitat. It is surrounded by the universe. The sun is at the centre of the solar system. There are many other stars in the space. Moreover, the Moon (satellite), the Earth (planet), comets, meteors and nebulaes are there in the space. The universe is made up of small particles, and insects on earth, distant seen and unseen stars. In this article, we will discuss space, universe, solar system, earth etc.

At the end of this chapter, we will be able to:

• Describe the location and characteristics of the solar system, earth and other planets and satellites.

• Describe the nature and diameter of earth and satellite.

• Explain the importance of lines of latitude and longitude.

• Identify different places using latitude and longitude.

• Explain rotation and revolution.

• Analyze the cause of day and night, its increase and decrease and its impact.

• Cause of season change and its impact.

• Make the model of solar system using different materials.

• Have more interest to know about our only place of habitat, earth.

Space and Universe

The sky we see above us is limitless. This is called space Our Earth, Sun, Moon and innumerable stars, plantes and sattelities are the parts of this sky. They move around the space their own axis at a certain motion. Among them some have light of their own and some don't have. At present Sun, Moon, planets, stars, comets, meteors, nebulaes, pulsars, black dwarfs, black holes etc. are called extra terrestrial body. Nobody knows how big the universe is. Nobody knows the nature and form of this universe. Many scientists believe that the universe has no beginning and ending. Some still believe that the universe has form and diameter. Scientists are discovering new things about the Universe everyday but most of the things are still unknown.

Stars

The terrestrial body which has light of its own is called Star. There are innumerable stars in the Universe ( fig. 2.1 ). We can see some of them with our maked eyes. Some of them can be seen from the Earth only through powerful telescopes. The stars are burning gasballs, made of hydrogen and helium gases. These gases are burning at a very high temperature (6000 Celsius). Other stars are not seen at day time due to the scorching light of the sun.

It seems that all the stars are lying on the same level when seen from the earth. Actually, they are lying at different distances from the earth. The distances between the earth and stars are so great that it cannot be measured by kilometres. These are measured by light years. The distance covered in one year is called one light year. Light passes about three lakh kilometres per second. The takes 8 minutes 19 seconds to the closest star to the Sun is our nearest star. Light Sun is Proxima Centauri. Its distance come to earth from the Sun. from the Earth is about 4.2 light years.

Constellation : At night some stars are seen in groups.These groups of stars are called Constellation.Astrologers of ancient time gave them different names based on their appearance, some of them look like bear or hunter. Therefore they are named as Great Bear, Orion, Cassiopea, Little Bear, Canis Major etc.

Galaxy : Planet, stars, dust, comets, vapours together make a galaxy or star world. There are one hundred billion galaxies in the space (fig. 2.2).They are of different sizes and forms, but most of them are snakelike or parabolic. Snakelike galaxies are large in size and parabolic galaxies are very bright. They move at great distance from each other. A small part of the galaxy is called Milky Way.

Nebulae : A nebulae is an interstellar cloud in outer space that is made up of dust, hydrogen and helium gases, and plasma. It is formed when portions of the interstellar medium collapse and clump together due to the gravitational attraction of the particles that comprise them.

Milky Way : The Milky Way is a spiral galaxy with a concentration of stars at its centre. This gives the galaxy a central bulge from which arms of stars radiate out. We live in one of these arms. Like all galaxies, the Milky Way is moving. Not only is the whole galaxy travelling through space, but the stars within it are continuously moving around the galactic centre.

Meteor : A meteor is a meteoroid or a particle broken off an asteroid or comet orbiting the Sun that burns up as it enters the Earth's atmosphere, creating the effect of a 'shooting star'. Meteoroids that reach the Earth's surface without disintegrating are called Meteorites (fig. 2.3).

Comet : Comets are often referred to as 'dirty snowballs'. They contain billions of icy lumps. When the gravity from a large passing body like a star, becomes strong enough, some large chunks of ice get pulled away from the cloud and head toward the Sun (fig. 2.4).As that ball of ice gets close enough to the Sun, its heat begins to melt some of the ice that makes up the comet. The melted ice becomes a gaseous tail that extends away from the source of the heat i.e. the Sun. English scientist Halley calculated the comets orbit around the sun which brings it closer to the Earth every 76 years. So it is named after him. Halley’s comet has been seen regularly since 240 BC and last came in 1986.

Planet : A planet is a celestial body orbiting a star or stellar remnant that is massive enough to be rounded by its own gravity. Unlike stars, planets do not give off light. They shine at night because they reflect light from the Sun. The planets and other objects which orbit the Sun travel in flattened circles called Ellipses. In the solar system there are eight planets, namely Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.

Satellite: A satellite is an object that goes around, or orbits, a planet.While there are natural satellites, like the Moon, hundreds of man-made satellites also orbit the Earth. The man-made satellites which are moving around the earth are used for weather forecasting, information technology, telecommunication, detection of mineral resources etc.

Solar System

The Earth is one of eight planets which orbit the Sun, and these planets and their moons make up the solar system (fig. 2.5). The word solar means 'of the Sun'. The solar system also contains thousands of minor planets, called Asteroids, and countless comets. The planets, asteroids and comets are all held in their orbits by the Sun's gravity or Pulling force.

Sun : The sun is a star. It is a middle sized yellow coloured star. The original source of heat and light of earth, other planets and their satellites is the sun. Its diameter is approximately 13 lakh and 84 thousand kilomiters and mass is 1.99 x 10¹³ Kilogram. Eight planets are moving round the Sun. They can be listed from the nearest to the furthest as follows: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. The largest planet is Jupiter and the smallest one is Venus. Mercury, Venus, Mars, Jupiter and Saturn are quite bright and can be seen without any instrument from the earth. Uranus and Neptune are less bright and they cannot be seen without telescope.

Mercury : Mercury is the smallest and nearest planet of the sun. Its average distance from the sun is 5.8 crore kilometres and its diameter is 4,850 kilometres. As it is closest to the Sun intense light sometimes makes it invisible. It takes 88 days to move around the sun and so,88 days make one year in Mercury. Its gravitational power is so weak that it cannot retain in the atmosphere. Mercury has no satellite.

Venus : You must have heard about the morning star or the evening star and might have seen it too. Venus in fact, is not a star. It glows in the sky like a star which prompts us to call it a star.Venus is covered with dark cloud. So, the sun can never be seen from its surface. Cloudy atmosphere mainly consists of carbon dioxide. It is the brightest and hottest planet of the solar system. The distance between venus and sun is 10.8 crore kilometres. No significant difference oflight between day and night is seen. It rains here but it is acid Rain. Its diameter is 12,104 kilometres. It takes 225 days to move around the sun. So, its year is of 225 days. It doesn't have any satellite. Though all planets move around on their own axis from west to east, venus moves from east to west.

Earth : Earth is our habitat. It is the third nearest planet from the Sun. The average distance from the sun is 15 crore kilometres, and the diameter is nearly 12,667 kilometres. Earth takes 365 days to orbit the Sun. Moon is the only satellite of the Earth. Earth is the only planet where the atmosphere contains oxygen, nitrogen, and carbon dioxide in proper amount for the plants and animals to survive. Earth is the only planet in the solar system where life exists.

Mars :Mars is the nearest neighbour of Earth.Average distance from the sun is 22.8 crore kilometres and the diameter is 6,787 kilometres. Length of day and night is equal. It takes 687 days to orbit the Sun. In this planet there is scarcity of water and the amount of carbon dioxide in the air is very high which is the cause of no life on Mars. Mars has two satellites. One of them is Phobos and the other is Deimos.

Jupiter : Jupiter is the largest planet of the solar system. Its diameter is 1,42,800 kilometres.It is 1,300 times larger than the Earth.It is 77.8 crore kilometres away from the Sun. Jupiter's atmosphere is made up of hydrogen and helium. It takes 4,331 days to orbit the Sun. Jupiter has 67 satellites.

Saturn : Saturn is the second largest planet of the solar system. Its distance from the Sun is 143 crore kilometres and the diameter is 1,20,000 kilometres. Atmosphere contains a mixture of hydrogen and helium gas, methane and amonia. It takes 29.5 years to orbit the sun once. Saturn has the brightest rings and 62 satellites.

Uranus : Uranus is the third largest planet of the solar system. This planet is 287 crore kilometres away from the Sun. It takes 84 years to orbit the sun once. Diameter of the Uranus is 49,000 kilometres. Methane gas is very high in the atmosphere. It has rings around it but not bright like the Saturn. Uranus has 27 satellites.

Neptune: Its distance from the Sun is about 450 crore kilometres. Light and heat of the Sun is less. Its diameter is 48,400 kilometres. Its area is as large as 72 Earths and the atmosphere is made up of Methane and Amonia. Neptune has 14 satellites.

✔ Learn about The Universe and Our Earth

✔ Learn about  Size and Shape of the World

✔ Learn about Important Lines Described in Geography 

✔ Learn about The Movement of the Earth

✔ Learn about The Change of Season on Earth