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More about Space

Why  we must never look at Sun ?

Not even sunglasses fully protect your eyes from the sun’s dangerous ultraviolet (UV) rays. UV can burn your eyes and make you blind. If you want to see the Sun safely , ask an adult to show you how to project its image on to a sheet of paper.

Why does the Moon have so many craters ?

Because it has been pelted by so many space rocks and has no atmosphere to protect it . One of the biggest craters, called Bailly, is nearly 300 km across. You can make out some of using a good pair of binoculars.

Does Mars have ice at its poles ?

Yes. Its south pole is mostly ‘dry ice’,which is frozen carbon dioxide  gas.At north pole there may be frozen water , mixed with the frozen carbon dioxide . There may be frozen water underground on Mars, too.

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                 What is the universe ?

We will try to understand the meaning of universe by taking an imaginary journey through space. your spaceship is now blasting off into space.

You are now 1.6 million (1.6 x 10 6) kilometers into space . The earth looks big and bright  in the darkness of space. The moon looks small.

         How was the universe formed ?

In the beginning , there was just a point of infinite density and energy. Some 15 billion years ago, a fiery explosion now called the “big bang “  occurred . Immediately after the explosion , the universe  expanded rapidly from the size of a pin to about 2,000 times the size  of the sun.When the universe  was less then a second old , it was dense as iron and it was also opaque . After 500,000 years , the universe gradually cooled to ~ 3,000oK. The elementary particles  fused to formed hydrogen and helium gas – the life in blood of the universe .  Hydrogen and helium formed gas pockets at random .In these pockets proto-galaxies  began to form . Between one and two billion years after the big bang , the proto-galaxies gave birth to galaxies, stars and another member of the universe.

         Is the universe expanding ?

The ever expanding universe

Till the early part of the twentieth century, astronomers believed that the universe was infinitely large , but did not change size or shape.

However , towards the end of the 1920’s, Edwin p. Hubble showed that , the galaxies were moving away from each other and moving in all directions. That is, the universe is expanding all the time in all directions.

     Edwin Powell Hubble (1889 – 1953)

Hubble is considered to be the founder of extragalactic astronomy – the branch of astronomy that studies the existence of other galaxies . He was  the first to observe the evidence of the expansion of the universe . He discovered that all nebulae in the sky are not part of the Milky Way galaxy . until his observation in 1924 , astronomers believed that all the nebulae were part of our galaxy.

Hubble is made his second major discovery – In 1927 – that all galaxies he observed were  moving away from our galaxy . In 1927 – the universe was expanding. H u b b l e  received many honors for his outstanding contributions to astronomy . The most advanced telescope to study intergalactic world is named after him.

After the Big Bang, Big crunch ?

Will the universe expand forever ?Or will it collapse at some point of time signify the end?

The density of the hydrogen atoms/m3 and the fate of the universe

Some, modern astronomers believe that : if the density of the universe is less than 3 hydrogen atoms/m3, its gravity is not enough to hold the matter together; i.e the universe will expand forever . If its density is more than this , the gravity will cause the collapse of the universe and the big crunch will occur.

           The sun – our nearest star

The distance between the sun and the earth is ~ 150,000,000 km. So , the light rays from the sun have to travel 150,000,00 km to reach earth. Astronomers have found that a ray of light from the sun covers this distance in 8.3 minutes.


Ancient sky- watchers or astronomers noticed that “stars”  that did not twinkle “wandered” through the sky . They called these “stars”, wanderers or planet (Greek word).

They named them after their gods – Venus,jupiter,Mars. According to them ,  the sun and the moon were also planets ! Now we know better. planets “shine” steadily . They do not have light of their own .They merely reflect sun’s light. They do not “twinkle”, because their flat discs reflect a lot of light. We can view the surface of a planet through a telescope .


Galaxies are system or families containing millions of stars . In addition to stars , galaxies also contain cosmic dust and gases .Sir William Hershel, the famous 18 th century  astronomer , called them “island in the sky”. There are millions of galaxies in the universe . Galaxies are millions of light – years apart from each other . There is vast empty space between them.

                  Milky Way galaxy


The Milky Way galaxy contains around 200 billion stars. The stars are too far away from us to be seen  individually or by the naked eye . The light from these stars forms a glowing haze in the sky as their light blends with the inter-stellar dust and gas.

This glow obviously has been seen by people from the early times.  The ancient Egyptians called it Road of Souls and the bushmen of the Kalahari desert called it the Blackbone of Night. In India, it is called Akash Ganga. Astronomers call it the Milky Way galaxy , our home in the vast universe.

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These are the 8 planets of solar system. There are Mercury , Venus , Earth , Mars , Jupiter , Saturn , Uranus and Neptune.

1. Mercury

This is the smallest and closest planet  to th sun. It takes only 88 Earth days to go round the sun once. It has no satellites and no atmosphere .


It is the second planet in the solar family. It revoles around the Sun from east to west. After the Sun and the Moon , Venus is the brightest natural object in the sky. It is also called morning star or the evening star because on some days we can see it with the naked eye just before the sunrise or sun set.

3 . Earth

The third planet from the sun is the Earth. It is the home to all living things as it fulfills their basic needs. The Earth is neither too close nor too far away from the sun. It supports life and hence called the living planet. The surface of the earth is made up land and water.  About 71 % of the Earth’s surface is covered by water and 29 % with land.

4 . Mars

It is the fourth planet in the solar family. Inactive volcanoes , rocky deserts and ice covered poles were discovered. The minerals and the iron present in the soil in Mars give a red color to this planet . It is a cold and dusty planet. It has 2 moons .

5 . Jupiter

It is the fifth and the largest planet in our solar system .The surface of the planet is surrounded by dark red and yellow clouds made of gases and dust.The color of the clouds depend on the gases. It takes 12 years to make one revolution. It has 16 moons.

6. Saturn
Saturn is the sixth planet . It is a planet , mostly made up of helium and hydrogen. It is surrounded by gases , dust , rocks and icy boulders which make it look beautiful with its ring . For that reason it is also known as ‘ringed planet’ . It has 30 moons.

7. Uranus

Uranus is the seventh planet. Unlike the other planets it does not spin on its axis . It rolls around the sun . This planet is made up of hydrogen, along with methane and helium. It is bluish green in color. The dust around is look like a ring around it. It has 15 moons.





8. Neptune

It is the eighth and the farthest planet. It appears blue like ocean. So the Romans named it after the god of the sea. It is made up of hydrogen , helium , water , and methane . It has 13 known moons.

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Save Planet Earth

Hi kids !

How can we save planet Earth. Say no to Dead Tree edition of Books. Use ebooks.

Get an Ipad or Android based Tablet. All books are available as ebooks in many formats like mobi,epub,pdf,pdb etc. Read these books on your tablet. You can save a tree that would otherwise have been felled to produce the papers of your favorite story book.

There are some websites to get ebooks ,

Around 6 billion trees are cut each year. About 35% of that is for the paper industry.

We should not cut trees.

Trees give oxygen , food , creates Ozone Layer to protect us from UV rays from Sun.

When we breath we  inhale oxygen and give out carbon-di-oxide Then the tree takes carbon-di-oxide and gives out oxygen.

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