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Tuesday, August 4, 2015

Earth Atmosphere our armour

We know that oxygen is vital for our existence. We get this oxygen from the atmosphere. This not the only function of the atmosphere. The atmosphere also acts as a protective shield to us from the debris of space that are attracted towards the earth by its gravitational force. 

Various meteorites, rocks, asteroids etc of different sizes, some a few centimeters across are constantly moving towards the earth. When they enter the atmosphere they have to overcome the resistance offered by Earth's atmosphere. This results in friction between the object and the atmosphere, the debris becomes hotter and hotter and ultimately melts off and is converted in vapour. Thus saving the earth from the bombardment of this debris.

Only a few meteorites of very large size are able to make it through the atmosphere and reach earth most of them fall into the oceans, since a major part of the earth is covered by oceans. A few do reach the land. On a clear night you might have seen shooting stars. This are  rocks from space that are burning due to the friction with earth's atmosphere. Most of them never reach the earth's surface.

We have seen meteorites being found from different places on earth. Till now I have seen only one TV report when a large meteorite fell on some one's garage and damaged their car. However the family got an excellent amount of money for that meteorite. (I unfortunately don't remember the details of it since I believe I saw that in a Discovery channel programme some 18 years ago or more.).

Of course we know that there is belt between the orbital paths of Mars and Jupiter that comprises of thousands of asteroids of various shapes and sizes. This are believed to be the remnants of an ancient planet that no longer exists. This belt has a significant importance in the history of Earth. Millions of years ago when dinosaurs were everywhere around the earth. A large asteroid from that belt, started moving towards the sun, after being thrown of its orbital path and on the way it was attracted by the earth's gravitational field. This asteroid rammed into the earth. 

It was too big to be burnt off by the earth's atmosphere.  The collision of the asteroid resulted in shock waves across the planet. It triggered a chain of events that lead to a huge cloud formation around the earth that blocked sunlight for years. The asteroid was 15 kilometres across. It also triggered tsunamis across different parts of the world. More details are mentioned in this Science Daily news report .

This event wiped off most of the living beings from the planet. The dinosaurs became extinct since they needed lot of food for survival because of the size of their bodies. Only the smaller creatures survived and later evolved, once the clouds cover went away. Without this event probably mammals won't have existed on earth and human beings who are the most advanced mammals, won't have existed on earth either. 

The solar system is so huge that its scale model won't fit a piece of paper. Take for example the distance between the sun and earth. Now if on paper we plot the sun as an object that has a diameter of one centimetre, then the distance between the earth and the sun has to be approximately 230 cms, and the diameter of earth has to be less than 1 mm. 

This gives us an idea about the vastness of our solar system. Also the fact that this large size reduces the probability of collision with an extraterrestial object. So the possibility that our planet would be hit by a massive object in the future is very low but it is not zero. However the smaller bodies that enter our atmosphere will be burnt off by the atmosphere and our lives will be saved. 

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