Sunday, 29 July 2012

Why are all the planets in the universe spherical in shape?

Dip a finger into a bowl of water and then take it out.Now watch the drop of water as it trickles down the finger and drops down. You will notice that the drop of water acquires a spherical shape.Place a drop of mercury on a smooth surface.It attains a spherical shape,this phenomena is due to the cohesive force (force of attraction between the molecules of same element) which brings the molecule closer.
               But then why does it take a spherical shape, why not a cubic one? This is because, out of all multidimensional geometric figures, sphere has the least surface area. Thus all particles try their best to attain a spherical shape in order to reduce their surface area. It is for the same reason that when you pour any liquid in space they attain a spherical shape. But this is not the case with solids since their molecules are compactly packed and cannot be displaced. When a new star is born the gas clouds around it condenses   to form planets. The dense gas passes through three states, the gaseous state , the molten state and finally the rigid solid state. When a planet is in the first two states it attains a spherical structure due to the cohesive force as mentioned in the illustration. Later the molten planet solidifies into a rigid planet like Earth.

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