Harish Jharia

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06 November 2011

Solar Eclipse: How the Sun Turns Dark Under Eclipse

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© Harish Jharia


What is solar eclipse?


Solar eclipse is a celestial constellation in which we are not able to see the sun partially and in another case the view of the sun is completely blocked. These eclipses are called ‘partial eclipse’ and ‘total eclipse’ respectively.  Let us discuss solar eclipse in common man’s language, without using scientific or astronomical terminologies.    


How does solar eclipse occur?


Eclipse of sun commonly known as solar eclipse takes place only on the new moon days that means on the days when the moon moves to the side of the earth  where there is day-time rather than appearing at night as usual. 


During solar eclipse, similar to the new-moon’s situation, moon comes in between sun and earth in a straight line. In this situation moon obstructs sunrays falling on the earth and eventually forms two types of shadows on the earth’s surface. 


The Umbra:
One of the shadows is the dark circular shadow called ‘umbra’ which is formed due to complete obstruction of sunrays by the moon. This is the area on the earth’s surface from where the view of the sun is completely blocked by moon, resulting into total eclipse. That means total eclipse would be visible from this area of dark circular shadow (Umbra). 


The Penumbra:
The other shadow is a lighter circular shadow called ‘Penumbra’ which spreads outside and concentric to the dark circular shadow (Umbra). This is the area, outside the periphery of dark shadow on the earth’s surface, from where partially blocked view of the sun is visible, resulting into partial eclipse. That means partial eclipse is visible from the lighter circular shadow (Penumbra). 


You may refer the above illustration in which the sun, moon and earth are shown in a straight line. The paths of sunbeams are also shown emerging from the sun and obstructed by the moon, before falling on the earth. You may clearly see a dark triangular portion, like a tunnel, behind the moon where sunrays are not penetrating. This dark tunnel forms a dark circular shadow (Umbra) on the earth’s surface. You may also notice the lighter circular shadow (Penumbra) around the dark shadow. 


Exclusive views of ‘total eclipse’, ‘partial eclipse’ and that of the earth with shadows of moon ‘umbra’ and ‘penumbra’ formed on the earth’s surface are also provided at the bottom of the illustration. 


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