Is the Earth's gravity same everywhere?

Earth's gravity measured by NASA's GRACE missi...
Earth's gravity measured by NASA's GRACE mission, showing deviations from the theoretical gravity of an idealized smooth Earth. (Photo credit: Wikipedia)
When you drop something, it falls downwards towards the ground. Why does it fall down? Why not up? All such questions were answered with a 7 lettered word-GRAVITY. Gravity is an attractive force and is stronger on Earth as compared to our Moon due to larger mass. When you drop an object it falls towards the ground and when it is dropped from a greater height it falls towards the ground with greater speed and impact. The greater impact and speed is attributed to acceleration (the rate of change of speed) which is higher due to gravity.

The force of gravity is inversely proportional to the radius of the Earth, that's what our textbooks said in school. But a recent press release from the European Space Agency, showed that the shape of the Earth is not a perfect sphere but a geoid or ellipsoid, bulging slightly at the equator and flat at the poles. Below is a best representation of the Earth's surface that we have so far.



The question that arises now, is whether our Earth’s gravity the same everywhere?

 So, looking at the shape of the Earth, we would answer the above question with a 'NO' and rightly so. The radius at equator is more than that at the poles.It has been observed that the value of gravity is 9.78 m/sat the equator and about 9.83 m/sat the poles . So, in order to appear lighter, all weight conscious girls should check their weights at the equator, since the weight is the product of your mass and force of Earth's gravitation. (While your mass stays the same, your weight will definitely be lesser at the equator).

But the shape is not the only reason for gravity variation around this planet! The different types of rocks also make a difference to gravity. The force is observed to be slightly greater over an area covered with highly dense rocks in comparison to the force over an area of less dense sediments. These findings have come from the GOCE (Gravity field and steady state Ocean Circulation Explorer) a probe that flies 260kms above the Earth and has been measuring the variances in the Earth's gravitational field since 2009. GOCE was launched by the European Space Agency to study the interiors of the Earth by studying the variations in the gravitational field. This will help us know more about ocean circulation and energy exchanges involved therein which determine the climate of many regions on the Earth.


Contributed by Sneha Shenoy 

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4 comments:

  1. and nasa always show their perfect sphere on ALL their photos of earth... NASA is a bunch of liers.

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    1. Dear Reader,

      We would like to clarify that not all images of the Earth available on the internet are released by NASA.

      The first image showing differences in Earth's gravity was also released by NASA.

      So NASA is not trying to lie to you about the Earth being round nor are others. Its just not a perfect sphere and it would be difficult to make this out by just looking at images from the space.

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