Electric vs. Gravitational shielding [duplicate]

There are great similarities between electric and gravitational fields and, furthermore, a room can be electrically shielded so that there are no electric fields simply by surrounding it with a conductor. Why can't the room be gravitationally shielded? Does it have anything to do with mass?

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Possible duplicate: physics.stackexchange.com/q/2767/11062 –  Waffle's Crazy Peanut Mar 24 at 7:00
Although that question asks specifically about waves, while this seems to about statics, it boils down to the same reason. –  DarenW Mar 24 at 7:16

marked as duplicate by Waffle's Crazy Peanut, Qmechanic♦Mar 24 at 12:00

Charuhas got a nice point that gravity is always attractive because mass is always positive. There is a nice article in Wiki for Gravitational Shielding. It has something clear...

The term gravitational shielding refers to a hypothetical process of shielding an object from the influence of a gravitational field. Such processes, if they existed, would have the effect of reducing the weight of an object.

In case of electrostatic shielding, the charges redistribute themselves in an electric field, producing their own field which opposes the applied field. But in the case of gravity, you can't do that (till now). Whenever you place the massive object in the field, the objects attract towards each other and move towards the source of the field, which is not shielding but instead, attracting. Though gravity is a long-range force, the field is much weaker than electrostatic attraction. I don't want to do much calculations, but a simple plugging shows that roughly, electric field is about $10^{40}$ times stronger than that of gravity. So, you can't achieve this effect in many possible ways. That maybe a reason why it's hypothetical...

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