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Can we use some type of magnifying glass to magnifying gravity react on a body by theoretical physics?

If so, could someone use it to destroy the earth

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Gravity is a very weak interaction . It bends light and presumably would bend gravitational waves and a lens might be constructed by superbeings, but there are much simpler ways,not involving orientable galaxies, to destroy the earth using gravity. A comet would do it for example. – anna v Sep 28 '12 at 3:38
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As Anna says, in practice gravity is too weak a force to be used as a death ray, however it is possible.

You may have heard that gravity can focus light. For example the most distant galaxy known was discovered just a couple of weeks ago, and it can only be seen because a galaxy cluster in between the galaxy and us is focussing it's light and making it more intense. Well in principle, you could use a similarly high mass to focus a source of gravity waves on a planet. This would heat it up, just as the moon Io is heated by tidal forces from Jupiter.

But, this is pure science fiction. Firstly generating intense gravity waves requires huge masses, for example two colliding black holes. Secondly you need something with the mass of many galaxies to focus the waves. While these do exist in the universe, how are you going to move them around to focus on your target?

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