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A comment on Military Has Been Researching "Anti-Gravity" For Nearly 70 Years. Parent comment

Re:Military Has Been Researching "Anti-Gravity" For Nearly 7... by timonoko on Thursday October 31, 2019 @02:58AM (#21406309)
It is an illusion. You are floating freely in the space, but massive mass near-by is causing curvature in space-time. In other words: Time goes more slowly in your shoes, because they are closer to the mass. This causes any movement to be circular movement, which is pressing you to the near-by mass, which you experience as "gravity".
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Re:Military Has Been Researching "Anti-Gravity" For Nearly 7... by majke on Thursday October 31, 2019 @06:01AM (#21407129)
Wow, what an excellent way of phrasing it. Give me more. Why "any movement is circular"?
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Re:Military Has Been Researching "Anti-Gravity" For Nearly 7... by Firadeoclus on Thursday October 31, 2019 @07:37AM (#21407625)
It seems to me that, as soon as there is mass in the universe which curves space-time, all paths of movement are closed. To a first approximation, for anything close to a single large mass that means an elliptical path.

That assumes, of course, that an instantaneous "path of movement" is something that is even worth considering, given that it ignores the time dimension and the fact that all those other objects aren't remaining in a static configuration around the object whose path we are considering.

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Re:Military Has Been Researching "Anti-Gravity" For Nearly 7... by TeMPOraL on Thursday October 31, 2019 @08:44AM (#21408104)
I would think that parabolic trajectories only close in infinity, and hyperbolic not even there? Or both close only in infinity? The math on that is currently out of my brain's cache.
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Re:Military Has Been Researching "Anti-Gravity" For Nearly 7... by rbanffy on Thursday October 31, 2019 @03:03PM (#21412404)
They all close. Worst case is they'll get longer and longer as the universe expands and the objects will never be able to complete them and come back for a second lap.
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