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Gravity Defying Ships Cause Time Dilation and Paradoxes?

  1. Nov 20, 2016 #1
    If a ship could cancel out the effect of gravity, wouldn't it be able to pass through the event horizon of a blackhole, and take a tour of the singularity, and then just report back with its observations?

    Also, if a ship had the capability to cancel out the effect of gravity, wouldn't this cause time dilation according to General Relativity? So that if it completely cancels out gravity, it also cancels out time?
  2. jcsd
  3. Nov 20, 2016 #2

    Vanadium 50

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    If it's fiction, you can do whatever you want.
  4. Nov 20, 2016 #3

    Jonathan Scott

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    At present, there is no scientific basis for any form of direct "anti-gravity", and most ideas for how that might work would violate multiple physical laws (especially conservation of energy and momentum), so you can't integrate such an idea with standard physics.

    However, you can have many forms of indirect "anti-gravity" which do comply with the laws of physics, varying from the trivial (such as legs or rocket engines) to three-phase electromagnetic levitation (allowing hovering over a metal surface). If you want your fiction to be plausibly consistent with the laws of physics, anything which resists gravity without expending propellant must do so by somehow pushing or pulling against something at a distance in order to be consistent with conservation laws.
  5. Nov 20, 2016 #4
    Fair enough Mr. Scott, but I have 2 follow up questions to clarify the points you raised regarding the violations of energy and momentum:

    Energy: Are you saying that such a device would actually be creating energy by defying (i.e. modifying) gravity? I don't see how that would necessarily happen as a consequence of such a device... Such a device may transfer gravitational energy into another form of energy, but that would not be a violation... yes?

    Momentum: Are you saying the M*V transfer due to collisions would be violated because M1 and M2 would not be operating under the same laws? If M1 is 'antigravitational' and M2 is a regular mass, then the net effect would not be an equal transfer of momentum? Again, would this be necessarily true?
  6. Nov 20, 2016 #5

    Jonathan Scott

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    Energy: If a device could allow the gravitational potential energy of an object to be increased without supplying the full corresponding amount of energy from another form, that would violate conservation of energy. Any sort of passive "gravity shield" idea generally runs into that problem. For example if you can move something over a "gravity shield" with a small amount of energy, then lift it up within the shielded zone, then move it out into normal gravity, you can then lower it back down and extract free energy. So there is no way to be "immune" to gravity; you have to supply at least the amount of energy necessary to work against it in a given context.

    Momentum: If a device allows one object to be pushed in some direction (especially upwards) without causing something else to be pushed or pulled in the opposite direction by the same impulse, it violates conservation of momentum.
  7. Nov 20, 2016 #6
    Understood Mr. Scott, and thanks. I wonder though, besides these empirical contradictions you pointed out, if the logical contradictions in the OP also stand? Wouldn't such a "gravity shield" also become a "time shield", according to general relativity?
  8. Nov 20, 2016 #7

    Jonathan Scott

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    I can't say, as it's not very meaningful to assume something which clearly violates laws of physics then ask how it would behave according to the laws of physics!
  9. Nov 20, 2016 #8
  10. Nov 20, 2016 #9


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    Please be sure that you are posting in the correct forum, and try to pretend to follow the rules. The science fiction and fantasy forum is for discussing existing books, comics, movies, etc...
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