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Thread: Law of gravity incomplete

  1. #1 Law of gravity incomplete 
    Forum Masters Degree Numsgil's Avatar
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    Found this interesting article. Apparently for objects the size of spacecraft there is a small, but non 0, and consistent, deviation from trajectories expected with present gravitational equations. In effect gravity seems stronger for a smaller object (spacecraft) than for a larger object (planet). The effect has been observed with a handful of recent spacecraft, plus the voyagers.

    Discuss.


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  3. #2 Re: Law of gravity incomplete 
    . DrRocket's Avatar
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    Quote Originally Posted by Numsgil
    Found this interesting article. Apparently for objects the size of spacecraft there is a small, but non 0, and consistent, deviation from trajectories expected with present gravitational equations. In effect gravity seems stronger for a smaller object (spacecraft) than for a larger object (planet). The effect has been observed with a handful of recent spacecraft, plus the voyagers.

    Discuss.
    That issue has been on the table for a while. However, I am not sure whether or not the measured deviations from predictions are continuing to hold up. Have you seen an references of a more recent nature?


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  4. #3  
    Forum Masters Degree Numsgil's Avatar
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    Well it talks about the gravity assist from the Rosetta mission, which is a modern ESA mission, so it hasn't been ruled a fluke of older designs or anything like that. Apparently it's still an observed phenomena, still seems fairly predictable in its deviation, and still entirely unexplainable.
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  5. #4  
    Moderator Moderator Dishmaster's Avatar
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    Many explanations have been put forward. It reaches from very trivial causes to highly speculative theories about a modified gravitational law, e.g. in the framework of MOND and TeVeS theory. In fact, the perturbations are that small, that even a tiny asymmetry in the self-radiation of the spacecrafts could be responsible for the additional acceleration (photon momentum).

    A link to a PDF document with serious physics behind it is this one:
    http://arxiv.org/PS_cache/gr-qc/pdf/0604/0604052v1.pdf
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  6. #5  
    Forum Masters Degree Numsgil's Avatar
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    I hadn't thought of dark matter and energy as also being symptomatic for the need for a new physics.

    I wonder if the next paradigm shift will make physics more confusing or less confusing.
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  7. #6  
    . DrRocket's Avatar
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    Quote Originally Posted by Numsgil
    I hadn't thought of dark matter and energy as also being symptomatic for the need for a new physics.

    I wonder if the next paradigm shift will make physics more confusing or less confusing.
    Dark matter may or may not require new physics. There is a good chance that it may.

    Dark energy almost certainly will require something new. Even if a positive cosmological constant provides a good model, a reason for that constant is needed. The zero point energy of the quantum vacuum can explain a postiive constant, but the current calculations overpredict the magnitude by about 120 orders of magnitude. That is a really big error.
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