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Thread: gravitational attraction

  1. #1 gravitational attraction 
    Forum Radioactive Isotope
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    from my limited research into films set in space I understand that there is such a thing as artificial gravity and also that a gyroscope has gravitational effects.
    So my question is whether a planet or a star that is spinning on its axis has a stronger gravitational atraction (on a neighbouring star) than it would if if was stationary.
    Also if an object is moving (or accellerating) with respect to another will its gravitational pull likewise be different?


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  3. #2 Re: gravitational attraction 
    Moderator Moderator Janus's Avatar
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    Quote Originally Posted by geordief
    from my limited research into films set in space I understand that there is such a thing as artificial gravity
    The only type of "artificial gravity" based in actual fact is designed around the centrifuge. You stand on the inside of a spinning cylinder. This does not create any real gravity. The "force" you feel is just your natural tendency to travel in a straight line.

    and also that a gyroscope has gravitational effects.
    No it hasn't

    So my question is whether a planet or a star that is spinning on its axis has a stronger gravitational atraction (on a neighbouring star) than it would if if was stationary.
    Also if an object is moving (or accellerating) with respect to another will its gravitational pull likewise be different?
    No. (barring relativistic effects, which are negligible at normal speeds of rotation)


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  4. #3 Re: gravitational attraction 
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    So my question is whether a planet or a star that is spinning on its axis has a stronger gravitational atraction (on a neighbouring star) than it would if if was stationary.
    Also if an object is moving (or accellerating) with respect to another will its gravitational pull likewise be different?[/quote]

    No. (barring relativistic effects, which are negligible at normal speeds of rotation)[/quote]
    thanks
    Well when do the relatavistic effects kick in (at what percentage of the speed of light of the rotation)?
    And to what degree do they boost the gravitational force?
    Is it infinitely?
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  5. #4  
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    Relativistic effects are always present. As you approach the speed of light they become more noticeable. For low speeds they can be ignored, but as you approach c they have a greater impact.

    Your system determines at what speed you start to notice the effects, and it will be different for nearly everything.
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  6. #5  
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    Seems like a simple question with a simple answer-NO
    force of g depends on mass not rotation.
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  7. #6  
    . DrRocket's Avatar
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    Quote Originally Posted by fizzlooney
    Seems like a simple question with a simple answer-NO
    force of g depends on mass not rotation.
    Janus is being careful and precise. He is alluding to a subtle effect of rotation in general relativity called the Lens-Thirring effect or "frame dragging".

    It is real but it is very small in normal situations, ie except for very high spin rates.
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  8. #7  
    Administrator KALSTER's Avatar
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    It is real but it is very small in normal situations, ie except for very high spin rates.
    So small in fact that it hasen't even been detected yet, as you'd know.
    Disclaimer: I do not declare myself to be an expert on ANY subject. If I state something as fact that is obviously wrong, please don't hesitate to correct me. I welcome such corrections in an attempt to be as truthful and accurate as possible.

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