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B Is gravity attractive or repellent?

  1. Jul 9, 2016 #1
    Am I missing something? For if Gravity is an attractive force is there not a repellant force? Or is gravity the only force?
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  3. Jul 9, 2016 #2


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    Gravity isn't a force in general relativity. But there isn't a form of repulsive gravity, no.
  4. Jul 9, 2016 #3


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    Your question is very unclear. Please be more precise and give proper reference to where your ideas are taken from.

    It is also very clear that your question is not A-level. An A tag indicates that you have an understanding of the subject equivalent to that of a graduate student in physics working with GR. I am changing the thread tag to B-level.
  5. Jul 9, 2016 #4


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    Careful. The effects of dark energy (or other things with a similar stress-energy tensor, such as a scalar field) can be viewed as "repulsive gravity"--for example, making the universe's expansion accelerate instead of decelerate. A better way of saying what I think you're trying to say here is that there are not two "gravities"; there is just spacetime curvature, which is related to stress-energy by the Einstein Field Equation. Different kinds of spacetime curvature can have different effects, not all of which look like ordinary "gravity"; but they all come from one fundamental equation, not two.
  6. Jul 9, 2016 #5
    In addition GR allows for negative pressure which would create 'repulsive gravity'.
  7. Jul 9, 2016 #6


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    Negative pressure--more precisely, negative pressure with a magnitude greater than 1/3 of energy density--is what makes dark energy, a scalar field, etc. create "repulsive gravity" (make the universe's expansion accelerate).
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