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Gravity and the effects of.

  1. Jun 30, 2003 #1
    I have got many questions:
    1. Is the anywhere that gravity is not present?
    2. If there was two planets of equal size and mass, they were a distance apart. And an object was equal distance from both would the influence of gravity cancel each other out therefore making this an area gravityless??
    3. Does gravity move faster than light?
    4. Why does gravity effect a path of light i.e. why are blackholes invisable does light really get pulled towards it?
    Any answers or theorys are welcome.:smile:
     
  2. jcsd
  3. Jun 30, 2003 #2

    chroot

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    1. No. In the Newtonian picture, gravitational fields extend to infinity. The strength of the gravitational force falls off as the square of the distance, but never reaches zero until you're at infinite distance. In the post-Newtonian (general relativistic) picture, gravitational fields are just artifacts of the curvature of space. Every point in space always has a curvature (even if that curvature is zero), thus "gravity exists" everywhere.

    2. The point halfway between two equally-massive bodies is called the "first Lagrange" point, called L1. It is an unstable place to be, very much like sitting on the apex of a barn roof. The gravitational forces due to the two bodies cancel at L1 -- but, of course, the rest of the universe may impose additional forces.

    3. No one is quite entirely sure yet. Relativists would like to believe that no information can propagate faster than the speed of light, and thus that gravitational influences propagate at or less than the speed of light. Some experiments have been performed, but their validity has been questioned. If gravitation actually does propagate faster than light, it can lead to some rather weird conclusions.

    4. In general relativity, gravitation is the result of bodies moving through the straightest possible lines in curved space. Light is not immune to the curvature of space, and follows those curves just like anything else.

    - Warren
     
  4. Jul 7, 2003 #3
    I see thanks for answering my quams!!!!
    ----------------------------oozie--------------------------
     
  5. Jul 8, 2003 #4
    3. It is generally believed that gravitation moves at the speed of light.
     
  6. Jul 8, 2003 #5
    Bonjour, IMHO,

    1. Is there anywhere that gravity is not present?
    If somewhere you don't have gravity, you wouldn't have time.

    2. If there was two planets of equal size and mass, they were a distance apart. And an object was equal distance from both would the influence of gravity cancel each other out therefore making this an area gravityless??
    Gravitational forces shall be equal in intensity and opposite in direction, then you'll be "weightless". But if you point your arms in direction of each planet, they will be oppositively attracted. You still have two gravitational fields but in opposite direction cancelling out effects but not removing the cause, the fields.

    3. Does gravity move faster than light?
    I would said that the "speed of light" shall be labelled "maximum speed of event". You wouldn't be able to observe an event where the gravitational force's effect propagates faster than c. Else you shall modify one (or both) of the metrics, meter and time.

    4. a) Why does gravity effect a path of light i.e. b) why are blackholes invisable does light really get pulled towards it?
    a) Explanations may take different approachs. One of these is: gravitational field creates gradient (non-uniform) where the electromagnetic path seams apparently to be curved, but, in fact, this path is the shortest space-time path and therefore a straight space-time line.
    b) Light, like any other types of energetic objects, is attracted by gravity. I will vulgarize my explanation but, I hope, this will help to figure out some light behaviors in presence of a black hole.
    Figure it's saturday night and you (the light) want to leave home for a party (pointing away). Your father (black hole) try to retains you at home. Option 1: You have enough energy to leave home for ever... Option 2: You have enough energy to leave home but not so much and come back home later... Option 3: You don't have enough energy and stay at home. Your friends will never see you.
     
  7. Jul 9, 2003 #6
    Re: Re: Gravity and the effects of.

    How did you come to that conclusion? Gravity WARPS time, not creates it.

    Anyway, as long as there is at least one particle in the universe, there will be gravity anywhere at some time ('at some time' because graavitation doesn't travel faster than light). It might be very much imperceptible, but it's there.
     
  8. Jul 9, 2003 #7
    Gravity WARPS time? Please explain!
     
  9. Jul 9, 2003 #8
    I am out of order but i think he or she may have come to that conclusion because of relativity. In relativity spacetime is defined by the gravitational field, how the field lines cross and or knot. If there were a place with no gravitational field there would necessarily be no spacetime. Which means there would be no "time" either. One runs into problems like this when one says time instead of spacetime.

    Imagine, "warps" is just another way of saying that the geometry(the way relativists describe a particular coordinate system)of space changes around a massive(not a large body but one that posesses mass=energy) body.
     
  10. Jul 10, 2003 #9
    Merci Vedder !
     
  11. Jul 10, 2003 #10
    Exactly, vedder! Oh, and I'm a she...
     
  12. Nov 10, 2004 #11
    hello i have a question
    my question about gravity and how about canceling it ?
    and the research of dr Abd salam at germany at this field
     
  13. Nov 10, 2004 #12
    cancel gravity

    dr Abd salam at Germany said that may be he can cancel gravity and he made a research about that and he succeeded partely saying that tha big egyption pyramed was built as no gravity at this aria
     
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