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Gravity waves and a disapprearing sun.

  1. Dec 24, 2006 #1
    I was thinking of a scenario where the sun suddenly disappeared into thin space as if it were blinked out of existence. Aside from this being an absurd possibility, the more interesting question is how space around the sun would react to the giant loss of mass. Would it be correct in thinking that Mercury would fly out of its orbit around the sun before the earth flew out of its orbit? Since no force exceeds the speed of light C, gravity is still subject to propogate outwards from the sun towards the planets at a speed of C. The sun would stop emitting gravity waves and these gravity waves would no longer reach the planets and one by one the planets would be slung off into space in whatever random vector they were travelling at minus the influence of the sun's gravitational waves. What would these waves be like? Would dissappearance of the waves give a planet like earth a instant jolt into its random vector into space or would it be somewhat smooth? Are there any good analogies that can describe how the interaction between a planet and ?
     
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  3. Dec 24, 2006 #2

    disregardthat

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    It is just a theory about the gravitons, or these gravity waves you are talkign about.

    Gravity is a "bending" of space, where mass will attract mass. If the sun disappeared planets flying around the sun continue in the direction they were heading as the sun disappeared. If you don't add the other planets gravity into the equation (or the stars). The planets have little effect on eachother in the beginning although they might crash into eachother if they were heading somehoe the same direction of another planet in the same solar system...
     
  4. Dec 24, 2006 #3

    ShawnD

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    Correct. Well before the idea of gravitons came into play, Einstein had a theory that nothing can go faster than light, not even gravity. The gravity and light waves of this happening would be going at the same speed, and Earth would start to lose its orbit at the same time we noticed the sun is missing, which is about 10 minutes after it really happened.
     
  5. Dec 24, 2006 #4
    You mean to say that the planets will continue in the direction they were heading minus the sun's gravitational vector component I think.
     
  6. Dec 24, 2006 #5
    What would it look like when the final gravity wave passed through the earth 10 minutes after the sun dissappears? Would the Earth be instantly effected or is the interaction smoother?

    Furthermore, are gravity waves theorized to always travel at C, or are they subject to similar index of refraction laws like EM waves are? In other words does gravity slow down in dense regions of space and speed up in thin ones?
     
  7. Dec 24, 2006 #6

    ShawnD

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    I'm not sure, but I assume the gravity effects would be instant after 10 minutes. Try to think of it like turning a light on and off. Now you see light, now you don't. Now you have gravity, now you don't.

    I have no idea if gravity can slow down the way light does in other media.
     
  8. Dec 24, 2006 #7
    Newton's theory 'Action at a distance' was instantaneous gravity froce which I think works when using his equations, I might be wrong here. Later Einstein came up with 'c' or the speed limit of light. Gravity waves should not be able to travel faster then light which creates a paradox. I have read that the gravity pull toward the sun is where the sun in now but the light we see emanating from it is 8 minutes old or where the sun was 8 minutes ago. So what is Gravity then?
     
  9. Dec 24, 2006 #8
    Not only is the light 8 minutes old, the gravity is too. Gravity's speed is bound by the upper limit of C, I'm not sure if it always travel's at C, but it surely cannot travel any faster. Therefore, gravity from the sun reaches us at least 8 minutes after its emitted, if not more.
     
  10. Dec 24, 2006 #9

    Janus

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    Well, it wouldn't be "instant" as it would take the wave front something like 4 milliseconds to traverse the diameter of the Earth.
     
  11. Dec 24, 2006 #10

    That's an interesting point Janus. Do you think the earth would be ripped apart by the 4 millisecond traversal of the wave? Also, are you suggesting that the wave has a front? I always thought of it as the last wave's tail traversing through the earth, not some king of wave front.
     
  12. Dec 24, 2006 #11
    Is there a possibility that the sudden loss would have to be caused by a rarefaction (negative/repulsive anomaly) in the gravity field which would when it hits earth could cause it to explode?
     
  13. Dec 24, 2006 #12
    Yes that's what I was trying to get at too. If the rarefaction takes 4 milliseconds to traverse the earth's diameter, one would think that the turbulence caused could damage the earth.
     
  14. Dec 24, 2006 #13
    But perhaps because the Earth's gravity field is much stronger here than the effect of the sun's gravity field we would just feel lighter (assuming a rarefaction) for an instant. I don't know what would happen, maybe the earth would jolt? but if a point in the earth, and all the other points around it are all jolted at the same time, the earth might expand slightly which could induce long period oscillations. I don't think this would cause any damage to the earth, unless the expansion was very large in which case I'd imagine the earth could explode.
     
  15. Dec 25, 2006 #14
    A theoretical gravitational wave or perhaps a graviton probably would travel at the speed of light or less but has gravity been proven to propagate through waves or emit graviton particles? To jump to the conclusion that gravity is a wave or a particle might answer this question incorectly and then what would we learn.

    What I do know for sure is that gravity is still an unknown force and we should treat it as such. Look at what the evidence shows and not try to make old theories fit.
     
  16. Dec 25, 2006 #15

    disregardthat

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    First of all, I don't think gravity are any kind of waves, or particles. I think they are "bending" of space. Mass bends space, more mass bends the space more. It might be that the bending goes away as the sun disappeared in the speed of c, I don't know.

    And I really doubt we on our earth woudl take any effect of the loss of the sun thinking about gravity. Since our orbit aroudn the sun is a gravitational force, which means that we don't orbit because of any inertial force. the earth is "freefalling" aroudn the sun. When the sun disappears the earth might have changed acceleration but only in it's free fall. No inertial force would add to the earth change in speed, direction or acceleration. That means that we wouldn't feel anything else than free fall (0G) if you don't add the earth's gravity into the equation.
     
  17. Dec 25, 2006 #16
    I have read through this topic and my vagueness about gravity comes even worst. For me it is difficult to imagine how gravitons that come from masses can pull these masses closer. The bending of space created by mass is even more difficult to understand.
    Anyone who can explain that in some sentences which are clearer to me and of course to many more, please help.
     
  18. Dec 25, 2006 #17

    ranger

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  19. Dec 25, 2006 #18

    ShawnD

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    As long as you're not a real physicist, you can think of anything in any way you want as long as it works.
    I think of gravity as being like those magnets in cartoons that had waves coming from them. The coyote points a big magnet at something metallic, a bunch of waves shoot from the magnet, and a metal object moves towards the magnet. Gravity is the same basic idea. The sun shoots out gravity waves, these waves travel at the speed of light, and the earth moves towards the sun once these gravity waves get here, which is something like 8 minutes (I think I said 10 before).

    For the sake of simplicity just ignore the idea of gravitons. As far as I know, gravitons aren't even a fact at this point. They're a product of the string theory where some guy was doing calculations and came upon the idea of a massless particle that seemed to fit with the concept of gravity. It can be shown through math, but it has never been seen in any lab test. I would really like to believe that string theory is true, but at this point in time it cannot be proven or disproven.
     
  20. Dec 25, 2006 #19

    disregardthat

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    Is there any numbers of how many sceintist that tilt in the general relativity direction and those who tilt in the string theory direction? I thought that it was the general relativity that was the theory most people thought was true, and the bending of space seems quite logical, of course not fully logical. But the gravitrons is kind of not possible in my mind. I'll check up on it on wikipedia
     
  21. Dec 25, 2006 #20

    ShawnD

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    Physics isn't exactly black and white where one thing is wrong and one thing is right.
    Newton made some theories about gravity that are basically true. Einstein added some new theories that are also thought of as true, but claimed gravity is limited to the speed of light, making Newton's theory slightly incorrect but still usable. Do the theories disagree? Yes. Are both theories correct? Pretty much. String theory sort of goes a bit farther with everything and tries to use more of a quantum mechanics approach; explain large scale things (general relativity) using small things (gravitons).

    I think the answer to your question is that people who believe in string theory will also agree with general relativity.
     
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