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Gravitational wave/pulse

  1. Jun 16, 2012 #1
    I need a reference. The orbits of pulsars PSR 1913+16 are shrinking. It seems that is because of the energy the pulsars are losing by emitting gravitational waves. General relativity predicts that. So far, so good; now the question.

    Is there an article where I can find the experimental/observational evidences of the structure, speed, and polarization of the gravitational waves? [According to general relativity, the structure is as if emanating from quadrupole source, the speed equals the speed of light, and polarization is 2 as of light.]

    By the way, I need some help re ellipses. Please give me an expression for the angle between the generatrix (the “radius” from a focus to a point on the ellipse) and the tangent at that point? I want to use the angle to calculate the values of some of the properties of gravitational waves.
     
  2. jcsd
  3. Jun 18, 2012 #2

    nicksauce

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    I'm not sure what you're expecting to find. Gravitational waves have never been directly detected, so there does not exist any experimental/observational evidence of their structure, speed or polarization.
     
  4. Jun 18, 2012 #3
    To nicksauce at Post 1238:

    Thank you for the answer. I know that gravitational waves have not veen detected (by LISA or LIGO). But there are indirect evidences from observing PSR 1913+16. I have been away from general relativity. I am catching up, but I thought I may have missed something meanwhile. Thanks again.

    I have developed a gravity model, which I cannot post on the Forum. The model says that there are no gravitational waves but only gravitational pulses propagating at 18.5% of the speed of light with four degrees of polarization. If I know the eccentricity of the ellipses of PSR 1913+16's orbits and their max and min orbital speeds, I can calculate the total gravitational energy emitted in a given time. If you have those data, please let me know. I will be much oblidged.

    [I do wonder -- how come gravitational interactions which are 10**40 times weaker than electromagnetic interactions can generate gravitational waves travelling at the speed of light? Look at waves on a taught string, sound waves in materials. For examples, sound travels at 350 m/s in air, at 1400 m/s in water, and 5000 m/s in steel.]
     
  5. Jun 18, 2012 #4

    nicksauce

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    Well, just going to the wikipedia page, we have the information you are looking for

    http://en.wikipedia.org/wiki/PSR_B1913+16

    Well just look at the derivation of the wave equation from perturbation theory, and it's pretty clear how the speed comes out to be c.
     
  6. Jul 5, 2012 #5
    I used my model. I get total gravitational radiation power from PSR 1913+16 to be 7.87 x 10**26 watts. Moreover radiation from the various points on the orbits is not uniform.
    Of course, the wave equations was was formulated with c.
     
  7. Jul 5, 2012 #6
    In what way are pulses not waves? I think the paper by Hulse and Taylor probably contains the calculated radiated energy you are looking for.

    I don't see how the amount of energy has any effect on the propagation velocity, and the example you have given of waves propagating through a medium are quite different. What is the medium your pulses are travelling through? In GR the waves are changes in curvature not the displacement of a medium.
     
  8. Jul 6, 2012 #7
    To cosmik debris at Post 190:

    Sound waves. I agree the sound waves need media to travel. But the underlying interactions and their strengths determine the speed of propagating waves.

    EM waves. There is no medium. Only fluctuations of coupled electric and magnetic fields. It's the coupling strength between the fields which determine the speed of em waves in vacuo. When light goes through a medium (such as water), it slows down. Why? Because the originial light is gone, it interacts with atoms and reappears continuously until it is out of the medum. These processes take time, albeit infinitetimal, thus slowing dowm light.

    My model gives me two pulses from a mass in an elliptical orbit. No pulses from a circular orbit! One pulse from an accleration along an arbitrary trajectory. Pulses are like radar pulses.

    I am unable to comment on disturbances in space-time geometry fields. I go along with them as long as I do not have any contrary evidence. LIGO and LISA have not detected gravitational waves so far. LISA now has been defunded. Pulsars 1913+16's orbits are said to be shrinking due to gravitational radiation they emit. Fine, so far so good. But still there is no evidence on the nature of gravitation radiation!

    I am now devoted to gravitational radiation. More than one theory may explain a particular gravitational phenomenon, and inclusion of higher-order effects (special relativity, et al.) should improve the theory, but one and only one theory will explain the structure, speed, and polarization of gravitational radiation. Maxwell already taught us so. Maybe Heraclitus would be kind to us.

    Thank you for the dialogue. Please keep me enlightened.
     
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