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    Re: gravitational fields
    From: Peter Fogg
    Date: 2008 Mar 15, 20:27 +1100

    Bill wrote:
    Our Sun is
    gone in a nanosecond. Light continues to come our way for approx. 8 minutes.
    What happens to gravity (Sun's) the moment it ceases to exist?

    "The light from the Sun takes 8 minutes to reach the Earth, so that if the Sun suddenly disappeared it would take 8 minutes before it got dark. Similarly the Earth would also feel the effects of the Sun's gravity for 8 minutes after it magically vanished ...

    In September 2002, two US scientists made some very accurate measurements of the position of a quasar as it passed behind Jupiter ...

    The measurements they took then proved that the speed of gravity is the same as that of light, ruling out some of the more bizarre modifications to the laws of gravity which have been proposed, and further backing General Relativity ...

    However, other astronomers disagree that the experiment is able to measure the speed of gravity, arguing that the effect is much smaller than the scientists claim and that (in effect) they got their arithmatic wrong when they decided that the speed of gravity did come into the equations. They are not claiming that the speed of gravity is different to that of light, just that it could not be measured in the experiment."
    http://curious.astro.cornell.edu/question.php?number=573

    For a general history of this Speed of Gravity, see:
    http://en.wikipedia.org/wiki/Speed_of_gravity


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