Short-period comets

Discussion in 'Astronomy, Exobiology, & Cosmology' started by Zeno, Jan 21, 2018.

  1. exchemist Valued Senior Member

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    Yeah I know. Toodle-oo, I'm a teapot.
     
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  3. Janus58 Valued Senior Member

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    Light is a radiation, gravity is a field.
    While both follow the inverse square law, there are differences.
    If I took the Earth and spread it out as a thin sheet, I could capture more of the Sun's light, but doing so does not mean that I will "capture" more of the Sun's gravity. This is a difference between emitted radiation and a field.
     
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  5. Michael 345 Bali in Nov closer Valued Senior Member

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    I get that. Spread the Earth out, keep the mass. No problem

    I think I'm going back to the thought if the Sun was to zap out of existence

    residual light would take 8 minutes to arrive so we could exclaim "The Sun's gone" but

    if the gravity field goes with the Sun we would know instantly the change in our orbit

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  7. Janus58 Valued Senior Member

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    No, changes in the gravitational field can only propagate at c. (This is what Gravitational waves do, they carry information about changes in the field from point to point.) So if the Sun where to mysteriously disappear, it would take ~8 min for the Earth to notice this gravitationally. The same is true for the electromagnetic field. Turn on an electromagnetic, and a piece of iron 100 m away won't feel it until 1/3000 of a sec later. Turn it off and it will take another 1/3000 of a second for the iron hunk to notice. Turn the magnet on and off at a frequency of 620 khz and you will be sending 620 khz "ripples" propagating through the electromagnetic field at c. Those "ripples" are radio waves at the low end of the AM band. (By modulating the amplitude of those ripples you are broadcasting an AM signal that could be picked up on any AM radio.)
     
  8. Michael 345 Bali in Nov closer Valued Senior Member

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    OK get it

    I was not trying to contend any Faster than Light Theory

    More removing the Suns gravitational field "attached / surrounding" the Earth at the same instant the Sun is plucked away

    It still seems strange the gravity field of the Sun remains after the Sun has left the building

    Light I follow because it becomes detached from the Sun when the Sun leaves and light is not a property of the Sun

    Gravity being a property I would think is linked IN WITH the Sun as a package deal. One out both out

    So it now appears to my 3 neurone brain while gravity is a property of mass it operates in a field of some sort seperate and independent from its mass

    This has to be a 10 mug of coffee, at least, thought bubble

    Thanks

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  9. DaveC426913 Valued Senior Member

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    In the most popular of models, gravity is a field. It is everywhere, always. Every single point in space has a gravitational value, even if that value is somewhat low. Gravity has a value even inside opaque sealed containers.

    That is not the same as light. Light is emitted from somewhere, and ends up somewhere. It is possible, at least in theory, to define a volume that contains no light.

    So, Earth is floating in an existing sea of gravity. The only thing that propagates from the sun is changes in that sea.
     
  10. DaveC426913 Valued Senior Member

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    OK, but it is a Christian website:

    "Answers in Genesis is an apologetics ministry, dedicated to helping Christians defend their faith and proclaim the gospel of Jesus Christ."
     
  11. Michael 345 Bali in Nov closer Valued Senior Member

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    Got it

    Thanks for your patience

    Coffee time. Cheers

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  12. exchemist Valued Senior Member

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    That is what they think they are, no doubt. Just as ISIS thinks it is the authentic voice of islam.
     

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