Gravity:general question.

Discussion in 'Astronomy, Exobiology, & Cosmology' started by Snoopd0ug, Feb 18, 2011.

  1. Vern Registered Senior Member

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    695
    Hi Billy T. I enjoyed your book and continue to be impressed by your thinking.

    I think we have finally agreed that photon's gravitate. Maybe gravity is a property of photons and propagates away from them in all directions at light speed as they move through space. Lets call this property, gravitons. Then the photons on the way to your eyes must swim through all the gravitons of all other photons in space.

    I can't get my mind around how this would pull the moving photons into single lines.
     
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  3. Dywyddyr Penguinaciously duckalicious. Valued Senior Member

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    I think this comes under the heading of "Total failure to read other posts".
     
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  5. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

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    I think it should happen for the same reason that hydrogen atoms collected into gas clouds, which collected into stars, etc. I.e. any slightly higher density in the light streaming from a star would attract more photons into its streaming path.
     
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  7. tashja Registered Senior Member

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    I was once told that radiation ( like photons) contains a huge amount of energy and momentum flux, and therefore the gravity it produces is not purely ''attractive,'' and it's very, very different from the gravity produced by a mass.

    Maybe Prometheus or someone else can help me understand how the gravity produced by radiation is different from the gravity produced by a mass.

    Please Register or Log in to view the hidden image!

     
  8. orcot Valued Senior Member

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    I think your mixing this universe with the fictional mass effect universe gravity does not change by electrically charging a object
     
  9. KilljoyKlown Whatever Valued Senior Member

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    I'm not sure what you just said, but I'll be glad to take your word for it. I only made a comment about all the information on photon mass on the Internet. It looks like a lot of scientists to me. But search engines do produce a lot of overlap and duplication so maybe not.
     
  10. D H Some other guy Valued Senior Member

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    Parts II (Gravitational Action of a Pencil of Light) and III (Gravitational Action of a Pulse of Light) of the paper cited in post #79 addresses your concerns, Billy T. Two parallel pencils / pulses of light do not gravitate toward one another. Just another weirdness of general relativity.
     
  11. Vern Registered Senior Member

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    I'm not sure how weird current thinking has become, but I don't like the idea of two different kinds of gravity. Also, I don't like the idea of two different kinds of massiveness.
     
  12. Vern Registered Senior Member

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    695
    If gravity is a property of photons, as I suspect it is, and if it propagates at the speed of light, then photons running parallel couldn't feel the gravity from each other. They should outrun it, it seems to me.
     
  13. KilljoyKlown Whatever Valued Senior Member

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    I'll second that sentiment.
     
  14. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

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    I am not sure that gravity propagates (at speed of light, or any other speed) but assuming it does, there would be photon "A" slightly closer to Earth on the path towards Earth whose gravity has had time to propagate to photon "B", a little more distant from Earth, on a near by path towards Earth. etc. the gravitationally force of A on B would have a component trying to accelerate B, but that can not happen and would not as photon "C" following behind "A" on the same path as A but with twice the AB spacing is trying to retard B. etc.

    As photons fall radially inward towards a mass they don't go faster but shift to higher frequency to replace the gravitational energy they they are losing (conservation of system energy) - I think that is correct, but can't use GR to show it mathematically.

    There is a related problem with gravity propagating at speed of lght: The sun is not pulled towards Earth, but to where Earth was about 8 minutes ago. Years ago I read some papers that "took care" of this problem but forget them and never was completely satisfied. As no new source of gravity can come from nothing, but only a source whose gravity is reduced, I tend to think of gravity a "space warping" but the warp can change its shape/ deformations as masses move.
     
    Last edited by a moderator: Feb 27, 2011
  15. Vern Registered Senior Member

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    695
    Yes; that would seem so. But there is a way around it. What if the, "gravitons," once loosed from their source operate independently from their source. Now we have photons swimming through gravitons that are already in place. So, no delay.

    Would that work?
     
  16. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

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    Thanks for the link reference. I have skimmed it, jumping over all the math. At top of page 607 (and many other palces) I find they are discussing the effect of a line of light along the x-axis from source at x = 0 to sink at x = L “on the form of the line element” (which is nearby and “parallel” to the x-axis)

    Are they, when speaking of the “form of the line element” speaking of what I might call the curvature of the line segment between (0.4L, 0.0001) to (0.6L, 0.0001) where my 0.0001 is trying to capture the “nearby” to x-axis and the 0.4L & 0.6L are centering this “line element segment” on the light beam leaving the origin and going to (L,0)

    I.e. are they telling how the line y = 0.0001 is “warped”? I.e. that a test pulse of light would travel on this “line element” – if so they seem to be saying that the test pulse would follow a path that I would call a curved path, but they also seem to conclude it would not be attracted towards the x-axis. So I am too confused to try to follow better. Can you say any words to help me?
     
  17. NMSquirrel OCD ADHD THC IMO UR12 Valued Senior Member

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    do black holes die?
    if not then i would say that scenario is just as plausible as any.

    other than that ,to speculate,
    how would that affect hawking radiation?
    could hawking radiation be related to dark matter/energy?
    where is gravities evil twin?
     
  18. KilljoyKlown Whatever Valued Senior Member

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    That's a very good question, and as far as I know everything in nature has a lifecycle. Whatever the possible lifecycle of a black hole might be, it involves more time than even our visible Universe has in it's lifecycle.

    In any event to even entertain the idea that there might be a behemoth massive black hole just outside our visible Universe. You have to believe that the current Big Bang model of our Universe has some glaring problems.

    Basically you have to believe that our visible Universe is just a very small part of a very much larger cosmic structure. Then if you can still believe that a possible behemoth black hole exist just outside of our visible Universe. What's to stop you from believing there might be lot's of behemoth black holes completely surrounding our visible Universe, with the one causing the dark flow being the closest one?

    If you can get that far into the speculation, you would have to start thinking that's a frikken lot of gravity completely surrounding our visible Universe. Only speculating, but what would all that gravity look like from our point of view while not being aware of the possibility of all those behemoths? Answer: Dark Energy

    As far as Hawking radiation goes, I read an article that stated that a black hole of only 3 solar masses would take about 67 billion years to start showing a noticeable loss of mass. Need I say more about that?

    Gravities evil twin. Is there anything in nature that says I should worry about that?
     
  19. Emil Valued Senior Member

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    2,801
    There are two "types" of mass: rest mass(reduced mass) and effective mass.
    rest mass
    reduced mass
    and effective mass
    Experimental determination

    So
    photon has no rest mass only effective mass.
    Experimental checks on photon mass


    Contributions to the mass of a system
     
    Last edited: Feb 27, 2011
  20. KilljoyKlown Whatever Valued Senior Member

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    @ Emil

    That was a truly excellent posting. Thank You
     
  21. common_sense_seeker Bicho Voador & Bicho Sugador Valued Senior Member

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    Very good question. It's due to an Archimedes screw acting as an unseen particle called a graviton. Newton and Einstein both missed this trick to explain the spooky action at a distance, i.e. the force of gravity. I've just entered this idea in a prestigious physics competition with a potential prize of $10,000. See here Essay competition
     
  22. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

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    Thanks for the laugh - Good to see you have not lost your touch / talent for creative stupidity.
     
  23. common_sense_seeker Bicho Voador & Bicho Sugador Valued Senior Member

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    That's not what the other essay authors are saying though. Just you wait Mr Billy T..

    Here's an example:

     

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