Gravity Again

Discussion in 'Physics & Math' started by Just Curious, Jun 3, 2011.

  1. Just Curious Registered Senior Member

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    At the instant of the Big Bang we are told that there were four forces of equal magnitude one of which was Gravity. Then Gravity became relatively weak and String Theorists believe this is because Gravity “leaked” into the other dimensions supposedly present but not observable. Whilst this maybe true how does this view of Gravity fit with the known fact that Gravity is not a force but the consequences of curved space-time caused by mass. At the instant of the Big Bang there was no mass thus no Gravity.
     
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  3. James R Just this guy, you know? Staff Member

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    As well as being caused by mass, gravity is also caused by energy. There was a lot of energy available at the big bang.
     
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  5. Just Curious Registered Senior Member

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    Thanks James but your answer is more tantalising. Can you explain or give me a link to where I can understand how Gravity is caused by energy.
     
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  7. arfa brane call me arf Valued Senior Member

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    It has to do with the equivalence of gravitational 'forces' and inertia.

    Mass is a density, and the higher the velocity of an object, the greater the apparent density and inertia of the object. Mass is relativistic, except at low velocities it looks constant. The relativity of mass (and its energy) explains why stars collapse--roughly speaking, mass accelerates inward and its energy increases, which increases the gravitational 'pressure' in the interior.
     
  8. quantum_wave Contemplating the "as yet" unknown Valued Senior Member

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    First of all I don't think String Theorists agree with Big Bang theory, at least not entirely. There was an event but String theory doesn't think that everything came into existence in the entire universe when the Big Bang occured as far as I know. Someone out there will object to me saying anything about it and claim that String theory is beyond my layman understanding but they probably will agree that in String Theory there at least were preconditions to the Big Bang, like you say they do.

    If you question that gravity can be invoked by the curvature of spacetime by mass/energy then your view is nothing new. If you want to discuss an alternative then you have to say what it is or all you will get is current Lorentz invariant theory or you will get an alternative theory that is incompatible with General Relativity, I bet. You have to decide for yourself what model you like but be prepared to know why.

    Take an hour or so, start here and watch all six files if you want to get a pretty current view of the state of alternative theory:

    http://www.youtube.com/watch?v=_bGx3UB-Slg

    Dr Laura Mersini-Houghton, University of North Carolina, is using String Theory mathematics to define a cosmology that addresses observations like the void in the CMBR, unexplained motion or Dark Flow, and odd temperatures to predict the presence of neighboring universes. A link on the void and one on dark flow:

    This link

    And this link

    “In 2007, Mersini-Houghton claimed that the observed CMB cold spot was "the unmistakable imprint of another universe beyond the edge of our own", just as she and her collaborator had predicted in her theory 8 months earlier.”]
     
    Last edited: Jun 4, 2011
  9. AlexG Like nailing Jello to a tree Valued Senior Member

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    Another statement on something you know nothing about.
     
  10. quantum_wave Contemplating the "as yet" unknown Valued Senior Member

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    Don't be a jerk. The comment was a reply aimed at the apparent wonderment of the OP followed by legitimate content, and not meant to explain the vast differences between theories of which I am familiar on a laymen basis. You, as an apparent professional should give up the trolling and try to be constructive. I've yet to see that from you. Try learning something by viewing the video in the link I gave Just Curious. Then tell us something of merit. Trolling is the work of a jerk.
     
    Last edited: Jun 4, 2011

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