Is expansion a result of gravity?

  • Thread starter binbots
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  • #1
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Main Question or Discussion Point

Is the expansion of space time a result of a galaxies gravity? If we take the classic trampoline example of space time I can explain what I mean. Each galaxy makes a dent in the trampoline, the more mass a galaxy gains the deeper the dent. Now if we take 2 bowling balls and place them far enough away on our trampoline that they don’t get stuck in each other’s dent then the space between them will stretch. As each galaxy gains more mass or fall into their own black hole then the space will continue to expand. It seems that the expansion of space time is a result of gravity. So why do we require dark energy?
 

Answers and Replies

  • #2
Nabeshin
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You are stretching the analogy of bowling balls on trampolines a bit far here. To derive the expansion of the universe, we actually consider the universe to be completely homogeneous and isotropic. That is, there are no density fluctuations (galaxies, people, planets, stars, anything!). This is actually a fairly good assumption on very large distance scales. When we do this, and work through the maths, we simply find a dynamic universe, that is one that is in general expanding or contracting. And observational evidence shows, of course, that it is expanding.

Individual galaxies really have nothing to do with it. And dark energy is only postulated to explain the acceleration of the expansion of the universe.
 
  • #3
Chronos
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The rubber sheet analogy creates more confusion than it dispells. It is wonderful for the unwashed masses - not so good for those who think outside the box. The tripping block is math. Cosmology is impossibly complex for those lacking advanced math skills.
 
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  • #4
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The Hubble universe constantly expands (all zones or spheres, some of which might be as small as the Planck length, do not necessarily contract after expansion) and inrushing energy feeds the spinning fractal. As in the vortex of a tornado, the spin draws in surrounding energy leaving a depleted zone around the vortex-sphere. This third vacuum, a surface-vacuum, attracts other fractals, while the constantly expanding (Hubble expansion) spinning surface repels them. The dynamic thus created between repulsive and attractive forces is the dynamic tension that underlies all matter. At this pre-particle, fractal level no thing exists that can interfere with the expanding and spinning vortex. Stability and permanence and inertia are created by Hubble expansion. Dark matter, and its theoretic “extra” gravity, may not be matter – but the temporary attenuation of the every part of the field.
 

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