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Theory or Fact

  1. Jan 5, 2005 #1
    Is it theory or fact that the universe is 4% baryonic, 23% Dark matter, 73% Dark energy.

    Theory right?

  2. jcsd
  3. Jan 5, 2005 #2


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    Everything is theory. That particular theory, however, has pretty decent evidence in its favor. The mass density of the universe is measurable by several methods. The most basic method is by comparing the ratio of visible light to mass in large scale structures, such as galactic clusters. For decades evidence has consistently mounted that there is not enough ordinary matter to account for the 'flat' geometry indicated by measurements [especially WMAP data of the CMB anisotropy]. The missing mass been named 'dark matter' because it is not emitting visible light. It may or may not be baryonic matter. The consensus is that most of it is a yet to be identified form weakly interacting particles similar to neutrinos.

    Dark energy is the force that drives the expansion of the universe. Like dark matter, its nature is not fully understood. It may simply be the zero point energy of the vacuum. Expansion is measured throught the redshifts of distant galaxies and the apparent brightness of Type 1a supernovae found in them. These measurements suggest that the expansion of the universe is accelerating.

    The geometry of spacetime [curvature] is deduced from measurements of temperature fluctuations [anisotropy] in the cosmic microwave background [CMB] radiation, a remnant of the Big Bang. Current data indicates the universe is flat or very slightly open.
    Last edited: Jan 5, 2005
  4. Jan 5, 2005 #3


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    An accurate statement.
  5. Jan 7, 2005 #4


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    worth mentioning...
    scientific definitions of fact & theory from the National Academy of Science...

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