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Loeb's perspective on emergence of structure

  1. Apr 15, 2008 #1


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    This is an invited review paper by a worldclass authority, so it could be useful.

    Let there be Light: the Emergence of Structure out of the Dark Ages in the Early Universe
    Abraham Loeb (Harvard)
    32 pages, 18 figures, an invited review for the UNESCO EOLSS Encyclopedia
    (Submitted on 14 Apr 2008)

    "The initial conditions of our Universe can be summarized on a single sheet of paper. Yet the Universe is full of complex structures today, such as stars, galaxies and groups of galaxies. In this review I describe the standard theoretical model for how complexity emerged from the simple initial state of the Universe at early cosmic times through the action of gravity. In order to test and inform the related theoretical calculations, large-aperture telescopes and arrays of radio antennae are currently being designed and constructed. The actual transition from simplicity to complexity has not been observed as of yet. The simple initial conditions were already traced in maps of the microwave background radiation, but the challenge of detecting the first generation of galaxies defines one of the exciting frontiers in the future of cosmology. Once at hand, the missing images of the infant Universe might potentially surprise us and revise our current ideas."
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  3. Apr 16, 2008 #2


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    I think Loeb has done an admirable job assembling a state of the universe presentation. He captures the open issues well, IMO.
  4. Apr 16, 2008 #3
    "As the universe expands, photon wavelengths get stretched as well. The factor by which the observed wavelength is increased (i.e. shifted towards the red) relative to the emitted one is denoted by (1+z), where z is the cosmological redshift. Astronomers use the known emission patterns of hydrogen and other chemical elements in the spectrum of each galaxy to measure z. This then implies that the universe has expanded by a factor of (1 + z) in linear dimension since the galaxy emitted the observed light, and cosmologists can calculate the corresponding distance and cosmic age for the source galaxy."

    I do not agree with that at all, where does general relativity demonstrate that the frequency of photons along the path between emission and absorption is modified by spacetime curvature?
  5. Apr 16, 2008 #4
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