Abstract
In standard Big Bang cosmology, the universe expanded from a very dense, hot and opaque initial state. The light that was last scattered about 380,000 years later, when the universe had become transparent, has been redshifted and is now seen as thermal radiation with a temperature of 2.7 K, the cosmic microwave background (CMB). However, since light escapes faster than matter can move, it is prudent to ask how we, made of matter from this very source, can still see the light. In order for this to be possible, the light must take a return path of the right length. A curved return path is possible in spatially closed, balloon-like models, but in standard cosmology, the universe is “flat” rather than balloon-like, and it lacks a boundary surface that might function as a reflector. Under these premises, radiation that once filled the universe homogeneously cannot do so permanently after expansion, and we cannot see the last scattering event. It is shown that the traditional calculation of the CMB temperature is inappropriate and that light emitted by any source inside the Big Bang universe earlier than half its “conformal age” can only become visible to us via a return path. Although often advanced as the best evidence for a hot Big Bang, the CMB actually tells against a formerly smaller universe and so do also distant galaxies.
Highlights
Introduction toCosmology. 2016.Is the topic of the opinion article discussed accurately in the context of the current literature? NoAre all factual statements correct and adequately supported by citations? NoAre arguments sufficiently supported by evidence from the published literature? NoAre the conclusions drawn balanced and justified on the basis of the presented arguments? NoAuthor Response 18 Dec 2020Hartmut Traunmüller, Stockholm University, Stockholm, Sweden Reviewer’s comment: The author assumes that at the time of recombination, there was only matter inside a volume with a 0.95 Gly comoving radius, so that light released after recombination is only emitted from within this volume
In the present standard model, the cosmic microwave background (CMB) radiation density is still calculated in the traditional manner as if the Big Bang universe, whose comoving radius was ≈ 0.95 Gly when it became transparent, was filled with a photon gas within an imaginary box whose volume V expands at the same rate as the material universe, so that V ∝ a(t)3 (Ryden, 2017, section 2.5)
The paper "Does standard cosmology really predict the cosmic microwave background?" by Hartmut Traunmüller examines the claim made by the Big Bang model that the cosmic microwave background (CMB) has its origin in the thermal light of last scattering at the time of recombination
Summary
In the present standard model (Ryden, 2017; Smoot, 2007), a “cosmogonic” flat and non-reflective Big Bang model (model 1), in which the universe expanded out of a singularity in spacetime, developed as summarized in the Introduction, and is highly non-homogeneous, as described under Model 1, is supplemented with a model that has its origin in the otherwise reasonable but contrary assumption that the universe is, at large, homogeneously filled with matter and blackbody radiation. In the present standard model, the CMB radiation density is still calculated in the traditional manner as if the Big Bang universe, whose comoving radius was ≈ 0.95 Gly when it became transparent, was filled with a photon gas within an imaginary box whose volume V expands at the same rate as the material universe, so that V ∝ a(t) (Ryden, 2017, section 2.5).
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