The Significance Of The Erosion Of The Prohibition Against Metabasis To The Success And Legacy Of The Copernican Revolution

Although one would not wish to classify Copernicus’ own intentions as belonging to the late-medieval and Renaissance tradition of nominalist philosophy, if we are to turn our consideration to what was responsible for the eventual success of the Copernican Revolution, we must also attend to other features of the dialectical context in relation to which the views of Copernicus and his followers were articulated, interpreted, and evaluated. Accordingly, this paper discusses the significance of the erosion of the Aristotelian prohibition against metabasis to the eventual success of the Copernican Revolutio

CMB observations in LTB universes: Part I: Matching peak positions in the CMB spectrum

Acoustic peaks in the spectrum of the cosmic microwave background in spherically symmetric inhomogeneous cosmological models are studied. At the photon-baryon decoupling epoch, the universe may be assumed to be dominated by non-relativistic matter, and thus we may treat radiation as a test field in the universe filled with dust which is described by the Lema\^itre-Tolman-Bondi (LTB) solution. First, we give an LTB model whose distance-redshift relation agrees with that of the concordance $\Lambda$CDM model in the whole redshift domain and which is well approximated by the Einstein-de Sitter universe at and before decoupling. We determine the decoupling epoch in this LTB universe by Gamow's criterion and then calculate the positions of acoustic peaks. Thus obtained results are not consistent with the WMAP data. However, we find that one can fit the peak positions by appropriately modifying the LTB model, namely, by allowing the deviation of the distance-redshift relation from that of the concordance $\Lambda$CDM model at $z>2$ where no observational data are available at present. Thus there is still a possibility of explaining the apparent accelerated expansion of the universe by inhomogeneity without resorting to dark energy if we abandon the Copernican principle. Even if we do not take this extreme attitude, it also suggests that local, isotropic inhomogeneities around us may seriously affect the determination of the density contents of the universe unless the possible existence of such inhomogeneities is properly taken into account.Comment: 20 pages, 5 figure

Inhomogeneous cosmologies, the Copernican principle and the cosmic microwave background: More on the EGS theorem

We discuss inhomogeneous cosmological models which satisfy the Copernican principle. We construct some inhomogeneous cosmological models starting from the ansatz that the all the observers in the models view an isotropic cosmic microwave background. We discuss multi-fluid models, and illustrate how more general inhomogeneous models may be derived, both in General Relativity and in scalar-tensor theories of gravity. Thus we illustrate that the cosmological principle, the assumption that the Universe we live in is spatially homogeneous, does not necessarily follow from the Copernican principle and the high isotropy of the cosmic microwave background.Comment: 17 pages; to appear in GR