The farther away we look, the closer in time we’re seeing toward the Big Bang. As our observatories improve, we may yet reveal the very first stars and galaxies, and find the limits to which, beyond them, there are none. Even though the more distant objects recede from us incredibly rapidly, the expansion of the Universe obeys a very simple relationship between distance and apparent recession speed, with the relationship given by what we call the Hubble constant.
Cosmic inflation preceded the Big Bang, forming atomic nuclei, atoms, stars, and galaxies successively. The quantum fluctuations that occur during inflation get stretched across the Universe and when inflation ends, they become density fluctuations. This leads, over time, to the large-scale structure in the Universe today, as well as the fluctuations in temperature observed in the CMB. New predictions like these are essential for demonstrating the validity of a proposed fine-tuning mechanism, and to test alternatives.
, P. Oesch , R. Bouwens , I. Labbe , Cosmic Dawn Center/Niels Bohr Institute/University of Copenhagen, Denmark)Various components of and contributors to the Universe’s energy density, and when they might dominate. Note that radiation is dominant over matter for roughly the first 9,000 years, then matter dominates, and finally, a cosmological constant emerges. Neutrinos first behave as radiation, and later, as matter.