Expansion Everlasting

Chapter 5 presents experiments illuminating the cosmological evolution of the universe and its energy budget, accounting for its longevity. The observations establishing the Hubble’s Law linear relationship between intergalactic distances and recession speeds, and their interpretation in terms of the expansion of cosmic space, are reviewed. The evidence for big bang cosmology from nucleosynthesis and the cosmic microwave background (CMB) is presented. The measurements that establish the ongoing acceleration of the cosmic expansion are reviewed: distant supernova recession speeds, tiny CMB anisotropies, baryon acoustic oscillations, and gravitational lensing. Excellent model fits to these data, assuming general relativity, cold dark matter, and a cosmological constant, lead to precise determinations of both the age of the universe and the energy budget of the universe. The cosmic history of the expansion rate and the energy budget are inferred, along with the remarkable flatness of cosmic space within the observable portion of the universe.