Title: Young universe cosmology

Author: B.M. Johnson

Category: Stellar and Planetary Sciences

Conference Year: 2018

Abstract: Distant starlight is one of the most challenging natural phenomena to reconcile with a recent creation. Most creationist cosmologies attempt to address this apparent contradiction between God's two books by appealing to the flexibility associated with our definition of time (Hartnett 2007; Humphreys 2008; Lisle 2010). In their current formulation, these cosmologies allow for long cosmological times periods while preserving short time periods on earth (they can thus be viewed as young earth but old universe cosmologies). Assuming that astronomical distance measurements are accurate, a consistent young universe cosmology would appear to require either some form of mature creation (i.e., local generation of starlight that is only apparently distant) or a variation in the speed of light. There is a vast literature on a variable speed of light (both creationist and non-creationist), often accompanied by a fair bit of controversy and misunderstanding. Creationist explorations have relied on suspect extrapolations of uncertain historical measurements to argue for a speed of light that has decreased since the time of Creation (Setterfield 1987). However, a speed of light that varies with gravity stands on much firmer theoretical footing. In particular, there is a direct mathematical analogy between weak-field gravity and a varying speed of light (Barceló et al. 2011). This paper will explore some of the implications associated with assuming that this analogy represents an underlying physical reality. One implication of this picture is that cosmological redshifts are due to a spatial variation in the speed of light (Dicke 1957) rather than to the expansion of space, although in principle both physical effects could be operating in concert. If light propagates faster in regions of space where gravity is weak, the extremely low gravitational potential of cosmological voids may be sufficient to put the entire universe in causal contact with the Earth on the time scale of Biblical history. Attributing cosmological redshifts to a spatial variation in the speed of light alone would obviate the need for dark energy, and a model in which the speed of light increases in the outskirts of galaxies has the potential to explain galactic rotation curves without invoking dark matter or modifying Newtonian dynamics. Finally, the model predicts a redshift evolution for the Tolman surface brightness signal (Hubble and Tolman 1935) that differs from that predicted by an expanding universe model, with the current model being more in line with observations. Not only does this hypothesis provide a straightforward solution to the problem of distant starlight, its connection with gravity also points the way towards the development of a robust and predictive young universe cosmological model.