The Proceedings of the Eighth International Conference on Creationism (2018)

account of origins, it seems appropriate to limit its application to miraculous events such as Creation and the Noahic Flood. The regular and predictable operation of the natural world, which is so often used today as an argument against God’s existence or involvement with His creation, is in fact a great testimony to His faithfulness and immutability. While it is true that God upholds the universe by the word of His power at all times (Hebrews 1:3), the essence of miracles lies in their rarity: “The sun stopped in the midst of heaven and did not hurry to set for about a whole day. There has been no day like it before or since, when the LORD heeded the voice of a man” (Joshua 10:13b-14). The mature creation of light signals from distant stars that mankind observes in the course of history essentially collapses all of observational astronomy outside of a ~6000 light-year horizon into the miraculous. This is not an argument against the use of mature creation in principle, but rather an argument that it should be applied to distant starlight only as a last resort. The basic assumptions of a young universe cosmology as I am defining it here are these: 1) the time frame of the earth can be applied to the entire universe (i.e., there are no relativistic effects on cosmological scales), 2) the universe (not just the Earth) has been in existence for only thousands of Earth years, and 3) light signals that we receive on Earth from distant sources were generated at their apparent sources within that time frame . The only resolution to the distant starlight problem under these assumptions is an increase in the speed of light signals as they propagate through space between their sources and earth. I will begin by showing that a variable speed of light is consistent with Einstein’s theories of relativity. I will then review some of the existing (non-creationist) literature on a varying speed of light as an analog of weak field gravity, along with some of the basic physics of wave propagation in an inhomogeneous medium. I will go on to give some observations of my own that suggest this analogy may point to an underlying physical reality, and discuss some of the implications this idea has for a young universe cosmology. MAIN Skepticism towards a variation in the speed of light is well founded, since physical laws, along with their associated fundamental constants, can and should be relied upon in the natural realm (although the level of certainty we attribute to them is often unjustified by actual experience). Well established physical laws can of course be modified based upon new understanding or new experiments, the modification of Newton’s laws by Einstein’s theories of relativity being a prime example. Such modifications are not arbitrary, of course: Einstein’s theories reduce to Newton’s for velocities that are small compared to the speed of light. But they remain genuine modifications, and as long as new theories do not contradict established theories where their validities overlap, attempted modifications are a perfectly reasonable (albeit difficult) undertaking. All such new theories, of course, require confirmation by experiment in order to be established. Similar considerations apply to the fundamental constants. The well established value for the speed of light (c 0 = 3 x 10 10 cm/s) has only been measured within the Solar System, and while Einstein’s theories are consistent with this value being a universal constant, they do not require it (to insist that they do is to affirm the consequent). The only requirement for the validity of Einstein’s theory of special relativity is that the speed of light be independent of the velocity of an observer, not that it be a universal constant. As with all physical theories consisting of a set of differential equations, the theory is local, connecting only adjacent points in spacetime, and it has nothing to say about either the value of c or its variation with space and time. The fact that numerical calculations in relativity can be (and typically are) done with c = 1 is one indication that their results are independent of the value of the speed of light. The best way to think about the role of c in the theory of relativity is that it sets a limiting value for velocity. The theory does not say what that limiting value is, nor does it require it to be constant with space or time. To see that this is true, one has only to consider a meta-material in which the speed of light varies (Genov et al. 2009) to see that the theory of special relativity would apply to such a material, with the only difference being that the speed of light would be modeled as c ( x , y , z , t ) rather than as a constant. We are accustomed to regarding the speed of light in vacuum as a universal constant, but one can derive the theory of relativity without that assumption (Frank and Rothe 1911; Berzi and Gorini 1969), and the only experimental result that can be stated with certainty is that c 0 = 3 x 10 10 cm/s in the Solar neighborhood. Not only that, but the theory of general relativity (in the weak field regime) can be formulated precisely in terms of a varying speed of light. One of the earliest explorations of this idea was by Dicke (1957), who showed that gradients in the vacuum permittivity μ and permeability ε (recall that ) could mimic a gravitational force field. These ideas eventually developed into scalar-tensor theories of gravity. In addition, there is a vast literature on analog theories of gravity, one of which is a varying vacuum permittivity and permeability, or equivalently, a varying speed of light (Barceló et al. 2011). I will not review these theories in detail here, but the important point is that the theory of gravity in the weak field regime (i.e., where a test mass does not distort the space time continuum in its vicinity) is entirely equivalent to the theory for a varying speed of light. It is instructive to consider the propagation of sound through earth’s atmosphere as an analogy for a spatially varying speed of light. The dispersion relation is the same for sound waves as for light waves: ω = ck , where ω and c are the frequency and speed of the wave, and k = 2π / λ is the wave number, with λ the wave length. The speed of sound varies with altitude, since c ~ √ T and the temperature varies with height. The temperature gradient in the atmosphere changes sign several times between the troposphere and the thermosphere, so the speed of a sound wave will either increase or decrease depending on the layer of the atmosphere in which it is propagating. If the atmosphere is in a steady state, the frequency of the sound wave will remain constant and the wavelength will vary as λ ~ c -1 ~ T 1/2 , i.e., it will increase (decrease) when the temperature decreases (increases). By analogy with visible light, an increase (decrease) in the wavelength of a sound wave corresponds to a red (blue) shift. The ratio of wavelengths is given by λ o / λ e ≡ 1 + z = c e / c o , (1) Johnson ◀ Young universe cosmology ▶ 2018 ICC 47