In the past, we have had many metaphysical astronomical theories. Today, Hubble's law is the mainstay of modern theories which reasonably explains the Observed Universe. Some theories attempt to explain phenomena of observational astronomy alleged beyond the Observed Universe summarized in Hubble's law. Modern physical cosmology is dominated by the Big Bang metaphysical theory, which attempts to bring together observational astronomy and particle physics. Many questions of astronomy turn on the speed of light. Do we know the speed of light is a constant value at all distances in and beyond the Observed Universe? As determined by Hubble's law, this book finds that the value of the speed of light is constant within the Observed Universe. Beyond the Observed Universe, we do not know if the speed of light is a constant value.