recent astronomical measurements suggest that the universe has a mass density slightly less than the so-called critical density necessary to stop the expansion of the universe, thus ensuring that the universe will never recollapse.54 Also, the expansion of the universe may actually be accelerating,55 perhaps as the result of what astrophysicists call “dark energy,” a postulated but unidentified form of energy that putatively permeates all of space and exerts an outward pressure on it.56
