Now, since entropy increase characterizes the passage of time, this suggests that time itself is nothing else but entropy increase. In such a view, entropy constitutes what we perceive as the arrow of time. If, as argued above, entropy is a feature of a coarse-grained and somewhat arbitrary perspective onto the universe, and if the quantum universe as the fundamental description of nature has vanishing entropy, it thus appears likely that the quantum universe as a whole is timeless. This is exactly what has been found in quantum cosmology.
