Time
The passage of time is a medium/anomoly we all experience and share. The pulse of time can be measured in various ways from the trickle of sand, the drip of water, the swing of a pedulum or the vibration of an atom. What we all sence is that we seem to be on a stream that moves forward from the past that we remember, to the present that we experience and the future that is unknown.
Is this direction from the past to the future via the present dependant on an expanding universe? If so if the expansions slows or reverses what would we then experience at that line known as the present that separates the past from the future as time runs backwards.