Time
The subject lusted after by sci-fi is one of the greatest gifts of God, and our travel through it is a single speed and direction
Often we find ourselves thinking about time. When we are older, we concern ourselves with how little time there ever was. When we are young, we lament the amount that lies ahead. Rarely do we consider the gift and mystery it is. The angels have no opportunity for repentance, however, we have been given the opportunity to accept salvation in time and through the cross of Christ, who thence redeems time. It is precisely this redemption that of time that shows us "The Lord is not slow about his promise as some count slowness, but is forbearing toward you, not wishing that any should perish, but that all should reach repentance." (2 Peter 3:9). God is the Lord of time, in time He created all things.