While the quantity of energy remains the same (the first law of thermodynamics), the quality of energy deteriorates gradually over time (the second law of thermodynamics). That is, energy tends to become less usable over time.
This is expressed with the concept of entropy, which is a measure of energy usability within a closed or isolated system (the universe, for example). As usable energy decreases and unusable energy increases, entropy increases.
Since the minimum entropy is zero, one conclusion is that the universe must have had a beginning with zero or very low entropy, like a clock that was wound up and continues to wind down. But some say that any increase in entropy is bad, which shows the imperfection of the physical universe.
Is increasing entropy inherently bad, so that it may have begun with the Fall of humanity? No, increasing entropy is not all bad; it leads to good things, too, as pointed out here:
- solar heating of the earth (heat transfer from a hot object to a cold one is the classical case of the Second Law in action),
- walking (requires the highly entropic phenomenon of friction, otherwise Adam and Eve would have slipped as they walked with God in Eden!),
- breathing (based on air moving from high pressure to low pressure, producing a more disordered equalized concentration of molecules),
- digestion (breaking down large complex food molecules into their simple building blocks),
- baking a cake (mixing the ingredients produces a lot of disorder), etc.
“It is more likely that God withdrew some of His sustaining power at the Fall. He still sustains the universe (Col. 1:17) otherwise it would cease to exist.”
Moreover, increasing entropy may well continue into the age to come, the eternal age of everlasting life. Yet that would seem to imply that bodies will continue to wear out and need to be restored.
Have you never read these words? —
Then the angel showed me the river of the water of life, bright as crystal, flowing from the throne of God and of the Lamb through the middle of the street of the city; also, on either side of the river, the tree of life with its twelve kinds of fruit, yielding its fruit each month. The leaves of the tree were for the healing of the nations. Revelation 22:1-2
Whether these leaves are literal or symbolic, the implication is clear: people will still have to come to “God and the Lamb” to be renewed. A self-sufficient creation does not exist, no matter how perfect. God and his holiness will always be needed to maintain life even in a perfect world.