Why does earth-time go in only one direction?
Nearly all the equations that describe physics run in the both directions. The equation for a ball falling is the same for a ball propelled upwards. The math cannot tell you which way time runs!
If, for example, you took a film of the solar system, with all the planets, moons, and asteroids circling (ellipsing, really) around the sun and each other, you couldn’t tell whether the film were running backwards or forwards!
Of course, we all experience irreversible events. When you bite an apple, well, a film of that run backwards would plainly be wrong! But why?
The one law of physics that runs only one direction with time is the law of entropy — the Second Law of Thermodynamics, which says that closed systems become less organized over time.
For example, you put a cup of hot tea in an unplugged refrigerator. The tea cools and the surrounding air warms, until it’s all the same.
Now, if you plug the refrigerator in, it all gets colder and eventually freezes. It becomes more organized and entropy goes down. But entropy cannot decrease. So what happened?
The electricity that makes the refrigerator work was made by burning coal in a power plant, and the total entropy (disorganization) in the universe went up because the burning of the coal created lots of entropy, more than offsetting the freezing of the tea. All organization — all work — is bought at the price of greater entropy somewhere else.
Just so, in making memories, your brain creates organization. Some molecules are created that store the memory. Organization goes up. Entropy goes down. But the energy to do this came from your breakfast, which has become vastly less organized! The universe — on the whole — has become less organized and entropy has — on the whole — gone up.
Therefore, memory can only go in one direction because entropy can only go in one direction — because you have to expend energy to make memories.
The universe has a beginning and can only wind down. Entropy must always go up. Memories always point toward the beginning.
Second theological point: (wait for it)
This is easily demonstrated by the fact that heaven lasts forever. If entropy were a problem, then heaven simply could not last that long. In the created universe, at some point entropy increases to its limit, and when that happens, the universe will be dead. Life (and the making of memories) will all end. No work will be possible. It’s a mathematical certainty. But not in heaven.
Therefore, God can remember the future. He’s made of different stuff that obeys different rules — and we have to be careful not to impose our limits on God when we think about God things.
Of course, remembering the future is just an odd way of saying seeing the future or knowing the future or foreknowing, right? But this is kind of cool, I think.
Cause and effect
Now, remember the backwards film of the solar system? The film of the revolution of the planets can go forwards and backwards equally well because there’s no change in entropy as they move. They don’t need motors to go. It’s all inertia. Where no energy has to be expended for something to happen, without a watch, you can’t distinguish cause and effect.
In this universe, we tell the difference between cause and effect by time. Cause comes before effect. Physicists see things a bit differently: the cause has less entropy than the effect. Doing work to make something happen requires the use of energy, which increases entropy. Cause is only before effect because, almost always, effects require the use of energy.
But in a world where the Second Law of Thermodynamics has no effect, effect can precede cause.
(Many physicists think this is true in this world in certain quantum (subatomic) reactions. Quantum mechanics often involve no work (expenditure of energy) and hence aren’t restrained by entropy. And they are reversible until they increase entropy.)
Third theological conclusion — God can make effects occur before the cause
Therefore, in heaven, if God wants it to be true, an effect may be before the cause. Why not? Weird? Yes. But not that weird. It’s just that God’s made of different stuff.
But this shouldn’t be surprising. He forgave sins long before the death of Jesus by the power of that death.
(Heb 9:15) For this reason Christ is the mediator of a new covenant, that those who are called may receive the promised eternal inheritance — now that he has died as a ransom to set them free from the sins committed under the first covenant.
Nothing says the sins were “rolled forward.” Rather, scores of passages speak of sins being forgiven before Pentecost. Jesus forgave sins while he walked the earth. John the Baptist’s baptism was for the “remission of sins.” Leviticus promises forgiveness right away.
The effect precedes the cause. But that’s okay. God isn’t governed by the Second Law of Thermodynamics.