Time invariant systems

When a system do not absorb photons or emit photons, that system is time invariant. Take Brownian motion, here cause and effect do not exist.we can't say atom A struck atom B, and then B struck C. Here there is no flow of time. Electrons bound to an atom is the same, in it there is no flow of time. That's why we refer to the electron as a probability wave or cloud. Time is invariant to what happens there.

Then consider two entangled photons or electrons, there is no flow of time within the system of two electrons or photons. This system breaks when the spin of one electron is measured. Until the measurement there is no flow. So even is the two electrons are far apart, since there was no flow of time, to the system they are together. Since when the system started they were together, and ended when the measurement is made they are together.

Time has two aspects, one is man made. Our brains have created the concept of time. We see that when marble A strikes marble B, B starts to move. Our brain sees that the strike happened before and causes the movement of B started after that. Then you will ask explosion of a supernova, is it happens in our brain. We sees the moon shine dies that happen in our brain. In these cases there is a flow of time.

For time to flow the system should be unstable. There should be an outflow of energy. Therefore it is not possible to reverse it, they is only one way flow.

So events of time is partly made by brain. Other part out flow of energy gives the direction of flow. The brain, our teachings or upbringing and may be also our genes gives us the direction of flow of time.