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Reversing Time and Entropy and electron distribution.

I read some books and listened to some lectures on this material as I worked on the 2nd law. In one lecture, the professor said something to the effect that all microscopic interactions are reversible. So that, if we took took a motion picture of gas collisions and then ran it backwards, it would work fine, according to the laws of physics.

In fact, we wouldn't be able to tell if the film was running forward or backwards since the laws of physics are symmetrical with respect to time. So how do we now if the film is running forward or backwards. Follow the entropy trail. We drop an egg and its obvious which way the film is moving. So, that is how we tell which direction time is moving. We can't do it by looking at microscopic interactions.

Well, this is simply not true. We can tell the direction of time by watching molecular collisions. The trick is to simply note that the electron clouds are positioned differently in a multi-molecular collision depending on whether the fil is running forward or backward. It even works for a 2 molecule collision but we wouldn't be able to see it. But, for a multi collision, the velocity vectors would be wrong if we reversed the film.

Could we look for internal structure in the electron by checking reverse collisions? Millions of collisions, reverse them and look for statistical differences. Just a thought

Finally, I have been looking(minds eye) at various microscopic interactions, chemical reactions for example and they all leave telltale signs of the direction of time. I suspect that we can always tell whether the film is running backwards if we can look closely enough. So, we don't need entropy to show time's direction.



Time reversal Collisions

Time reversal Collisions