Entropy increases in both the future and past?

[revo74]

Is it true that entropy increases no matter what direction you move in (past or future)? I find this hard to believe. Additionally, Isn't there a difference between entropy and disorder?

Here is passage from "The Fabric of the Cosmos" by Brian Greene

But the key fact to notice is that the second law is derivative: it is merely a consequence of probabilistic reasoning applied to Newton's laws of motion.

This leads us to a simple but astounding point: Since Newton's laws of physics have no built-in temporal orentation, all of the reasoning we have used to argue that systems will evolve from lower to higer entropy toward the future works equally well when applied toward the past. Again, since the underlying laws of physics are time-reversal symmetric, there is no way for them even to distinguish between what we call the past and what we call the future. Just as there are no signposts in the deep darkness of empty space that declare this direction up and that direction down, there is nothing in the laws of physics that says this direction is time future and that direction is time past. The laws offer no temporal orientation; it's a distinction to which they are completely insensitive. And since the laws of motion are responsible for how things change--both toward what we call the future and toward what we call the past--the statistical/probabilistic reasoning behind the second law of thermodynamics applies equally well in both temporal directions. Thus, not only is there an overwhelming probability that the entropy of a physical system will be higher in what we call the future, but there is the same overwhileming probability that it was higher in what we call the past.

 

[Forestman]

How far have you read into the book?

 

[revo74]

How far have you read into the book?

I haven't read the book at all. I saw it posted on a forum.

 

[Forestman]

I have read the book, but it has been several years now. Anyway though he might be trying to point out in the beginning that Newtons laws don't make a time distinction, like you posted, but I think that as the book goes on he goes on to explain how a time distinction can form on the macroscopic scale. It results from the fact that there are many more ways to create a disordered system, than there are to create an ordered one on the macroscopic scale. That is why entropy increases as time goes by, which in turn leads to the arrow of time.

 

[sardar]

I can confirm that the statement "entropy increases in both the future and past" is true. Entropy is a measure of the disorder or randomness in a system, and it is a fundamental property of the universe. According to the second law of thermodynamics, the total entropy of a closed system will always increase over time. This means that the disorder or randomness in the system will also increase, regardless of whether we are moving forward or backward in time. This is because the underlying laws of physics, which govern the behavior of all systems, are time-reversal symmetric. This means that they are equally valid in both the future and the past, and they do not differentiate between the two.

It is important to note that there is a difference between entropy and disorder. While entropy can be thought of as a measure of disorder, it is a more specific and quantitative concept. Disorder is a more qualitative concept and can be subjective, while entropy is a well-defined physical quantity that can be calculated and measured.

Overall, the idea that entropy increases in both the future and past may seem counterintuitive, but it is a fundamental principle of the universe based on the laws of physics. As scientists, we must use probabilistic reasoning to understand and predict the behavior of systems, and this applies equally in both temporal directions.