# Do chaotic systems point to a direction of time?

1. Sep 5, 2011

### luckystrikes

Hi first time poster. I have a question which has been intriguing me for some time. Are most chaotic systems also chaotic if played backwards in time? For example if we played a video of a double pendulum, will it exhibit the similar chaotic behaviour if played to someone in reverse? I guess the reason I ask this question is because I wonder do the the chaotic systems we observe in our lives point to a direction of time the same way entropy does?

2. Sep 5, 2011

### torquil

Not really. If a chaotic pendulum is registered to end up at a particular position, our inability to measure that position presicely will make us unable to determine the details about what the pendulum has done in the past.

This is exactly the same as our inability to measure the initial position of the pendulum makes it impossible for us to predict details about its movement in the future.

3. Sep 5, 2011

### luckystrikes

It makes its the more fascinating how life has evolved in that we can recollect things that have happened in the past with such accuracy compared to our ability to predict things in the future. But I guess this is more to do with how we have evolved to take advantage of entropy, but I digress... Thanks for the quick answer!

4. Sep 5, 2011

### torquil

Yes, memory is a fantastic thing. It records information, so that it becomes much easier to know prior events. On the other hand, towards the future we have no such "event log", so we have much weaker tools to determine what will happen than what has happened.

Information about past event are also sometimes "frozen in time" due to slow natural phenomena, making it possible for us to determine what has happened in the past without having to extrapolatedifficult equations of motion backwards in time.

Say an incredicly powerful wind makes a tree fall unto an analog clock, breaking it. When we discover it later, we know a very particular piece of information about the weather at a particular past point in spacetime. This would be imossible for us to determine backwards in time from the current state even if we had know the exact equations of motion of the weather, if it had not been for the broken clock.

Interesting!