No meaning to go backwards in time

[Flatland]

Flatland, you are treating this problem like the universe has 6 spatial dimensions. This isn't the case there are only three. You can move positive and negative in each of these directions. YOu're acting like moving negative along the horizontal is like moving positive in a totally separate dimension.

I don't understand what you mean. I am not treating the universe as having six dimension. A dimension by definition is a plane that is completely perpendicular to all the other planes. Ok, not exactly the greatest definition but you get the point.

 

[J77]

If you move a clock's hand forward half a turn, do you not go back in time by moving the clock hand back half a turn.

ie. you have returned the system to it's original position.

I guess this is more a case of what frame you measure time from.

In a lot of dynamical systems you can usually reverse time by setting t=-t. This means that you can go backwards in examine how the system was in the past - even though you only know the present.

In some systems, eg. those which depend on the past - modeled by delay differential equations - you can only do this time reversal when the system is locked to some predictive path, eg. a periodic oscillation.

To this effect, I would say that, in real life, if the future is somehow determined by what happened in the past - in a nontrivial way, you won't be able to go back in time.

Or am I ranting into a Friday philosophical discussion here...

 

[Flatland]

Well, I for one believe there are many reasons why you can't go back in time. This is just one of them.