Thoughts On Time Or Thoughts In Time
Some thoughts as a response to last lecture (first lecture on Arrow of Time 1/4/14):
Can we reverse time?
We can mathematically (substitute –t for t), but can we do this experientially? To my knowledge, no one has experienced time in reverse. This statement assumes that they would know that they were going backwards in time because causality seemed in reverse in reference to a previous memory of forward time (if they could hold that memory!). Causality might seem “proper” or in reverse to a person who was outside of time and looking “in at” either –t or t arrow experience, but this would be to say that they held an idea of what causality or time should be from prior experience within some time dimension.
My point then is this: can cognition, and it’s required aspect memory, occur outside of time? Is time a necessary aspect of cognition or even perhaps a broader notion of consciousness – thoughts seem to progress.
If time cannot be experienced in reverse unless outside of our experience, then it is possible it cannot. Time’s reversibility can only surely be mathematical and this is considered within the experience of actual time – we do the math of time’s reversing within “forward” time.
Also, can time be considered as a separate factor in GR where time is inextricably linked with matter.
All of this has me wondering whether “real time” (whatever that is) is a real and separable thing, or more of an experience of duration, as Bergson would have it.
Perhaps, as many have pondered, it is a construct of consciousness to prevent everything from seeming to occur at once.

Senan.




As usual, all your questions are good questions!

It's probably worth separating three main questions:

1. time-symmetry of physical laws

2. connections between physical time and perceived time

3. making time go backwards

The lectures are only about problems 1 and (briefly) 2. I don't say anything about making time go backwards unless you count reversing the momentums (momenta if you prefer) of things, as in the billiard ball example, which is pretty simple and something we do all the time (pun not intended). I guess you might count those examples as making time go backwards in some sense, but those very simple experiments don't raise any philosophical problems that I can see. There would be bigger problems if we tried to reverse time on a large scale or in a more thorough way than just reversing the movements of things.

So I haven't said anything about 3, and I'm not planning to. I'm planning to stick to what the natural world tends to do, not what we can do.

The reason problem 1 is a problem is that nature apparently gives us a lot more processes going in one direction (entropy increasing) than in the other. This is not really a deep problem with the nature of time either; it is a deep problem in cosmology, and I'll get to that in today's and tomorrow's lectures.

I AM going to talk about problem 2, but all I'm going to say is that however physics connects to perceived time (which IS DEFINITELY a deep problem, but I have nothing deep to say about it) it's going to work backwards if entropy decreases. I have trouble finding much to say about that — you can find a LOT written elsewhere if you're interested, starting with the course reading by Savitt, and a lot of it's good but, IMO, rather repetitive.

So that's me. Now by all means let's talk about your other questions too. I just wanted to make really clear what I think I'm doing in the lectures.

Jason