From: lal@cs.arizona.edu (The New Sun)
Newsgroups: sci.physics
Subject: Re: Understand...!!!!
Summary: Time flow is at any rate
Date: 30 Sep 92 01:40:46 GMT

In article <1992Sep29.193609.27350@galois.mit.edu>, jbaez@riesz.mit.edu (John C. Baez) writes:
> In article <1992Sep29.171545.806@prim> prim!dave@germany.eu.net (Dave Griffiths) writes:
> 
> >The wierdest thing about time is the fact that you can sit there and
> >observe it flowing at a certain "rate". 
> 
> Really?  How?  
> 
> Imagine doing this and measuring this rate precisely.  How would you do
> it?  What would you get - one second per second?

It is quite easily shown that talking of rates of time flow is useless.
Suppose you are an observer ina system with a certain time flow rate.  
If time slows down, will you notice? - No since your mind and body will
also slow down. If time stops, will anone notice? - No! you cant
notice anything as everything including yourself has stopped. And finally
time reverses itself, still it cannot be noticed since the observer is also time reversed. 

This shows that talking about the passage of time is nonsense. Time does not pass, or flow, it merely sits on its ass - - whatever it does it is not empirically deductable.

> 
> >If you imagine our four dimensional
> >universe as being like a reel of film, why does a character in any one
> >frame have the impression that he is travelling in a particular direction
> >with a particular speed through the film? To be aware of time flowing
> >almost seems to require one to be outside it.
> 
> Time has puzzled people for a long time.  We are so used to being within
> spacetime that when we imagine ourselves outside it, watching peoples
> wormlines as if they were carved in a block of glass, we feel the 
> need to imagine a "hypertime" to keep track of the rate at which the 
> "now" slides along these worldlines like a glowing spot.  This is NOT
> the right way to think of it.  Instead, ponder that block of glass
> and the worldlines of all the people in it, the worldlines of the 
> photons going from the Sun to their eyes (let's leave QM out for now!!),
> the worldlines of the electrons moving in their brains, etc., until
> you see how "from within" that spacetime could seem just like our world.  
> 
> It's only when you spend hours doing this that you really understand
> the concept of spacetime at a gut level.  At least that was the case
> for me.

I totally agree with your point of view. I just wanted to point out some
observations of a similar line that I have on this issue.

Thought Experiment:
What if someone finds a pocket where time is flowing at a different rate?
How do you prove this?
If you go into the pocket with a clock, you will not be able to
observe anything useful. But once you return from this pocket,
you will find that your clock is no longer synchronized with
the other clocks with which it was synch. before you left for
the pocket.

Isn't this analagous to  exactly what happens in SR?

So it is possible to compare relative time flow?
No absolute time, but a relative time?
Let proper time := 1 t.
Then a person who goes on a spaceship close to the speed of light and returns
to earth will find, for example that his clock measures one year while an earth clock measured ten years. So the ave. time flow rate in his space ship was 0.1 t. If he travelled more than a light year, during his year he measures his proper speed to be >1c, therby moving faster than the speed of light.

This astronaut is travelling thru space at V>1c and is also travelling thru time at reciprocal(0.1t) = 10t, where 1t is proper time.

What does all of this mean?

SR allows you to measure yourself at v > c but does not allow observers
to measure anything else at v > c, ( or to have someone else measure them
at v > c ).

Entropy is not symmetric about time? It increases as time increases.
But how do we know that time is not decreasing or at a standstill?

Cleary we can't tell which way time is flowing but how does it
still make sense to talk about entropy.

Does entropy 'know' which way and at which rate time is flowing?

I refer anyone interested in time and entropy to Illy Priginone's
Order Out of Chaos which I read about 5 years ago. She
won a Nobel prize for her work. I remember being fascinated by it.

Is d(entropy)/dt prop. to time rate? But this still doesnt help us
in anything but a relative way.

So you can have varying rates of time throughout the universe due to statistical fluctuations?
Is there any other so called "Arrow of Time"?

It's time to talk about time,
lets do it before there is
no more time tobe timed.

Abhinav Lal.
P.S. an interseting fact, we 'live in the past', not in the present as photons take a finite time interval to reach our retinas and it takes time for the brain to process the information.