Why is time special?

[Mise]

In maths, time is merely another dimension. But in physics, time is special. It is set up such that things happen forward in time. We are generally interested in the evolution of a system through time, because that is how we perceive motion. Why is time special? Why do we move through space as the clock ticks constantly, instead of moving through time as the meter-rule slides? I'm sitting still in space, as time passes. Why can't I sit still in time, as space passes? I can certainly travel in the x direction whilst remaining stationary in the y and z. But I can never be stationary in t. Why not? In terms of maths, "still" means that dx/dt = 0. Why can't dt/dx = 0? I suppose it would mean that, instead of me staying still as time moves forward, I move forward as time stays still, which would mean I would be everywhere at once. I suppose this makes sense, given that dt/dx = 0 -> dx/dt = infinite (i.e. infinite velocity).

But time is special. We know that the universe has no prefered direction in space; physical laws are isotropic. But the universe is not symmetric in time -- both entropy and the weak interaction violate the symmetry of time. Is this a product of how we perceive time in our consciousness? Or is our consciousness a product of the asymmetry of time?

 

[El_Machinae]

I'd answer, but it's time for me to catch my bus...

Stephen Baxter had a short-story about an organism that lived backwards in time. In Vacuum Diagrams, I believe.

 

[Tenochtitlan]

If you sit still, time for you is still. (Provided all particles in your body become stationary, frozen)

Time is not real, it is a relative measurement of movement. It does not really exist, time is just another way of looking at how fast things move in comparison to eachother's movement.

 

[warpus]

Time isn't special in physics either - it is only special for us - beings capable of looking at the universe and asking questions.

In physics though - nothing in the math indicates that time is a 'special' dimension - ie. that it moves in one direction or another.

 

[Mise]

Well, it *is*special in physics, given that the fundamental physical forces are symmetric in space, but not in time. And entropy quite clearly states that time moves in one direction only (i.e. in the direction of increasing entropy)!

 

[Azkonus]

Simple:

While -dx is meaningful, -dt can not be defined.

 

[Erik Mesoy]

Because the arrow of entropy and the arrow of memory point in the direction of time.

 

[warpus]

Well, it *is*special in physics, given that the fundamental physical forces are symmetric in space, but not in time. And entropy quite clearly states that time moves in one direction only (i.e. in the direction of increasing entropy)!

You're right about that - but the idea of time being special was introduced by man and put into those equations.

That's what I mean. We have formulas in physics that describe how the Universe operates - none of these formulas indicate that time is special - unless that is specifically indicated by a human.

We realize that either a) time is special or b) our perception of the universe makes us think that time is special, but so far we haven't been able to figure out why this is so.

I think I read an article a couple years ago about a theory as to why exactly it's special.. but it was inconclusive and I don't even remember the content.

 

[Mise]

@Azkonus and Erik: Why?

Why is -dt meaningless?

Why doesn't entropy increase as one moves forward in the x-direction? (Like an escalator.)

 

[Mise]

You're right about that - but the idea of time being special was introduced by man and put into those equations.

That's what I mean. We have formulas in physics that describe how the Universe operates - none of these formulas indicate that time is special - unless that is specifically indicated by a human.

We realize that either a) time is special or b) our perception of the universe makes us think that time is special, but so far we haven't been able to figure out why this is so.

I think I read an article a couple years ago about a theory as to why exactly it's special.. but it was inconclusive and I don't even remember the content.

So you'd agree with the first part of this then?:

Is this a product of how we perceive time in our consciousness? Or is our consciousness a product of the asymmetry of time?

IOW, time is special because our brains are hard-wired to see the world that way?

 

[Azkonus]

For x you can create an origin and can take it as a reference.
If you move +x and come back -x you will find the exact same location.

This is not the case with time; time has a moving origin, you are always at the origin. (your point of reference is always with you). To put it another way it is impossible for you to find the exact same time.

 

[I am the Future]

As said Earlier,
Time is not special. Time is a comparison of speed of movement to other items. In our case the comparison of how quickly things move by comparison of the speed the earth rotates. If you were on another planet then time would be different; if you were in space, time would be different; if you were in another solar system, time would be different; simply put, time is a measure of rate of movement of two or more items compared to eachother.

 

[warpus]

As said Earlier,
Time is not special. Time is a comparison of speed of movement to other items. In our case the comparison of how quickly things move by comparison of the speed the earth rotates. If you were on another planet then time would be different; if you were in space, time would be different; if you were in another solar system, time would be different; simply put, time is a measure of rate of movement of two or more items compared to eachother.

I think the idea here is that time is special in the sense that it's apparently moving in one direction - and not the other.

 

[I am the Future]

I think the idea here is that time is special in the sense that it's apparently moving in one direction - and not the other.

That is a false idea, IMHO.

Time is only the measure of speed of 2 items,
it is only changeable if the items slow or speed up.
On Earth that doesnt seem likely to happen.

 

[Birdjaguar]

simply put, time is a measure of rate of movement of two or more items compared to each other.

Time is an indicator of change. Without change, there is no time. Time is a way to calibrate change. Humans invented the concept of "time" as a way to calibrate changes they noticed.

 

[warpus]

Time is an indicator of change. Without change, there is no time. Time is a way to calibrate change. Humans invented the concept of "time" as a way to calibrate changes they noticed.

Time works so well as a seperate dimension in the math that we use in physics to describe the universe that it's very tempting to dismiss what you're saying without a thought.

Most of the Universe is still a big mystery to us though - and the basic ideas behind quantum physics seem counter-intuitive to say the least - so who knows? Our models could be partially correct - but maybe they're just unnecessarily introducing the dimension of time?

Some of the basic ideas we have about the Universe must be true. There have been too many tests - some things just stand up to scrutiny too well. It's because of this that I don't think that we're totally off base, but we could have some things wrong - including time.

So you'd agree with the first part of this then?:

Is this a product of how we perceive time in our consciousness? Or is our consciousness a product of the asymmetry of time?

I think that our consciousness is a product of time, period. If time flowed in the other direction, we'd simply see the future as the past and the past as the future. So no clear answer really, sorry

Certain things make sense in only one direction only to us. But do quantum physics make sense?

 

[cgannon64]

I've been reading The Fabric of the Cosmos for school, and from it I've gathered this:

Time does not flow; that answers most of your questions, if not all. Why we think it flows - that is the real question.

 

[warpus]

^^ It doesn't flow because it's discrete, is that what you mean?

btw that is a great book

 

[cgannon64]

Yeah. His argument in the book is good, and I'll try to summarize it here.

The future can't be uncertain, because relativistic effects can allow us to be part of the "future"; but, time could still be said to "flow" from already existent past to future, right? Well, he argues, that would mean that time is like a movie reel: the past and the future are unlit, and the present is "lit up" by consciousness, and then that frame falls dark as it moves into the past. But a fundamental moment cannot change, right? If it could, it wouldn't be indivisible and fundamental - it could be divided further. Thus, any idea of present is artificial, although damned convincing - and why we even think this exists, and can't rid it from our experience, is a huge mystery.

 

[warpus]

^^ That's pretty interesting - just a couple days ago I was attempting to convince one of my friends that we were not in the same frame of reference - implying that his present was not the same thing as my present, etc. but that our frames of reference were so similar that it didn't really matter, as far as we were concerned.

That's the thing though - If you get down to enough detail no two observers will ever agree on what the present is or what the past was - even if the instruments they use to measure their frame of reference are identical in every respect. If it can be said that time flows in any sense of the word - then time flows differently for each observer in the Universe.

We can all agree on the general direction it flows in, though - at least on this planet.