[rvt]

Hey all,

I was thinking a bit about it (but I am a nOOb in this)
They say that we humans experience 4 dimensions (XYZ + time) does that then automatically mean we can exchange any dimension for Time, or is Time special?

Ries

[Vern]

Hey all,

I was thinking a bit about it (but I am a nOOb in this)
They say that we humans experience 4 dimensions (XYZ + time) does that then automatically mean we can exchange any dimension for Time, or is Time special?

Ries

With our special gadgetry, computers and the maths, we need only mark down a comma then a number to create another dimension. I suspect that leads us to ponder too easily into extra dimensions, and leads us to consider that they might be reality. The real world, to me, consists of three spacial dimensions and one time dimension.  That is where we live.

 

[DoctorBeaver]

You can discuss milk without referring to tea, but you can't discuss tea without referring to milk.  But I don't think that's relevant.

I don't take milk in tea. But even if I did, I could hold forth on the subject of tea without mentioning milk.

[LeeE]

You can discuss milk without referring to tea, but you can't discuss tea without referring to milk.  But I don't think that's relevant.

I don't take milk in tea. But even if I did, I could hold forth on the subject of tea without mentioning milk.

I'm sure you could, but I bet you'd have to make a conscious effort to do so []

[LeeE]

Hey all,

I was thinking a bit about it (but I am a nOOb in this)
They say that we humans experience 4 dimensions (XYZ + time) does that then automatically mean we can exchange any dimension for Time, or is Time special?

Ries

No, and yes, respectively.

There is a clear difference between them, or so it seems to us, but this doesn't necessarily mean that the difference is because the dimensions are fundamentally different; the perceived difference could actually be be due to us, or at least something about us that is different with regard to the temporal dimension and the spatial dimensions.

In the model I've been playing with, the apparent difference between the spatial and temporal dimensions is really due to the nature of our movement through those different dimensions; we move in a fundamentally different way through space when compared to the way we move through time and it is this that accounts for the apparent difference we see between the spatial and temporal dimensions.

[DoctorBeaver]

You can discuss milk without referring to tea, but you can't discuss tea without referring to milk.  But I don't think that's relevant.

I don't take milk in tea. But even if I did, I could hold forth on the subject of tea without mentioning milk.

I'm sure you could, but I bet you'd have to make a conscious effort to do so []

Not at all. I could make a reference to milk insofar mentioning that some people take it in their tea, but that certainly would not be necessary.

[Vern]

In the model I've been playing with, the apparent difference between the spatial and temporal dimensions is really due to the nature of our movement through those different dimensions; we move in a fundamentally different way through space when compared to the way we move through time and it is this that accounts for the apparent difference we see between the spatial and temporal dimensions.

I like this explanation. Plus; we can control our movement through the spacial dimensions; so far we are completely captive to the temporal one; we move through it, not at our own choosing but in complete lock step with everything else we know about.

[DoctorBeaver]

In the model I've been playing with, the apparent difference between the spatial and temporal dimensions is really due to the nature of our movement through those different dimensions; we move in a fundamentally different way through space when compared to the way we move through time and it is this that accounts for the apparent difference we see between the spatial and temporal dimensions.

It could also mean that we move through time in a fundamentally different way because time is fundamentally different from spatial dimensions. I fully appreciate that GR says space & time are inextricably linked, but I think I'm right in saying that it doesn't explain why they are.

My feeling is that there is a fundamental difference between them.

But, then again, what is a dimension? It can be defined as 1 of the values needed to fix the position of an event in spacetime. Using that definition, time has to be just another dimension. But it must be remembered that this definition of a dimension is no more than a mathematical construct that allows us to think about time in a fairly simple way. The truth may be very different,

[Vern]

Yes; DB I think the truth is fundamentally different. We can think of the temporal dimension as a continuum and imagine moving back and forth through it, just like the spacial dimensions; however, we can not control our movement through time; we can only experience it as plodding ever onward at it's own pace.

 

[LeeE]

I've mentioned it before, but the best way of showing how the spatial and temporal dimensions are fundamentally the same is by referring to the phenomenon of relativistic time-dilation.

Relativistic time dilation is the phenomenon where the movement of something through space affects the local rate of movement through time; the rate of time for a moving object is lower when compared with the rate of time for a stationary or more slowly moving object.

The relationship between speed through space and the rate of time is simple and direct; the sum of the movement vectors through time and though space always equals 'c'. Thus, when stationary the spatial movement vector = 0 and the movement vector through time = 'c', but as the spatial movement vector becomes non-zero the temporal movement vector must decrease to maintain the same summed vector of 'c'.

Because these two apparently different vectors can be so summed indicates to me that they are of the same type.

[yor_on]

LeeE, you are definitely correct in that there are a symmetry to time and distance, but that symmetry seems to exist with density too? If we were on a neutronstar for example, not that we are, but if, time would slow down for us considerable, as measured from a observer outside that gravitational field. Shouldn't there also be a Lorentz contraction observed in that gravitywell, thinking of it?  I find your idea interesting but you will need to explain why 'matter/density' have the same effect I think.

---------
http://sci.tech-archive.net/pdf/Archive/sci.physics/2005-04/msg00366.pdf

[Vern]

The relationship between speed through space and the rate of time is simple and direct; the sum of the movement vectors through time and though space always equals 'c'. Thus, when stationary the spatial movement vector = 0 and the movement vector through time = 'c', but as the spatial movement vector becomes non-zero the temporal movement vector must decrease to maintain the same summed vector of 'c'.

That is a very good explanation LeeE. I had never before thought of that kind of vector analysis but it is simple and direct, as you say. But the same relationship would exist with the Lorentz version of space and time.

[km2g]

what if time is at a constant speed? would it mean speeding up to times' speed would make time stop to you since its not flowing past you at its rate? Would it mean that if I was to stop dead right now in this point, in the expanding universe, then I would age rapidly? Maybe time is speed and we measure it like we would measure a flow of water; the more we flow with the water the less pressure we measure ( to us the flow seems to be slowing down the faster we move with it). Time does not slow down the faster we move to the speed of light but rather we are catching up to the speed of time and therefore time effects become less irreverent.

[km2g]

Maybe stars collapse tears into the fabric that contains time thus allowing time to flow into a timeless pocket. Who knows just maybe "The Big Bang" was a result of another dimension ripping (aka black hole) and allowing time and material to flow from it to our timeless pocket.

[Vern]

Shouldn't there also be a Lorentz contraction observed in that gravity well, thinking of it?

I can understand time slowing in a gravity well, but can't quite get length contraction to work. If it is like the Lorentz contraction, it would be only in one direction. I'm not sure what GR says about contraction in a gravity well; I don't remember reading anything about that.

[Vern]

what if time is at a constant speed? would it mean speeding up to times' speed would make time stop to you since its not flowing past you at its rate? Would it mean that if I was to stop dead right now in this point, in the expanding universe, then I would age rapidly? Maybe time is speed and we measure it like we would measure a flow of water; the more we flow with the water the less pressure we measure ( to us the flow seems to be slowing down the faster we move with it). Time does not slow down the faster we move to the speed of light but rather we are catching up to the speed of time and therefore time effects become less irreverent.

I don't think that is quite mainstream thinking; but it makes just as much sense to me as does the mainstream version. []

[LeeE]

LeeE, you are definitely correct in that there are a symmetry to time and distance, but that symmetry seems to exist with density too? If we were on a neutronstar for example, not that we are, but if, time would slow down for us considerable, as measured from a observer outside that gravitational field. Shouldn't there also be a Lorentz contraction observed in that gravitywell, thinking of it?  I find your idea interesting but you will need to explain why 'matter/density' have the same effect I think.

The wiki article on gravtational time dilation says:

Clocks which are far from massive bodies (or at higher gravitational potentials) run faster, and clocks close to massive bodies (or at lower gravitational potentials) run slower. This is because gravitational time dilation is manifested in accelerated frames of reference or, by virtue of the equivalence principle, in the gravitational field of massive objects.

Which basically says both forms of time-dilation are due to your inertial mass being equivalent to your gravitational mass.

Another way of looking at it is that space is distorted in a gravity well and this distortion, in changing the shape of space, changes it's size too, so everything moving within that distorted region of space is effectively moving further, equivalent to moving faster.  Don't forget that even if you're sitting still within that gravity well, all the atoms and molecules that everything is made from will still be moving.

[yor_on]

Planck scale units can be derived from solving for the point where a quantum theory of gravitation is needed (for some, but not all, formalisms).  What actually happens at the Planck scale is quite another story — we don't have the ability to do experiments at that level.  Planck's original determination happened before QM, and were just a convenient unit system from setting c, G and hbar to 1.  So take any statement that says the Planck time is the smallest unit of time with a quantum of salt.

I liked this definition, simple and clear. If time 'tick', I don't think we ever will measure it anyway, as that have to be under the Planck scale.

[LeeE]

The relationship between speed through space and the rate of time is simple and direct; the sum of the movement vectors through time and though space always equals 'c'. Thus, when stationary the spatial movement vector = 0 and the movement vector through time = 'c', but as the spatial movement vector becomes non-zero the temporal movement vector must decrease to maintain the same summed vector of 'c'.

That is a very good explanation LeeE. I had never before thought of that kind of vector analysis but it is simple and direct, as you say. But the same relationship would exist with the Lorentz version of space and time.

Sorry - must have missed this earlier.

The same relationship exists with the Lorentz equations because they are the same thing.  Have a quick look at the Lorentz equations and you'll see that they are basically Pythagorus's right-angle triangle solution, where instead of solving for the hypotenuse, you're solving for one of the sides (time), the hypotenuse (c) and other side (speed) being known.

[LeeE]

Planck scale units can be derived from solving for the point where a quantum theory of gravitation is needed (for some, but not all, formalisms).  What actually happens at the Planck scale is quite another story — we don't have the ability to do experiments at that level.  Planck's original determination happened before QM, and were just a convenient unit system from setting c, G and hbar to 1.  So take any statement that says the Planck time is the smallest unit of time with a quantum of salt.

I liked this definition, simple and clear. If time 'tick', I don't think we ever will measure it anyway, as that have to be under the Planck scale.

I agree that if time does 'tick' then we wouldn't be able to measure it, although this is not necessarily because it might be less than the Planck time unit.  If we move through time in discrete steps, or ticks, then nothing could happen between successive ticks; all we could see would be a sequence of different states, but not the transitions between them.

That things happen in durations smaller than the Planck time unit, or over distances smaller than the Planck length unit is indisputable; if you travel a distance of one Planck length unit and it takes you one Planck time unit to do so, your speed is 'c', so how does anything travel slower than 'c' or accelerate and decelerate?