Fourth dimension=time?

[Rade]

....a good question would be: is it possible to describe reality without some concept of time?

Sure, but not in this universe, all it would require is that the 'reality' not have any motion. You see, imo, the 'now', the 'moment', the 'present' is outside of time and whatever reality is within the 'now' or the 'moment' or the 'present' can be described without time if it (the reality) has no motion. But such is not possibility in our universe for all things that are real are in motion, thus all attempts to describe reality must include some concept of time. This is how I see it, comments welcome.

[modest]

I think VSL is so controversial mainly because there is so much confusion and misunderstanding about it.

 

I guess... in deference to the physics community: rejection in the face of so much confusion and misunderstanding could be called a valid application of Occam's razor

 

I think Poincaré is correct here (in that the latter would be widely considered the more advantageous):

One geometry cannot be more true than another; it can only be more convenient. Now, Euclidean geometry is and will remain, the most convenient... What we call a straight line in astronomy is simply the path of a ray of light. If, therefore, we were to discover negative parallaxes, or to prove that all parallaxes are higher than a certain limit, we should have a choice between two conclusions: we could give up Euclidean geometry, or modify the laws of optics, and suppose that light is not rigorously propagated in a straight line. It is needless to add that every one would look upon this solution as the more advantageous.

-Henri Poincaré

Certainly if the flat spacetime/VSL physics is "most convenient" as he assumed it would be then I couldn't imagine it finding any controversy at all.

 

~modest

[LaurieAG]

Hi Modest,

 

Yeah, and lines of longitude seem closer together near the north pole versus the equator because the speed of a plane flying east-west near the pole is greater (in degrees of longitude per hour) versus the speed of an equivalent plane flying east-west over the equator (in equivalent units).

 

So a Cartesian projection, as opposed to a real projection, is used because it reduces the distortion of normal mapping (i.e. poles where you cannot tell whether you are arthur or martha) on a spherical shaped object for navigation purposes.

 

This is a problem that arises when you use a sphere as a universal model as opposed to a sphere as being a byproduct of our observation limits. All you hilight is mapping problems with sperical objects so thank you for reinforcing my argument.

[LaurieAG]

Hi Modest,

 

I think Poincaré is correct here (in that the latter would be widely considered the more advantageous):

One geometry cannot be more true than another; it can only be more convenient. Now, Euclidean geometry is and will remain, the most convenient... What we call a straight line in astronomy is simply the path of a ray of light. If, therefore, we were to discover negative parallaxes, or to prove that all parallaxes are higher than a certain limit, we should have a choice between two conclusions: we could give up Euclidean geometry, or modify the laws of optics, and suppose that light is not rigorously propagated in a straight line. It is needless to add that every one would look upon this solution as the more advantageous.

-Henri Poincaré

 

At the time he wrote this Poincare was unaware of gravitational lensing, i.e. the 'straight' line is bent due to the proximity to mass along its path (relative to source and viewer) and therefore, if we use Euclidian geometry consistently, it appears that the speed of light changes due to this distortion (i.e. distance travelled changes not the time it takes to travel a fixed distance).

[arkain101]

Sure, but not in this universe, all it would require is that the 'reality' not have any motion. You see, imo, the 'now', the 'moment', the 'present' is outside of time and whatever reality is within the 'now' or the 'moment' or the 'present' can be described without time if it (the reality) has no motion. But such is not possibility in our universe for all things that are real are in motion, thus all attempts to describe reality must include some concept of time. This is how I see it, comments welcome.

 

If we consider time a property type of concept, then motion isnt really the key relationship to be associated is it?

 

It seems to me that a universe with no time only requires that it have no mass. In our universe, if we try to move something, it responds proportional to the time of change. If we move something quickly it resists more, than if we try to move it slowly.

 

If we had a universe with no mass, the rate we moved anything would have no dependency on the concept of time.

 

Furthermore, isn't motion something that is determined strictly by the mind?

 

For example: If you have ever played a video game online, you might have experienced a lagging effect. Lets use the imagery of a person moving about a surface. When there is no lagging occuring the person moves smoothly, at some 60 positions per second (lets say). Now, lets keep adding greater and greater (packet loss of information).

 

Packet loss at 25%. The person moves about the surface in chunks of pictures separated by a distance of some 5 feet, seemingly in somewhat of a motion.

Packet loss at 50%. The person warps around the surface, and it becomes harder and harder to discern the path the person has took to get from A to B, pictures separated by 15 feet.

Packet loss at 90%. The person appears in entirely random locations, and has no motion at all, we see a freeze frame picture every (1 second) persay.

 

The only information being computed is 10% of the possible information for the system. We lose the concept of motion with the loss of information, and our ability to predict the path and direction of the motion decreases with the loss of information.

 

I am no quantum physicist, but it is my understanding that a very similar effect occurs when we try to observe motion(or momentum) and position. Furthermore, electron orbital 'shells' change instantaniously in a kind of series of blocky of forms, instead of a fluid change.

 

So I wonder, how much credit should we give to the idea of motion (that is a motion concept beyond our minds intuition of distance to time change)?

 

And secondly, some physicists have said "time is something that prevents everything happening at once", however, anything that happens only happens at once, if we don't apply a world view to the universe, then wouldn't it all just happen at once?

 

Its tricky to discuss, because it seems time is related to mass, and yet, is also a part of a minds world view.

[Qfwfq]

I guess... in deference to the physics community: rejection in the face of so much confusion and misunderstanding could be called a valid application of Occam's razor

An alternative is that many objections to VSL are strawman arguments. ;)

 

Many topics are controversial because each has his own understanding of it. In some cases, some are understanding and others are misunderstanding. This is not quite what Occam's razor is about, it is applied when one idea is intrinsically and unnecessarily much more abstruse. I don't find this so for VSL, it is very simple to interpret the Schwarzschild metric as being a comparison between values of [imath]c[/imath] at different values of [imath]r[/imath]. This is not to say the idea would hold up to any gravitational field that could be described as spacetime curvature, but I don't think we have observations yet that can decide the matter.

 

The main caution I give on VSL is due to the fact that folks always tend to call [imath]c[/imath] the speed of light because of how SR came about. In order for the principle of equivalence to hold it's actually [imath]c[/imath] that must be affected, so PV isn't sufficient.

[modest]

So a Cartesian projection, as opposed to a real projection, is used because it reduces the distortion of normal mapping (i.e. poles where you cannot tell whether you are arthur or martha) on a spherical shaped object for navigation purposes.

 

This is a problem that arises when you use a sphere as a universal model as opposed to a sphere as being a byproduct of our observation limits. All you hilight is mapping problems with sperical objects so thank you for reinforcing my argument.

 

Seems more an issue of a choice of coordinates.

 

At the time he wrote this Poincare was unaware of gravitational lensing, i.e. the 'straight' line is bent due to the proximity to mass along its path (relative to source and viewer)

 

Well, spacetime wasn’t yet a concept when Poincaré wrote that. I don’t think he was referring to time or gravity. His point was that there is no single experiment that can be done to determine the “correct” geometry on which a person should do physics—something I thought you might find agreeable (I’ve been assuming you’re advocating Euclidean space, no?).

 

and therefore, if we use Euclidian geometry consistently, it appears that the speed of light changes due to this distortion (i.e. distance travelled changes not the time it takes to travel a fixed distance).

 

Prior to 1915 Einstein derived half the correct deflection of light (and half the correct coordinate velocity of light) on Euclidean space. With the full development of GR some months later straight lines at the sun were no longer considered straight to infinity allowing the derivation of the full value of deflection.

 

YOu can interpret deflection with a changing speed of light. But I'm not so sure it would be so easy on flat spacetime.

 

~modest

[modest]

An alternative is that many objections to VSL are strawman arguments. ;)

 

Many topics are controversial because each has his own understanding of it. In some cases, some are understanding and others are misunderstanding. This is not quite what Occam's razor is about, it is applied when one idea is intrinsically and unnecessarily much more abstruse. I don't find this so for VSL,

 

I thought you were referring to the field theoretic formalism of gravity (where Einstein's equations are expressed as a rank 2 tensor of gravitational potential on flat spacetime rather than with Riemannian geometry). Flat spacetime + observation = VSL. This is what I was thinking in saying Occam's razor. Given your next quote, I now don't know if you mean something similar to that by "VSL model" or not.

 

it is very simple to interpret the Schwarzschild metric as being a comparison between values of [imath]c[/imath] at different values of [imath]r[/imath].

I agree, the coordinate velocity of light changes (with r in the the Schwarzschild metric): c® = dr/dt = c(1 − 2GM/rc2). There is no controversy or confusion over this as far as I know and I'm not sure what equivalence it would have with a flat spacetime VSL theory^(*).

 

~modest

[Qfwfq]

As I hinted, it seems that VSL means different things to different people and the same for some other terms, so it's kinda like the tower of Babel and the blind men with the elephant. For one, you get into subtle epistemologic issues when talking about "physical velocities" as opposed to coordinate speeds. Many consider VSL as distinct from GR, and yet some eminent general relativists have worked on it without ceasing to be such; e. g. Fernando de Felice continued to hold the GR course in Padova (although I followed it when it was temporarily being held by Riccardo D'Auria). Notice that the paper is published in General Relativity and Gravitation and that Einstein himself first suggested the idea.

 

The point here certainly isn't to say whether VSL is better or worse, I only wanted to caution against so easily dismissing it as being utter crap. :smilingsun:

[Jway]

Time is maybe an effect of something else but the effect is real. I suggested that time is our perception of a forth dimension, as in if the universe is a hypersphere it contains an infinite number of 3d spheres. Each one of these 3d universes would represent an instant in time in the 4d sphere. We travel through the 4d universe in a 3d sphere moving from instant to instant, 3d sphere to 3d sphere in some ways like the frames in a film.

 

I like this conceptualization.

[Rade]

If we consider time a property type of concept, then motion isn't really the key relationship to be associated is it? It seems to me that a universe with no time only requires that it have no mass. In our universe, if we try to move something, it responds proportional to the time of change. If we move something quickly it resists more, than if we try to move it slowly. .

Hi. I have no idea what you mean by saying ...'if we consider time a "property type of concept"... ? How do you define "property type" ? The best definition I can find that has a philosophic/scientific meaning is that a property is "any trait or attribute proper to a thing". Well, in that case, then no, I find your first assumption to be incorrect, we cannot consider time to be a "property type" of concept for the simple reason time is not a "thing"---as I have stated, time is a type of "number", and this is very different than a thing. Thus, yes, motion really is the key relationship associated with time, not mass. Furthermore, I know of no thing with mass in the universe that does not have a property of motion associated with it. A thing with mass without any potential for motion is outside of time. Well, this is an interesting discussion and above are my views. I find my previous post about the OP question to hold true.

[arkain101]

Hi. I have no idea what you mean by saying ...'if we consider time a "property type of concept"... ? How do you define "property type" ? The best definition I can find that has a philosophic/scientific meaning is that a property is "any trait or attribute proper to a thing"

 

I was following the context of the discussion. I must of got mixed up, missed a quote.. I wasnt implying you thought of time as a physical property.

 

 

What i wan to know is this, is time a dimension, an emergent property, or a basic property of reality?

 

After reading all the posts in this thread i say time is a basic property of the universe no matter what it's reality is.

I think this is where I got the property impression.

 

....a good question would be: is it possible to describe reality without some concept of time?

 

You responded that no time means no motion. I believe I was arguing that, maybe motion is not the key thing to consider if we want consider time a property.

 

In other words, to model time as a property, I suggested we should consider it connected to mass. That is they share a relationship. Regardless if a clock turns to measure anything, objects resist change. If I wiggle a peice of metal it will eventually bend if it is wiggled too quickly, demonstrating that the rate at which change occurs (time) on mass, effects the forces involved.

 

I'm not alluding that time is a property. I am only saying that if one were to model time as a property of the universe then mass should have some kind of direct correlation with it.

[modest]

For one, you get into subtle epistemologic issues when talking about "physical velocities" as opposed to coordinate speeds.

 

If I follow what you mean then I think so too. The physical interpretation that I'm familiar with (of schwarzschild coordinates) is that proper length and proper time approach the coordinate length and coordinate time as r approaches infinity, so that the metric describes things from the perspective of an observer at infinity—outside the gravitational field (and static).

 

Many consider VSL as distinct from GR, and yet some eminent general relativists have worked on it without ceasing to be such; e. g. Fernando de Felice continued to hold the GR course in Padova (although I followed it when it was temporarily being held by Riccardo D'Auria). Notice that the paper is published in General Relativity and Gravitation and that Einstein himself first suggested the idea.

 

Thank you for providing an example. I think I understand better now where you're coming from. I didn't know what you'd meant before saying "PV"... polarizable-vacuum :D

 

I think I would personally characterize a polarizable-vacuum representation of GR as an Analogue model of gravity, and closely related to GR. I'm unable to read the specific article you link without purchasing it, but I looking at some reviews last night such as:

 

Polarizable Vacuum “Metric Engineering” Approach to GR-Type Effects

 

I agree with what you said in an earlier post—that this type of model (PV-GR model) is distinguishable from GR not just in interpretation, but also its predictions (in particular: strong field predictions). From the link above:

Here we encounter our first major departure from the standard GR approach to gravitational radiation in that we deal with a scalar disturbance that propagates as a longitudinal mode, rather than with a tensor disturbance that propagates as a transverse mode. However, the outcome predictions are surprisingly similar in several particulars, while the differences constitute a testbed for discriminating between the two theories when considered as competitive alternatives.

It also looks like Felice's PV approach might be limited to electromagnetic phenomenon (without looking at the paper, I wouldn't want to say this is the case for sure). The co-writer of the review above elsewhere writes:

The original preamble misleadingly gave the impression that PV is an EM theory of gravity, whereas neither PV nor the (GR-correct) analogue theory of gravity by de Felice (1971) model anything other than the passage of light through a gravitational field electromagnetically.

 

Talk:Polarizable vacuum - Wikipedia, the free encyclopedia

(Michael Ibison)

 

The point here certainly isn't to say whether VSL is better or worse, I only wanted to caution against so easily dismissing it as being utter crap. :)

 

"Utter crap" :) A reasonable caution, I should think.

 

On a flat map of earth a plane on the equator travels slower east-west than does a plane near a pole. On a globe each has the same apparent speed. The choice between map/globe is axiomatic and we can either say that distance in degrees of longitude doesn't change from equator to pole while the speed of the plane does change (the map) or we can say that distance in degrees of longitude does change and the speed doesn't (the globe).

 

Saying "it's the speed of the plane that changes from the equator to the pole, not the units of distance" is analogous to "it's the speed of light that changes with distance from a mass, not the units of time". Poincaré and Einstein both used an equivalent analogy, saying that an unevenly-heated disc populated with 2D creatures could model their world as non-Euclidean by considering their measuring rods as rigid undergoing no thermodynamic expansion or they could model it as Euclidean by accounting for variable measuring rods. From the point of view of the 2D creatures where all their measurements are confined to the surface of the disc, it's impossible to tell which is the case.

 

I believe Laurie's claim that the standard interpretation of curved time is untenable. As a claim of validity it's just completely unsupportable. The claim was also unrelated to the post it was responding to, so it looked like bait to me (i.e. I assumed Laurie was looking for the response "You can't be correct about that" or "The speed of light is always constant") [i apologize, Laurie, if that wasn't the case—it's just the impression I got]. Given that impression, I presented the above analogy in a rather oblique (and perhaps even rather glib) manner which looks to have left the impression that the analogy and my posts could mean one or more of the following:

• VSL is utter crap
  
• I object to VSL with confusion and misunderstanding
  
• I object to VSL with a strawman
  
• I object to VSL because it is not equivalent to gtr

So, by my usual failure of successful communication, Laurie's blind rejection of the standard interpretation prompts a warning against blindly rejecting its alternative. Needful to say, I agree and hoped not to imply otherwise.

 

In any case... Laurie, are you perhaps considering starting a thread on VSL? I think that would be a very interesting topic. :)

 

~modest

[Qfwfq]

It is all subtle and confusing.

 

One thing that's all too easy to overlook is that an diminished value of "the speed of light" doesn't necessarily imply the value of [imath]c[/imath] being diminished, that's why I said PV isn't sufficient. In order for the principle of equivalence to hold, it must actually be [imath]c[/imath] that is affected around a mass. This is a coordinate choice away from the geometric interpretation but not all spacetime manifolds, possible according to differential geometry, could be given by this idea.

[Solve]

You can see the present and the past (the sun is 8 minutes old when you see it).

But you can't look into the future, probably because nothing is going on in the future yet and evolution evolved it out as we were being evolved.

 

Solve :)

[arkain101]

You can see the present and the past (the sun is 8 minutes old when you see it).

But you can't look into the future, probably because nothing is going on in the future yet and evolution evolved it out as we were being evolved.

 

Solve :)

 

Partially agreed. That is why I think there are two concepts of time.

 

1)Time as an inherent property of space: another name for energy, multi-directional / non-linear.

ie, what past event will I see next?

 

2)Time as linear and singular directional concept based on mass and action:

 

ie, what state will matter become?

[modest]

I'm not convinced that we can see the past. The sun's photons which we see originated 8 minutes ago from our perspective, but when we see the photon it exists here and now for us. When a photon hits my pupil I'd prefer to think of it as here and now. The principle of locality I guess.

 

~modest