What is time?

[dkv]

Originally Posted by alexander

I'm sorry, i was just browsing through some threads, and i came across a post here that sort of put me in the mood, so i decided to stop by and share




Entropy is an indirect way to show the vector time direction. It is the only quantity, though i would think more in the delta form of it, the change in entropy defines the direction of time in that time frame.

The law says that in an isolated system, the entropy of the universe tends to increases. as wiki so eloquently puts it: "In simple terms, the second law is an expression of the fact that over time, ignoring the effects of self-gravity, differences in temperature, pressure, and density tend to even out in a physical system that is isolated from the outside world." Entropy does not change time, it will even out the temperature of the universe, but even in this dead state, time continues to be time...

It is fair to say that without time, entropy would not exist, but that is not to say the opposite. Please don't make the mistake simply basing it on reverse logic.


On the topic of "What is time?", to me, it seems like the same type of an open-ended discussion question with no end, as say "What is the meaning of life?" or "What is wrong with scientology?"...

What is entropy ?
Classical definition says that is the amount useful energy lost as heat.
In other words Entropy depends on (total useless energy/total energy)
The classical defintion doesnt apply when we discuss one or two particles..
We use quatum mechanical description for such cases.
Higher entropy means higher ratio of useless energy.
If we use the classical definition of time then one can measure time only if there is way to harvest the energy to make clocks...(or to find the periodicity in the system..imagine a pendulum clock which runs at the risk of vibrations every now and then)
When all the energy gets converted into useless energy it is obvious that all objects used to measure time will spread into maximum number of states... thus loosing the sense of time...

This explains the meaning of what I said earlier.
(the intrinsic time which I defined later has got nothing to do with this analysis)

[modest]

Originally Posted by Overdog

No, you don't have to abandon it. You can believe it on Faith. But continuing to argue it is real, while avoiding the question "How do you know?" begins to sound a bit religious.

EDIT:

I'm not saying we should assume the axiom is false, I'm asking how you know it's real.

Edit Further clarification:

Also I'm not saying "Abandon the Axiom", I'm saying abandon the claim to knowledge.

I do understand what you're saying. What I'm saying is that we can know something is real without touching it. You can't look at gravity under the microscope, but that doesn't imply that gravity is just a concept in the human mind. The one doesn't follow the other. Despite the constant assumption in this thread - something doesn't have to be tangible or physical to be real in our universe.

Besides, even when something is physical, there is still plenty of philosophical room to say it isn't real - or that it's only real to us and there's no way to prove just how really real it really is. This is the philosophy of George Berkeley or Ernst Mach and in my opinion, it shouldn't be a stumbling block to understanding the universe and how it works.

The only way to properly and completely describe the universe is with time. Thus it is real. Describe a universe without time and you've described a universe unlike ours. The evidence is therefore that the axiom is true.

Sure, the map isn't the territory and Mankowski spacetime only describes this real thing - it isn't the thing in and of itself. Nevertheless, being about to model something with such precision goes a long way toward understanding what it is. Can someone why says time is just a human concept do that? Can they properly model the universe and its workings? No.

~modest

[AnssiH]

Originally Posted by modest

No. Change is how humans think of movement. There is no physics definition of change. If you want to think that change is something fundamental that's happening in our universe then that's fine. But from a physics standpoint it is properly understood as movement.

Physics is different from ontology. I think you are missing slightly the topic of this discussion when you bring in absolutely standard definitions of standard physics models. The discussion is about what is reality like; what is it that makes those physics models valid. Validity of a model means here that it produces correct predictions. The same observable predictions can always be achieved through different assumptions about unobservable reality (and different classification of the observable reality). But you keep insisting "time" is fundamental because you see it in our physics definitions. Other people are discussing what is it in our knowledge that allowed us to define something like "time" in our physics models.

Nothing can change without movement

Likewise, nothing can move without change. That is what ldSoftwareSteve was saying. The idea being that things change in our experience, and therefore a definition of time is sensical and can yield (together with identifying "objects") a valid predictive model of reality.

Note that when the sensory data, that is to be interpreted, is changing, you still need to assume that at least some patterns are referring to the "same" element from one moment to the next (=identify "objects"), before the concept of "motion" arises.

If you investigate how reality is, you can't really begin from established concepts; you need to investigate how did those concept come to be. (yes, turns out such investigation is possible, and yields very interesting results)

To the both of you, I would just like to remind that all these three concepts, "time", "motion" and "change", are something we understand against our conception of reality. Whichever you wish to see as fundamental depends on your perspective, or from what angle you happen to be discussing about reality.

That is, it is not really invalid when Modest says "time" is required by the physics models and without it motion could not be described. It is required by the physics models, but that does not mean reality works that way. You can take "motion" or "change" as fundamental (=without cause) property of reality, albeit you are not really able to defend this (and why that is so, should be pretty clear if you think about how we conceive anything in reality)

Likewise, it is not really invalid when ldSoftwareSteve says "change" gives rise to the definitions of "motion" and "time", when you talk about how do we come about perceiving reality the way we do.

You guys see how you are talking slightly next to each others?

Please give me a precise definition of change that is more fundamental.

Like I mentioned before, the definitions of DD's epistemological analysis have got "changes" (to the undefined data) underlying concepts like "motion" and "time". But that is not an assertion about reality; it is just an assertion about our knowledge; We cannot really investigate objectively what is the underlying cause of the changes in that data, as we can only investigate that matter through the model we have built according to that data. It is important to note the word "model", because in that data by itself there are not explicit "objects" that "move".

Well said. It doesn't matter how beautiful your description of reality is. If it doesn't make useful predictions of the future it's worthless.

Yeah exactly, but also other way around, it doesn't really matter how ugly your description of reality is; if it makes correct predictions for the future it is valid. I have hard time understanding why some physicist comment that string theory, since it seems to have only unobservable properties differing from older physics models, is merely a philosophical bastardization of those old models. That implies that those physicist believe the old models somehow have ontological truth to them more than string theory.

Well, both models yield same predictions; it would be far more objective to see them both as equally valid; I really don't see how either one could somehow be closer to ontological reality than the other if they really do yield exactly the same observable predictions. I see the arguments for and against equally valid models as the same as people arguing whether everything moves by invisible fairies carrying them or is it rather invisible elves. Neither can be said to be ontologically valid apart from simply believing so.

(Note btw how the definitions of string theory are also suddenly seen as ontologically real... "Reality has got 11 dimensions" etc... Ehh.... that's part of the definitions of the model, it means it is valid to model reality with such and such number of dimensions, but it doesn't mean suddently that is somehow ontologically valid. Who defined reality before we did? God? Don't think so)

I will outline this for people who don't see where I'm coming from.

Change is a human concept that describes movement. I can say this confidently because there is no example of change that didn't require movement.

That is also semantics. One can conceive a situation where one particle disappears and another appears. Is that better described as "movement" or "change"? And who cares? More interesting is that you can also say quite confidently that there's no example of movement that didn't require change. Just, in a nutshell, we are not talking about how specific concepts are defined in specific physics models, but how do we come about defining any concepts at all, in ANY possible valid models.

It could be you don't see it reasonable at all to investigate epistemological issues behind our valid models, but I think it is reasonable already for the reason that it forces you to think about your models more objectively. It is like General Semantics in that it forces you to perform some mental hygiene; it forces you to classify certain features of your reality as semantical of nature, and certain features as objective logic. It makes you less prone to make arguments that are purely based on belief. You need belief in your everyday conception of reality, but not in your assertions about how reality is or what is "fundamental" (whatever "fundamental" means)

Time and space are the fundamental dimensions that describe our world.

...it makes you less prone to make assertions like this. For someone coming into this discussion and not knowing you are referring to standard physics models rather than ontological reality when you say that, they would immediately assume you think that time is an ontological dimension, like a static canvas where future and past exists all the time and that you assume only your consciousness moves through that time.

I doubt you see things that way, I can only assume you don't see ontological considerations of spacetime as reasonable at all? Since you know it is called Minkowski spacetime, I assume you also know that Einstein was not thinking in terms of spacetime at all when he put out the first papers of Special Relativity. That interpretation arose later. Have you thought what other interpretations are possible? Did you read the "An unorthodox view on relativity" thread? It would be interesting to hear what you think about it. (I think I have provided enough material about ontological perspective of this for you to understand that predictionwise validity of relativity is not questioned at all)

http://hypography.com/forums/philoso...elativity.html

Are we rebuilding science from the ground up because you like the word "change" better than "movement" or "movement" better than "time"?

Absolutely not. Physics is different from ontology and they should not be confused with each others. Valid model makes correct predictions in terms of things have been defined by them

Look at the definition of "Ontology" and the paragraph following it at the post #272:
What can we know of reality?

Originally Posted by modest

No axiom can be proven with direct observation. That doesn’t mean we should assume all axioms are false.

No, but objectively thinking, we should not assume any ontological reality to them either. An axiom is "true" within the model itself; it can be part of a valid (=makes correct predictions) and self-coherent worldview.

(I'm just jumping in here because it is clear you are dismissing many arguments by forgetting the difference between ontology and valid models)

What I'm saying is that we can know something is real without touching it. You can't look at gravity under the microscope, but that doesn't imply that gravity is just a concept in the human mind.

Gravity is a good example because there exist many valid ways to model it and those valid ways can be interpreted ontologically differently. Objectively thinking, we should not make any assumptions as to the ontological reality behind the phenomenon we call "gravity". In that sense it is in fact somewhat wrong to say "gravity is ontologically real", since it is possible to model reality without ever invoking the idea of "gravity" as anything by itself; in general relativity for example, it is just a side effect of how "matter" and "spacetime" interact. i.e. just a name for some pattern we see.

I should mention also that seeing something "under the microscope" doesn't yield its ontological reality because we see reality the way we conceive it in our minds.

This is the philosophy of George Berkeley or Ernst Mach and in my opinion, it shouldn't be a stumbling block to understanding the universe and how it works.

And it isn't. In my opinion it is only helpful. Mental hygiene.

Sure, the map isn't the territory and Mankowski spacetime only describes this real thing - it isn't the thing in and of itself. Nevertheless, being about to model something with such precision goes a long way toward understanding what it is.

This also implies you are confusing ontology and physical models. What we have is a model that predicts the future of some data. The explicit meaning of that data is not known, as the predictive model includes many arbitrary choices. That map not being the territory means exactly that; The map is a (valid) conception of the terrain.

Can someone why says time is just a human concept do that? Can they properly model the universe and its workings? No.

Nor are they trying to do that. Physics is different from ontology. The realization is that we are absolutey required to create mental concepts in order to conceive reality at all. That is why there's a concept of "noumena", it refers to reality before it has been classifyed as "anything" by any predictive model, and one cannot make any predictions about such form (nor can such a form be conceived mentally, because mental conception is those concepts that have been created about the data)

Trust me, it is helpful to understand that distinction. Plus, suddenly reality seems even far more beautiful than how you first conceived it

-Anssi

[Overdog]

Originally Posted by modest

...
The only way to properly and completely describe the universe is with time. Thus it is real. Describe a universe without time and you've described a universe unlike ours. The evidence is therefore that the axiom is true.
~modest

Well, I don't think I can do a better job of responding to your last post than AnssiH just did, so I will just ditto his post and agree with him that you still seem to be confusing ontology with physical models.

When you say:

The only way to properly and completely describe the universe is with time. Thus it is real.

I observe that others have made this same statement about their fundamental axiom of the universe, god.

I have only to replace the word "time" with the word "god" to see that you either do not recognize the validity of the epistemolocigal and ontological points being made, or do not understand them.

And your last sentence, "The evidence is therefore that the axiom is true", suggests to me it is the latter, that you are confusing the axiom itself with the question that is being asked.

We could be talking about any axiom of any world view, the epistemolocigal and ontological points here apply to them all.

[alexander]

Originally Posted by dkv

What is entropy ?
Classical definition says that is the amount useful energy lost as heat.
In other words Entropy depends on (total useless energy/total energy)

classical definition of entropy in thermodynamics goes something like: It is a measure of the randomness of molecules in a system.

In other words entropy is a measure of the unavailability of a given system’s energy to do work.

If we use the classical definition of time then one can measure time only if there is way to harvest the energy to make clocks...(or to find the periodicity in the system..imagine a pendulum clock which runs at the risk of vibrations every now and then)

*pictures cesium atom vibrating*
The inability to measure it, though, does not mean that time slows down, or dissapears all together. If you can't measure the force of attraction between vector gauge bosons and quarks, it does not mean that they are one single particle (and the two names sort of indicate that)

It seems that your view of time is not as wide, um, in a way that you are not looking at a big enough picture. If our universe collapses to a singularity, time still exists for an outside frame of reference, if such exist...

When all the energy gets converted into useless energy it is obvious that all objects used to measure time will spread into maximum number of states... thus loosing the sense of time...

once again, according to what frame of reference? if you were looking at the system from the side, with a watch, your time will still tick, even though in that universe, all the energy was depleted.

[dkv]

Everything thing changes at high energies..
1.The fundamental principle behind the working of LHC is that kinematical events like collision can change the momentum,energy and number of particles...
Time as currently understood depends on something called as clock which are based on forces which mechanical or quantum mechanical.. at high energies these forces can no longer remain hidden... and get subjected to laws of motion.
2.In order to define classical time we need useful energy to keep it linear...one vibrating cesium atom is insufficient to define time...but Millions of such atoms can define time if their properties remain unchanged with high entropies.
3.Due to high degrees of freedom at high entropies I think that time is intrinsic to particles...i.e each particle carries its own clock and rod...
4.The difference between my proposed time and classical time is that at high entropies the classical time vanishes.. and gets replaced by particle dependent frame of references....

[alexander]

Originally Posted by dkv

Time as currently understood depends on something called as clock which are based on forces which mechanical or quantum mechanical.. at high energies these forces can no longer remain hidden... and get subjected to laws of motion.

the measurement of time depends on a clock, time itself depends on change in a given universe, space, and frame of reference.

In order to define classical time we need useful energy to keep it linear

so you are saying that time is linear.... mk

I think that time is intrinsic to particles...i.e each particle carries its own clock and rod...

right, but you can't claim that at high entropy time stops existing, just because you think that particles carry their own clocks, its a theory of yours, yes, but no clamey clamey. when that particle stops all motion and vibration, time itself stops. It's like that whole falling into a black hole thing, while your particles are stretched and slowed and possibly stop moving very much, a person standing outside the event horizon will continue seeing their clock tick...

The difference between my proposed time and classical time is that at high entropies the classical time vanishes.. and gets replaced by particle dependent frame of references....

i get where you are getting that from, though once again, it's an opinionated, more then a definitive explanation.

[dkv]

Tell me where I am getting that from ??
And why shouldnt I claim the statements I make?
When one atoms stop vibrating then what you are saying is no different from what I am saying but when we discuss more than one atom then the time can vary from particle to particle.
Not only time but the space is also particle dependent...
What we see at macro scale is the average of these clocks and rods..

Time is not just about change... a change can occur in several ways ... In order to define time we need periodicity...

Time and space is both linear and non-linear...because the particles decay changing the clocks and rods.

[alexander]

And why shouldnt I claim the statements I make?

because i take claims to be different from statements. claim to me is something that is a scientifically proven idea, and it may still be a theory, but with lots of backing. If you think that something works in a way you think it does, my belief is that you should state that it's the way you feel, and took you a few posts to say that, so i was rather confused as we were discussing separate states of time...

Tell me where I am getting that from ??

internal frame of reference, when referring to a system with a high entropy and very little to no change, almost an equilibrium system.

Not only time but the space is also particle dependent...

according to my understanding, spacetime exists with or without particles.

In order to define time we need periodicity

of some sort, yes

When one atoms stop vibrating then what you are saying is no different from what I am saying but when we discuss more than one atom then the time can vary from particle to particle.

yes, i am saying that according to outside frame of reference of a particle, the time no longer moves, though for the stopped particle, time still continue ticking, i make a differentiation that it does not seize to exist as an entity. Also if that particle stops moving, while observed from another particle, it will still continue to exist through time, but the time it will continue to exist relativistic to the moving particle, will be
approaching infinity...

[dkv]

your understanding is correct with respect to the accepted scientific understanding of space time but offcourse the understanding has failed to reach to any conclusion so far and that is why this debate is taking place.
I gave an alternative idea based on observer -observed reasoning.

As far as entropy is concerned it is becomes increasingly difficult to define the classical time and space when the degrees of freedom is very high(i.e high entropy)
A frame of reference can measure only if it cause no change due to measurement.
Einstein's theory neglects this aspect of logic.
Original derivation of Special theory of relativity involved light signals in the thought experiment.. later SR was extrapolated mathematically to GR.

Light signals do not change the state of macro systems.. however at small distance it becomes significant.

for example try to move the frame of reference inside the sun.(this is possible if frame of reference can moved to any coordinates anywhere in the universe)
No experiment can define the location and path of object satisfactorily unless it is massive.
No experiment can define the time at which the observation was made because drifting plasma which can change the speed of light.
Moreover and most importantly there will be no significant amount of useful energy to conduct the experiment in the first place.
That is why I said that it concept of classical time and space vanishes at high entropies.
Following link might help you to understand what happens inside the moving plasma
Wave propagation through an inhomogeneous plasma

Therefore it is wise to state that time and space are intrinsic properties of matter.