What is time?

[dkv]

Given an object how do we associate time to it such that it can measured in any random coordinates system?

That will give you the answer.

[dkv]

actually time vanishes as there is an increase in the entropy.

[steve 9]

:rolleyes: Steve9, what do you hope to accomplish by repeatedly, and without increased qualification and specificity, asking “what is time”? What value is what you hope to accomplish to anything that I, or any other user of physics, do when using physics?

 

It would be much easier to understand what you are asking, if you would explain why you are asking it. Judging by the many objections to your approach in asking your question, many others find your approach bizarre, un-useful, and annoying. If you would explain why you are asking “what is time?”, your questions might be greeted with more enthusiasm.

 

Fair enough, point taken. I will take your suggestion and approach this from a different angle. I will take some time to think about what you have said and get back to you. Thanks.

[Overdog]

Uh... are you sure you read what I wrote?

 

Real change requires real movement. Nothing can change without moving. No example can be given otherwise.

 

Real movement requires real time. Nothing can move without time. No example can be given otherwise.

 

~modest

 

PS - change is not a basic physics concept. Change is how humans think of movement. The more fundamental of the two is movement. More fundamental than movement is space and time.

 

Time, Distance, and Mass are the fundamental units of physics.

 

I think I did. But did you understand my question was "How can you Know"?

 

Ok, let me try to explain what I and some others are saying.

 

Lets take Plato's definition of Knowledge as Justified, True, Belief.

 

Epistemology - Wikipedia, the free encyclopedia

 

You've got the Belief part, and you've given excellent Justification. All that now stands in the way of an assertion that time has objective reality is the True part.

 

And this is where we run into a problem, because whatever time is, we can't observe it under a microscope. And the excerpt I posted from the Stanford Philosophy of Science site says knowledge of unobserved phenomenon is impossible.

 

How can we get around this? How can we Know time has objective reality?

 

EDIT:

 

Or did I misconstrue/misunderstand what you were saying?

[ldsoftwaresteve]

I think a good example of change is radioactive decay. For example, if we have a sample of carbon and we measure how much carbon-14 is in it then we can predict how quickly the C-14 will turn into nitrogen. It's a very basic process in nature that happens at a predictable rate. One gram of C-14 will be half a gram in 5730 years.

 

So, change is a good word to describe what's happening. Certainly carbon is changing into nitrogen via beta decay. But, change is incomplete. It doesn't completely describe the situation. Saying one gram of C-14 changes into a half a gram of C-14 is not the whole story. For the whole story we have to say how quickly it changes, how much time it takes to change.

 

So, it's not so much that time 'drives' change. It's more that change is meaningless without time. Consider change in position. Let's say there is a ruler that is one meter long lying on a lab table. We roll a ball from the zero position to the 100 centimeter position. So then:

Change = 1 meter

I wouldn't say time drove that change or caused that change. But I would say there is no way to discuss how fast the ball went without a very real process of the universe called time. Speed is change in position divided by change in time. If it took the ball one second to change position then the ball moved at one meter per second.

 

Change requires both space and time - two dimensions. It is impossible to describe change without both. So, time is not just a human concept. It is a human concept that describes something real about the universe.

 

~modest

You make good points. Especially about change being meaningless without time to describe it and I think I agree with you completely. Time is our way of understanding and giving meaning to change. The 'something real about the universe' is that change appears to be constant and one kind of change can be compared to another kind of change. That implies that all changes have a common cause, a common motive force.

 

The laws of physics are our identifications of how things act. Whether it's regarding motion or mass or chemical reactions or radioactive decay, what would be wonderful is to find a common cause for all of it. So far we haven't. Time has been the placeholder for the cause.

 

The ingenuity of man is such that we can work with flawed theories and don't need to change them as long as they work. When they don't work, then we change them. There really isn't much impetus to change when we can work within our current framework.

 

If there is value in this discussion, it's in questioning the concept of time - a very important part of our current framework. Personally, I think it stops us from seeing change in a different light. It takes an act of will to step outside our framework and consider change without time associated with it or at least to consider the cause of change that way.

 

Let's assume two things for the sake of argument. 1. there is a common cause for all changes. 2. that change is constant.

 

The problem with lumping all changes together in my previous statement is that there seems to be two kinds of changes that might not be related: changes in material structures and changes in position.

 

The concept of time allows us to bring these two kinds of changes together under its umbrella. Perhaps that has clouded our understanding. If we take 'time' out of the focus, we have two kinds of changes to account for and perhaps it's an easier starting point.

 

What if we say that chemical reactions and motion have nothing in common? Ultimately they might, but for now why not assume they don't. Just for grins. It could be that all motion was initially caused by a chemical reaction. That would make all change, including positional changes, relative to physical structural change. And for the moment, let's leave 'space' out of the focus too as it might muddy the waters so to speak.

 

Ok then, what drives chemical reactions? What drives change to take place at the smallest levels? What makes an electron fly around the nucleus of an atom? What is driving that stuff if it isn't time?

 

If everything that takes place happens because our universe started with a big bang, it would seem that the total 'energy' in the universe would be constant and would eventually run down and stabilize (assuming that all matter attempts to reach a state of equilibrium). Why hasn't it? Or are we operating on the assumption that it is running down? What if it isn't? Then we'd need to know where the motive force is coming from and what is driving the universe of change.

 

If it's not time and it's not magic, what is it?

[AnssiH]

No need to correct him. Ross isn’t talking about interpreting math. The “conceptual interpretation” refers to the theory or model.

 

Judging from the quote you pasted, I believe he is saying that "just because the math works, it doesn't mean it captures how reality is." He went on to say "each theory contains a conceptual interpretation that assigns meaning to its mathematical expressions". That is somewhat ambiguous statement; it could be interpreted as claiming that the conceptual interpretation suddenly does capture how reality is. And that would obviously not be a justified assertion at all. That is why I pointed out; "The mathematical form of each theory can be "conceptually interpreted" in a multitude of different ways"

 

In this context it is completely meaningless what was in the mind of the person who formed the theory in the first place, because his view of reality is also a semantical model, just like everybody else's. The math describes the behaviour of "semantically" defined entities.

 

Yes, only one ontology of space and time are correct to our universe. That, at least, sounds sensible to me.

 

Well, here I think I need to probe little bit to see where you stand.

 

Even if there is one "correct" way to define time and space - i.e. correct in that it perfectly coincides with the way time and space are metaphysically - do you think we would be able to find out? Considering that each definition contains a lot of unobservable features. (Note here that I include the ontological assumptions as part of our "definition of time and space")

 

Do you think it can be ontologically valid to identify some patterns ("objects") of reality as "ontologically same" from one moment to the next? (any definition of space requires you to do this for many patterns)

If it can be valid, do you think we could find out whether our definitions happen to coincide with some "ontological identity of things"?

 

You may be still using the word "ontology" differently than I do, and I may be reading you wrong, but it does seem to me like there are quite a few naive realistic assumptions in your thinking. So I thought I should remind you that my perspective on this is that the worldview - where the definitions for time & space exist - is something that is used to interpret a "data stream". I.e. the data coming from sensory organs is not metaphysically pictures and sounds; it's data to be interpreted as pictures and sounds (according to what the meaning of our sensory data is believed to be). Any aspect of that interpretation that you take as ontologically real amounts to a belief.

 

Hence any definition of space has to do with how some patterns have been identified in that stream. Whatever "space" means is largely a semantical issue.

 

As an interesting side note, all human communication includes a component of ambiguity exactly because of this reason; we all interpret each others according to our very own worldview... ...human communication becomes very tricky when we don't share the same paradigms. We are often so convinced of the validity of our own worldview that we don't think it's even possible to interpret the other person intelligibly... Like Kuhn said, one paradigm cannot be investigated from another.

 

Additionally I should mention that DD's epistemological analysis has to do with that same perspective; that we do not know anything about reality, but somehow we infer the meaning from completely unknown data. The investigation of "how that data can be modelled" has to do with certain symmetries that must exist in our view on that data exactly because we do not know what is its "ontological origin", so to speak. Certain interesting requirements for our models of time and space arise.

 

Admittedly this is somewhat tricky issue to communicate clearly when the other party is using different terminology and looks at reality somewhat differently. It's kind of like trying to explain to someone pre-Newton how a spaceship from Earth to Mars cannot really be said to "fly through space", apart from our conception of the situation. Certainly that person would take that assertion as clearly invalid, since he can clearly see the spaceship flying through space... ...the point is to concentrate on what semantical matters there exists. Like, is it Mars flying through space rather than the spaceship? And then to realize just what do we mean by "space" and what does it mean to "fly through it" etc... To see just to what extent human definitions give rise to our conception of reality.

 

Look at the spactime separation formula. There is already meaning there. dS and dT already have a definition in that formula - you can't just interpret it any way you like.

 

You can make a multitude of ontological intepretations that conform to the predictable observations, because here the ontological interpretations are the assumptions regarding what happens behind our observations. Just like is the case with the different interpretations of QM.

 

The assumption that reality is a static spacetime block is just one interpretation.

 

Another would be that reality does not exist in any definite "now-state" before it is being observed.

 

Or one could imagine each inertial frame is part of a multiverse, i.e. we switch to a different "space" (where the "now"-states really exist differently from each others)

 

I would imagine, that in the middle of assumptions as far fetched as any of the above, one would be somewhat motivated to investigate the possibility that relativistic time relationships arise from our ways of defining reality rather than from these ontological options. I.e. take a look at that epistemological analysis.

 

The fact that different frames measure a different frequency for the same source of light is key to relativity. Frequency is per unit time and time is relative. This shows how Einstein derived gravitational redshift which demonstrates. You are confusing variables with laws of physics. All laws of physics are postulated to be the same in all inertial reference frames - not just the speed of light.

 

I said it is a semantical issue what is considered a variable and what is considered "law of physics". We created the definitions that lead us to such and such laws for those semantically defined entities. I think your comment "you are confusing variables with laws of physics" just shows that you assume the "laws of physics" and "parameters" are ontologically real, embedded somewhere in metaphysical reality rather looking at them as "tools of predicting reality".

 

Despite what you said, I can prove time dilation is more than "just mental construction" - of course. Something that's just a mental construction has no basis of fact in reality. Unless you're arguing from an entirely phenomenalistic point of view then time dilation has real effects. A person on a mountain ages faster.

 

Do you really think I was claiming that time dilation does not happen? I was just saying that in order for us to understand something as "time dilation", we had to define quite a few things in our worldview that way, and that there are always many possible paradigms that we could use the understand the same situation. Both would be just as valid predictionwise, and neither can be defended to be more real ontologically.

 

Relativity is not a model. I normally wouldn't correct that, but it's important in the context of this discussion.

 

Interesting; I would have said the exact opposite for the exact same reason; in the context of this discussion is important to understand just how relativity is a model. Perhaps I don't understand how you mean your assertion, or perhaps you have a naive realistic view on relativity. Well, in any case it would be interesting to know whether you abide to the "static spacetime block" view of relativity, or whether you have even thought about what reality might look like behind the math?

 

Perhaps it is helpful to know that I am coming at this largely from the angle of General Semantics;

General semantics - Wikipedia, the free encyclopedia

 

Also I noticed the Wikipedia page for "Metaphysics" includes "Space and time" section which includes metaphysical questions of space that just reveal some of those semantical aspects regarding how we understand time and space;

Metaphysics - Wikipedia, the free encyclopedia

 

I skipped few things because I didn't think they were very relevant. If you want a comment on something I've skipped, just ask.

 

-Anssi

[AnssiH]

Take a stand. Just tell us what you think time is. Is it like matter? Is it like energy? Start somewhere and build your case.

 

I'm not sure if anyone disagrees with you about time being a concept. I mean we have just been talking about what sorts of features we attach to "time" in our conception of reality, and whether we can always define (~conceptualize) time in many valid ways to explain our subjective experiences.

 

But I think there are few communication failures in your conversations with others. I think when people insist time is nevertheless "real", they may be only saying that there must be something in objective reality that makes a concept like "time" valid for interpreting reality... ...without really taking a stance what that might be.

 

When I read your posts, it only occurs to me that since you have thought about purely conceptual aspects of the definition of "time" so much, you might want to consider what conceptual aspects there is in, say, definition of "matter".

 

-Anssi

[AnssiH]

PS - change is not a basic physics concept. Change is how humans think of movement. The more fundamental of the two is movement. More fundamental than movement is space and time.

 

That is entirely a belief, spoken from your personal worldview. There is no objective justification in the claim that one is more fundamental than the other, as you are merely talking about concepts that are defined in terms of each others.

 

Change requires both space and time - two dimensions. It is impossible to describe change without both.

 

It is impossible to describe "time" without change. One can say "there's no time if nothing moves/changes in the universe".

 

That is because if there is a universe where nothing moves, there is nothing to hang any definition of "time" to; time cannot be defined/conceived in any valid way at all!

 

(and btw, from the point of view of explaining completely unknown stream of data, "change" is what makes the definition of motion & time possible... ...but that really says nothing about the real ontological reality)

 

The matter of the fact is that concepts like "movement", "time" & "change", are associated with each others; they are all understood against each others. That is why we can say "one cannot exist without another".

 

The reason why you should not say "nothing can move without time" is that it implies time is something that is moving forward in some sense even when absolutely NOTHING else is in the universe; it implies a completely naive realistic view of time. (The alternative view (only semantically different) is that motion/change exists fundamentally - without cause - and gives rise to the definition of time)

Speed is change in position divided by change in time. If it took the ball one second to change position then the ball moved at one meter per second.

 

Or it managed to move "one meter" while another apparatus managed to move its thin handle by 6 degrees. Just underlying the fact that "second" is not measurable by itself; what we see is how objects change around us in relation to each others. We cannot see any "rate" of time in any objective sense.

 

-Anssi

[dkv]

Observation changes the observables... the effect is obvious when we discuss microscopic world. The true postion and momentum can not be known simultaneously similarly true time and energy can not be known at the same time.

And if observation can not guarantee invariant measurement of time in a stationary frame of reference then it is obvious that the time is not a property which remains independent of the nature of observation.

But there is a possibility that an intrinsic time can be associated with every particle in the universe.

Similarly an intrinsic space can be associated with every particle in the universe.

For example a particle with a spin can intrinsically define time similarly a particle with a internal void can intrinsically define space..

If this is true then every particle has its own clock and rod to measure the universe.

[ldsoftwaresteve]

Observation changes the observables... the effect is obvious when we discuss microscopic world. The true postion and momentum can not be known simultaneously similarly true time and energy can not be known at the same time.

And if observation can not guarantee invariant measurement of time in a stationary frame of reference then it is obvious that the time is not a property which remains independent of the nature of observation.

But there is a possibility that an intrinsic time can be associated with every particle in the universe.

Similarly an intrinsic space can be associated with every particle in the universe.

For example a particle with a spin can intrinsically define time similarly a particle with a internal void can intrinsically define space..

If this is true then every particle has its own clock and rod to measure the universe.

lol. Excellent observation! So all we need to do is identify the smallest particle and it's characteristics will become the standard units of measure. I really like this point of view!

[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 :hihi: mood, so i decided to stop by and share

 

actually time vanishes as there is an increase in the entropy.

:(

 

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?"...

[modest]

Time is our way of understanding and giving meaning to change.

 

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. Nothing can change without movement and movement has a precise geometric definition. So nothing is added to the discussion by saying "change". It's nothing more than a human concept that is mathematically defined under a different name.

 

[math]\mbox{Motion} = \frac{ \Delta \mbox{space}}{ \Delta \mbox{time}}[/math]

 

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

 

That implies that all changes have a common cause, a common motive force.

 

This is why I sometimes dread philosophy. The idea that motion requires a force may give you some philosophical insight. But, what force are you talking about? How does it work? Can we make predictions based on its existence?

 

The laws of physics are our identifications of how things act. Whether it's regarding motion or mass or chemical reactions or radioactive decay,

 

Chemical reactions and radioactive decay are motion.

 

The ingenuity of man is such that we can work with flawed theories and don't need to change them as long as they work. When they don't work, then we change them. There really isn't much impetus to change when we can work within our current framework.

 

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.

 

The problem with lumping all changes together in my previous statement is that there seems to be two kinds of changes that might not be related: changes in material structures and changes in position.

 

Change in material structure requires movement.

 

What if we say that chemical reactions and motion have nothing in common?

 

Chemical reactions are the rearrangement of atoms and molecules - in other words, they are moving around.

 

Ok then, what drives chemical reactions? What drives change to take place at the smallest levels? What makes an electron fly around the nucleus of an atom? What is driving that stuff if it isn't time?

 

"Driving" change is not something I understand.

 

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. Since movement is easier and better defined in physics, I'm sticking with it.

 

[math]\mbox{Motion} = \frac{ \Delta \mbox{space}}{ \Delta \mbox{time}}[/math]

 

Thus motion requires two things. Space and time. We can graph them:

 

 

Someone who says movement is more fundamental than time would have a hard time flipping this around and putting 'movement' in thousands of equations of physics. Time and space are the fundamental dimensions that describe our world. If you want to say something different is the cause of movement they you'll have to rebuild things like relativity on different axioms. Good luck with that.

 

For now the fundamental units of physics have meaning and power in their ability to predict useful things. It's weird how many people here are willing to say everything that science has ever described and understood might just be wrong because of their intuition about time. Really? Are we rebuilding science from the ground up because you like the word "change" better than "movement" or "movement" better than "time"?

 

~modest

[Overdog]

I ask everyone to consider the turn this discussion took when it began addressing the question of whether time has objective reality.

 

It became, at that point, a discussion about what is knowable, not about time or physics.

 

In that respect, we could just as well have been discussing god here, as time, because the same philosophical argument (we've been discussing) applies equally to both, and for exactly the same reasons.

 

This same philosophical argument has been used to dismiss claims and/or proofs that god is real. It works equally well for dismissing claims that time is real.

[freeztar]

I ask everyone to consider the turn this discussion took when it began addressing the question of whether time has objective reality.

 

It became, at that point, a discussion about what is knowable, not about time or physics.

 

In that respect, we could just as well have been discussing god here, as time, because the same philosophical argument (we've been discussing) applies equally to both, and for exactly the same reasons.

 

This same philosophical argument has been used to dismiss claims and/or proofs that god is real. It works equally well for dismissing claims that time is real.

 

That's a very keen (and sobering) observation, Overdog!

 

So where do you suggest we go from here?

[ldsoftwaresteve]

Modest, I am simply saying that change happens prior to our being aware of it. We make sense out of change and measure it with concepts such as time.

 

There might indeed be a common cause to all change and I don't for a moment believe it is God. There just might be a single physical phenomena that could be at the bottom of all physical properties and laws.

 

I am not saying that mathematics doesn't work. It does. I am not saying that without concepts of time and space our understanding of existence would have meaning, it wouldn't.

 

What I am saying is that by considering time and space as fundamental drivers involved in the fabric of existence, we might be blinding ourselves to truth which is below the level of our current understanding.

[Overdog]

That's a very keen (and sobering) observation, Overdog!

 

So where do you suggest we go from here?

 

Well, I would suggest that anyone who is clinging to an assertion that time has objective reality do as I did when faced with a proof I could not refute, abandon the assertion.

 

Else refute the proof that says knowledge of unobservable phenomenon is impossible, or show how time is in fact observable.

[modest]

Well, I would suggest that anyone who is clinging to an assertion that time has objective reality do as I did when faced with a proof I could not refute, abandon the assertion.

 

Else refute the proof that says knowledge of unobservable phenomenon is impossible, or show how time is in fact observable.

 

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

 

Any real system needs time to be completely and properly described. No real system need god to be completely and properly described. So even though we cannot test the axiom of time “under the microscope” we do have extensive evidence of its reality - opposed to god.

 

So, no, you don't have to "abandon the assertion" of any and all axioms.

 

~modest