Is Time Truly a Dimension or Something Else Entirely?

[BWV]

In economics you have lots of arbitrary dimensions that are really just categorizations - like 10 different economic sectors (finance, industrials, energy etc.) which could be used in regressions. So I get that, but in spacetime you have the concept of orthogonality between these dimensions correct? This does not really apply to the category-dimensions that I am more familiar with. How does orthogonality work with 4 dimensions and how is time orthogonal to the three space dimensions and does it make sense to think of y being orthoganal to x,z &t ?

 

[Fredrik]

What do you think time is? You gave examples of time used in math, but do you think time is more than an equation.

Time is certainly more than that mathematical expression, but any answer to the question of what time "is", will always be in the form of a mathematical model and a set of instructions about how to use that model to make predictions about the real world. The best answer we have so far is the one provided by general relativity. The relevant "instruction about how to use the model to make predictions" says that what a clock measures is the proper time of the curve that represents the clock's motion. I don't think anyone has a better answer than that at this time.

Note that two definitions of time are needed. First we have to define time in a mathematical model (in this case as a certain integral), and then we have to define it operationally (as "what a clock measures"). Then we postulate how the two are related.

 

[Fredrik]

So I get that, but in spacetime you have the concept of orthogonality between these dimensions correct?
...
How does orthogonality work with 4 dimensions and how is time orthogonal to the three space dimensions and does it make sense to think of y being orthoganal to x,z &t ?

You should think of the spacetime manifold as the set of all events, and a coordinate system as a function that takes a point in spacetime to an ordered 4-tuple (t,x,y,z) of real numbers. The direction in which t is increasing is not necessarily orthogonal to the direction in which x is increasing for example.

That being said, in special relativity there's a class of coordinate systems that are "special" in a certain sense. They are called "global inertial frames" or just "inertial frames". If we use an inertial frame, then the t direction is orthogonal to the x direction in the sense that if u and v are two vectors in the t and x directions respectively, we have g(u,v)=0, where g is the metric.

So what does that have to do with orthogonality? Consider the definition of a "scalar product" (a.k.a. "inner product"). It's a function (x,y)\mapsto\langle x,y\rangle that takes two vectors to a number and satisfies the conditions (i) <x,y>=<y,x>, (ii) <ax+by,z>=a<x,z>+b<y,z> and <x,ay+bz>=a<x,y>+b<x,z>, (iii) <x,x>\geq0 and <x,x>=0 only when x=0. The Cauchy-Schwarz inequality tells us that

\frac{|\langle x,y\rangle|}{\|x\|\|y\|}\leq 1

and that means that we can define an angle between any two vectors in an inner product space by

\cos\theta=\frac{\langle x,y\rangle}{\|x\|\|y\|}

That angle is zero when <x,y>=0. Now, a metric isn't exactly the same as a scalar product, because it doesn't satisfy condition (iii) above. (g(u,u) can be negative, and it can be zero for non-zero u). That means that it doesn't satisfy the Cauchy-Schwarz inequality, and that the "angle between vectors" isn't well-defined. But if we want to, I suppose we can ignore that and say that u and v are "orthogonal" if g(u,v)=0. If we choose to do that, then the t and x directions (defined by an inertial frame) are orthogonal.

 

[Dale]

Yes in physics equations the concept of time is symbolized with the letter t. So let me ask you, in all physics equations, does this symbol "t" represent a real physical thing or a concept?

Obviously a real physical thing. How can you get more physical than a physical variable measured by a physical device that operates according to a physical principle?

I have disassembled some clocks and wristwatches and have never observed a physical thing you describe as a "d/dt term" somewhere in these time pieces.

Then you didn't understand what you were looking at.

 

[meteor9]

That's true that we should rely on maths to have a quantitative explanation of everything we want to be 'logic'. But I think that mathematic equations, formula and theories are just good for the train of the 'daily life' , to manage things and predict the phenomena. Our brain , our memory is something much more sophisticated than some formula and it escapes the 'limits' of mathematic language which is just a tool . Do animals have the same conception of time ? Does time have any meaning to them? So I deduce that our brain is designed on such an unknown basis which enable us to 'perceive' and 'measure' time. Another example, it is about the conceptual ability of some primitive tribes around the world about the 'time' : for them the concept of 'tomorrow' doesn 't exist AT ALL , they don't see the 'future' , they just live in some 'momentum' , they can't anticipate the things which could happen in the 'future'. At this moment i write this and i experience it like all the other billion alive people around the world , 'yesterday' along with million million years ago are the same ,e.g. an 'illusion'. What in the world can prove that we don't 'live' in a sort of 'Closed Matrix' where time and space are static , and all we perceive as motion and movement are nothing but a static time? When we dream , we are motionless ourselves, but we 'see' the scenery in motion and we are unable to determine the time flown , we can dream just in few minutes some scenery and events as if they took some years, and vis-versa , we can dream a dream within 24 hours and having the impression that it last just few minutes. How can we quantify such a mysterious phenomenum which is the Time?

 

[Alfi]

Just like cutting up a clock ever finer and still never finding the t in the thing.
We can cut up a human to atoms and never find a bit of conscience.
But, being a conscience creature immersed in four dimensions, I can say I have some kind of awareness of time. Is it part of the equations? Does Science math have a problem if it includes the concept of awareness into the time concepts.

 

[Fredrik]

Meteor9, all of your statements are either obviously irrelevant (to those of use who understands what science is) or obviously false. (Do you really think that there are primitive tribes where no one who looks at a pregnant woman is capable of thinking that she's going to have a child in the future?) How we feel about time is completely irrelevant. Science is about finding theories and testing them, and there are some theories about time that have passed some amazing tests. The best one is general relativity.

 

[Fredrik]

But, being a conscience creature immersed in four dimensions, I can say I have some kind of awareness of time. Is it part of the equations? Does Science math have a problem if it includes the concept of awareness into the time concepts.

It wouldn't be a problem if you could find a theory that defines that concept and uses it to predict the results of experiments as well as GR or better. But there's no such theory today and it's very likely that there never will be.

 

[meteor9]

OK Fredrik , all my statements are 'irrelevant' and 'false' in 'your' sight , i just expressed my opinion about time because John asked everyone to say what they 'think' about that. I never imprison my mind and my point of view in the 'jail' of theories and formula , i just try going beyond the conventional scales . To answer your question about the pregnant women in primitive tribes or their vision about the seasons ,day and night , etc , i should say NO , they don't realize that something would happen in the 'future' , and don't perceive a concept we call 'time'. For example if any of them find him/herself in a critical situation , they just die , because they don't see the 'tomorrow' and can't visualise a change in that situation in the 'future'. On the other hand , for example when we travel in some different countries or regions with different culture or tradition , 'apparently' we have moved in the space , i mean we find ourselves in a different location , but in reality we just did a travel in some other time. We notice that in the new 'space' , time flows totally differently from the one we lived in previously. There we should adapt ourselves with the new 'time' and not the new 'space' (location). Even in a given 'advanced' country , rural area and regions have a different 'time' than the one of the big industrialised and modern cities . So Time is a 'versatile' and 'polymorph' entity .

 

[atyy]

Just like cutting up a clock ever finer and still never finding the t in the thing.
We can cut up a human to atoms and never find a bit of conscience.
But, being a conscience creature immersed in four dimensions, I can say I have some kind of awareness of time. Is it part of the equations? Does Science math have a problem if it includes the concept of awareness into the time concepts.

Try:

Block time: Why many physicists still don't accept it? by Hrvoje Nikolic
http://fqxi.org/community/forum/topic/259

"Forget time" by Carlo Rovelli
http://fqxi.org/community/forum/topic/237

Essentially, the notion of time we use when talking about music and memory is a different from the notion of time in our current theories of nature. They are presumably related, but not very directly. You can also look up the "binding problem" in neurobiology, but I am not aware of any generally accepted solution to the question.

 

[atyy]

To answer your question about the pregnant women in primitive tribes or their vision about the seasons ,day and night , etc , i should say NO , they don't realize that something would happen in the 'future' , and don't perceive a concept we call 'time'. For example if any of them find him/herself in a critical situation , they just die , because they don't see the 'tomorrow' and can't visualise a change in that situation in the 'future'.

That's interesting. Any references you recommend for reading about this?

 

[meteor9]

atyy , as a reference for that , you can search on 'arte channel' , anthropology documentary about massaii and pigmy tribes in africa, or just use google search.

 

[Fredrik]

OK Fredrik , all my statements are 'irrelevant' and 'false' in 'your' sight , i just expressed my opinion about time because John asked everyone to say what they 'think' about that.

It's fine to express opinions, but don't forget that this is a science forum. Your statements were irrelevant. E.g. the fact that we might feel that more (or less) time has passed in a dream is completely irrelevant to science.

I never imprison my mind and my point of view in the 'jail' of theories and formula , i just try going beyond the conventional scales .

I don't think you realize what you're saying. Science is about finding theories that do a good job predicting the results of experiments. There's no other way to obtain knowledge about how the universe behaves. So if you can go beyond the "jail" of theories, you can go beyond science and know things that are unknowable.

...they don't realize that something would happen in the 'future' , and don't perceive a concept we call 'time'...

I don't see how you (or anyone) can believe that this is true, and even if it is, it has nothing to do with science.

 

[Dale]

This thread is getting off-topic again. If y'all want to have a conversation about consciousness and the perception of time or on social aspects of time please start a new thread in the philosophy or social sciences forum. It doesn't belong here.

 

[john 8]

Time is certainly more than that mathematical expression, but any answer to the question of what time "is", will always be in the form of a mathematical model and a set of instructions about how to use that model to make predictions about the real world. The best answer we have so far is the one provided by general relativity. The relevant "instruction about how to use the model to make predictions" says that what a clock measures is the proper time of the curve that represents the clock's motion. I don't think anyone has a better answer than that at this time.

Note that two definitions of time are needed. First we have to define time in a mathematical model (in this case as a certain integral), and then we have to define it operationally (as "what a clock measures"). Then we postulate how the two are related.

Thank you for your answer. I noticed that you say time is more than a mathmatical expression and then go on to describe how time is a mathmatical expression.

So I guess what I want to know from you is, what is your understanding of time? Do you think that time is a thing that exists in the physical universe as some form of matter or energy, or do you think that it is something else?

I say that the concept of time is just that, a concept of man and nothing more.

 

[john 8]

Obviously a real physical thing. How can you get more physical than a physical variable measured by a physical device that operates according to a physical principle?

OK DaleSpam. You say time is a physical thing. I am interested to hear more about this idea that you have that time is physical. I have yet to see any physical evidence or scientific reference that provides evidence of this time thing being physical. If you want to say that time is physical then can you at least tell me in what way time is physical?

Is it a solid?
Is it a gas?
Is it some form of energy?

What exactly do you mean when you say time is a real physical thing? Can you provide more information on this?


Lets now look at what you said was observational evidence of time in post #19.

IMO, time is simply the "t" in the "d/dt" terms from all the physics equations. As far as observational evidence goes, every clock is based on some physical mechanism that has a "d/dt" term in it somewhere, so there is probably evidence on your wrist.

Here was my response to your evidence.

"I have owned many clocks and wristwatches. I have disassembled some clocks and wristwatches and have never observed a physical thing you describe as a "d/dt term" somewhere in these time pieces. I know that what I just said may seem a bit silly, but you said that a clock has a "d/dt" term in it somewhere.

Do you see how what you said is not a description of any observation of a physical thing called time, you just talked about equations."



And here is your response to that.

Then you didn't understand what you were looking at.

Now it seems that you have missed my point.

You said:
"every clock is based on some physical mechanism that has a "d/dt" term in it somewhere, so there is probably evidence on your wrist."

Now remember you said that this was observational evidence.

I will tell you right now with 100% certainty that if you look (observe) at or in any clock or wristwatch all you will see is physical matter in one form or another. All clocks and such are made from physical matter, there is no physical mathematical term that exists in a clock or wristwatch. So by saying that some physical mechanism has a "d/dt" term in it somewhere is observational evidence of time is wrong. A physical mechanism will be made of electrons, protons and neutrons, physical mechanisms are not made of symbols.

Observational evidence means that it can be seen by our eyes. By looking somewhere in a clock you will not see "d/dt". This may sound obvious, but when I said that I did not see this thing "d/dt" when I disassembled a clock, you told me that I did not understand what I was looking at.

Really? I did not understand. When I look at a clock disassembled, or not, all I or anyone will see is physical matter that has the ability to reflect light so that we can perceive it.

So you see, if something is going to be used as observational evidence than it will have to be observed by our eyes. The term "d/dt" is not a physical thing, so it does not reflect light, and it is not a thing that exists in or on clocks that is observable.

If you want to give observational evidence of time than just make sure that this evidence can actually be observed.

Thank you.

 

[Fredrik]

I noticed that you say time is more than a mathmatical expression and then go on to describe how time is a mathmatical expression.

That's not what I said. Please read my answer again.

So I guess what I want to know from you is, what is your understanding of time? Do you think that time is a thing that exists in the physical universe as some form of matter or energy, or do you think that it is something else?

I don't have anything to add to the answer provided by general relativity. To do that, I'd have to come up with a better theory myself first, and that isn't easy to do.

It's however very clear that time isn't a form of matter.

I say that the concept of time is just that, a concept of man and nothing more.

No, the word time is a concept of man, just like the word "hammer", but if you hit yourself on the thumb with a hammer it still hurts.

I would also like to remind you that this is a science forum. The things you say don't seem to have anything to do with science. If you feel that they do, you should try to make the connection more clear.

 

[Dale]

OK DaleSpam. You say time is a physical thing. I am interested to hear more about this idea that you have that time is physical. I have yet to see any physical evidence or scientific reference that provides evidence of this time thing being physical. If you want to say that time is physical then can you at least tell me in what way time is physical?

"Physical" means "of or relating to physics". Time is an integral part of every mainstream physical theory -
Newton's laws: f = dp/dt
Thermodynamics: dS/dt >= 0
Maxwell's laws: del x E = -dB/dt
Relativity: ds² = -dt² + dx² + dy² + dz²
etc.

These physics theories, which all include time, have been experimentally verified with more than a century of accumulated physical evidence each. If centuries of peer-reviewed experimental evidence are insufficient then consider the additional fact that each of these theories have been used to develop a wealth of material devices which all work in the manner predicted by the physical theory.

Given all of this, consistent physical theories using time, centuries of data verifying those theories, practical devices functioning according to the theories, how can you not understand that time is physical? I suspect that you do understand but are simply trolling.

If you are not trolling and actually hypothesize that time is not physical then please post (on the independent research forum) your alternate scientific theory that does not use time to make its physics predictions.

 

[john 8]

That's not what I said. Please read my answer again..

I read your post again. You talk of time in terms of math.



Here is what you said:

Time is certainly more than that mathematical expression, but any answer to the question of what time "is", will always be in the form of a mathematical model and a set of instructions about how to use that model to make predictions about the real world. The best answer we have so far is the one provided by general relativity. The relevant "instruction about how to use the model to make predictions" says that what a clock measures is the proper time of the curve that represents the clock's motion. I don't think anyone has a better answer than that at this time...

Note that two definitions of time are needed. First we have to define time in a mathematical model (in this case as a certain integral), and then we have to define it operationally (as "what a clock measures"). Then we postulate how the two are related. ...

What you said here does not definitively state if you think time is a physical thing or not. This is important to know since we are discussing time at this moment. You just need to define your terms so that what you are saying is not vague or ambiguous, like you said this is a science forum and you are participating in this discussion, I will assume that you have some scientific understanding of what time is.

I don't have anything to add to the answer provided by general relativity. To do that, I'd have to come up with a better theory myself first, and that isn't easy to do...

Science is about looking about the world around you and trying to figure out what it is and how it works through already established facts.

I asked you what you thought time was. I am sure that you can make your own observations and conclusions without depending on some authority on the subject. We all know what Einstein has to say about time. So I ask you, after getting an understanding of what Einstein said about time and by your personal experience of the world around you, what conclusions have you come up with?

From everything that you have read and experienced in regards to time, what is your understanding of time? Is time a real physical thing or not? That’s all, simple as that.

It's however very clear that time isn't a form of matter...

Alright, so what do you think time is?

No, the word time is a concept of man, just like the word "hammer", but if you hit yourself on the thumb with a hammer it still hurts..

Yes the word hammer describes a real physical thing, a hammer by any other name is still a hammer.

The word hammer is a man made word used to describe a real thing. There is no doubt or argument that the word hammer describes a physical object. There is no doubt or argument that the object described by the word hammer is a real physical thing.

So the word time is a man made word used to describe WHAT?

Does the word time describe a physical thing? If so please elaborate.

I am sure you must have some clear understanding of what time is, so just simply say what that understanding is. Time is either a physical thing or not.

I would also like to remind you that this is a science forum. The things you say don't seem to have anything to do with science. If you feel that they do, you should try to make the connection more clear.

Yes I know this is a science forum. Time is one of the basic foundations on which the science of physics is based on. It is completely relevant to ask questions about time in order to gain a better understanding of time. My questions are direct and concise.

Do you think time is a physical thing or not.

I have come to the understanding that time is not a physical thing and is just the concept of man. I have read other people say that time is not a concept, yet they will not say what it is. So that is why I am asking you about time, you seem to think that time is more than just a concept, so fill me in, what do you know?

What evidence am I lacking that definitively proves that time is more than a concept?

Just show the observational science, please.

Thank You.

 

[john 8]

"Physical" means "of or relating to physics". Time is an integral part of every mainstream physical theory -
Newton's laws: f = dp/dt
Thermodynamics: dS/dt >= 0
Maxwell's laws: del x E = -dB/dt
Relativity: ds² = -dt² + dx² + dy² + dz²
etc..

Yes time is part of physics. That is obvious. I am not asking if time is part of physics. I am asking if time is physical per the definition of physical that state:

Physical.
of or pertaining to that which is material: the physical universe.

Pertaining to the properties of matter and energy other than those peculiar to living matter.

"These physics theories, which all include time, have been experimentally verified with more than a century of accumulated physical evidence each. If centuries of peer-reviewed experimental evidence are insufficient then consider the additional fact that each of these theories have been used to develop a wealth of material devices which all work in the manner predicted by the physical theory.

Given all of this, consistent physical theories using time, centuries of data verifying those theories, practical devices functioning according to the theories, how can you not understand that time is physical? I suspect that you do understand but are simply trolling.

If you are not trolling and actually hypothesize that time is not physical then please post (on the independent research forum) your alternate scientific theory that does not use time to make its physics predictions.

Right, rocks are a physical thing and physics can described exactly with precise definitions and observational evidence what the nature of rocks are. Physics puts the rock and all other things that are made in similar ways to the rock in the category of matter.

Heat is a physical thing that can be described and defined so as to give a clear understanding of what heat is. Physics describes heat and all those things with similar attributes in the category of energy.

Physics is a branch if science that is concerned with the laws that govern the structure of the universe, and the investigation of the properties of matter and energy and their interactions.

When I ask you if you think time is physical and you tell me that it is physical because it is part of physics, well I will have to ask you to be very specific and tell me what category of physics time is a part of. Since you pointed out that time is part of physics, and physics deals with matter and energy, which category do you think time belongs in?

I have stated that I have come to the understanding that time is just a concept based on what I have observed in the world around me and by the complete lack of any physical evidence that disproves my understanding.

So this brings me to the point of why I am asking you what your understanding of time is. I might be wrong, and so you can correct me.

This is not trolling, it is going on a science forum and discussing an aspect of physics with those people who are interested and have some understanding of physics and time.

This is the place to discuss science topics and learn more about these topics.

Asking you to explain in what way you think time is physical is a legitimate question and should be very easy to answer. Just because I may disagree with you on the nature of time is in no way a sign that I am trolling. I have stated my view on time based on observation and lack of evidence to prove that I am mistaken. I have asked you to just explain how you think time is a physical thing, which is a normal type of question that is required when someone may have a disagreement with what the other person said.

So, to sum this up, please provide a more detailed explanation of what you mean by the statement that time is a physical thing.

Thank You.

 

[Makep]

It has been an interesting journey of discussion and thoughtful discourse of time thus far. It makes me wonder, when I read through, about the concept of matter, energy, space and time. I would like to pose some of these in here, and see if they are related. As much as we have talked about time:
1. What is space?
2. What is energy?
3. What is matter / antimatter?
4. And I pose again the question, What is time?
Can any of them exist independantly? I suppose the big question is, 'Can matter exist without space?' What came first, matter or time or space or energy? Is our current science up to this to give us the anwer. If we know which came first, then we can hypothesize as to why others would follow, and device experiments to prove or disprove. In asking what is time, it is like asking what is matter, or energy or space? We really do not know. We take it for granted as an abstract entity that we utilize to explain changes happening with space, energy and matter and time itself.
We speak of time, space and matter. But now we have the concept of anti-matter. We should also have the concept of anti-space, anti-time, and anti-energy. Perhaps by understanding the opposite of time, can we know time itself. The fundamental question is: Which came first - matter or energy or space or time? How have they been interacting to keep in check the physical laws as we know them? I am dumbfounded.

 

[petm1]

It's however very clear that time isn't a form of matter.


Why is this very clear? All atoms may not occupy the same space second to second, but they do occupy their own time, by some thought their duration has been in the present for about thirteen billion years and counting. On the other hand you may be right, time isn’t a form of matter, but I would think that matter does appear to be a form of time, after all our very concept of time comes from the intrinsic motion of matter.

 

[Dale]

Right, rocks are a physical thing and physics can described exactly with precise definitions and observational evidence what the nature of rocks are. Physics puts the rock and all other things that are made in similar ways to the rock in the category of matter.

Really, so what is mass?

The reason I ask is because in the final analysis there are no physics definitions of any of these things outside of the type of definition that I provided for time (a theory using a quantity and an experimental/operational method for measuring it). I.e. mass is the thing represented by m in the physics equations. You can measure it with a balance scale. You can use the equations to describe its relationship to other things and to predict experimentally measurable outcomes, but beyond those what is mass?

When I ask you if you think time is physical and you tell me that it is physical because it is part of physics, well I will have to ask you to be very specific and tell me what category of physics time is a part of. Since you pointed out that time is part of physics, and physics deals with matter and energy, which category do you think time belongs in?

I wouldn't categorize physics like that, nor have I ever seen anyone else do so. Since you are making up this categorization, which category do you think distance belongs in? You should put time in the same category.

Also, what is your time-free definition of energy?

I have stated my view on time based on observation and lack of evidence to prove that I am mistaken.

A typical troll/crackpot comment. I notice that you failed to post your physical theory without time.

 

[Fredrik]

I read your post again. You talk of time in terms of math.

But I didn't claim that time is a specific mathematical expression, which is what you've been saying that I've been saying.

Here is what you said:

It seems that you completely ignored the stuff I said after the parts you underlined. Those things are no less important.

What you said here does not definitively state if you think time is a physical thing or not.

What do you mean by "a physical thing"?

You just need to define your terms so that what you are saying is not vague or ambiguous,

There's nothing vague or ambiguous about what I said.

Science is about looking about the world around you and trying to figure out what it is and how it works through already established facts.

That's actually a pretty naive view of science. What you don't seem to understand is that the only established facts are statements of the form "prediction W of theory X agrees with the result of experiment Y with accuracy Z".

I asked you what you thought time was. I am sure that you can make your own observations and conclusions without depending on some authority on the subject. We all know what Einstein has to say about time. So I ask you, after getting an understanding of what Einstein said about time and by your personal experience of the world around you, what conclusions have you come up with?

As I've been trying to tell you, every answer to the question of what time "is" must be in the form of a theory that accurately predicts the results of experiments. If it isn't, it's not really an answer. It's just irrelevant BS. So there are only two ways to interpret your question: You're either asking me to show you a theory that's better than GR, or you're asking me to answer with irrelevant BS.

I don't have a better theory than GR (obviously), and I don't have time for irrelevant BS.

 

[Fredrik]

Why is this very clear?

Concepts like "time" and "matter" can only be unambiguously defined within the framework of a theory. What I meant is that it's easy to see that time and matter are two completely different things in all of the current theories. If I'm not allowed to use the definitions of "matter" and "time" provided by the current theories, then I consider the question "Is time matter?" ill-defined, since neither of the concepts have an exact definition.

 

[CosmologyHobbyist]

Hello! I find this thread fascinating. This discussion reminds me how scientific concepts need good visuals to be understandable to laymen. Please allow me to make an attempt, not using GR, but using basic mechanics.
A person who recognizes the concept of "before" and "after" recognizes the concept scientists call time. A person who recognizes that he himself is aging, recognises time as an external agent of change, not as an internally generated self-perception.
But is time a real thing? Time is no more or less real than distance, they are neither solid, liquid, gas, nor energy. Time and distance are both measurements, and as such, must be taken into accounts as parameters in scientific equations.
Even a culture that has no concept of time passage, but lives in eternal "now", still utilises the concept of time if it can distinguish between "fast" and "slow". The formula Velocity=Distance/Time means the measurement (or even perception) of different speeds involves using time as a reference.
On the other hand, the concepts "near" and "far" do not involve time, but only involve distance, unless travel time brought up. "Big" and "little" also involve distance, but not time.
On a less obvious level, the concept of force, the difference between a tap and a heavy blow, uses time in the measurement formulae. Please correct me if I'm wrong, but I believe this also includes the measurement of the force of gravity on an object, so the distinguishing between "heavy things" and and "light things", utilises the concept of time, in an indirect manner.
Is the "concept of time" a real thing? It is just as real as the concept of distance. Both have their place is scientific formula, and are just as required and real in those formula, as mass or energy. But obviously, time is not mass or energy, or it would not need its own parameter. Although time is similar to distance in that both are measurements, they are separate identities, and are not usually interchangeable. So from this point of view, time is as real as distance, mass or energy.
A culture that has no concept of the passage of time, still makes indirect reference to the scientific concept of time whenever making reference to velocity or force. Such a culture can not be considered as free from a misconception; it has probably dropped the references to passage of time because there is no need to work within that concept. I have no need to know the value of a Euro because I don't use Euros, I do know the value of a dollar because I use dollars. A culture that does not use something, has no requirement to retain it in its language or thinking.
On the other end of the scale is scientific formula, which are use very useful for making predictions about behaviours of atomic constituents, and about behaviours of astronomical objects. On these very small and very large scales, common behaviour is often difficult to understand from our human perspective. However, because the formula is so useful in making predictions, the formula and extrapolated ramifications becomes more important than being able to relate it to human-scale experience.
In answer to BoySherpas original question, Is time a dimension? I'm not qualified to answer that question from a GR perspective, and the question was asked in a GR forum. But it would be helpful to laymen if someone brilliant with visuals can come up with GR illustrations. One of my favorites concerns the precession of the orbit of Mercury, that really helped me get my head around the effect of gravity on spacetime. And when I understood how gravity can change space distances or time measurements, it made space and time both seem more understandable, even if they remain intangible.

 

[CosmologyHobbyist]

That may have been a bit longwinded, but the point is that some good visuals could help laymen understand some common applications of scientific theory.

 

[ThomasT]

I have been trying to figure this one out for some time now. I have read much on the subject, but it seems to be dealt with in such a cavalier fashion. So, here goes...

We speak of space-time as if it were something packaged. I have a problem with this. Let me list the difficulties I have:

Concerning position:
1. In physical 3-space, I can position an object anywhere I like, relative to an arbitrary (0,0,0) position.
2. After any arbitrary operation, the objects position can be anywhere in 3-space, including any previous position.
3. The object may be placed in + or - position relative to the origin.
4. Any operation changing the objects position instantiates or necessitates the creation of time. Without a change of position, there is no need to speak of time.
5. Changes in position may be made with an infinity of possible velocities and accelerations, positing "time"
Concerning time:
A. I have no control over the timing of an event - it always occurs at the present - dissimilar from item 1.
B. I can never reuse the present or a previous time - dissimilar from item 2.
C. Causality forces only forward motion in time - dissimilar from item 3.
D. The flow of time does not instantiate a change of position - dissimilar from item 4.
E. Time does not seem to have various rates of flow (relativity excepted) - dissimilar from item 5.

It would seem, then, that time is only superficially similar to 3-space, in that it operates in some mathematical models in a fashion similar to the spatial distances. However, A-E behaviors are distinctly different from 1-5 behaviors.

So, how can we group time with space? It would seem time is something wholly different, and perhaps not of the same substance.

Any help?

Three dimensional space refers to a backdrop for communicating positions and orientations (arrangements, configurations) of physical objects. Time refers to changes in, or the fact of different, positions, orientations, arrangements, configurations of some set(s) of physical objects in that space.

Space is configurations.
Time is incongruent configurations.

 

[john 8]

But I didn't claim that time is a specific mathematical expression, which is what you've been saying that I've been saying.


There's nothing vague or ambiguous about what I said.


That's actually a pretty naive view of science. What you don't seem to understand is that the only established facts are statements of the form "prediction W of theory X agrees with the result of experiment Y with accuracy Z".


As I've been trying to tell you, every answer to the question of what time "is" must be in the form of a theory that accurately predicts the results of experiments. If it isn't, it's not really an answer. It's just irrelevant BS. So there are only two ways to interpret your question: You're either asking me to show you a theory that's better than GR, or you're asking me to answer with irrelevant BS.

I don't have a better theory than GR (obviously), and I don't have time for irrelevant BS.

My first post on this thread was that I said that time was not a physical thing and was just a consideration.


Dalespam said this in response to the physical nature of time.

“IMO, time is simply the "t" in the "d/dt" terms from all the physics equations. As far as observational evidence goes, every clock is based on some physical mechanism that has a "d/dt" term in it somewhere, so there is probably evidence on your wrist. “


So Dalespam says time is the symbol “t” that is used in a math equation. Dalespam says that this is observational evidence of time. So if this is observational evidence that means that time can be seen with our eyes. So based on the observational evidence that Dalespam gave, what does time look like?


Fredrik said the definition of time is:


“Regarding the definition of time...

We can define a coordinate system in Newtonian mechanics, SR and GR as a function , where M is spacetime, and then define "coordinate time" as a component of that function. In SR and GR it's also necessary to define "proper time", which is the integral of along a curve.

That takes care of the definitions in the mathematical models used in these three theories, but the theories must still include postulates that tell us how these things are related to what clock's measure. In Newtonian mechanics, clocks measure coordinate time. In SR and GR, a clock measures the proper time of the curve that represents its motion.”


Does this definition of time give a physical description of a thing called time?

Or is this a mathematical description of time?

So far what type of description of time has been given? Physical? Mathematical?



I asked Fredrik if he thought that time was more than a mathematical equation and he gave this response:

“Time is certainly more than that mathematical expression, but any answer to the question of what time "is", will always be in the form of a mathematical model and a set of instructions about how to use that model to make predictions about the real world. The best answer we have so far is the one provided by general relativity. The relevant "instruction about how to use the model to make predictions" says that what a clock measures is the proper time of the curve that represents the clock's motion. I don't think anyone has a better answer than that at this time.

Note that two definitions of time are needed. First we have to define time in a mathematical model (in this case as a certain integral), and then we have to define it operationally (as "what a clock measures"). Then we postulate how the two are related.”


Fredrik said time was more than math and then proceeded to show how time can only described in the form of a mathematical model.

I am not trying to harass Fredrik or Dalespam, I am just pointing out the fact that up to this point no physical description has been given of this thing called time.

I will continue to show you that no one will give a physical definition, reference, or observation that proves that time is a physical thing.






The following post was directed toward Dalespam:

Originally Posted by john 8
Yes in physics equations the concept of time is symbolized with the letter t. So let me ask you, in all physics equations, does this symbol "t" represent a real physical thing or a concept?


Dalespam’s response:

Obviously a real physical thing. How can you get more physical than a physical variable measured by a physical device that operates according to a physical principle?

Here Dalespam says that time is physical. Still no physical description has been provided. Saying that something is physical just because you say it is physical is not science. What needs to be provided is some physical evidence.

This conversation is akin to discussions about the existence of God with believers. They all say God exists yet not one speck of physical proof. So since this is a science form, and we do not, as logical thinking people go on faith or our feelings to prove our claims, I would like to see someone provide some cold hard facts that back up the claim that time is a physical thing.

Dalespam, you say time is a physical thing. Please get on with it and describe to the rest of this forum in what way time is a physical thing. Instead of saying time is physical, just let the facts speak for themselves.

As I've been trying to tell you, every answer to the question of what time "is" must be in the form of a theory that accurately predicts the results of experiments. If it isn't, it's not really an answer. It's just irrelevant BS. So there are only two ways to interpret your question: You're either asking me to show you a theory that's better than GR, or you're asking me to answer with irrelevant BS.

Look Fredrik, if you think that time is a physical thing then just explain what physical evidence has lead you to this conclusion.

Again, if we were debating the physical reality of a rock, car, water, electricity or any of the other physical things in this universe all you would have to do is tell me to look up the references and definitions or even just look at the world around me to discover that any physical thing that we talk about is indeed physical. So just provide evidence that time is physical. What has brought you to the conclusion that time is a physical thing? What physical evidence have you percieved. Which bodily sense was stimulated by the presence of this physical thing called time that gave you certainty that time is a physical thing.

Please describe the physical properties of this thing you call time. That is it, keep it simple and scientific.

Thank you.

 

[meteor9]

I didn't want burdening this thread because some people found all my statements 'false and irrelevant' , so i posted my conception of time in the other thread 'Time dilation confusion' , if by any chance you are interested you can visit that thread .

Thank you !