What is time?

[Overdog]

Originally Posted by AnssiH

Well, please read this, see what you think;

All right, I see that I have a couple of beliefs I have never really questioned, that I need to think about....

Thanks for the insights.

[AnssiH]

Originally Posted by modest

Allow me to quote Dr. Kelly Ross (philosophy of science professor):

Or to be more exact "The mathematical form of each theory can be "conceptually interpreted" in a multitude of different ways"

Additionally, even when we stick with math, the same logic can be expressed in many different ways. These different mathematical forms may each imply different sort of ontology (i.e. people would have the tendency to make different conceptual interpretations).

Sure. There may well be no limit to variations on how it’s ”seen”. But, how many interpretations of space and time can derive time dilation, agree with all known observation, and be used to predict the future evolution of a system? It would not make good sense to me if the answer was greater than one in our one universe.

If you don't place any constraints onto how complex the worldview is allowed to be, an infinite number. Of course in such case most candidates would simply be too complex to amount to anything useful at all (as it would be practically impossible to even "think about them"

But since you are saying you'd expect only one interpretation to be possible, I must say I am little bit confused about what you might mean with "interpretation of space and time". I mean, don't all the different ontological interpretations of relativity count as different interpretations of space and time, since they amount to different assumptions regarding the reality of spacetime?

Actually I'm not sure how do you interpret relativity exactly; do you see reality in terms of static spacetime block?

We can safely take it one step further and say we know how much slower Tommy ages.

Yes, or in slightly more objective terms, a valid model of reality must explain all of our past, one way or another. That obviously includes experimental confirmations of relativity.

The consistency of the speed of light between inertial frames is reflective of the more fundamental postulate that all laws of physics are the same in all inertial frames.

This is little bit off the track, but I must mention that I don't think the above is exactly fair assertion, although it is often heard. The assertion implies that if different inertial frames measured different speed for light, they could not be described by the same "laws"

But that all depends on what exactly is considered "laws" and what is considered "parameters" to those laws. I.e. it is possible to conceive a universe where "light" is not passed at isotropic speeds but the same "laws" still describe each inertial frame. After all, not all properties of light are isotropic; different frames measure different frequency for one. Just that they measure something differently doesn't mean the "laws" differ, depending on how those laws are presented.

Anyway, back to the actual topic;

So, I look at this situation and say that space and time as described by Minkowski are the axiomatic reality of our universe. Being axioms, they cannot be directly tested; and that is an interesting conundrum for a student of philosophy. But a physicist or mathematician will acknowledge the entirety of physics that is built on that axiom as both internally consistent and in agreement with observation which verifies the axiom beyond a shadow of a doubt.

Yeah, the predictionwise validity of a model can be verified, at least for our past.

I'm not sure if your paragraph also implies that you see the additional ontological interpretations as unnecessary. If so I have to say I'd disagree. For one, any new predictive model is a result of someone having formed a new "conceptualized view", and expressing that in math. Whatever conceptual view of reality you have in your mind, will directly affect what kinds of models you can build on top of it. I.e, failure to recognize what parts of your thinking are "semantics" and what parts are pure logic, will prevent you from finding many valid models (because you are investigating them from within a "wrong" paradigm, as Thomas Kuhn might say... well not really investigating as they would not even occur to you as possibilities)

Here I think you’re trying to describe different interpretations or perhaps foundations for relativity. Some things like “just mental construction” I understand and would be able to refute.

By that you mean you can prove that spacetime is ontologically real entity?

Or just that you can prove that spacetime has got its roots in reality one way or another?

Or are you just referring to those time dilation experiments?

Other things like “our methods of defining entities in unknown data” are completely lost on me.

For that you need to investigate this;
http://hypography.com/forums/philoso...elativity.html

I'm not that far myself yet so I don't understand all the steps of the logical proof. But I should warn you beforehead that that thread does not actually make any claims about what the ontology behind relativity is. It only has to do with how undefined data can be defined when not making any undefendable assumptions about the meaning of the data. The significant issue being that relativistic description arises as (predictionwise) valid description even when we have not made any claims about the true ontology behind that data whatsoever. Yes, "time dilation" would be valid concept in a model for that data.

That may sound impossible at first, but it is in fact quite possible, as long as you keep in mind that whatever you can conceive is part of your own definition of reality. Objects, space, time...

But like I said, I need to pick up the math of that thread much better before I could really see how it all unfolds in more detail. If that claim interests you, you should discuss it more in that thread with DD. (One of the main purposes of most of my posts in this thread has been to point out just in what sense relativity cannot be taken as ontologically granted just by the virtue that it makes correct predictions)

I will say: the relationship between space and time that allows relativity to work is very well defined. To reinterpret time or space and end up deriving relativity which agrees with observation would be something quite amazing.

Well each new "revolutionary" model has been like that. A new way to define reality, that simplifies all of our known past.

Besides, to my knowledge these kinds of models exist already? They just are complicated in some manner, or people don't accept transformation to some laws of physics between inertial frames. I'm not saying these models are "better" in any way. Just saying if they explain all of our past, they are "valid models". As long as people just didn't get so hung up on what kind of ontology different models seem to imply. :P

Really, it’s all the same. The difference is between Galilean absolute time and Lorentz variable time. This is true regardless of which particular aspect of relativity you want to look at. The universe would work differently depending on which type of time it kept (I should say more properly - how the universe keeps time).

I need to still comment on this because this is just the kind of view that would prevent you from seeing what that "unorthodox view on relativity" thread is about. To be more objective, we should say the universe does not really keep time one way or another, we do. By that I mean, it is part and parcel of our definitions of reality, how we understand something like "time". What we see as "time dilation" can be validly explained by defining a relativistic spacetime & lorentz transformation between frames, or alternatively through defining very many things very much differently. Because we can define these things differently but still end up with valid model, we don't really know how and where the model grounds to reality exactly. We still don't know if reality is a static spacetime block, or something else.

By observation we know it isn’t Galilean or Newtonian absolute time but is truly relative in a way that follows the Lorentz transformations.

We know it is valid to model reality one way, but invalid to model it the other way.

I have a feeling you'll probably have a problem with some things I've said, so I'd still like to remind you that I'm not insisting on validity of newtonian time or invalidity of relativity. I am insisting on invalidity of seeing relativistic spacetime as the "only valid way of understanding reality". If you think it is, you are just constraining yourself into your personal worldview too much to see how many parts of it really can be moved. (And consequently how many parts of it have epistemological roots rather than ontological)

-Anssi

[modest]

Originally Posted by AnssiH

Or to be more exact "The mathematical form of each theory can be "conceptually interpreted" in a multitude of different ways"

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

• Consider some math:
  1.0 - 0.80 = 0.20
• and an explanation:
  At the convenience store I noticed a dollar bill on the floor. I picked it up and decided to go wild and buy myself a Snickers bar. I went home with a Snickers, two dimes, and a smile on my face.

You wouldn’t point out to the person in the explanation that there are 15 different things in the store that also cost $0.80 and therefore 15 different interpretations of the math - because we're not explaining math. We are explaining something real and the math is part of that explanation.

Originally Posted by AnssiH

Additionally, even when we stick with math, the same logic can be expressed in many different ways. These different mathematical forms may each imply different sort of ontology (i.e. people would have the tendency to make different conceptual interpretations).

I’m not entirely sure what you mean by “stick with math”, but it seems you most likely are still looking at this a bit backwards. The normal development of a theory in physics starts with a postulate, thought experiment, or a hypothesized understanding of the way something should work. A formal derivation can then lead to some prediction that will either agree with observation or not. You don't usually start with the math then work out an understanding - that would be backwards.

For example, Newton did not write down then try and figure out if the interpretation of the math meant gravity is an attractive or repulsive effect. Kepler did not write down then try and figure out if the orbits speed up or slow down with distance. That would we backwards.

By and large this is how laws, theories, and models develop.

Originally Posted by AnssiH

If you don't place any constraints onto how complex the worldview is allowed to be, an infinite number. Of course in such case most candidates would simply be too complex to amount to anything useful at all (as it would be practically impossible to even "think about them"

Ok, I was just asking about one specific example. I don't think we need an infinite number. Here is somebody who tried to use Euclidean geometry (or an Euclidean interpretation of space and time) to get relativity:
Euclidean Relativity
He is ultimately unsuccessful, and if you follow what he did, it becomes immediately clear the difficulties involved.

Originally Posted by AnssiH

But since you are saying you'd expect only one interpretation to be possible,

Yes, only one ontology of space and time are correct to our universe. That, at least, sounds sensible to me. The only exception I see possible is if the strong equivalence principle is false.

Originally Posted by AnssiH

I must say I am little bit confused about what you might mean with "interpretation of space and time". I mean, don't all the different ontological interpretations of relativity count as different interpretations of space and time, since they amount to different assumptions regarding the reality of spacetime?

Interpreting relativity isn't exactly what I'm talking about. I was talking about deriving relativity and making good predictions. There are assumptions you have to make about space and time in order to get relativity. You can't just start with any metric space. You can't start with any definition of space and time. Look at the online descriptions of Minkowski space. Is there a definition of causality there? What about a world line or proper time? 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.

Originally Posted by AnssiH

This is little bit off the track, but I must mention that I don't think the above is exactly fair assertion, although it is often heard. The assertion implies that if different inertial frames measured different speed for light, they could not be described by the same "laws"

But that all depends on what exactly is considered "laws" and what is considered "parameters" to those laws. I.e. it is possible to conceive a universe where "light" is not passed at isotropic speeds but the same "laws" still describe each inertial frame. After all, not all properties of light are isotropic; different frames measure different frequency for one. Just that they measure something differently doesn't mean the "laws" differ, depending on how those laws are presented.

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.

Originally Posted by AnssiH

By that you mean you can prove that spacetime is ontologically real entity?

Or just that you can prove that spacetime has got its roots in reality one way or another?

Or are you just referring to those time dilation experiments?

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. To say that's true because of a mental construction is unsupportable.

Originally Posted by AnssiH

I have a feeling you'll probably have a problem with some things I've said, so I'd still like to remind you that I'm not insisting on validity of newtonian time or invalidity of relativity. I am insisting on invalidity of seeing relativistic spacetime as the "only valid way of understanding reality". If you think it is, you are just constraining yourself into your personal worldview too much to see how many parts of it really can be moved. (And consequently how many parts of it have epistemological roots rather than ontological)

-Anssi

Yeah, I got that. I think also we've minsuderstood eachother slightly on that I've been talking about what is necessary in order to derive relativity - assumptions about space and time that are necessary to get an equation that will predict effects of relativity. You've also been talking about interpreting relativity itself which is very much different.

But, this whole issue is difficult without a counterexample. Until there is some alternative way of treating time and space that has the consistency and validity of the current treatment - there's not much for me to argue against.

Originally Posted by AnssiH

Relativity is a model where space and time get somewhat entangled to each others (because of what I explained regarding how a different notion of "simultaneity" affects the supposed geometry of a "moving" object). It is only if you are talking about relativity when you can say "it doesn't make sense to think of time independently of space".

Relativity is not a model. I normally wouldn't correct that, but it's important in the context of this discussion. Think of the solar system model of an atom that represents an electron as a planet. Relativity doesn't represent time with an analogous system. It's just time. Time in relativity is the same time in every other standard theory of physics.

Also, Overdog is right. Space and time are linked always. No measurement of duration that humans have ever made was independent of space. Everywhere is moving relative to somewhere else and everywhere has at least some gravitational field. Time depends on that gravitational field and that movement so it is never in isolation.

~modest

[modest]

Originally Posted by ldsoftwaresteve

Modest:

Beautifully expressed Modest. If, however, the accuracy of our observation is not 100%, then there still remains a shadow of doubt on all of our beliefs. Until we can see the underlying activity of particles and verify our current models by seeing them in action, there will be at least some shadow of doubt.

Quantum electrodynamics is a relativistic quantum field theory. It is built on the assumptions of space and time I've been advocating. The wikipedia article on QED accuracy says:

The agreement found this way is to within ten parts in a billion . This makes QED one of the most accurate physical theories constructed thus far, after special relativity, which currently is tested to

So, I believe these theories are accurate to extraordinary precision which does indeed verify the axioms they are built on.

~modest

[Overdog]

Originally Posted by modest

So, I believe these theories are accurate to extraordinary precision which does indeed verify the axioms they are built on.

Unless I'm mistaken, this link may be relevant to where the discussion seems to have gone.

Scientific Realism (Stanford Encyclopedia of Philosophy)

6.6 Concluding Remark
Scientific realism is, by the lights of most of its defenders, the sciences' own philosophy of science. Considerations of the significant philosophical challenges which it faces indicate that it can be effectively defended only by the adoption of a metaphilosophical approach which is also closely tied to the science, viz., some version or other of philosophical naturalism.

Based on what I read in the above posted link, there appears to be no way to answer the question "What is time" without facing some seriously profound phiilosophical argument of one kind or another.

I'm not sure this is a question that will be settled anytime soon.

[steve 9]

Alright, since my last post I can see that many people have some very interesting views on what time is. The explanation of what time is by a few of you has covered some unusual concepts. Some have tried to explain what time is by using math (numbers). Someone has suggested that time is a measurement. There was some talk of rainbows on this thread about time. There has been discussion of what is reality. It has been suggested that the problem in defining what time is, is due to the fact that we may define time, motion and real all a bit differently. The term ontological has been used quite often. The topic of time then drifts a bit toward comparing time to space and then gets into philosophy, then back to the concept of space and something about conceptual interpretations. And all of this talk is simply summed up with the last post #425.

“Based on what I read in the above posted link, there appears to be no way to answer the question "What is time" without facing some seriously profound philosophical argument of one kind or another.

I'm not sure this is a question that will be settled anytime soon.”

All this talk on time, 425 posts and what has been resolved? What progress has been made? In a forum dedicated to science and with all participants to this forum having access to the whole world through the internet, I find it a bit unusual that this question of what is time cannot be resolved.

Look, this whole topic on time can be simply resolved and the answer can be found if you just use the process of elimination. Decide what time is NOT untill you narrow it down to what time could be. From there you can then work on what exactly time is, get rid of all the data that does not fit or work when trying to establish the true nature of time.

Here are some examples of how one can approach this topic and weed out what time IS and IS NOT.

Ask yourself questions like these.

Is time like matter? Y/N.

Is time like energy? Y/N.

How is time not like matter?

How is time not like energy?

What other thing that is known to be a real physical thing can time be compared to?

Is time an object?

Is time a force?

Hit the subject from many different angles. Go with what you know is a real existing thing and then compare time to that thing. Use many diferent things.

Use the scientific method to help resolve this issue.

Scientific method refers to the body of techniques for investigating phenomena, acquiring new knowledge, or correcting and integrating previous knowledge. It is based on gathering observable, empirical and measurable evidence subject to specific principles of reasoning. A scientific method consists of the collection of data through observation and experimentation, and the formulation and testing of hypotheses.


If you think that scientific method does not apply or work in discovering what time is, then ask yourself why. What is it about your idea of time that prevents you from scientifically dissecting this subject of time.

This is a very easy question to resolve once you apply 100% science and get rid of any preconceived notions that you may have on what time is. Just do some good old fashioned scientific research and discovery using all the tools that are available and have been used to resolve such questions. This whole subject on one of the basic aspects of physics can be resolved by using the very tools that have been used to find all the facts and data that make up the field of knowledge known as science. Time is not a mystery, this is a perfect opportunity to do some actual research on an issue on which you are unsure of. Simply use science to find out what the answer is.


I still say time is just a concept. Use scientific methods and known data to find out for yourself what time is. Is time only a concept or is it more than that? Use this forum, the internet, and all of your science books to narrow down what time is exactly. If you disagree with me that time is just a concept then just tell me why according to what your research has uncovered.

Come on people! Use standard research to find out what time is, I know you can do it if you just put forth a little effort.

Happy Hunting.

[CraigD]

Originally Posted by steve 9

Is time like energy? Y/N.

This is a puzzling question, analogous to the question “is a width like a rectangle?”

Ignoring complicating theories such as Relativity – assuming the simplest physics capable of describing something like our perception of reality – events are simply 5-dimensional objects, 3 space-like dimensions conventionally called length, width, and height, a mass-like dimension conventionally called mass, and a 4th time-like one conventionally called duration.

To describe energy, or the simpler concept, velocity, one must describe objects with at least 1 space-like, 1 mass-like, and 1 time-like, dimension. Such a 3-dimensional universe, though it doesn’t agree with out intuitive perception of reality, has well defined concepts of distance, velocity, acceleration, force, and work/energy. Without any of these 3 dimensions, it doesn’t.

Asking if time is real strikes me as a miss-ordered questions. A well-ordered questions, I think, is, does a reality described by at least classical mechanics require time. The answer is demonstrably yes.

[Overdog]

Well, all of my instincts tell me that time is somehow real, but until I can put a piece of it under a microscope, I can't prove it.

The best I can do is say that it is a concept, which may or may not have any objective reality.

[steve 9]

Originally Posted by CraigD

Asking if time is real strikes me as a miss-ordered questions. A well-ordered questions, I think, is, does a reality described by at least classical mechanics require time. The answer is demonstrably yes.

So CraigD, What is time? You mention classical mechanics REQUIRE this thing called time, but you do not actually mention what this time thing is. What is time? Stop beating around the bush and just tell us what you think time is. Is it a physical thing, is it a concept, or is it something else? What is time, what is this thing that you say is required by classical mechanics?

[Michaelangelica]

Um, Something humans use clocks to measure?