What is time?

[AnssiH]

You're not wrong, you're just inhibiting yourself. It wasn't that long ago people were honestly trying to figure out if the solar system was geocentric or not. Understand, we had a model that described the motion of the planets in the sky without the 'correct' (earth orbits around the sun) description. So there were two models and neither really worked any better than the other.

 

So, people I'm sure asked which was real - which was in the middle, the sun or the earth. You would have said "faeries vs. elves" and stayed above the stench. Good for you, meanwhile we did figure out which model was correct.

 

Same will no doubt happen with curved spacetime vs. gravitons or many other differences in interpretation we have today. Yeah, believe it or not, one of these interpretations is the more correct one.

 

"faeries vs. elves" :phones:

 

~modest

 

EDIT:

 

We've both dragged this thread off topic. I appreciate that you will want to reply to this, and you should, but we're not getting anywhere and we should respect the topic me thinks.

 

I would just comment quickly that from my perspective, the inhibiting factor is that many people tacitly view the elements of some specific (theirs) valid worldview as ontologically real; i.e. assume those elements exist independent of that particular valid worldview. When they do that, they loose perspective on what sorts of valid models can really be built. They may think any model that does not define "photons" or "electrons" cannot possibly be correct, or indeed, any description where simultaneity is not relative to inertial frame cannot be correct.

 

Likewise, in my view it is not really inhibiting to stay away from the ontological arguments and rather investigate the constraints on valid worldviews (especially as it appears there exists surprisingly specific constraints if you take into account what sorts of assumptions would be undefendable). Even when you don't take any ontological preferences, you can investigate whether geocentric or heliocentric model is valid predictionwise... ...also in this case it is interesting that geocentric model can be twisted into a valid view by changing your perspective on space and inertia and such things - i.e. one could see the situation as geocentrism by changing completely what it means to "go around something". That of course would amount to much more complicated worldview than the heliocentric one.

 

That is to say, someone who did not take any ontological preferences, could have compared the heliocentric & geocentric models, and said over the heated debates; "it is much simpler to explain our night sky by the definitions of the heliocentric model, plus its definitions of space are simpler than what the geocentric model requires. You probably want to use heliocentrism in your descriptions of the situation".

 

That is in fact completely in line to Kuhn's description of scientific revolutions. E.g. some new observation (planets moving backwards for brief moments in our sky) makes the description of the situation more complicated when you describe it in terms of an old model (if you believed in geocentric models, you saw that observation as figure-8 orbits or perhaps as even more complicated motion). But someone realized that by changing some definitions/assumptions, the description of the situation suddenly became much simpler -> heliocentrism.

(That someone is often from a new generation of scientists; someone whose mind was not yet too entangled together with the existing models)

 

It is quite likely that our current scientic models have got some overly complicated ways to describe some situations. Dark matter comes to mind. It is not trivial to make new definitions that yield simpler overall model, but to my knowledge all the attempts to redefine space/gravity to explain away dark matter have been met with fair bit of resistance for no objective reason at all. Dark matter itself is often presumed to be ontologically real element, existing independent of our definitions in our worldviews.

 

Oops that wasn't quite as quick comment as I hoped for... Well I suspect this was useful or interesting commentary for some people anyway... I won't drag this thread off the subject more.

 

-Anssi

[Overdog]

I just googled Time, and discovered that my wife's seemingly (to me) brilliant view of it was developed by Gottfried Leibniz and Immanuel Kant a long "time" ago. I should have known that.

 

Sorry for wasting everyone's "time" with that post.

 

Hmmm...Can the universe waste time?

 

It seems we can conjecture and theorize about time until it runs out. Ah well, it seems this thread is timeless.:phones:

[AnssiH]

I might get some resistance by putting this in the language of physics, but I think it's best described with a lightcone:

 

 

described on wikipedia where the "hypersurface of the present" is outside our past light cone and therefore we do not experience it - we have no direct knowledge of it. I think this implies quite a bit about the workings of time and space. In particular, how our experience is limited to events not spatially separated from us. The further an event is spatially distant from us, the further in the past that event must be.

 

Since you pasted that picture, I should comment that when I was referring to the "ontology of the simultaneity planes", I was talking about what is dubbed "hypersurface of the present" in that picture. With the definitions of relativity, the visualized surface is for an observer who is not moving in that picture. If the red dot was moving in that pictured frame, his "surface of the present" would be tilted. Depending on the observer's speed, it could be tilted in any angle as long as it did not penetrate the light cones.

 

That means, if the observer was changing directions, its "surface of the present" would be said to tilt back and forth in such manner that some events would move through the present "backwards"; i.e. some things around the observer would move backwards in time (of course beyond the sight of the observer).

 

I.e, if you take relative simultaneity as ontologically real, you also assume that things around you in your "present moment" can move backwards in time if you change directions, but you just can't see it.

 

Of course at this point I should remind you that it is possible to build a valid view of reality where such simultaneity planes are not ontologically real. I think that is just one particularly interesting aspect of modern definitions on "time".

 

-Anssi

[Overdog]

Ok all, it's been fun, but I'm beginning to percieve that no matter what time is, this thread is a black hole that is sucking vast quantities of it right out the fabric of my reality. Since I have only a limited supply of it, I'm going to have to leave orbit, now....:phones:

[ldsoftwaresteve]

I have really enjoyed this discussion. I have seen beautifully elegant descriptions from many different points of view and witnessed folks expanding their world to include a little doubt, which I think is very healthy. We're strong enough to move forward with our eyes completely open.

 

And I think I finally understand, at least in part, what DD has been talking about thanks to Ansii's repetition of constraints on worldviews. I may not be smart enough to abstract out those constraints and deal with them as building blocks, but at least I am able to see that if there are patterns in the constraints or relationships between them something pretty important might be identified.

 

Just one more thing and I'm done. I wish we had some tools to go back over this thread and somehow tie things together with other threads. I guess I'm talking about a manual abstraction process where we can 'back out' and look for patterns in arguments, etc.

 

In other words, threads could be of two basic types: initial discussions covering a wide set of views - and mature threads, meaning, the thread has been analyzed and integrated into other structures. I'm not smart enough to do that so somebody else can think about it, ok? :phones:

 

I have to go now for a while. We just bought a house and are moving. So much to do and so little time to do it.

[modest]

Since you pasted that picture, I should comment that when I was referring to the "ontology of the simultaneity planes", I was talking about what is dubbed "hypersurface of the present" in that picture. With the definitions of relativity, the visualized surface is for an observer who is not moving in that picture. If the red dot was moving in that pictured frame, his "surface of the present" would be tilted. Depending on the observer's speed, it could be tilted in any angle as long as it did not penetrate the light cones.

 

That means, if the observer was changing directions, its "surface of the present" would be said to tilt back and forth in such manner that some events would move through the present "backwards"; i.e. some things around the observer would move backwards in time (of course beyond the sight of the observer).

 

I.e, if you take relative simultaneity as ontologically real, you also assume that things around you in your "present moment" can move backwards in time if you change directions, but you just can't see it.

 

Of course at this point I should remind you that it is possible to build a valid view of reality where such simultaneity planes are not ontologically real. I think that is just one particularly interesting aspect of modern definitions on "time".

 

-Anssi

 

I'm glad you clarified that because I had no idea that's what you meant. It's described a bit on wiki's world line:

 

The present instant is defined for a given observer by a plane normal to her/his world line. It is the locus of simultaneous events, and is really three-dimensional, though it would be a plane in the diagram because we had to throw away one dimension to make an intelligible picture. Although the light cones are the same for all observers, different observers, with differing velocities but coincident at an event or point in the spacetime, have world lines that cross each other at an angle determined by their relative velocities, and thus the present instant is different for them. The fact that simultaneity depends on relative velocity caused problems for many scientists and laymen trying to accept relativity in the early days. The illustration with the light cones may make it appear that they cannot be at 45 degrees to two lines that intersect, but it is true and can be demonstrated with the Lorentz transformation. The geometry is Minkowskian, not Euclidean.

 

And your particular objection is called the andromeda paradox:

 

Rietdijk-Putnam argument - Wikipedia, the free encyclopedia

 

which is only a paradox (like so many things in SR) if you assume a person can receive information faster than light or assume people can know things which are impossible to know. In other words, only by making bad assumptions is the relative plane of simultaneity a problem rather than always perfectly consistent with observation.

 

~modest

[Doctordick]

...which is only a paradox (like so many things in SR) if you assume a person can receive information faster than light or assume people can know things which are impossible to know. In other words, only by making bad assumptions is the relative plane of simultaneity a problem rather than always perfectly consistent with observation.

But, my point is that Einstein's picture “is making those bad assumptions” by his definition of time; and it does indeed lead to some subtle problems. Consider a world where clocks accurate enough to be used as “the definition of time” were small enough to wear as wrist watches by everyone. Then everyone would know exactly what time it was (by definition) and no two people would agree as to what time it is. Add to that the fact that things can only physically interact when they exist at the same time and “time” seems to have failed in its purpose. That is why I say “time is not a measurable variable” and it only has meaning along the evolving path of an entity. It is a useful parameter for describing the phenomena impacting the evolution of that entity and any additional properties can not be defended.

 

My definition of time stands! The past is "what we know" and the future is "what we do not know". The present then becomes the boundry (of our knowledge). The fact that we find it convenient to think of what we know (the past) as a collection of "presents" for the purpose of ordering our world view (and the evolution of specific phenomena) does not make time a measureable variable. That is an unjustifieable leap of faith enjendered by the success of Newtonian mechanics. He introduced the idea that the future could be known if the past were known and Einstein's picture is soundly based upon that erroneous illusion. That is precisely the source of the problems between general relativity and quantum mechanics.

 

Have fun -- Dick

[AnssiH]

And your particular objection is called the andromeda paradox:

 

Didn't mean to object the validity of relativity at all, if that's the implication you got.

 

btw, rather interesting that the "Rietdijk-Putnam-Penrose argument" refers to something that surfaced as late as in the sixties. That implication regarding "present moment" should be abundantly obvious immediately from the premise of relativity. I'm sure many people have made comments about it, including Einstein.

 

Rietdijk-Putnam argument - Wikipedia, the free encyclopedia

 

which is only a paradox (like so many things in SR) if you assume a person can receive information faster than light or assume people can know things which are impossible to know. In other words, only by making bad assumptions is the relative plane of simultaneity a problem rather than always perfectly consistent with observation.

 

Yes, in other words the simultaneity planes themselves are not observable at all; they are things we have defined as part of relativistic spacetime, but their ontological reality is an assumption.

 

Following that, when people think about the implications of relative simultaneity, many end up assuming there is then no specific "present moment" existing at all; that it's not fair to say whether Andromedian invaders are underway or not, but rather future and past exists "all the time". That obviously leads to rather specific assumptions to explain our subjective experience, where things still seem to be "moving".

 

Well, if that's now clarified, one should pay attention to the possibility of modeling reality with absolute simultaneity, or technically with just about any sort of simultaneity. By defining simultaneity as it's defined in relativity, it makes certain aspects of our description of nature very simple. Yet, it being valid does not constraint the reality itself into a static spacetime block in any ontological sense. It is poor judgment when people think relativity = static spacetime.

 

That is not to condone the ontology of absolute simultaneity as much as it is to point out that spacetime is also part and parcel of our conception of reality; A matter of defining (many) things that way. Referring to DD's analysis, it is rather interesting that it seems it is the symmetries in our "definitions of entities" that make relativistic descriptions valid.

 

Ps. Note that the Wikipedia page listed as one of the references "A Rigorous Proof of Determinism Derived from the Special Theory of Relativity".Well, that is simply not valid. Someone is seeing that as "proof" because they take some assumptions in their worldview as ontologically valid, on pure faith.

 

-Anssi

[modest]

But, my point is that Einstein's picture “is making those bad assumptions” by his definition of time; and it does indeed lead to some subtle problems.

 

I think Einstein's definition leads to problems with your world view. His definition has never led to problems of agreement with observation.

 

Consider a world where clocks accurate enough to be used as “the definition of time” were small enough to wear as wrist watches by everyone. Then everyone would know exactly what time it was (by definition) and no two people would agree as to what time it is.

 

Time is relative. What's the problem here?

 

Add to that the fact that things can only physically interact when they exist at the same time and “time” seems to have failed in its purpose.

 

You want Einstein's definition of time to fail in its purpose which would then support your personal philosophy of anti-realism. However, such a thing cannot be managed. Relativity is one of the most successful theories of all time. It has yet to disagree with observation. The only way to attack such a theory is to make a better one that makes better predictions with better theoretical structure. Your sentence above doesn't accomplish that.

 

That is why I say “time is not a measurable variable” and it only has meaning along the evolving path of an entity. It is a useful parameter for describing the phenomena impacting the evolution of that entity and any additional properties can not be defended.

 

By this reasoning length is not a measurable variable. The front and back of a train have spacetime separation and therefore a train has no length. That's not useful.

 

My definition of time stands! The past is "what we know" and the future is "what we do not know". The present then becomes the boundry (of our knowledge).

 

This is not a definition of time. I appreciate that it has meaningful constraints that are related to time. But, taken literally "the future is "what we do not know"" means anything we do not know is in our future. This is untrue because what we "know" is not an exact way of describing our past lightcone.

 

Perhaps you meant to say "we can only know things from our past".

 

The fact that we find it convenient to think of what we know (the past) as a collection of "presents" for the purpose of ordering our world view (and the evolution of specific phenomena) does not make time a measureable variable.

 

Yet there is something (some concept) that distinguishes two past events that are exactly the same in every way except for 'time' that separates them. Your definition makes no allowance for that. It is therefore incomplete at best.

 

That is an unjustifieable leap of faith enjendered by the success of Newtonian mechanics. He introduced the idea that the future could be known if the past were known and Einstein's picture is soundly based upon that erroneous illusion. That is precisely the source of the problems between general relativity and quantum mechanics.

 

Have fun -- Dick

 

I agree that the usefulness of the concept (and the normal definition) keeps it alive and kicking.

 

~modest

[modest]

Yes, in other words the simultaneity planes themselves are not observable at all; they are things we have defined as part of relativistic spacetime, but their ontological reality is an assumption.

 

I think you're the only one assuming it has any ontological reality. I honestly don't think that would be a normal assumption. The present instant is no more real than a world line.

 

~modest

[Doctordick]

Hi modest, I have found your posts to be quite rational; however, you seem to entirely miss the issues I am trying to put forth.

I think Einstein's definition leads to problems with your world view.

I firmly hold that this is a simple consequence of the fact that you have no idea as to what I am saying. You are operating under the presumption that I am presenting an alternate way of explaining these issues of significance. This is not at all the basis of my presentation. My comments are merely addressed to the reasons why the adherents to Einstein's theories totally fail to comprehend the view I am presenting.

 

Reductionism is a conceptual building block of modern science. The philosophical problem with reductionism is the idea of infinite reduction; it is necessary to terminate this reduction at some point and that point is usually referred to as the fundamental ontology which is essentially reality itself. This requires us to “know” reality so we stand around, guessing what this fundamental ontology might be, and measuring our success by building logical structures and comparing them to our experiences. Essentially, this relies on the validity of the very world view we are trying to construct. It is inherently a circular construct.

His definition has never led to problems of agreement with observation.

That is not the issue I am addressing.

Time is relative. What's the problem here?

The problem is the very definition of time.

You want Einstein's definition of time to fail in its purpose which would then support your personal philosophy of anti-realism.

Exactly where did you get the idea that I was suggesting a “philosophy of anti-realism”?

The only way to attack such a theory is to make a better one that makes better predictions with better theoretical structure. Your sentence above doesn't accomplish that.

I am neither suggesting a theory nor complaining about a current theoretical structure. What I am talking about are the constraints which must be satisfied by any epistemological structure. You make it quite clear that you have not understood my opening arguments., I am sorry; you may be a very intelligent person but you obviously have no idea as to what I am talking about. I am not at all surprised by this as I am working with a perspective on reality which, to my knowledge, no one has ever taken. (Anssi is of course a specific exception, leading me to suspect there are others, whom I have never had contact with, who have at least thought about these issues.)

 

But that is all beside the point. What is significant is that I have derived a fundamental equation which must be valid for any self consistent epistemological construct. The structure and the implications of this equation should be examined carefully; something which the entire academic community has utterly refused to do.

By this reasoning length is not a measurable variable. The front and back of a train have spacetime separation and therefore a train has no length. That's not useful.

Perhaps this is true; if you understand the issues, show me the consequences of such a proposition.

This is not a definition of time.

That appears to be an assertion! Please show me why I can not use that as a definition of time!

I appreciate that it has meaningful constraints that are related to time. But, taken literally "the future is "what we do not know"" means anything we do not know is in our future.

Are you asserting that there exist things you do not know which are not in your future? It appears that you are asserting that there exists things in the past which you do not know, but that idea presumes that you understand reality. The fact that you assign a time to new knowledge which yields temporal continuity to your world view (i.e., things that occurred in the past) is no defense that these supposed events actually occurred in the past (your awareness certainly occurred in the future).

Perhaps you meant to say "we can only know things from our past".

Now here you show a slight comprehension of the fact that our mental image of reality is based upon what we know of the past. What you miss is the fact that our explanation of the past is free to assign any time parameter to the events of interest having nothing to do with the order in which we came to learn these things.

Yet there is something (some concept) that distinguishes two past events that are exactly the same in every way except for 'time' that separates them.

This is a consequence of your interpretation of these events. You are the one who has decided that these two past events are exactly the same. Have you considered the possibility that you are wrong?

Your definition makes no allowance for that.

Exactly, that is why my deductions are so astounding. It appears that the allowance is simply not a required part of a rational world view.

It is therefore incomplete at best.

Is it now? Then please explain why Schroedinger's equation can be deduced from such a perspective.

 

I am afraid that the real issue here is that you simply do not understand what I am talking about.

 

Have fun -- Dick

[AnssiH]

I am a bit puzzled by your reply. I had to go back to my post to see what exactly did I say, in order to try and understand what are you saying.

 

Yes, in other words the simultaneity planes themselves are not observable at all; they are things we have defined as part of relativistic spacetime, but their ontological reality is an assumption.

 

I think you're the only one assuming it has any ontological reality. I honestly don't think that would be a normal assumption. The present instant is no more real than a world line.

 

By that, do you mean to say that I am the only one to presume, that anyone would assume ontological reality to the "present moment"?

 

Or to the "relativistic present moment"?

 

In our everyday conception of reality, I think just about everyone do assume reality is in some specific state at "present instant" even before they themself see that state.

 

Of course if one assumes the relativistic description of "present moment" to be ontologically correct, they are forced to change their assumptions of how world looks like right "now", beyond their natural senses.

 

Since you say "the present instant is no more real than a world line", I am interested to hear what you think world looks like beyond your sight. Is it a mixture of all the possible states?

 

Also, from a physics standpoint, people regularly make assertions that hinge completely on the assumption that "relativistic present moment" (inside relativistic spacetime) is ontologically correct. For example that "Rigorous Proof of Determinism..." that I just mentioned (and the whole Andromeda invaders Wikipedia page for that matter). And length contraction and isotropic speed of light. They are not ontologically correct descriptions if simultaneity is not ontologically relative. Different models would communicate the same reality rather differently.

 

-Anssi

[ldsoftwaresteve]

DD:

My definition of time stands! The past is "what we know" and the future is "what we do not know". The present then becomes the boundry (of our knowledge).

This is the only definition of time that makes any sense if one's worldview says time has no ontological reality. Everyone who thinks otherwise will fight it tooth and nail.

I don't see how both views can be wrong since a thing cannot both be and not be at the same time, so, at least one view is correct and since they contradict each other .... only one will be correct.

What would the definition of time be from the other perspective?

[Doctordick]

What would the definition of time be from the other perspective?

I have been told many many times that the definition is merely "time is what clocks measure!" I personally find that a rather sloppy definition of time but no one seems to share my discomfort.

 

Have fun -- Dick

[Erasmus00]

That is an unjustifieable leap of faith enjendered by the success of Newtonian mechanics. He introduced the idea that the future could be known if the past were known and Einstein's picture is soundly based upon that erroneous illusion. That is precisely the source of the problems between general relativity and quantum mechanics.

 

This simply isn't true. If it were true, Newtonian mechanics would also fail to be quantized (as you say, Newton introduced the assumption). However, non-relativistic mechanics (Newton) can be quantized, as can special relativistic mechanics with a few subtleties. These theories have the same suppositions about time.

-Will

[Erasmus00]

I have been told many many times that the definition is merely "time is what clocks measure!" I personally find that a rather sloppy definition of time but no one seems to share my discomfort.

 

How then do you define space, other then what rulers measure?

-Will

[swampfox]

My thoughts:

 

It's an unfolding of a dynamic process between two stable states: Need to view the Universe as one big non-linear dynamo that was set in motion by trajecting the pre-existence through a critical point.

 

Time does not exist without change. Before the Big Bang, the pre-existence may have been in a stable state: there was no change, there was no time. Something happened which pushed the pre-existence past some critical point: Like a piece of concrete stressed pass it's breaking point, it abruptly trajected towards some final stable state which it has been moving ever since: Like a vase pushed pass the critical point of balance over the edge of a table: The trajectory of the vase from table to floor is akin to the entire history of the pre-existence as it moves between two stable states with the dynamics of motion between these states being perceived by us as time.