The train and diesel fuel example above, was not about sensing motion or acceleration. Rather it was about viewing two study state references after all the acceleration is done. Both parties go into the final references, blind to any energy balance. This allows both references can apply the relative reference assumption in good conscience. — wellwisher

Fine. The total energy and momentum is conserved in the frames of each of the observers, but they're not the same to each other.
A rock (as a sole existent) in a frame where it is stationary has zero total momentum, where in a different frame where it is moving, the same rock has nonzero momentum. Conservation of momentum is within one frame and does not mean that energy or momentum is the same in different frames. You seem to think otherwise. All this is Newtonian mechanics.

However, since a third party knows the energy conservation answer before the two references tell us what their reference appears to say, we have a way to prove if their assumptions are true or an illusion.[/quote]Wrong. The total energy was always different in the different frames. It changed in neither, since it is conserved.

If we did not know how much fuel was used such that the energy balance was left open ended, then the illusion would work.

Fuel consumption does not change total energy. It just changes form from chemical energy to kinetic energy and heat. Total energy is conserved in both frames, but was never the same in either frame.

The train and landscape may not be a good example, since rational common sense would say the landscape can't move, unless the entire earth was moved, which is unlikely due to the energy needed.

It doesn't take energy to move or even accelerate. It takes force. The Earth happens to move quite a bit with significant acceleration, all without expenditure of energy. The velocity of Earth is entirely dependent on the frame in which it is considered. Its acceleration is not frame dependent, and is about .06% of the acceleration of a dropped rock here on Earth.

When we look at the universe , we do not have an accurate energy balance. The idea of no preferred reference or center of the universe tells us that. We know the Conservation of energy applies, but we don't have a hard starting number.

We actually have a starting number for energy, which is zero. Gravitaional potential energy is negative, and it seems to exactly cancel out the positive energy. Total momentum also seems to be zero from any viewpoint or frame, which is unintuitive, but it follows from the universe being infinite, to which any finite adjustment for frame is meaningless.

Metaphysician Undercover,

Physical time is the concept time used in physics. Physics as an empirical science doesn't make metaphysical claims, but only makes models that have predictive value. The predictions pertain to the empircal world, but models themselves do not necessarily.

How we use clocks and agree upon time, also don't necessarily make metaphysical claims about time. It's just a convention that has pragmatic value if you will. Let's call that conventional time.

We do not experience time as such, we experience change or motion. Anything that makes definate claims about time goes beyond that and is metaphysics, because it cannot be veryfied or falsified by physical phenonoma. That is metaphysical time.

Physical time is the concept time used in physics. — ChatteringMonkey

Any concept, in the sense that it is "a concept" is metaphysical. Do you not agree? Unless you subscribe to Platonic realism, in which concepts are eternally existing independent things, every concept is based in, and derived from metaphysical principles. But even Platonic realism is a metaphysical stance so the nature of "a concept", is still metaphysical.

Physics as an empirical science doesn't make metaphysical claims, but only makes models that have predictive value. — ChatteringMonkey

I agree with this, but physics, as an empirical science utilizes metaphysical principles, just like any other science does. The nature of "space", the nature of "time", and the nature of "spacetime" are such metaphysical principles. What space is, what time is, and the relationship between these, what spacetime is, is not itself empirical science. These are metaphysical principles. What space is, and what time is, and the relation between them, has not been empirically observed. So I agree, it is as you say, "science doesn't make metaphysical claims", but physicists use metaphysical claims in their activities, such as the assumptions about the relationship between space and time. These assumptions are utilized in the model building.

How we use clocks and agree upon time, also don't necessarily make metaphysical claims about time. It's just a convention that has pragmatic value if you will. Let's call that conventional time. — ChatteringMonkey

Unless it is completely random, any convention is based in metaphysical claims. Conventions concerning time are clearly not random, therefore they are based in metaphysical claims.

We do not experience time as such, we experience change or motion. — ChatteringMonkey

I think you are confusing "experience" with "observation". We observe change and motion. "Experience" refers to facts, knowledge, which we abstract from the observations. Time is such an abstraction, so it is classed with "experience".

Anything that makes definate claims about time goes beyond that and is metaphysics, because it cannot be veryfied or falsified by physical phenoma. That is metaphysical time. — ChatteringMonkey

Quite right ChatteringMonkey, and this is exactly why physics utilizes metaphysical claims about time. Physics utilizes claims about space and time which go beyond direct observation of space and time. How could one even directly observe space and time? We observe the activities of physical things. We make metaphysical claims about space and time (these are things which have not been directly observed so the claims are metaphysical). When we abstract principles concerning the nature of space and time from these observations of activities of physical things, we make metaphysical claims. These metaphysical principles are utilized by physicists.

.

OK, I think I understand what you are arguing now. You are saying that some metaphysicians such as presentists, claim that human beings experience the passing of time. Others. like eternalists claim that what human beings experience and call "the passing of time" , is not really the passing of time, it's something different. — Metaphysician Undercover

I wouldn't call all of them metaphysicians since most people have no idea that some of their assumptions fall under the category of metaphysics. I like to confine that word to those that have given the matter explicit thought, such as those on these forums.

Further, you have already claimed that there is something called "the passing of time", which physicists measure with clocks.

That was your claim. Mine was that clocks measure physical time (duration), and they do so accurately. Furthermore, I assume (cannot prove) that human experience is a physical (natural) process that measures time similar to clocks, so what we experience is physical time, not metaphysical time.

My opinion, is that this distinction you make is unwarranted. I think that what a metaphysician refers to as "the passing of time" is the exact same thing as what the physicist refers to as "the passing of time".

Yes, I've noticed this.

The two, the metaphysician, and the physicist, just utilize different measurement techniques, one the human experience, the other a physical clock. This is very clear from the fact that human beings synchronize their experience with the clock, in our day to day life. That the physicist employs a more accurate measurement technique than the metaphysician is irrelevant to the fact that the two are measuring the very same thing.

Agree that they're measuring the very same thing, but none of it is metaphysical. The interpretational difference (flow or not flow, 4D spacetime or 3D state that changes at some unitless rate) is undetectable, and the rate of that flow (if it exists) is undetectable since experience would be the same if the rate was halved, tripled, or there was no rate.

I think we are talking past each other. Sure, metaphysical time is an interpretation of empirical physical time. In that sense, they are the same thing. But experience and empirical tests are all the same thing, and none of that makes any difference to the various valid interpretations. If you think the 4D model would result in a different experience, then you don't understand it or the interpretation is invalid. If the universe changes in time, the rate of that change is inexpressible, let alone measurable. If the rate changed, no device or experience would detect that. That flow or the rate of it is nonexistent in eternalism, but is the thing that I refer to as metaphysical time.

That means there is no metaphysical time in eternalism. The phrase is simply a reference to an ontological addition made by a different view. Time is pure physical under eternalism, and is essentially a 4th dimension of a single structure that has no present state.
An eternalist would say time is real if the structure is real. Time has the same ontology as space.
A presentist would say time is real because there is a real current state of space.
Asking both if time is real results in them talking past each other, and I think we're doing that.

Metaphysician Undercover,

No i don't agree that concepts or abstractions are metaphysical, if we only use them because they have utility, and don't believe they literally exist. And I think that platonic realism is a prime example of metaphysics because there the concept are seen as real.

And i don't think that concepts in physics are metaphysical for the same reason, because they don't pretend to make claims about what is real. They only really care, or are supposed to anyway, about models having predictive value. The models are just equations, and like a map, they are not the world itself.

That was your claim. Mine was that clocks measure physical time (duration), and they do so accurately. Furthermore, I assume (cannot prove) that human experience is a physical (natural) process that measures time similar to clocks, so what we experience is physical time, not metaphysical time. — noAxioms

OK, so it is exactly as I argued, there is absolutely no difference between what you call "physical time" and what you call "metaphysical time". What human beings experience as the passing of time, and what physicists measure as duration are each, both the exact same thing, under different names. You choose to call this "physical time". But, that these are both the same is a metaphysical principle, so it is really "metaphysical time", and you are improperly calling it "physical time".

Agree that they're measuring the very same thing, but none of it is metaphysical. — noAxioms

This is where I think the root of your mistake lies. Duration is not a physical thing. Therefore if there is something which is measured as duration and it is called "time", time is not physical and so it must be metaphysical.

I think we are talking past each other. — noAxioms

I don't think it's the case that we're talking past each other. I am insisting that "time" is a metaphysical subject, and you are insisting that "time" is a physical subject, and we are both giving the reasons for our respective beliefs.

What confuses me though, is that you allow that there is both a "metaphysical time" and a "physical time". For the sake of argument, let's suppose that both physics and metaphysics may each study, in its own way, the subject of time. This does not mean that there are two distinct subjects, metaphysical time and physical time, it simply means that there are two distinct ways of studying the same subject, time.

That means there is no metaphysical time in eternalism. — noAxioms

I don't see how you can say this. Eternalism is itself a metaphysical view of time, so you cannot say that there is no metaphysical time in eternalism, that doesn't make sense. It seems like what you are arguing is that time is really a physical subject, and there is no such thing as "metaphysical time", i.e. time as a metaphysical subject. You are arguing that any metaphysician who thinks that time is a metaphysical subject is actually wrong, because real time is a physical subject and there is no such thing as time as a metaphysical subject.

But I think that you are actually wrong. Time is not a physical thing, we cannot observe it with our senses. We observe change and motion and abstract the concepts of time and space, so time and space are not physical things at all, they are metaphysical. So I think that time is really only a metaphysical subject, having no empirically observable existence, and there is no such thing as "physical time".

No i don't agree that concepts or abstractions are metaphysical, if we only use them because they have utility, and don't believe they literally exist. And I think that platonic realism is a prime example of metaphysics because there the concept are seen as real. — ChatteringMonkey

But even if you assume that concepts are not "real" in the sense of Platonic realism, this is still a metaphysical assumption. So no matter how you approach the existence of concepts and abstractions, this is a subject of metaphysics. Whether you affirm or deny that concepts "literally exist" you are taking a metaphysical stance.

And i don't think that concepts in physics are metaphysical for the same reason, because they don't pretend to make claims about what is real. They only really care, or are supposed to anyway, about models having predictive value. The models are just equations, and like a map, they are not the world itself. — ChatteringMonkey

Perhaps, a well-disciplined physicist will never claim that the concepts utilized in physics make any claims about what is real, and respect that only metaphysics does this. That is actually the point I am making, that we must turn to metaphysics for claims about what is real But most people do think that the concepts used in physics make claims about what is real. So for instance, when No Axioms talks about the physicist's concept of time, and the measuring of duration, I think that No Axioms believes that "duration", as that which is measured, is something real. Otherwise "duration" and "time" refer only to something metaphysical, and this would undermine No Axiom's argument.

Time and Space are dimensions of LIFE akin to length, width and height/depth. They may not be things in the tangible manner but they are things in terms of their effect on phenomena. For example, "how could a person perceive 3-dimensions if they were blinded against any one of its parameters?"
Having given the above opening, I posit that 'space-time' is incomplete in the way we represent it. For it to fully equate to our 3-D model of LIFE, a third parameter must be included. I insist it should be 'space-time-form'. Thus you have, "TIME - a representation of transiency/change (rate); SPACE - a representation of awareness/presence (range); and FORM - a representation of force/structure (quality and quantity)."

[Quality and quantity should be understood in analogy to how mass and volume interact to give density. There is a particular quality to every quantity, and vice-versa, so that every part of LIFE is balanced against these two parameters to determine an inherent condition which these two factors represent.]

I hear arguments about time-travel and often wonder why people don't realize how ridiculous they sound. (Perhaps I sound just as ridiculous to them when I refute it!) Anyway, there is a particular theory that I instinctively deny even without recourse to any viable experiments in its support. That is:

"According to relativity, nothing can travel faster than light. If we therefore sent a spaceship to our nearest neighboring star, Alpha Centauri, which is about four light-years away, it would take at least eight years before we could expect the travelers to return and tell us what they had found. If the expedition were to the center of our galaxy, it would be at least a hundred thousand years before it came back. The theory of relativity does allow one consolation. This is the so-called twins paradox mentioned in Chapter 2. Because there is no unique standard of time, but rather observers each have their own time as measured by clocks that they carry with them, it is possible for the journey to seem to be much shorter for the space travelers than for those who remain on earth. But there would not be much joy in returning from a space voyage a few years older to find that everyone you had left behind was dead and gone thousands of years ago. So in order to have any human interest in their stories, science fiction writers had to suppose that we would one day discover how to travel faster than light. What most of these authors don’t seem to have realized is that if you can travel faster than light, the theory of relativity implies you can also travel back in time, as the following limerick says:

There was a young lady of Wight
Who traveled much faster than light.
She departed one day,
In a relative way,
And arrived on the previous night

The point is that the theory of relativity says that there is no unique measure of time that all observers will agree on. Rather, each observer has his or her own measure of time. If it is possible for a rocket traveling below the speed of light to get from event A (say, the final of the 100-meter race of the Olympic Games in 2020) to event B (say, the opening of the 100,004th meeting of the Congress of Alpha Centauri), then all observers will agree that event A happened before event B according to their times. Suppose, however, that the spaceship would have to travel faster than light to carry the news of the race to the Congress. Then observers moving at different speeds can disagree about whether event A occurred before B or vice versa. According to the time of an observer who is at rest with respect to the earth, it may be that the Congress opened after the race. Thus this observer would think that a spaceship could get from A to B in time if only it could ignore the speed-of-light speed limit.
However, to an observer at Alpha Centauri moving away from the earth at nearly the speed of light, it would appear that event B, the opening of the Congress, would occur before event A, the 100-meter race. The theory of relativity says that the laws of physics appear the same to observers moving at different speeds. This has been well tested by experiment and is likely to remain a feature even if we find a more advanced theory to replace relativity. Thus the moving observer would say that if faster-than-light travel is possible, it should be possible to get from event B, the opening of the Congress, to event A, the 100-meter race. If one went slightly faster, one could even get back before the race and place a bet on it in the sure knowledge that one would win."
- A Brief History in Time by Stephen Hawking (Chapter 10).

[The above statement does not represent Stephen Hawking's theory of time-travel, rather, it is one of the more popular notions which he has discussed in the book.]

Firstly, time is not linear. It is a kind of a vector with a shifting magnitude and a variable direction (my own theory). Secondly, there is no theory of relativity which states that, 'nothing is faster than light'. Thirdly, even in Einstein's time, it was known that some light had greater frequencies than others and that the spectrum as they had discovered thus far was still quite incomplete and therefore white light could not be used as a standard of measure. Also, electrons could not be used as a standard of measure because they had begun to realize that they may not be the smallest/simplest organization of LIFE. Fourthly, we know that, any particle, whatever its characteristics, must take time while moving from point A to B which are separated by a certain distance. No matter how fast the movement, there will always be a delay as it traverses the space between the points A and B unless the particle lies over both points and therefore does not move. Therefore the idea that time could run backwards is absolutely absurd.

Lastly, I must reiterate that without understanding the 'Form' factor, those who theorize on time-travel would only be whistling dixie. There is a reason why every form, every body, every system/organization, has its unique inherent qualities. To begin assumptions where spacecrafts and people move at the speeds of light or beyond is in great disregard to the quality of the bodies involved. Even at the low speeds of boats (sometimes canoes), cars, planes, etc, there are people who get affected => sea-sick, car-sick, jet-lag. Why then would they jump to the conclusion that a huge metal chamber or the human system can suffer such torture as being propelled at the speed of light. Not unless they believe once the people were dead then their ghosts will whizz off against the spin of the clock (like in some 'ghost of christmas past' movie).
And for those who think that space-time could be folded or bent, think again. Even if space-time acted as a homogenous material, would it not have properties inherent to itself and its functionality? Then they would also need to be known and manipulated.
Thus, when philosophy hits the reality gong, sci-fi must go bye-bye (I'm still a big trekkie).

To this whole process, I remark that passionate as philosophers may be, they should attempt to keep a tight reign on their fancies else they lead themselves astray, or worse, a horde of fanatics!

THERE IS NO TIME-TRAVEL as we have been led to believe.

* I cannot refute the black-hole or worm-hole theories because I do not know what they (the black/worm-holes) are. However, from what I know about life, creation in six business days is more likely than time-travel.

They may not be things in the tangible manner but they are things in terms of their effect on phenomena. — BrainW

How do we know that time has an effect on phenomena? Does it make things change, or is it merely a measure of change, that is the question.

@ChatteringMonkey

Sorry for that, it wasn't the best way to express that point. What I meant was, "...they are things (factors) in terms of their relation to phenomena."

I hope that makes it clearer.

How do we know that time has an effect on phenomena? Does it make things change, or is it merely a measure of change, that is the question. — ChatteringMonkey

In the absolute sense, time (or any relative factor) does not affect phenomena, rather, phenomena manifest the condition called time. However, even as a relative aspect, it expresses an actual relationship. For example, length, like time, is a measure of something. Because the something is real, its measure must also be real, though relative (limited to that particular relationship only). When two realities interact, e.g., two people, everything about them interact including the conditions they manifest. I think in this way a consequence also becomes a causative aspect. It's like a chain reaction where the first cause is accompanied by the first consequence which then becomes a cause to the next, and so on.