Absolute motion

roosh

This question comes from a discussion on here, and elsewhere, which involved the idea of absolute motion; I just wanted to see what peoples thoughts on the subject were.

Historically, the concept of absolute motion seems to have been thought of as motion relative to an absolute reference frame; where the absolute reference frame is, in practicality, undeterminable. This to me seems to be somewhat of a contradiction in terms, because it suggests that absolute motion is relative i.e. relative to an absolute reference frame.

My understanding of the term "absolute" is

Philosophy

• a value or principle which is regarded as universally valid or which may be viewed without relation to other things:

OED - absolute

That is, what is absolute is not relative to something else; so absolute motion would be motion that is not necessarily relative to something else i.e. it is a kind of motion that is not relative. Absolute motion appears to be a perfectly suitable term in that regard.




In the real world
The above is all pretty theoretical, but I think it can be clarified by reference to real world scenarios, to try and give some contextual meaning.


Car
Imagine you are in a car on a long stretch of straight road; the car is stationary such that there is no relative motion between you and the road or the surrounding landscape.

Now, you start the car, put it into gear and press the accelerator, such that relative motion occurs between you and the road, and landscape. The question is, are you actually moving; does it make sense to you to ask the question, are you actually moving; is the rotation of your tyres propelling you forward?

This can be contrasted with the idea that your car is on a giant conveyor belt, and that when your tyres start rotating you actually remain stationary, and it is the road and surrounding landscape that is "doing the moving".

Would you agree that, in this scenario, even if we cannot determine which is actually "doing the moving", we can deduce that, at least, one or the other has to be actually "doing the moving"?


Escalator
Recall a time when you were on an escalator, or even try it the next time you are on an escalator - we'll say an escalator going up, for the sake of clarity.

As you stand on the escalator, are you actually moving; does the idea of "actually moving" make sense to you?

Would you say that you, and the escalator, are actually moving up, as opposed to the universe shifting around you in such a way as to give rise to the relative motion you would expect if you were "actually moving"?

Is it you and the escalator that are "doing the moving" or is it the entire universe?

If you couldn't determine which is the case, would you agree that, at least one of you has to actually be moving, in an absolute sense?


Walking down the road
As you walk down the road, is you that is actually moving, or are you walking on giant treadmill and it is the surrounding landscape that is actually moving? Do those questions make sense to you - even if you took it for granted what the answer was?



Active and Passive
I suppose the distinction I am trying to make is between active and passive relative motion.

When you drive down the road in your car, there is relative motion between you and the road; scientific principles suggest that we cannot determine the absolute nature of the motion of either object/observer, but can we deduce that the motion must be absolute - even if we can't determine who is absolutely moving?


When you walk down the road, relative motion manifests, but does it make sense to say that it is your active moving which is causing the relative motion to manifest, while the road is passively involved? That is, are you actually moving, or is it the road.

If we cannot determine, by experiment, which one is the true state, can we deduce that it must be one or the other?

stoneill

These examples are relative motion to you as an observer.
Take the car example - if you were to imagine looking down on the road system and see all the cars going in different directions, the occupants of each car are still with the universe moving about them - but only from their point of view.

Same can be said with the other examples - the escalator, what about the girl with the pretty smile on the down escalator - is her universe moving differently from yours?

roosh

stoneill wrote: »

These examples are relative motion to you as an observer.
Take the car example - if you were to imagine looking down on the road system and see all the cars going in different directions, the occupants of each car are still with the universe moving about them - but only from their point of view.

Same can be said with the other examples - the escalator, what about the girl with the pretty smile on the down escalator - is her universe moving differently from yours?

We can still draw the same conclusion, however; in the examples you give, it is either one or the other that has to be moving. For the occupants of other cars who are "still with the universe moving about them", it is the universe which is actually moving. The same for the girl on the escalator; one or the other has to be actually moving, for the relative motion to manifest.

Of course, it isn't possible to determine which is correct, but we can deduce that at least one of them has to be; and by extension, that it is possible for someone to be wrong.

Joe1919

It is your mind that moves? (Old Zen discussion)

http://www.buddhistdoor.com/oldweb/bdoor/archive/zen_story/zen4.htm

MungBean

Would you agree that, in this scenario, even if we cannot determine which is actually "doing the moving", we can deduce that, at least, one or the other has to be actually "doing the moving"?

Both can be "doing the moving" and everything is moving relative to something else. The car and road move relative to each other.

Roads are not stationary in space and time neither are the buildings that have escalators. If you know as I think you do that these things are not stationary but only stationary relative to an observer then how can you deduce that one or the other be doing the moving and not just moving relative to one another ?

roosh

MungBean wrote: »

Both can be "doing the moving" and everything is moving relative to something else. The car and road move relative to each other.

Roads are not stationary in space and time neither are the buildings that have escalators. If you know as I think you do that these things are not stationary but only stationary relative to an observer then how can you deduce that one or the other be doing the moving and not just moving relative to one another ?

As you mention above, "both can be doing the moving", but that just compounds the point about the existence of absolute motion; as does saying that roads are not stationary in space, nor the buildings.

If we take the example of a car stopped on a road; you are of course correct to say that the earth might not be stationary in space, but this just means we deduce that the earth is absolutely in motion.

But, it is possible for the earth to be moving through space and the car with it, only for the car to subsequently move along the surface of the earth; again, the deduction is that one of them, at least, is actually moving.

If the car and the earth were at rest relative to each other, then there would be no relative motion between them; in order for relative motion to manifest, at least one of them has to "do the moving", otherwise, they would remain at rest relative to each other.

Morbert

No frame of reference is more correct than any other frame of reference, as physics obeys the principle of general covariance. The velocity of an object is a function of the reference frame used. From my frame of reference, a car might be stationary. From the frame of reference of the sun, a car might be travelling at around 30 km/s. From the frame of reference of the galactic centre, the car might be travelling at 220 km/s. No frame of reference is more correct, so no description of the car's velocity is more correct. I.e. The physics is always the same.

So, to take the example tendered here: If we have two objects in motion, relative to each other, we cannot therefore say one reference frame is more correct than the other. I.e. We cannot say one reference frame must be "mistaken". To do so, we would have to assume a state of absolute rest exists, with which to benchmark the motion of the objects, and since no such state is postulated by relativity, or detected by physical evidence, it is a superfluous assumption.

roosh

Morbert wrote: »

No frame of reference is more correct than any other frame of reference, as physics obeys the principle of general covariance. The velocity of an object is a function of the reference frame used. From my frame of reference, a car might be stationary. From the frame of reference of the sun, a car might be travelling at around 30 km/s. From the frame of reference of the galactic centre, the car might be travelling at 220 km/s. No frame of reference is more correct, so no description of the car's velocity is more correct. I.e. The physics is always the same.

So, to take the example tendered here: If we have two objects in motion, relative to each other, we cannot therefore say one reference frame is more correct than the other. I.e. We cannot say one reference frame must be "mistaken". To do so, we would have to assume a state of absolute rest exists, with which to benchmark the motion of the objects, and since no such state is postulated by relativity, or detected by physical evidence, it is a superfluous assumption.

In your reference frame, where the car is stationary, then we cannot deduce that either one is actually moving, so we can ignore cases where objects remain at rest relative to each other; we only need to consider relative motion between objects to make the deduction. The measurement of the velocity, as such, is immaterial, or secondary at best.

We don't necessarily need for one reference fame to be more correct than any other, we only need to deduce at least one of the objects/observers is in absolute motion; this offers certain deductive consequences which we can take into consideration.

You are of course correct that the assumption of an absolute rest frame is a superfluous assumption, as it isn't required for the notion of absolute motion; absolute motion is motion that is not necessarily defined relative to something; attempting to define absolute motion as being relative to an absolute reference frame is to define absolute motion as being relative, which would be a contradiction in terms.

The assumption of absolute rest in relativity is a separate issue entirely.

Morbert

roosh wrote: »

In your reference frame, where the car is stationary, then we cannot deduce that either one is actually moving, so we can ignore cases where objects remain at rest relative to each other; we only need to consider relative motion between objects to make the deduction. The measurement of the velocity, as such, is immaterial, or secondary at best.

We don't necessarily need for one reference fame to be more correct than any other, we only need to deduce at least one of the objects/observers is in absolute motion; this offers certain deductive consequences which we can take into consideration.

You are of course correct that the assumption of an absolute rest frame is a superfluous assumption, as it isn't required for the notion of absolute motion; absolute motion is motion that is not necessarily defined relative to something; attempting to define absolute motion as being relative to an absolute reference frame is to define absolute motion as being relative, which would be a contradiction in terms.

The assumption of absolute rest in relativity is a separate issue entirely.

So long as "absolute motion" does not mean "motion with respect to absolute rest", then there is no major issue. The salient points are

1) Physics is invariant over all reference frames.
2) No reference frame is more or less "true" or "real" than any other.

MungBean

roosh wrote: »

As you mention above, "both can be doing the moving", but that just compounds the point about the existence of absolute motion; as does saying that roads are not stationary in space, nor the buildings.

If we take the example of a car stopped on a road; you are of course correct to say that the earth might not be stationary in space, but this just means we deduce that the earth is absolutely in motion.

But, it is possible for the earth to be moving through space and the car with it, only for the car to subsequently move along the surface of the earth; again, the deduction is that one of them, at least, is actually moving.

If the car and the earth were at rest relative to each other, then there would be no relative motion between them; in order for relative motion to manifest, at least one of them has to "do the moving", otherwise, they would remain at rest relative to each other.

But all your really doing is saying "motion exists". Which it does and can be observed as relative motion. I dont think you can say absolute motion exists without an absolute frame of reference as motion doesnt exist without a frame of reference. Does it ?

Morbert

MungBean wrote: »

But all your really doing is saying "motion exists". Which it does and can be observed as relative motion. I dont think you can say absolute motion exists without an absolute frame of reference as motion doesnt exist without a frame of reference. Does it ?

To phrase this question slightly differently: "Is there any statements we can make about motion that are independent of any reference frame?"

We can construct statements about the relationship between motion and forces, or we can look at formalisms of classical mechanics that relate motion to energy. I.e. We can build physical laws that are the same for all reference frames, but we cannot say "X is absolutely moving" or "Y is absolutely moving".

roosh

Morbert wrote: »

So long as "absolute motion" does not mean "motion with respect to absolute rest", then there is no major issue. The salient points are

1) Physics is invariant over all reference frames.
2) No reference frame is more or less "true" or "real" than any other.

I don't think I'd disagree with any of that, but absolute motion would have certain deductive consequences; not least pertaining to the path length of a photon in a light clock.

That is a separate issue though; the purpose of this thread is just to see if the idea of absolute motion, or "actually moving" makes sense.

roosh

MungBean wrote: »

But all your really doing is saying "motion exists". Which it does and can be observed as relative motion. I dont think you can say absolute motion exists without an absolute frame of reference as motion doesnt exist without a frame of reference. Does it ?

That is essentially all that is being said, that "motion exists"; but, more specifically, that a classification of motion exists that doesn't necessarily require a reference frame to define it.


I would say that absolute motion exists without the need for an absolute frame of reference, because that is what absolute motion is i.e. it isn't relative to anything.

To say that absolute motion requires an absolute reference frame, against which to relate it, is saying that absolute motion is relative motion, or absolute motion is relative (to an absolute reference frame). That would be a contradiction in terms.

Absolute motion would be a simple "yes or no" question; an "either, or" situations:
"is X moving?"
"is Y moving?"
"is X or Y moving?"


Absolute motion will always manifest with relative motion, but there would be a number of possible explanations that can account for the relative motion.

Example
If we take the example of the car on the road, again; when the car starts moving relative to the road, there are 3 main reasons as to why this relative motion can manifest:

1. The earth continued to rotate as normal, and continued, normally, on it's orbit around the sun, and it was the car that actively moved along the surface of the earth.

2. The earth suddenly changed it's rotation, and the turning of the cars wheels lead to the relative motion in a manner similar to someone running the wrong way down an escalator - except with the entire surrounding landscape being tied to the escalator - or akin to someone running on a log spinning in water.

3. Both of the above.


Here we have, again, a case where relative motion is observed, but the active agent, that causes the relative motion between the two objects is different.

It's like being on a train that is stopped, beside another train, in a train station; then the other train pulls out of the station, and for a split second you think that it is your own train that is moving.

You might ask yourself, "are we moving?"; but then you realise, "no it was the other train that was moving". Again, relative motion will occur, but the active role in causing that relative motion is ascribed to either one train, or the other.


Of course, we may not be able to determine which one is actually moving, but we can still deduce that one of them, at least, must be.

roosh

Morbert wrote: »

To phrase this question slightly differently: "Is there any statements we can make about motion that are independent of any reference frame?"

We makes statements about motion that are independent of any reference frame on a daily basis.

When stuck in traffic we say "I'm not moving", or "the traffic isn't moving"; when there is no traffic jam we might say "traffic is moving freely".

We make statements about water and electricity flowing; if we're on a train that is stopped at the train station, and the train beside us starts moving, we often think for a moment "we are moving", only to realise that "it was actually the other train that was moving".

Even though the observed motion is relative in all of these cases, none of the statements make reference to any reference frame; this isn't because relative motion is implied, it's because "actual movement", or absolute motion, is being ascribed to one or the other object

Morbert wrote: »

We can construct statements about the relationship between motion and forces, or we can look at formalisms of classical mechanics that relate motion to energy. I.e. We can build physical laws that are the same for all reference frames, but we cannot say "X is absolutely moving" or "Y is absolutely moving".

The crux of the issue is that, while we cannot definitively say that "X is absolutely moving", or that "Y is asbolutely moving" we can say that "either X or Y is absolutely moving".

Duggys Housemate

Gosh, this is verbose rubbish. The "stopped" train is moving relative to the moving train. It's isn't stopped from the framework of the other train. That's all. If the "moving" train is travelling at v relative to the stopped train, the stopped train is moving at -v relative to the moving train. Ignoring all other movement - the earth, the sun, the galaxy - both are moving relative to the other, neither is stopped.

18AD

To make a phenomenological description of movement (how predictable of me) and the example of the train you give. What tells you that it's the other train that's moving and not you? It's the proprioceptive feeling that you are not moving. When you don't feel the push of the train on you you know it's the other train that's movning. You can actually feel yourself moving or at rest. You settle into the objects movement eventually (hence the moon looking like it revolves around us).

In the three original examples you've given this experience occurs where you experience a change in your own acceleration.

And Zeno's arrow paradox for good measure:

1. When the arrow is in a place just its own size, it’s at rest.

2. At every moment of its flight, the arrow is in a place just its own size.

3. Therefore, at every moment of its flight, the arrow is at rest.

Duggys Housemate

The only thing that makes you feel like the train is "moving" is acceleration, or declaration. Trains tend to move a bit choppily, so you feel the "movement" which is small amounts of bumps etc. - effectively acceleration in a different direction. A totally smooth train would not feel like it is moving, transatlantic aeroplanes mid flight don't really fell like they are moving, you feel it on takeoff or landing, or turning. ( Or choppiness). Anything which changes acceleration or direction will be noticed.

Zeno's paradox has also been answered by calculus.

What this means is simple - the "stopped" train is moving relative to the moving train. Both are moving relative to another train, or plane. Neither train is at absolute rest.

When you look out to see the moving train, on your "stopped train", you are moving relative to it. Which means you are moving.

18AD

Duggys Housemate wrote: »

Zeno's paradox has also been answered by calculus.

How is that? I was under the impression that it couldn't be solved if you assume instants of time have zero duration. The arrow at every instant is moving at 0/0ms.

roosh

Duggys Housemate wrote: »

Gosh, this is verbose rubbish.

Forwarned is forearmed, they say; cheers DH

Duggys Housemate wrote: »

The "stopped" train is moving relative to the moving train. It's isn't stopped from the framework of the other train. That's all. If the "moving" train is travelling at v relative to the stopped train, the stopped train is moving at -v relative to the moving train. Ignoring all other movement - the earth, the sun, the galaxy - both are moving relative to the other, neither is stopped.

It's probably easier to think in terms of the two trains starting at rest relative to each other, where v=0.

Then the relative velocity between them increases to some value (v); the question is how/why does the relative velocity increase; how/why is there relative motion between the two trains?

roosh

18AD wrote: »

To make a phenomenological description of movement (how predictable of me) and the example of the train you give. What tells you that it's the other train that's moving and not you? It's the proprioceptive feeling that you are not moving. When you don't feel the push of the train on you you know it's the other train that's movning. You can actually feel yourself moving or at rest. You settle into the objects movement eventually (hence the moon looking like it revolves around us).

In the three original examples you've given this experience occurs where you experience a change in your own acceleration.

While I would be inclined to agree, I'm not sure if "the science" would, because we supposedly cannot determine, by experiment, if we are moving or not; I'm not sure if this extends to proprioception, or if the equivalence principle would account for the feeling of moving.

But still, the conclusion that could be drawn from that is that either your train or the other train is actually moving - in the example you give above, assuming it doesn't contradict with scientific theory, the conclusion drawn is that your train is actually in motion.

18AD wrote: »

And Zeno's arrow paradox for good measure:

1. When the arrow is in a place just its own size, it’s at rest.

2. At every moment of its flight, the arrow is in a place just its own size.

3. Therefore, at every moment of its flight, the arrow is at rest.

How would the observation of relative motion be accounted for in the context of Zeno's paradox?

Duggys Housemate

Then the relative velocity between them increases to some value (v); the question is how/why does the relative velocity increase; how/why is there relative motion between the two trains?

Because one accelerated? Acceleration is a bit more complex in terms of relativeness than velocity. See here

http://www.physicsforums.com/showthread.php?t=59283

roosh

Duggys Housemate wrote: »

What this means is simple - the "stopped" train is moving relative to the moving train. Both are moving relative to another train, or plane. Neither train is at absolute rest.

When you look out to see the moving train, on your "stopped train", you are moving relative to it. Which means you are moving.

The thing is, it is not possible to verify the claim that neither train is at absolute rest, because, as per the Principle of Relativity, the absolute nature of motion cannot be determined. Either train, but not both, could potentially be at absolute rest, it's just that it cannot be determined if that is the case.

But the idea of absolute rest is not necessarily relevant here; we don't need it; we only need to consider relative motion.

When you look out to see the moving train on your "stopped train", there is relative motion; your train is moving relative to the other train, and vice versa.

But if we bring the trains back to the train station, at rest relative to each other; then there are three possible, basic explanations which can account for the relative motion:
1) The other train actually started moving.
2) The entire universe moved while the "moving train" remained stationary
3) Both 1 & 2

If we consider the possible reality of the situation, where the earth is rotating and orbiting the sun, both trains start of at rest on the earth, but both are still actually moving; then one of the trains subsequently starts, actually moving along the surface of the earth.


We cannot determine which train actually started moving, but we can deduce that, at least one of them, actually, started moving.



It really shouldn't take this many words, because it should be fairly self-evident to anyone who has walked down the street, driven in a car, or ever experienced relative motion of any kind; but apparently it's not that straight forward.

It might be worth taking a walk and asking yourself, as you notice the relative motion; is it me that is moving, or am I walking on a giant conveyor belt i.e. is the universe moving around me?

Even if you cannot determine which one it is, you should be able to deduce that it is either one, or the other.

Duggys Housemate

roosh wrote: »

The thing is, it is not possible to verify the claim that neither train is at absolute rest, because, as per the Principle of Relativity, the absolute nature of motion cannot be determined. Either train, but not both, could potentially be at absolute rest, it's just that it cannot be determined if that is the case.

Neither can be at absolute rest. There is nothing, no frame, from which we consider them at absolute rest. If you can think of one, name it.

When you look out to see the moving train on your "stopped train", there is relative motion; your train is moving relative to the other train, and vice versa.

Yes, both are moving relative to each other.

But if we bring the trains back to the train station, at rest relative to each other;

yes? Both stopped now?

then there are three possible, basic explanations which can account for the relative motion:

Relative motion, so apparently not stopped now. YOU mean acceleration here.

1) The other train actually started moving.
2) The entire universe moved while the "moving train" remained stationary
3) Both 1 & 2

Again, acceleration, which is measurable, and can be agreed on by both parties is what is happening here. Acceleration can be measured. If I stay still and you accelerate you feel the acceleration and I don't, the physics forum I linked to has some on that. Though not all agree.

If we consider the possible reality of the situation, where the earth is rotating and orbiting the sun, both trains start of at rest on the earth, but both are still actually moving; then one of the trains subsequently starts, actually moving along the surface of the earth.

WEll, yes?

We cannot determine which train actually started moving, but we can deduce that, at least one of them, actually, started moving.

We can deduce which one started moving, because acceleration is not like velocity. Acceleration is a change in velocity. the one which started moving accelerated. YOu are confusing accelerating with velocity.

It really shouldn't take this many words,

thats right

because it should be fairly self-evident to anyone who has walked down the street, driven in a car, or ever experienced relative motion of any kind; but apparently it's not that straight forward.
It might be worth taking a walk and asking yourself, as you notice the relative motion; is it me that is moving, or am I walking on a giant conveyor belt i.e. is the universe moving around me?

Or I could stand still and look at the Sun and say is it slowly moving across the sky, as I stay still, or am I on something which is rotating at 700 to 900 miles to hour? If I were to rely on self-evidence it would be the former.


Sure, there is barely a breeze.

roosh

Duggys Housemate wrote: »

Because one accelerated? Acceleration is a bit more complex in terms of relativeness than velocity. See here

http://www.physicsforums.com/showthread.php?t=59283

Why would one of them accelerating cause relative motion to manifest?

Duggys Housemate

roosh wrote: »

The point was that neither of them needs to be at absolute rest; it isn't necessary for the purpose of the deduction.

But further, the earth could be at absolute rest, we just have no way of telling if that is the case.

No, we have a way. Since we can make any object the reference frame which appears to be at rest ( which you are doing with the "stopped" train), and this applies to any object in the universe, therefore we cannot say any object is at absolute rest. All are moving relative to each other.

There is no absolute rest. This seems simple to me, I don't get the difficulty ( I think there are two types of intelligence on this thread. Scientific and literate).

How/why does the acceleration of one train cause relative motion between the two trains?

Because acceleration increases the velocity of one of them relative to the other. Again, simples.

You seem to be suggesting there is a deeper meaning to all of this, but I am not really understanding the confusion.

roosh

Duggys Housemate wrote: »

Neither can be at absolute rest. There is nothing, no frame, from which we consider them at absolute rest. If you can think of one, name it.

The point was that neither of them needs to be at absolute rest; it isn't necessary for the purpose of the deduction.

But further, the earth could be at absolute rest, we just have no way of telling if that is the case.

Duggys Housemate wrote: »

Yes, both are moving relative to each other.

We're agreed on this at least.

Duggys Housemate wrote: »

yes? Both stopped now?

That depends on whether or not the earth is actually moving; but it isn't necessary to consider that for the purpose of the deduction, we only need to consider the relative motion of the trains.

By stopped I simply mean at rest relative to the earth, in the station.

Duggys Housemate wrote: »

Relative motion, so apparently not stopped now. YOU mean acceleration here.

Yes, apologies, I should have added the intermediary step of one train leaving the station.

Also, yes, one of the trains accelerates; but that isn't necessarily the issue.

Duggys Housemate wrote: »

Again, acceleration, which is measurable, and can be agreed on by both parties is what is happening here. Acceleration can be measured. If I stay still and you accelerate you feel the acceleration and I don't, the physics forum I linked to has some on that. Though not all agree.

How/why does the acceleration of one train cause relative motion between the two trains?

Duggys Housemate wrote: »

WEll, yes?

That just compounds the idea of absolute motion, becaue the earth is actually rotating and actually orbiting the sun, as opposed to the other way around.

Duggys Housemate wrote: »

We can deduce which one started moving, because acceleration is not like velocity. Acceleration is a change in velocity. the one which started moving accelerated. YOu are confusing accelerating with velocity.

The equivalence principle would suggest that we can't determine which one started moving, because the acceleration that is experienced could be a gravitational field; it is possible that both were free-falling in a gravitational field and hence experienced no gravity; one of them could then have used their engines (or something might have happened the earth) to cause them to remain stationary in a gravitational field, and hence experience what they think is acceleration.

Of course, given this scenario, we can still conclude that either one or the other actually moved, or was moving.

Duggys Housemate wrote: »

Or I could stand still and look at the Sun and say is it slowly moving across the sky, as I stay still, or am I on something which is rotating at 700 to 900 miles to hour? If I were to rely on self-evidence it would be the former.

Sure, there is barely a breeze.

Indeed you could, and under relativity this perspective is just as correct as a reference frame where the earth is rotating and orbiting the sun; but still, even given that scenario we can still deduce that it is either the earth that is actually moving, or it is the sun, or indeed, both might actually be moving, as I would be more inclined to think myself.

roosh

Duggys Housemate wrote: »

No, we have a way. Since we can make any object the reference frame which appears to be at rest ( which you are doing with the "stopped" train), and this applies to any object in the universe, therefore we cannot say any object is at absolute rest. All are moving relative to each other.

There is no absolute rest. This seems simple to me, I don't get the difficulty ( I think there are two types of intelligence on this thread. Scientific and literate).

To suggest that we have a way of determining the absolute nature of motion is counter to the scientific intelligence you believe is in this thread; i.e. to suggest we have a way of determining if an object is at absolute rest or not, is not supported by scientific evidence. The test of the principle of relativity states this quite explicitly.

To re-iterate, the earth could be at absolute rest, we just have no way of telling if it is or not. I think you may, also, have misunderstood what was meant by the "stopped" train, although that is largely due to my ambiguity, for which I apologise.

Duggys Housemate wrote: »

Because acceleration increases the velocity of one of them relative to the other. Again, simples.

How can acceleration increase the velocity of one of them relative to the other?

Duggys Housemate wrote: »

You seem to be suggesting there is a deeper meaning to all of this, but I am not really understanding the confusion.

That is because the confusion is on your part; it might be worth taking a quick walk outside, or even just down a corridor; where you won't be using mathematical reference frames, all you will have is empircal experience.

Take a walk down the hall, notice the relative motion and ask yourself are you actually moving, or is the hall behaving like a treadmill?

Apologies if I'm being too presumptuous that you've been on a treadmill before.

roosh

Just on the link to the thread you posted; am I right in saying that the term "absolute" is taken to mean "agreed on by everyone", if so, then that isn't necessarily what "absolute" means; there are different terms in the english language for that.

Insofar as acceleration is a measured quanity, it is relative, because measurement is, by it's very nature, relative.

This might be what you mean by scientific and literate intelligence, but where science uses the english language, it is probably better to try and use it more scientifically i.e. precisely.

Duggys Housemate

roosh wrote: »

Take a walk down the hall, notice the relative motion and ask yourself are you actually moving, or is the hall behaving like a treadmill?

Alright I am out - as if this is the best that philosophy can do it should be shut down and tossed out of the universities, I hope you are not an standard practicioner. YOu barely understand the terms you are talking about, and you answer back with the same logic, despite it being explained before. I would prefer to pluck my eyebrows out one by one than deal with this level of "knowledge".


Your reference to "common sense" perceptions of motion is meaningless. Humans are designed to perceive things that helped our ancestors.

For what it is worth it doesn't matter whether I am moving, or the hall is a treadmill. Either would do for the mathematics of relative motion, or indeed common sense.

It would be better to put me on a car or some externally powered machine ( otherwiseI would I would be applying energy to pedal or walk).

In this case were the hall moving backwards at a constant velocity I could not tell the difference between that and going forward. This is, in effect, what cartoons and games do. In 2d games ( and cartoons) the landscape scrolls left, and the character stays centred but apparently moving right. In 3d games your character stays centred, and the universe moves around you - that is how it modelled. Press forward, and the physics of the game redraws the road you are on so objects ahead move towards you, meaning they are redrawn bigger. In the logic of the game, moving forward is the same mathematically as bringing the landscape ahead backwards. As we would expect.

Now, back with me to science fora.

roosh

Duggys Housemate wrote: »

Alright I am out - as if this is the best that philosophy can do it should be shut down and tossed out of the universities, I hope you are not an standard practicioner. YOu barely understand the terms you are talking about, and you answer back with the same logic, despite it being explained before. I would prefer to pluck my eyebrows out one by one than deal with this level of "knowledge".

The issue probably lies in the simplicity of it.

The error lies in thinking that it has been satisfactorily explained; ultimately the explanation always comes back to "relative motion causes relative motion", which isn't a sufficient explanation.

As outlined, there are three scenarios which can result in relative motion; all of them involve active movement of one object or another i.e. an object has to actually move i.e. an object has to move absolutely.

Duggys Housemate wrote: »

Your reference to "common sense" perceptions of motion is meaningless. Humans are designed to perceive things that helped our ancestors.

Don't be confused by the term "common sense", I just mean that it is blindingly obvious.

Duggys Housemate wrote: »

For what it is worth it doesn't matter whether I am moving, or the hall is a treadmill. Either would do for the mathematics of relative motion, or indeed common sense.

The error lies in thinking that it doesn't matter; while the mathematics might be the same, there are deductive consequences which apply to the phyiscal world that the mathematics don't seem to highlight.

Duggys Housemate wrote: »

It would be better to put me on a car or some externally powered machine ( otherwiseI would I would be applying energy to pedal or walk).

It doesn't matter either way; the basic question is, are you capable of motion?

Duggys Housemate wrote: »

In this case were the hall moving backwards at a constant velocity I could not tell the difference between that and going forward. This is, in effect, what cartoons and games do. In 2d games ( and cartoons) the landscape scrolls left, and the character stays centred but apparently moving right. In 3d games your character stays centred, and the universe moves around you - that is how it modelled. Press forward, and the physics of the game redraws the road you are on so objects ahead move towards you, meaning they are redrawn bigger. In the logic of the game, moving forward is the same mathematically as bringing the landscape ahead backwards. As we would expect.

Now, back with me to science fora.

You seem to be missing the point; that you cannot tell the difference is entirely immaterial, that there is a difference, by your own admission, is the point.

The computer game example is a useful one, cheers. Again, however, it simply re-iterates the point, either you are actually moving, or the scenery is.

Morbert

roosh wrote: »

We makes statements about motion that are independent of any reference frame on a daily basis.

When stuck in traffic we say "I'm not moving", or "the traffic isn't moving"; when there is no traffic jam we might say "traffic is moving freely".

We make statements about water and electricity flowing; if we're on a train that is stopped at the train station, and the train beside us starts moving, we often think for a moment "we are moving", only to realise that "it was actually the other train that was moving".

Even though the observed motion is relative in all of these cases, none of the statements make reference to any reference frame; this isn't because relative motion is implied, it's because "actual movement", or absolute motion, is being ascribed to one or the other object

All of those statements make reference to a frame of reference. For example, "It was actually the other train that was moving" is from the reference frame of the earth. "We are not moving" is from the reference frame of the train. Water and electricity flow in the reference frame of the circuit. "Traffic is moving freely" in the reference frame of the road/earth.

The crux of the issue is that, while we cannot definitively say that "X is absolutely moving", or that "Y is absolutely moving" we can say that "either X or Y is absolutely moving".

If by this you mean "There is no reference frame which labels both X and Y as stationary." you are correct. You cannot, however, extend this to "At least one of X or Y must be moving with respect to absolute rest." without implicitly assuming absolute rest exists.

18AD

roosh wrote: »

While I would be inclined to agree, I'm not sure if "the science" would, because we supposedly cannot determine, by experiment, if we are moving or not; I'm not sure if this extends to proprioception, or if the equivalence principle would account for the feeling of moving.

But still, the conclusion that could be drawn from that is that either your train or the other train is actually moving - in the example you give above, assuming it doesn't contradict with scientific theory, the conclusion drawn is that your train is actually in motion.

The example I gave demonstrates that you are not the one that's moving, because you don't feel the exceleration of the train you're in. So you conclude it's the other one.

How would the observation of relative motion be accounted for in the context of Zeno's paradox?

I don't think it would be. It's all at rest. Perhaps a perceptual error? The greeks were fond of that.

roosh

Morbert wrote: »

All of those statements make reference to a frame of reference. For example, "It was actually the other train that was moving" is from the reference frame of the earth. "We are not moving" is from the reference frame of the train. Water and electricity flow in the reference frame of the circuit. "Traffic is moving freely" in the reference frame of the road/earth.

"The train is moving" is a statement about the absolute motion of the train, precisely because it doesn't make reference to a reference frame. It means that, regardless of what the train is moving relative to, it is the train that is actively "doing the moving", as opposed to the other object, relative to which it is moving.

Traffic is moving freely doesn't make reference to any reference frame either, it makes reference to the absolute motion of the traffic, because the statement is simply that it is the traffic that is moving - without qualification; this can be contrasted with the other possible cause of the relative motion, that the earth has changed its rotation, and is behaving like a giant conveyor belt/treadmill - akin to your spinning log analogy in another thread. That we cannot determine which is the case doesn't stop us from deducing that it is either one or the other.

To say that "we are not moving" is from the reference frame of the train, doesn't take into account the fact that the observers on the train can define their reference frame in such a way that labels the train as "moving". But, where they do label the train as being "at rest" the conclusion is simply reversed i.e. it is the earth and the surrounding landscape that is "doing the moving".


Reference frames
I think the constant recourse to reference frames might be obscuring the issue, because we are talking about absolute motion which isn't necessarily relative to anything; that we can define reference frames that labels one object as "moving relative to" another is essentially immaterial, because "absolute motion" isn't "moving relative to".

It might be helpful to do a field exercise, where you won't be using mathematical reference frames to define your movement; take a walk down the street, or a corridor, and notice the relative motion. First, notice the lack of relative motion as you stand at rest relative to the surface.

Then recall a time when you've been on a treadmill, and contrast it with a time when you've walked down the street. Now, ask yourself, what must occur for relative motion to occur between you and the area you are in - let's say it's a corridor.

Then start walking down the corridor towards a door; ask yourself, is it you that is moving towards the door while the corridor remains inertial, or are you remaining inertial while the corridor behaves like a treadmill and moves the door towards you?


Try not to get bogged down by the idea that we can define different reference frames which label it differently; because we can, and this isn't in dispute.

Morbert wrote: »

If by this you mean "There is no reference frame which labels both X and Y as stationary." you are correct. You cannot, however, extend this to "At least one of X or Y must be moving with respect to absolute rest." without implicitly assuming absolute rest exists.

If by this you mean that we can extend it to "at least one of X or Y must be moving, without the need to define it relative to absolute rest, because absolute motion is, by definition, not relative to anything", then you are correct.


There seems to be an attachment to the idea of absolute motion being relative to an absolute rest state; but this is a contradiction in terms, because it is saying that absolute motion is relative [to absolute rest]. The idea of absolute motion doesn't require absolute rest, because it is a simple "yes or no", "either, or" question.

When two things are moving relative to each other, it is a question of which one is "actually moving", or even if they are both "actually" moving, in an absolute sense, regardless of how they are labeled by an arbitrary, artificial co-ordinate labeling system.

It's not a question of "am I moving relative to something?", it is a question of "am I moving [full stop]." It can further be extended to the question "are you capable of movement? (without any qualification).

That we cannot tell if we are actually moving or not is immaterial, because where there is relative motion, something must actually be moving.

roosh

18AD wrote: »

The example I gave demonstrates that you are not the one that's moving, because you don't feel the exceleration of the train you're in. So you conclude it's the other one.

I would be inclined to agree with you 18AD, but the principle of relativity says that we cannot determine, by experiment, whether we are actually moving or not. I'm not sure if this extends to proprioception, or to factors that would affect our proprioception to make us think we are moving.


What would your thoughts be on the issue; would you say that absolute motion exist i.e. when you drive down the road are you actually moving, or is the road actually moving; or do you think it must be one or the other?

18AD wrote: »

I don't think it would be. It's all at rest. Perhaps a perceptual error? The greeks were fond of that.

18AD

roosh wrote: »

What would your thoughts be on the issue; would you say that absolute motion exist i.e. when you drive down the road are you actually moving, or is the road actually moving; or do you think it must be one or the other?

I don't know about absolute motion, since your body ignores motion you are with for a while. You don't notice whizzing through space on earth, the same way you don't notice being in a steady moving car.

But the change from one speed to another is defitely perceptible. To use the car example, you can feel the acceleration of your car. You can't tell if everything else is slowing down, it's simply not available information (except perhaps visually).

Also, if you're in a moving car you don't experience the world moving and yourself at rest. You could force the perception but then I'd say you're abstracting from perception.

roosh

18AD wrote: »

I don't know about absolute motion, since your body ignores motion you are with for a while. You don't notice whizzing through space on earth, the same way you don't notice being in a steady moving car.
.

Just to clarify, I meant absolute motion as opposed to inertial motion.

I would agree that accelerated motion is easier to determine, and that's why the example of two observers starting off at rest relative to each other is probably easier to imagine.

But if we take the example of walking down the road; it might be worth doing a little "experiment" the next time you're going for a walk.

Find a stretch of road where you will be walking straight for a reasonable distance; stop, so that you are at rest relative to the road and other objects at rest relative to the earth.

Ask yourself, what has to happen for relative motion to occur between you and the road. Would you agree that one of the following three scenarios would have to occur:

1) The Earth remains inertial, or continues either roating, orbiting, etc. as it is while you are at rest relative to it, and that your walking propels you forward, while the road remains passive.

2) The Earth has to behave like a giant treadmill, and the surrounding scenery has to behave as though on a conveyor belt linked to that treadmill, such that the relative motion results from you "walking on the spot" on a treadmill, while you remain inertial.

3) Both 1 & 2 above.

18AD wrote: »

But the change from one speed to another is defitely perceptible. To use the car example, you can feel the acceleration of your car. You can't tell if everything else is slowing down, it's simply not available information (except perhaps visually).

Also, if you're in a moving car you don't experience the world moving and yourself at rest. You could force the perception but then I'd say you're abstracting from perception

Would you agree though, that in a moving car, either your car is moving, or the world is?

Bearing in mind that the earth can be moving through space, and your car can, subsequently, move along the surface of the earth.

18AD

roosh wrote: »

Just to clarify, I meant absolute motion as opposed to inertial motion.

I would agree that accelerated motion is easier to determine, and that's why the example of two observers starting off at rest relative to each other is probably easier to imagine.

But if we take the example of walking down the road; it might be worth doing a little "experiment" the next time you're going for a walk.

Find a stretch of road where you will be walking straight for a reasonable distance; stop, so that you are at rest relative to the road and other objects at rest relative to the earth.

Ask yourself, what has to happen for relative motion to occur between you and the road. Would you agree that one of the following three scenarios would have to occur:

1) The Earth remains inertial, or continues either roating, orbiting, etc. as it is while you are at rest relative to it, and that your walking propels you forward, while the road remains passive.

2) The Earth has to behave like a giant treadmill, and the surrounding scenery has to behave as though on a conveyor belt linked to that treadmill, such that the relative motion results from you "walking on the spot" on a treadmill, while you remain inertial.

3) Both 1 & 2 above.

If you use your bodily experience to judge what is happening you will feel distinctly different effects if (1) you walk forward or (2) if the world behaves as a treadmill.

If you're just walking you propel yourself.

If the world moves you will have to compensate your balance. And you will feel that it is the earth that has moved. (Unless you have vertigo or something, in which case you might not be able to tell which of you is changing)

I think if you're seeing the world as moving as a treadmill you are abstracting from your experience, since you don't experience the world as moving as a treadmill, unless you force it. In which case I think you're privileging visual experience. (It can certainly look like the world is treadmilling)

Would you agree though, that in a moving car, either your car is moving, or the world is?

Bearing in mind that the earth can be moving through space, and your car can, subsequently, move along the surface of the earth.

As a theoretical point the car and the earth are both moving, flying through space.

From a phenomenological point you will be able to tell whether it is you or the world that is moving. (As in the case of the walking example above)

roosh

18AD wrote: »

If you use your bodily experience to judge what is happening you will feel distinctly different effects if (1) you walk forward or (2) if the world behaves as a treadmill.

If you're just walking you propel yourself.

If the world moves you will have to compensate your balance. And you will feel that it is the earth that has moved. (Unless you have vertigo or something, in which case you might not be able to tell which of you is changing)

I think if you're seeing the world as moving as a treadmill you are abstracting from your experience, since you don't experience the world as moving as a treadmill, unless you force it. In which case I think you're privileging visual experience. (It can certainly look like the world is treadmilling)

Don't get me wrong, I would be in agreement with you; personally I think it is our walking that propels us forward, although I might not have given a decent description of the world as a treadmill; it might be the case that the world is behaving like a treadmill when we are stopped, and we are going around with it, but when we start walking we then start walking against the conveyor belt.

The principle of relativity suggests that we cannot determine if we are actively "doing the moving", or if it is the conveyor belt earth that is actively "doing the moving" i.e. we cannot determine which one is actually moving.

Would you agree that those two options, or those two options combined, represent the only way in which the relative motion between you and the road can be accounted for, in a physical world?

Would you agree that, even if we cannot determine by experiment, whether we are actually in motion, or if the road is actually in motion, we could deduce that, at least, one of us has to be?

18AD wrote: »

As a theoretical point the car and the earth are both moving, flying through space.

From a phenomenological point you will be able to tell whether it is you or the world that is moving. (As in the case of the walking example above)

I would be inclined to agree with you, I think the earth is actually moving through space, and the car along with it; and that the car is subsequently actually moving again along the surface of the earth.

The principle of relativity suggests we cannot definitively say that this is the case; the earth could be at absolute rest, we just have no way of telling. We can also define reference frames that label the earth as stationary and everything else in the universe as in motion. But would you agree that, the fact that the sun and the earth move relative to each other means we can deduce that, at least one of them - and possibly both - is actually moving?

18AD

roosh wrote: »

Don't get me wrong, I would be in agreement with you; personally I think it is our walking that propels us forward, although I might not have given a decent description of the world as a treadmill; it might be the case that the world is behaving like a treadmill when we are stopped, and we are going around with it, but when we start walking we then start walking against the conveyor belt.

I don't think this analogy works. If walking means you walk against the treadmill of earth, then earth is effectively moving omnidirectionally because you can walk against the treadmill in any direction.

The principle of relativity suggests that we cannot determine if we are actively "doing the moving", or if it is the conveyor belt earth that is actively "doing the moving" i.e. we cannot determine which one is actually moving.

Would you agree that those two options, or those two options combined, represent the only way in which the relative motion between you and the road can be accounted for, in a physical world?

Would you agree that, even if we cannot determine by experiment, whether we are actually in motion, or if the road is actually in motion, we could deduce that, at least, one of us has to be?

If I could change the example a bit, just for my own sake. So there would be no experiment that could determine whether when I move my arm, whether it is my arm that I have moved or the entire universe has rotated around my arm?

As an aside: If we stay within the remit of phenomenology (which I'm trying to do) the experience of walking and the ground moving are experientially distinct phenomena. When I walk I am propelling myself, my senses tell me this. When the ground moves I have to adjust my balance, my senses tell me this (but I probably do it automatically). Regardless of experimental verifiability.

Whether either of us is absolutely moving or at rest is beyond the scope of this analysis.

roosh

18AD wrote: »

I don't think this analogy works. If walking means you walk against the treadmill of earth, then earth is effectively moving omnidirectionally because you can walk against the treadmill in any direction.

As far as im aware,that isn't an issue under the theory of reltivity;it is possible to define a reference frame where the Earth moves omnidirectionally.It wont necessarily state that the Earth is behving like a treadmill,but im not really aware of how relative motion could manifest otherwise.

I would say not to get too bogged down in the analogy;just consider it in its simplest form and see id you agree with the deduction. if you're walking down the street,or a corridor might be easier to imagine,or even try; start at one end of the hall,don't walk for a few moments,just consider the scenario;note that there is no relative motion between you and the rest of the corridor. Ask yourself,what must occur for relative motion to manifest?

Would you agree that either you or the hall/universe has to actually move?

Would you agree that,either your walking has to move you towards the other end of the hall,or the hall has to behave like a conveyor belt and move the other end towards you,with your walking motion being akin to walking on a treadmill?

or both of these together i.e. like walking the wrong way down an escalator,but where yur pace is quicker than the escalator.

18AD wrote:

If I could change the example a bit, just for my own sake. So there would be no experiment that could determine whether when I move my arm, whether it is my arm that I have moved or the entire universe has rotated around my arm?

To my understanding,you could define a reference frame that labels your hand as at rest and labels everything else in the universe as "in motion" or moving;if there were a mini-observer on your hand,honey i shrunk the kids style,there is no experiment that either you or he could conduct to determine if it was your hand that moved,or the universe.

but,even assuming that to be the case,would you agree that we could deduce that either your hand actually moved,or the universe did?

18AD

roosh wrote: »

I would say not to get too bogged down in the analogy;just consider it in its simplest form and see id you agree with the deduction. if you're walking down the street,or a corridor might be easier to imagine,or even try; start at one end of the hall,don't walk for a few moments,just consider the scenario;note that there is no relative motion between you and the rest of the corridor. Ask yourself,what must occur for relative motion to manifest?

Would you agree that either you or the hall/universe has to actually move?

Would you agree that,either your walking has to move you towards the other end of the hall,or the hall has to behave like a conveyor belt and move the other end towards you,with your walking motion being akin to walking on a treadmill?

or both of these together i.e. like walking the wrong way down an escalator,but where yur pace is quicker than the escalator.

Ok.

Without saying anything about absolute motion or anything, the phenomenological approach says that you can tell whether either you or the hall moves. Whichever of you moves is experientially distinct.

So if you walk, you move.
If the hall moves, you will walk as well (or fall over) but you will experience it as the hall moving.

Although both may appear, visually, exactly the same, they are experientially distinct.

So yes, you can tell which is moving.

To my understanding,you could define a reference frame that labels your hand as at rest and labels everything else in the universe as "in motion" or moving;if there were a mini-observer on your hand,honey i shrunk the kids style,there is no experiment that either you or he could conduct to determine if it was your hand that moved,or the universe.

but,even assuming that to be the case,would you agree that we could deduce that either your hand actually moved,or the universe did?

Again, experientially, I actually move my hand. I move it, I can feel it moving, because I move it. I like to move it, move it.

This is wild. So if I move my hand it is conceivable that I'm actually rotating the entire universe around my hand, instead of just moving my hand? I think for this view to be believable you have to remove agency. Otherwise by will alone I shift the entire universe just to reach my glass of water. That would mean that my will permeates the entire cosmos. (Which it does, but that's a lesson for another day)
Or you could just be a determinist. But that's so dated these days. :pac:

Morbert

roosh wrote: »

"The train is moving" is a statement about the absolute motion of the train, precisely because it doesn't make reference to a reference frame. It means that, regardless of what the train is moving relative to, it is the train that is actively "doing the moving", as opposed to the other object, relative to which it is moving.

Traffic is moving freely doesn't make reference to any reference frame either, it makes reference to the absolute motion of the traffic, because the statement is simply that it is the traffic that is moving - without qualification; this can be contrasted with the other possible cause of the relative motion, that the earth has changed its rotation, and is behaving like a giant conveyor belt/treadmill - akin to your spinning log analogy in another thread. That we cannot determine which is the case doesn't stop us from deducing that it is either one or the other.

To say that "we are not moving" is from the reference frame of the train, doesn't take into account the fact that the observers on the train can define their reference frame in such a way that labels the train as "moving". But, where they do label the train as being "at rest" the conclusion is simply reversed i.e. it is the earth and the surrounding landscape that is "doing the moving".


Reference frames
I think the constant recourse to reference frames might be obscuring the issue, because we are talking about absolute motion which isn't necessarily relative to anything; that we can define reference frames that labels one object as "moving relative to" another is essentially immaterial, because "absolute motion" isn't "moving relative to".

It might be helpful to do a field exercise, where you won't be using mathematical reference frames to define your movement; take a walk down the street, or a corridor, and notice the relative motion. First, notice the lack of relative motion as you stand at rest relative to the surface.

Then recall a time when you've been on a treadmill, and contrast it with a time when you've walked down the street. Now, ask yourself, what must occur for relative motion to occur between you and the area you are in - let's say it's a corridor.

Then start walking down the corridor towards a door; ask yourself, is it you that is moving towards the door while the corridor remains inertial, or are you remaining inertial while the corridor behaves like a treadmill and moves the door towards you?


Try not to get bogged down by the idea that we can define different reference frames which label it differently; because we can, and this isn't in dispute.

What is in dispute is whether or not a statement like "John is travelling at 60 mph." implies a reference frame that is no more or less true than a reference frame where "John is stationary". That is the crux of the issue. You disagree with the postulate that no reference frame is more or less correct than any other. I suspect this is because you want to recover presentism from relativity.

If by this you mean that we can extend it to "at least one of X or Y must be moving, without the need to define it relative to absolute rest, because absolute motion is, by definition, not relative to anything", then you are correct.

I don't mean that. You must always define a reference frame when describing motion. To quote Einstein himself.

"Strictly speaking, one should not, e.g., say that the earth moves around the sun in an ellipse, since this statement presupposes a coordinate system in which the sun is at rest, … In the investigation of the solar system nobody will employ a coordinate system at rest relative to the terrestrial body, since that would be impractical. But in principle such a coordinate system is according to the general theory of relativity fully equivalent to every other system."

There seems to be an attachment to the idea of absolute motion being relative to an absolute rest state; but this is a contradiction in terms, because it is saying that absolute motion is relative [to absolute rest]. The idea of absolute motion doesn't require absolute rest, because it is a simple "yes or no", "either, or" question.

When two things are moving relative to each other, it is a question of which one is "actually moving", or even if they are both "actually" moving, in an absolute sense, regardless of how they are labeled by an arbitrary, artificial co-ordinate labeling system.

It's not a question of "am I moving relative to something?", it is a question of "am I moving [full stop]." It can further be extended to the question "are you capable of movement? (without any qualification).

That we cannot tell if we are actually moving or not is immaterial, because where there is relative motion, something must actually be moving.

If the answer to "Am I moving [full stop]?" is "no". Are they in a state of absolute rest? Any definition of "absolute motion" which encompasses a state of "absolute rest" or "absolute 0 motion" is not supported by relativity. That is the problem with your understanding of motion.

Morbert

18AD wrote: »

Ok.

Without saying anything about absolute motion or anything, the phenomenological approach says that you can tell whether either you or the hall moves. Whichever of you moves is experientially distinct.

So if you walk, you move.
If the hall moves, you will walk as well (or fall over) but you will experience it as the hall moving.

Although both may appear, visually, exactly the same, they are experientially distinct.

So yes, you can tell which is moving.

Special relativity says you can detect "non-uniform" i.e. accelerated motion. (This is how the twin paradox is solved) So you can detect if the hall accelerates, but you cannot detect, say, its 230 km per second motion of the hall with respect to the centre of the galaxy.

roosh

Morbert wrote: »

What is in dispute is whether or not a statement like "John is travelling at 60 mph." implies a reference frame that is no more or less true than a reference frame where "John is stationary". That is the crux of the issue. You disagree with the postulate that no reference frame is more or less correct than any other. I suspect this is because you want to recover presentism from relativity.

Ok, I think I see where the issue lies; I'm not sure if I'll be able to illucidate it fully but hopefully, with some patience, on both our parts, I will be.

First, it is necessary to highlight that the implication of a preferred reference frame implied by the statement "John is travelling at 60mph", is not in dispute. I entirely agree that it is possible to define a reference frame which labels John as traveling at 60mph, as it is to define one where he is "at rest", just as one can be defined where his relative motion is that between him and the centre of the galaxy.

What is in dispute is the statement "John is moving", and whether or not this makes sense without reference to a reference frame; the contention is that, without this reference to a reference frame, the statement is a statement about John's absolute motion, precisely because it is a statement about John's motion without reference to a reference frame i.e. it is a statement about his state of motion, not what he is moving relative to.

The intention here isn't to try to find a way to recover presentism from relativity; this is entirely independent of the concept of presentism, and I'm not even sure if this concept of absolute motion will result in the conclusion of presentism. I personally think the universe is presentist, but that isn't something which plays a role in examining the relative motion between two bodies. This is simply a question of trying to develop a more accurate view of the world; this entails developing an understanding of what existing scientific theories say about the world and subjecting them to critical questioning.

The crux
The crux of the issue isn't so much whether there is a preferred reference frame, it's about what logical deductions we can make from about those reference frames. I see no issue with the idea of equally valid reference frames, so long as it is qualified with the idea that an observers instruments might be contracted by an amount unknown to themselves.

It comes down to something which doesn't seem to be illucidated by mathematical reference frames - that an observers instruments are contracted by an amount unknown to themselves is one such issue - to borrow 18ADs term, it comes down to a phenomenological description of the cause of the relative motion between two bodies.

Where there is relative motion between me and the street, either the earth has to be behaving like a giant treadmill, or spinning log as you mentioned elsewhere, or the earth is passive while I am actively "doing the moving", and my walking is propelling me forward.

The Earth can be moving relative to any other object in the universe, and us along with it, but the subsequent relative motion between us and the street has to be accounted for by one, or both, of the scenarios above. This offers three possible explanations as to how/why relative motion occurs between us and the street, one of which has to be correct. We can still define equally valid reference frames which label either as moving, but the three scenarios outlined have deductive consequences.

Morbert wrote: »

I don't mean that. You must always define a reference frame when describing motion. To quote Einstein himself.

"Strictly speaking, one should not, e.g., say that the earth moves around the sun in an ellipse, since this statement presupposes a coordinate system in which the sun is at rest, … In the investigation of the solar system nobody will employ a coordinate system at rest relative to the terrestrial body, since that would be impractical. But in principle such a coordinate system is according to the general theory of relativity fully equivalent to every other system."

I know that's not what you meant, but I'm pretty sure that, when you posted the same thing to me, you knew that that wasn't what I meant either.

You don't need a reference frame when discussing absolute motion, because absolute motion is a statement about the nature of the motion, as opposed to the measurement or qualification of it.

We can define a reference frame which labels the Earth as "in motion relative to the sun", the sun as "in motion relative to the Earth", and both are correct, there is no issue there; but where the sun and the Earth are moving relative to each other, either the sun has to actually be moving, or the Earth does, or both might actually be moving; in which case the instruments - or a light clock at least - of one of the observers will be contracted by an amount unknown to themselves.

Morbert wrote: »

If the answer to "Am I moving [full stop]?" is "no". Are they in a state of absolute rest? Any definition of "absolute motion" which encompasses a state of "absolute rest" or "absolute 0 motion" is not supported by relativity. That is the problem with your understanding of motion.

Did you not mention in the other thread that the state of absolute rest is perfectly compatible with relativity; you can either have it, or not have it?

I think this point, though, indicates a critical issue; the contention is that my "problem with [...] understanding motion" is that what I am saying doesn't agree with relativity, implying that, if it doesn't agree with relativity it can't be right; it almost seems like a conditioned attachment to "what relativity says" is the only way. The conditioning or training seems to be triggered at the first mention of "actually moving" or "absolute motion".

This isn't necessarily a negative thing, it's an entirely natural aspect of the human condition, but it can prevent us from looking at things more objectively. Of course, the same could be said for a belief in presentism, but both would depend on the level of sub-conscious attachment.


The answer to "am I moving [full stop]?" is "I don't know, but I'm either moving [full stop] or I'm not [full stop]."

Again, when you walk down the street and there is relative motion between you and the street, either the street is actively moving, behaving like a giant treadmill or spinning log, or the street is passive while it is you that is actively "doing the moving", or, of course, both could be the case.

All three scenarios have deductive consequences, which affect the path length of a photon in a light clock, and the conclusion that an observers instruments are contracted by an amount unknown to themselves; or at least, that time, for them, is dilated by an amount unknown to themselves.

Actually, this would still preserve the idea of relativity of simultaneity, depending on the assumptions made about the nature of time.

So it has little to do with presentism.

roosh

Morbert wrote: »

Special relativity says you can detect "non-uniform" i.e. accelerated motion. (This is how the twin paradox is solved) So you can detect if the hall accelerates, but you cannot detect, say, its 230 km per second motion of the hall with respect to the centre of the galaxy.

This is somewhat different to a statement about saying which one actually moves.

What does Special Relativity plus the equivalence principle say; does it allow you to say which one "actually moves" i.e. which one is absolutely moving?

Or does it say that we cannot tell which one actually moves, because the hall could be accelerating in a zero gravity region of space, or both you and the hall could be free-falling in a gravity well, and the felt acceleration could just be the hall coming out of free-fall to remain stationary in a gravitational well?

roosh

18AD wrote: »

As an aside: If we stay within the remit of phenomenology (which I'm trying to do) the experience of walking and the ground moving are experientially distinct phenomena. When I walk I am propelling myself, my senses tell me this. When the ground moves I have to adjust my balance, my senses tell me this (but I probably do it automatically). Regardless of experimental verifiability.

Whether either of us is absolutely moving or at rest is beyond the scope of this analysis.

Apologies, I had started replying to the post before you added this part.

I don't think the question of whether either of us is absolutely moving, or at rest, is beyond the scope of the analysis. I would say that we cannot determine which of us (us or the ground) is absolutely moving, but we can deduce that, at least one of us has to be.

As you mention, the experience of us walking and the ground moving are, at the very least, deductively different; I'm not sure if they are necessarily experientially different, because if we take the example of where the earth is always behaving as a treadmill, and you are being carried around with it, then you wouldn't be able to tell the difference; you're walking then would feel like normal walking; however, we can still deduce that they are different.


The question then becomes, what is "absolute motion"; "absolute" as I understand it means something which can be viewed without relation to other things i.e. something that is true, in and of itself. So absolute motion would be a state of motion which cna be viewed without relation to other things.

It would be a simple "yes or no", "either, or" question.

E.g. "Is X moving?" or "Is Y moving?", or "Is X or Y moving?"

On a more personal level it would be the question "Am I moving?", "am I moving, or is it the ground?", or "is our train moving, or is it the other train?".


Boil it down
I think we can boil it down to the following:

A and B start off at rest, relative to each other.

A and B start moving relative to each other.

A labels B as moving relative to A, while B labels A as moving relative to B; which is perfectly valid.

However, in order for relative motion to manifest between A and B, either A had to actually move, or B had to actually move; A and B can be you and the road as outlined above - this represents two different scenarios, with the same result.

However, we cannot determine whether it was A or B that actually moved.

We can deduce that it was either A or B, or both.

18AD

roosh wrote: »

Boil it down
I think we can boil it down to the following:

A and B start off at rest, relative to each other.

A and B start moving relative to each other.

A labels B as moving relative to A, while B labels A as moving relative to B; which is perfectly valid.

However, in order for relative motion to manifest between A and B, either A had to actually move, or B had to actually move; A and B can be you and the road as outlined above - this represents two different scenarios, with the same result.

However, we cannot determine whether it was A or B that actually moved.

We can deduce that it was either A or B, or both.

To look at the experience, yes, one has to actually move. If you are on the train you will only be able to tell either:

Your train has moved. You can't tell if the other one has.
Your train has not moved. You can tell if the other one has.

So if A moves, B is indeterminate.
If not A then B moves.

roosh

18AD wrote: »

To look at the experience, yes, one has to actually move. If you are on the train you will only be able to tell either:

You're train has moved. You can't tell if the other one has.
You're train has not moved. You can tell if the other one has.

So if A moves, B is indeterminate.
If not A then B moves.

I would slightly amend that, to reflect scientific principles, perhaps:

if you are on a train and relative motion arises;

You can't tell if your train has moved
You can't tell if the other train has moved

You can tell that either your train or the other train has moved.

18AD

roosh wrote: »

I would slightly amend that, to reflect scientific principles, perhaps:

if you are on a train and relative motion arises;

You can't tell if your train has moved
You can't tell if the other train has moved

You can tell that either your train or the other train has moved.

Well that makes you a bad phenomenologist. :pac:

Morbert

roosh wrote: »

Ok, I think I see where the issue lies; I'm not sure if I'll be able to illucidate it fully but hopefully, with some patience, on both our parts, I will be.

First, it is necessary to highlight that the implication of a preferred reference frame implied by the statement "John is travelling at 60mph", is not in dispute. I entirely agree that it is possible to define a reference frame which labels John as traveling at 60mph, as it is to define one where he is "at rest", just as one can be defined where his relative motion is that between him and the centre of the galaxy.

What is in dispute is the statement "John is moving", and whether or not this makes sense without reference to a reference frame; the contention is that, without this reference to a reference frame, the statement is a statement about John's absolute motion, precisely because it is a statement about John's motion without reference to a reference frame i.e. it is a statement about his state of motion, not what he is moving relative to.

The intention here isn't to try to find a way to recover presentism from relativity; this is entirely independent of the concept of presentism, and I'm not even sure if this concept of absolute motion will result in the conclusion of presentism. I personally think the universe is presentist, but that isn't something which plays a role in examining the relative motion between two bodies. This is simply a question of trying to develop a more accurate view of the world; this entails developing an understanding of what existing scientific theories say about the world and subjecting them to critical questioning.

The crux
The crux of the issue isn't so much whether there is a preferred reference frame, it's about what logical deductions we can make from about those reference frames. I see no issue with the idea of equally valid reference frames, so long as it is qualified with the idea that an observers instruments might be contracted by an amount unknown to themselves.

It comes down to something which doesn't seem to be illucidated by mathematical reference frames - that an observers instruments are contracted by an amount unknown to themselves is one such issue - to borrow 18ADs term, it comes down to a phenomenological description of the cause of the relative motion between two bodies.

Where there is relative motion between me and the street, either the earth has to be behaving like a giant treadmill, or spinning log as you mentioned elsewhere, or the earth is passive while I am actively "doing the moving", and my walking is propelling me forward.

The Earth can be moving relative to any other object in the universe, and us along with it, but the subsequent relative motion between us and the street has to be accounted for by one, or both, of the scenarios above. This offers three possible explanations as to how/why relative motion occurs between us and the street, one of which has to be correct. We can still define equally valid reference frames which label either as moving, but the three scenarios outlined have deductive consequences.

If I understand this correctly, you are saying the existence of a preferred reference frame (i.e. a reference frame that reflects the "true" motion of an object). The problem is you are begging the question. To reiterate, your line of reasoning is:

1) Two observers are moving, relative to each other.
2) Therefore at least one of the observers must have an absolute velocity, and one of their reference frames, on a metaphysical level, must be incorrect.
3) Therefore absolute velocities exist.

I am saying 2) does not follow from 1) unless you assume 3). You are implicitly assuming the very thing you are trying to show. Instead, relativity only permits us to say

1) Two observers are moving, relative to each other.
2) Therefore there is absolutely motion between the two observers.

To say/deduce anything else requires more assumptions.

Did you not mention in the other thread that the state of absolute rest is perfectly compatible with relativity; you can either have it, or not have it?

I did indeed. Which is why I said "is not supported" rather than "contradicted". You are not merely saying "absolute motion, in the sense of an absolute velocity, may or may not exist". You are saying it can be shown to necessarily exist, based on our current understanding of motion. I am saying our current understanding of motion does not support the notion of an absolute velocity.

I think this point, though, indicates a critical issue; the contention is that my "problem with [...] understanding motion" is that what I am saying doesn't agree with relativity, implying that, if it doesn't agree with relativity it can't be right; it almost seems like a conditioned attachment to "what relativity says" is the only way. The conditioning or training seems to be triggered at the first mention of "actually moving" or "absolute motion".

This isn't necessarily a negative thing, it's an entirely natural aspect of the human condition, but it can prevent us from looking at things more objectively. Of course, the same could be said for a belief in presentism, but both would depend on the level of sub-conscious attachment.

In the other thread, you make the argument that relativity implicitly assumes absolute motion, and I figured you were doing the same thing here. Can I assume you no longer believe relativity says absolute motion, in the sense of absolute velocity, exists?

The answer to "am I moving [full stop]?" is "I don't know, but I'm either moving [full stop] or I'm not [full stop]."

I assume by "moving" you mean absolute motion. If this is the case, "I am not [full stop]" has two interpretations. It means either I have an absolute velocity of 0, or it means absolute velocity, and hence absolute motion, does not exist.

<snipped redundant exchanges>

roosh

Morbert wrote: »

If I understand this correctly, you are saying the existence of a preferred reference frame (i.e. a reference frame that reflects the "true" motion of an object). The problem is you are begging the question. To reiterate, your line of reasoning is:

1) Two observers are moving, relative to each other.
2) Therefore at least one of the observers must have an absolute velocity, and one of their reference frames, on a metaphysical level, must be incorrect.
3) Therefore absolute velocities exist.

I am saying 2) does not follow from 1) unless you assume 3). You are implicitly assuming the very thing you are trying to show. Instead, relativity only permits us to say

1) Two observers are moving, relative to each other.
2) Therefore there is absolutely motion between the two observers.

To say/deduce anything else requires more assumptions.

OK; I think this is probably where the confusion lies. The contention isn't necessarily that there exists a preferred frame of reference, which reflects the true motion of objects. The contention is that we can deduce that at least one of two relatively moving bodies must be in absolute motion.

The existence of an absolute reference frame isn't a necessary assumption, because we are talking about the underlying physical process which the mathemeatical reference frames attempt to describe. We are talking about the nature of motion, as opposed to it's measurement.

The problem probably lies in the historical concept of what "absolute motion" means; it was taken to mean motion relative to an absolute reference frame; but that, of course, would be a contradiction in terms; because what is absolute is not, by definition, relative. So there is no necessity for an absolute reference frame to exist.

"Absolute motion" is a statement about the nature of motion of an object, which is not necessarily a measurable quantity, but it does have deductive consequences. "Absolute motion" is a "yes or no", "either, or" question:
"Is X moving?"
"Is Y moving?"
"Is X or Y moving?"

It is also unqualified statements such as "I am moving" or "I am not moving".

Physical processes
Absolute motion is probably easier to interpret using contextual examples; like the example of the observer walking along the earth. As you mentioned in another thread, the observer cannot determine if it is they that is moving, or if the earth is behaving like a spinning log. Here we have two deductively different scenarios which both account for the relative motion between an observer and the road - actually we have three, where the earth is behaving like a spinning log and the observer is walking at a pace that doesn't exactly offset the rotation of the log.

In all cases, the nature of motion ascribed to each object is different, but all result in the same relative motion. We cannot determine which of the three scenarios is the true one, but we can deduce that one of them has to be, because otherwise there would be no relative motion.

Just to reiterate, absolute motion is not relative i.e. it is not necessarily motion relative to an absolute rest frame, so such an assumption isn't necessary.

Morbert wrote: »

I did indeed. Which is why I said "is not supported" rather than "contradicted". You are not merely saying "absolute motion, in the sense of an absolute velocity, may or may not exist". You are saying it can be shown to necessarily exist, based on our current understanding of motion. I am saying our current understanding of motion does not support the notion of an absolute velocity.

I'm not necessarily saying that there exists an absolute velocity, because that would imply some measurable quantity; and measurement, by its very nature, is relative, not absolute.

I'm not so sure that I would say that absolute motion can be deduced from our current understanding of motion, becaues the idea of "our current understanding of motion" is somewhat vague; what is being said is that based on the observation of relative motion - not necessarily contemporary interpretation of that observation - we can deduce, in general, three different scenarios that can account for the relative motion between bodies; each of these scenarios, necessarily, distinguish between the nature of motion of the bodies involved, that is, they make reference to the motion of the body in a manner that isn't necessarily relative i.e. in an absolute manner.

We cannot determine which of the three scenarios is the true one, but we can deduce that one of them has to be, and therefore that at least one of the bodies must absolutely be in motion.

Morbert wrote: »

In the other thread, you make the argument that relativity implicitly assumes absolute motion, and I figured you were doing the same thing here. Can I assume you no longer believe relativity says absolute motion, in the sense of absolute velocity, exists?

No, I would still maintain that.

Morbert wrote: »

I assume by "moving" you mean absolute motion. If this is the case, "I am not [full stop]" has two interpretations. It means either I have an absolute velocity of 0, or it means absolute velocity, and hence absolute motion, does not exist.

Again though, we can outline three general scenarios to account for the relative motion between two bodies, each of which makes reference to the absolute motion of one or the other bodies i.e. by making a statement about the movement of the body, that isn't necessarily relative. So this determines that absolute motion does exist.

There might be some confusion being caused by the conflation of absolute velocity with absolute motion, where the former referes to a measurable quanity, while the latter refers to the nature of motion, which isn't necessarily measurable.

So, absolute velocity doesn't necessarily exist, because it implies some measurable quantity, and measurement is by nature relative, not absolute. Theoretically, if we could determine an absolute reference frame we could possibly perform a measurement which we could label "absolute velocity", even though it would technically be velocity relative to a body at absolute rest; but we cannot determine whether or not a body is at absolute rest or not.

Absolute rest
The issue of absolute rest is somewhat different, and you would be right in saying that it is possible that an absolute rest frame doesn't exist, but this in itself would have two interpretations; firstly, that mathematically constructed reference frames don't have phyiscal existence; and secondly, that an absolute rest frame doesn't exist because there is no object in the universe that is at absolute rest; that is, everything in the universe is absolutely in motion.