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the [possible] fallacy of Lorentz contractions

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Comments

  • #52
    Enkidu
    Registered Users, Registered Users 2 Posts: 1,005 ✭✭✭Enkidu


    I think you may be over complicating the notion of absolute rest roosh. Relativity says there is no absolute rest in the sense that there exists no experiment which all observers can agree on which would assign a velocity of v = 0 to some object. This is unlike acceleration, where everybody can agree if an object has a=0, since it will have no force exerted on it.


  • #53
    Enkidu
    Registered Users, Registered Users 2 Posts: 1,005 ✭✭✭Enkidu


    roosh wrote: »
    The co-ordinate labeling system labels Albert with a zero velocity and labels him as "at rest", despite the fact that there is motion relative to another reference frame. The question is, does this "at rest" mean at absolute rest, or not? Not expressly stating which it is, is fine; but we are free to deduce what it must mean i.e. what the tacit assumption (or consequence) must be.
    It is not at absolute rest. Relativity has no absolute rest. Rather one says Albert is inertial. That is, since he has "a = 0", something all observers agree on, there exists a frame with respect to which he is at rest.
    roosh wrote: »
    If Albert's reference frame, which is labelled as "at rest" is not at absolute rest, then as above, according to the law of the excluded middle, it must mean that Albert's reference frame is necessarily in motion.
    This is not valid reasoning. There is no absolute rest in relativity and neither is there absolute motion. All one says is that Albert is at rest in some frames and in motion in others. You are missing the point that if you can not absolutely say Albert is at rest, you cannot absolutely say he is in motion.


  • #54
    Morbert
    Registered Users, Registered Users 2 Posts: 3,457 ✭✭✭Morbert


    To echo what Enkidu has said, you are making a logic error.

    Analogously, you are trying to infer statements about the matrix from Newton's laws.
    That depends on what P and Q are though; when dealing with the law of the excluded middle, as I believe we are, not P does imply Q, just as not Q does imply P.

    You are not invoking the law of the excluded middle correclty, for two reasons. Firstly, in our case

    P: There exists a coordinate system where Albert is "at rest".
    Q: Albert is at absolute rest.

    What I am saying is
    P → (Q ∨ ¬Q)

    Hence, no implicit assumption is made about Q.

    Secondly, the law of the excluded middle is
    (Q ∨ ¬Q)
    Either Albert is at absolute rest (Q), or Albert is not at absolute rest (¬Q). If we introduce another proposition M "Albert is in absolute motion", then we have the relations

    Q → ¬M
    M → ¬Q
    ¬Q → (M ∨ ¬M)
    ¬M → (Q ∨ ¬Q)

    You are introducing a false dichotomy (Q ∨ M), and trying to justify it with the law of the excluded middle. Your dichotomy assumes absolute space exists, when the very message of relativity is that it is physically meaningless.


  • #55
    roosh
    Registered Users, Registered Users 2 Posts: 2,553 ✭✭✭roosh


    Enkidu wrote: »
    I think you may be over complicating the notion of absolute rest roosh. Relativity says there is no absolute rest in the sense that there exists no experiment which all observers can agree on which would assign a velocity of v = 0 to some object. This is unlike acceleration, where everybody can agree if an object has a=0, since it will have no force exerted on it.
    The point being made isn't so much that there is, or must be, an absolute rest frame, it is that the co-ordinate labeling system used in Einsteinian relativity treats specific reference frames, or observers, as being at absolute rest. For example, Albert's co-ordinate labeling system labels him as having a zero velocity, just as Henry's labels Henry as having a zero velocity.

    While Einsteinian relativity might not expressly say anything about absolute rest, or might even claim that there is no such thing, we can examine it critically and see that it is a tacit assumption, or consequence, of the co-ordinate labeling system.


    Enkidu wrote: »
    It is not at absolute rest. Relativity has no absolute rest. Rather one says Albert is inertial. That is, since he has "a = 0", something all observers agree on, there exists a frame with respect to which he is at rest.
    Again, we can critically examine the consequences of different scenarios and deduce that it is a tacit assumption, or consequence, of the co-ordinate labeling system. That it isn't expressly stated in the formalism of Einsteinian relativity is immaterial.

    Albert's co-ordinate labeling system labels him and "his" train (or platform) as having a zero velocity; that is, his reference frame is ascribed a zero velocity, despite there being motion relative another reference frame. 100% of the relative velocity is ascribed to the relatively moving reference frame à la an absolute rest frame.

    Enkidu wrote: »
    This is not valid reasoning. There is no absolute rest in relativity and neither is there absolute motion. All one says is that Albert is at rest in some frames and in motion in others. You are missing the point that if you can not absolutely say Albert is at rest, you cannot absolutely say he is in motion.
    We need to move beyond the fact that Einsteinian relativity doesn't expressly include an absolute reference frame, or even says that such doesn't exist; we need to apply reason to the possible scenarios and see that it can be deduced that it is a tacit assumption, or consequence, of the co-ordinate labeling system.

    Taking the simplistic example, Albert's co-ordinate labeling system will always label him as having a zero velocity, regardless of the motion relative to another reference frame. If a co-ordinate labeling system labels Albert as having a zero velocity, then that co-ordinate labeling system treats him as though he were at absolute rest.

    If Albert's "at rest" label doesn't mean "at absolute rest" then it must mean he is in motion relative to an undetectable reference frame, because his co-ordinate labeling system applies 100% of the relative velocity to all relatively moving, detectable reference frames.


  • #56
    roosh
    Registered Users, Registered Users 2 Posts: 2,553 ✭✭✭roosh


    Morbert wrote: »
    To echo what Enkidu has said, you are making a logic error.

    Analogously, you are trying to infer statements about the matrix from Newton's laws.



    You are not invoking the law of the excluded middle correclty, for two reasons. Firstly, in our case

    P: There exists a coordinate system where Albert is "at rest".
    Q: Albert is at absolute rest.

    What I am saying is
    P → (Q ∨ ¬Q)

    Hence, no implicit assumption is made about Q.

    Secondly, the law of the excluded middle is
    (Q ∨ ¬Q)
    Either Albert is at absolute rest (Q), or Albert is not at absolute rest (¬Q). If we introduce another proposition M "Albert is in absolute motion", then we have the relations

    Q → ¬M
    M → ¬Q
    ¬Q → (M ∨ ¬M)
    ¬M → (Q ∨ ¬Q)

    You are introducing a false dichotomy (Q ∨ M), and trying to justify it with the law of the excluded middle. Your dichotomy assumes absolute space exists, when the very message of relativity is that it is physically meaningless.

    Apologies, my formulation may have been a bit sloppy. Firstly though, the concept of "absolute rest" is indirectly referenced through the Galilean Principle of Invariance (PoI) and the special Principle of Relativity (PoR), in the stated consequence that relatively moving observers cannot determine, by experiment, which one is moving*.


    [EDIT]
    The stated consequence of the Galilean PoI, is that an inertial observer cannot determine if they are "in motion" or "at rest"; in the Galilean case it is indisputable that the concept of "absolute rest" is what is being referenced.

    PoR
    The special Principle of Relativity (PoR), together with the equivalence principle, is just an extension of this principle to include accelerating reference frames, such that two relatively moving observers cannot determine which one is moving. Again, this implies that one of the observers might not be moving.

    The question is, how can an observer not be moving, when there is relative velocity between them and another observer? The answer is: only if they are at "absolute rest" - a very old, and pretty well understood, concept in scientific philosophy.


    Put another way
    If we take the example of two lone observers, in the universe, at rest relative to each other; there is no experiment which they can conduct to determine if they are moving; this leaves two options: either they are moving, or they aren't.

    If they are moving, and it isn't relative to each other, then it must be relative to an undetectable reference frame.

    Clearly they can conduct numerous experiments to determine if the are moving relative to each other, so the only alternative is that they are at "absolute rest" - as per the well understood concept.

    [/EDIT]

    Assumption of absolute space
    Secondly, we don't need to assume that absolute space exists; the concept of absolute rest is a fairly well understood concept which has existed in scientific philosophy for hundreds of years, even if it has been rejected. All we need to do is to compare the Einsteinian thought experiment to this already existing concept and see what comparisons can be drawn. "Absolute rest" can remain a purely abstract, mathematical construct for the purpose of examination.



    Excluded middle
    What was intended with the point of the excluded middle is that something is either "at absolute rest" or it is "in motion"; if it isn't one, then, by definition, it is the other.

    You are saying that Albert's "at rest" doesn't imply he is at absolute rest, and you're right, it doesn't imply either absolute rest or absolute motion, but, logically, it must be one or the other.; it is either "at absolute rest" or it is "in motion". If it is "in motion" then it must be relative to an undetectable reference frame, and Albert's instruments must be contracted by an amount unknown to himself due to this motion - which would be the contention of Lorentzian relativity, not Einsteinian.



    *Note: this is not supposed to be an expression, or interpretation, of either principle, it is the often stated consequence of the same.


  • #57
    Morbert
    Registered Users, Registered Users 2 Posts: 3,457 ✭✭✭Morbert


    roosh wrote: »
    Apologies, my formulation may have been a bit sloppy. Firstly though, the concept of "absolute rest" is indirectly referenced through the Galilean Principle of Invariance (PoI) and the special Principle of Relativity (PoR), in the stated consequence that relatively moving observers cannot determine, by experiment, which one is moving*.

    [EDIT]
    The stated consequence of the Galilean PoI, is that an inertial observer cannot determine if they are "in motion" or "at rest"; in the Galilean case it is indisputable that the concept of "absolute rest" is what is being referenced.

    It is referenced to highlight that relativity says nothing about it. The same way the laws of physics say nothing about metaphysical claims about the matrix.
    PoR
    The special Principle of Relativity (PoR), together with the equivalence principle, is just an extension of this principle to include accelerating reference frames, such that two relatively moving observers cannot determine which one is moving. Again, this implies that one of the observers might not be moving.

    The question is, how can an observer not be moving, when there is relative velocity between them and another observer? The answer is: only if they are at "absolute rest" - a very old, and pretty well understood, concept in scientific philosophy.

    Hence, relativity says nothing about the claim in blue.

    It might be relevant (not sure yet) to point out that relativity does permit a form of absolute motion in the context of spacetime, if motion is defined as a non-geodesic spacetime path. But such a definition of motion and rest is only possible in the context of spacetime, and very different to the concept you are advocating. Hence Minkowski's famous quote:

    "Henceforth, space by itself, and time by itself, are doomed to fade away into mere shadows, and only a kind of union of the two will preserve an independent reality."
    Put another way
    If we take the example of two lone observers, in the universe, at rest relative to each other; there is no experiment which they can conduct to determine if they are moving; this leaves two options: either they are moving, or they aren't.

    The above includes the tacit assumption that absolute space is meaningful. You are tacitly assuming absolute space to argue that relativity assumes absolute space. The only thing the law of the excluded middle allows you to say is "They are at absolute rest or they are not". I does not allow you to say "If they are not at absolute rest they must be in absolute motion".
    [/EDIT]
    Assumption of absolute space
    Secondly, we don't need to assume that absolute space exists; the concept of absolute rest is a fairly well understood concept which has existed in scientific philosophy for hundreds of years, even if it has been rejected. All we need to do is to compare the Einsteinian thought experiment to this already existing concept and see what comparisons can be drawn. "Absolute rest" can remain a purely abstract, mathematical construct for the purpose of examination.

    Comparisons can indeed be drawn. And such comparisons show that relativity is independent of such a concept. You can suppose it, or you can reject it.
    Excluded middle
    What was intended with the point of the excluded middle is that something is either "at absolute rest" or it is "in motion"; if it isn't one, then, by definition, it is the other.

    You are saying that Albert's "at rest" doesn't imply he is at absolute rest, and you're right, it doesn't imply either absolute rest or absolute motion, but, logically, it must be one or the other.; it is either "at absolute rest" or it is "in motion". If it is "in motion" then it must be relative to an undetectable reference frame, and Albert's instruments must be contracted by an amount unknown to himself due to this motion - which would be the contention of Lorentzian relativity, not Einsteinian.

    *Note: this is not supposed to be an expression, or interpretation, of either principle, it is the often stated consequence of the same.


    What you are tendering as the law of the excluded middle is

    ¬Q → M

    which is not the law of the excluded middle. If something is not at absolute rest, it means either A) Something is in absolute motion, or B) Absolute space does not exist.


  • #58
    roosh
    Registered Users, Registered Users 2 Posts: 2,553 ✭✭✭roosh


    Morbert wrote: »
    It is referenced to highlight that relativity says nothing about it. The same way the laws of physics say nothing about metaphysical claims about the matrix.
    The concept of absolute rest is referenced in Galilean principle of invariance, not to demonstrate that Einsteinian relativity says nothing about it - for obvious historical reasons - but because the concept of absolute rest was a central concept in Galilean relativity.

    The special principle of relativity is just an extension of the Galilean principle - I'm not sure you could argue that it is referenced to demonstrate that Einsteinian relativity says nothing about it. Also, I'm not familiar with any principle of relativity that indirectly references "the matrix" for the purpose of highlighting that nothing is said about it.



    I don't think re-ordering the paragraphs, below, should affect the point, but let me know if it does.
    Morbert wrote: »
    Hence, relativity says nothing about the claim in blue.


    The above includes the tacit assumption that absolute space is meaningful. You are tacitly assuming absolute space to argue that relativity assumes absolute space. The only thing the law of the excluded middle allows you to say is "They are at absolute rest or they are not". I does not allow you to say "If they are not at absolute rest they must be in absolute motion".
    Just to address the point of the tacit assumption first.

    If we start with the stated consequences first, and then consider a number of applicable scenarios, we can see what can be deduced, as opposed to assumed:
    First
    Consequence: Inertial observers cannot determine, by experiment, if they are "in motion" or "at rest" (or if they are moving or not); this applies equally to Galilean relativity as it does Einsteinian, if I'm not mistaken.

    Scenario: Two non-accelerating observers at rest relative to each other .

    Conclusions: The observers can determine, by experiment, if they are at rest relative to each other - so this cannot be what is meant by the stated consequence above.

    If they cannot determine if they are "in motion" or at "rest" it means that they are either "in motion" or "at rest"; if they are "in motion" but not relative to each other then they must be in motion relative to an undetectable reference frame.

    If they are "at rest" then, relative to what, are they "at rest"? It can't mean relative to each other, for the reason stated above.

    If they are "in motion", relative to what are they "in motion"; obviously it isn't relative to each other?


    The point being made is that it references the well-known concept of "absolute rest"; not least because it appears to resemble it in every way.

    Second
    Consequence: Two inertial observers, moving relative to each other, cannot determine, by experiment, which one is moving.

    Scenario: As above.

    Conclusions: The consequence here can be fleshed out to include the one above; each observer cannot determine if they are "in motion" or "at rest", but because there is relative motion between them, at least one of them has to be "in motion", but they cannot determine which one it is.

    This allows for one of the observers being "at rest", while one is "in motion"; again, the question is, relative to what, is the observer "at rest"? This is where the claim in blue comes in, because the only other alternative is that both are "in motion" and neither is "at rest" i.e. one of the possibilities is that one of the observers is not moving. That Einsteinian relativity doesn't expressly state anything about the claim doesn't prevent deductions being made.

    Again, the point being made is that here "absolute rest" is tacitly referenced.

    Morbert wrote: »
    It might be relevant (not sure yet) to point out that relativity does permit a form of absolute motion in the context of spacetime, if motion is defined as a non-geodesic spacetime path. But such a definition of motion and rest is only possible in the context of spacetime, and very different to the concept you are advocating. Hence Minkowski's famous quote:

    "Henceforth, space by itself, and time by itself, are doomed to fade away into mere shadows, and only a kind of union of the two will preserve an independent reality."
    I was expecting this point to be made more forcefully; tbh, I'm not sure of the relevance either. I would say, though, that as long as the thought experiment referenced here is representative of Einsteinian relativity, the points should hold. I think if we treat reference frames as being at absolute rest, according to their own co-ordinate labeling system, then the conclusion we would draw would be similar, if not identical to, minkowski spacetime.


    Morbert wrote: »
    Comparisons can indeed be drawn. And such comparisons show that relativity is independent of such a concept. You can suppose it, or you can reject it.
    I think the comparisons show that the Einsteinian co-ordinate labeling systems resemble it in almost every way.

    Morbert wrote: »
    What you are tendering as the law of the excluded middle is

    ¬Q → M

    which is not the law of the excluded middle. If something is not at absolute rest, it means either A) Something is in absolute motion, or B) Absolute space does not exist.
    Apologies, my use of terminology is not precise at the best of time, but I think you know the point that is being made.

    I'm not sure that the concept of absolute space is required for the concept of absolute rest; it may indeed have arisen in that context, but I'm not sure it is required, in the Galilean or Newtonian sense. I think the fact that we cannot determine if we are "at rest" or "in motion" demonstrates that, because it is as true under Minkowskian spacetime as it is under absolute space and time.

    The notion of absolute space comes, I think, from the notion that absolute rest and velocity could, theoretically be measured; however, that would be a contradiction in terms, as measurement is, by it's very nature, relative. Absolute motion is a simple 'yes' or 'no' answer to the question, is there motion? Or, with regard to specific objects or observers, is the object/observer in motion, "yes" or "no"?

    If we consider the ancient belief that the earth was the centre of the universe and that everything was in motion around it, the idea of absolute space isn't really necessary. Every observable entity in the universe can be "in motion" while the earth doesn't move; of course, there is relative motion between the earth and everything else, but the earth is ascribed a velocity of zero and the relative velocity is ascribed to everything else - this is partly what makes geocentrism "technically plausible" even today.



    But, all that being said, we are still left with the question of what Albert's "at rest" means. If we consider just Albert and Henry alone in the universe, Albert's co-ordinate labeling system will still label him as "at rest" despite the relative motion between him and Henry. The question is, relative to what is Albert "at rest"?

    Is this "at rest" different to the "at rest" that Albert cannot determine through experiment?


  • #59
    Morbert
    Registered Users, Registered Users 2 Posts: 3,457 ✭✭✭Morbert


    roosh wrote: »
    The concept of absolute rest is referenced in Galilean principle of invariance, not to demonstrate that Einsteinian relativity says nothing about it - for obvious historical reasons - but because the concept of absolute rest was a central concept in Galilean relativity.

    The special principle of relativity is just an extension of the Galilean principle - I'm not sure you could argue that it is referenced to demonstrate that Einsteinian relativity says nothing about it. Also, I'm not familiar with any principle of relativity that indirectly references "the matrix" for the purpose of highlighting that nothing is said about it.

    Einstein's relativity is an extension of Galileo's relativity insofar as Galilean relativity was incompatible with electromagnetism (The laws of electromagnetism are not Galilean invariant). Einstein's principle of general covariance explicitly states that coordinate systems are constructs, and not fundamental properties. I.e. Physics is independent of any supposition regarding absolute rest.

    I don't think re-ordering the paragraphs, below, should affect the point, but let me know if it does.

    Just to address the point of the tacit assumption first.

    If we start with the stated consequences first, and then consider a number of applicable scenarios, we can see what can be deduced, as opposed to assumed:
    First
    Consequence: Inertial observers cannot determine, by experiment, if they are "in motion" or "at rest" (or if they are moving or not); this applies equally to Galilean relativity as it does Einsteinian, if I'm not mistaken.

    Scenario: Two non-accelerating observers at rest relative to each other .

    Conclusions: The observers can determine, by experiment, if they are at rest relative to each other - so this cannot be what is meant by the stated consequence above.

    If they cannot determine if they are "in motion" or at "rest" it means that they are either "in motion" or "at rest"; if they are "in motion" but not relative to each other then they must be in motion relative to an undetectable reference frame.

    If they are "at rest" then, relative to what, are they "at rest"? It can't mean relative to each other, for the reason stated above.

    If they are "in motion", relative to what are they "in motion"; obviously it isn't relative to each other?


    The point being made is that it references the well-known concept of "absolute rest"; not least because it appears to resemble it in every way.

    Second
    Consequence: Two inertial observers, moving relative to each other, cannot determine, by experiment, which one is moving.

    Scenario: As above.

    Conclusions: The consequence here can be fleshed out to include the one above; each observer cannot determine if they are "in motion" or "at rest", but because there is relative motion between them, at least one of them has to be "in motion", but they cannot determine which one it is.

    This allows for one of the observers being "at rest", while one is "in motion"; again, the question is, relative to what, is the observer "at rest"? This is where the claim in blue comes in, because the only other alternative is that both are "in motion" and neither is "at rest" i.e. one of the possibilities is that one of the observers is not moving. That Einsteinian relativity doesn't expressly state anything about the claim doesn't prevent deductions being made.

    Again, the point being made is that here "absolute rest" is tacitly referenced.

    Apologies, my use of terminology is not precise at the best of time, but I think you know the point that is being made.

    I'm not sure that the concept of absolute space is required for the concept of absolute rest; it may indeed have arisen in that context, but I'm not sure it is required, in the Galilean or Newtonian sense. I think the fact that we cannot determine if we are "at rest" or "in motion" demonstrates that, because it is as true under Minkowskian spacetime as it is under absolute space and time.

    The notion of absolute space comes, I think, from the notion that absolute rest and velocity could, theoretically be measured; however, that would be a contradiction in terms, as measurement is, by it's very nature, relative. Absolute motion is a simple 'yes' or 'no' answer to the question, is there motion? Or, with regard to specific objects or observers, is the object/observer in motion, "yes" or "no"?

    If we consider the ancient belief that the earth was the centre of the universe and that everything was in motion around it, the idea of absolute space isn't really necessary. Every observable entity in the universe can be "in motion" while the earth doesn't move; of course, there is relative motion between the earth and everything else, but the earth is ascribed a velocity of zero and the relative velocity is ascribed to everything else - this is partly what makes geocentrism "technically plausible" even today.

    But, all that being said, we are still left with the question of what Albert's "at rest" means. If we consider just Albert and Henry alone in the universe, Albert's co-ordinate labeling system will still label him as "at rest" despite the relative motion between him and Henry. The question is, relative to what is Albert "at rest"?

    Is this "at rest" different to the "at rest" that Albert cannot determine through experiment?

    The bit in blue is where the problem is. Absolute rest does indeed require an absolute space to define itself. So it is not a case of "at absolute rest" or "in absolute motion". Taking your second scenario as an example, you can say there is no coordinate label which says both observers are at rest. This does not mean, however, that one of the reference frames has to be incorrect, or "less representative of reality". What physically matters is that both observers' frames are inertial, and the fact that no coordinate system has both as "at rest" does not mean we can infer that at least one has to be in motion with respect to some absolute space. Hence, absolute space is not assumed.
    I think the comparisons show that the Einsteinian co-ordinate labeling systems resemble it in almost every way.

    And it also resembles a spacetime structure where no such absolute exists.


  • #60
    roosh
    Registered Users, Registered Users 2 Posts: 2,553 ✭✭✭roosh


    Morbert wrote: »
    Einstein's relativity is an extension of Galileo's relativity insofar as Galilean relativity was incompatible with electromagnetism (The laws of electromagnetism are not Galilean invariant). Einstein's principle of general covariance explicitly states that coordinate systems are constructs, and not fundamental properties. I.e. Physics is independent of any supposition regarding absolute rest.
    It was more the relativity principles of each that was meant.

    Morbert wrote: »
    The bit in blue is where the problem is.
    It is probably worth noting that in our deductive process we are speaking solely about relative motion, so the asserted problem with the bit in blue doesn't apply.

    A stated consequence of the PoR is that inertial observers cannot determine, by experiment, if they are "in motion" or "at rest".

    This leaves us with the possibilities that they are "in motion" relative to something or they are "at rest" relative to something. The question we are asking is, what is that something?

    Given that they can determine, by experiment, that they are at rest relative to each other, what is the something, relative to which they cannot determine their motion, or lack thereof?


    Similarly, inertial observers moving relative to each other cannot determine if they are moving or if their counterpart is moving; given that they can determine, by experiment, that they are moving relative to each other, relative to what can they not determine their motion?
    Morbert wrote: »
    Absolute rest does indeed require an absolute space to define itself. So it is not a case of "at absolute rest" or "in absolute motion". Taking your second scenario as an example, you can say there is no coordinate label which says both observers are at rest. This does not mean, however, that one of the reference frames has to be incorrect, or "less representative of reality". What physically matters is that both observers' frames are inertial, and the fact that no coordinate system has both as "at rest" does not mean we can infer that at least one has to be in motion with respect to some absolute space. Hence, absolute space is not assumed.
    Absolute motion is a simple "yes" or "no" answer to the question, is there motion? There is no need for absolute space to define it; equally, there is no need for absolute space to define absolute rest, it is, similarly, a "yes" or "no" answer to the question, is something moving. That we cannot determine if one thing or another is moving, does not mean we cannot determine that there is absolute motion; relative motion is proof of absolute motion.

    For two relatively moving observers is there motion? Yes, of course there is, so there must be absolute motion; we may not be able to determine which one is absolutely moving, but we can reason that one must absolutely be moving. If neither observer was in motion, then there would be no relative motion, they would be at rest relative to each other.

    If we take the example of two observers at rest relative to each other; then relative motion occurs. In order for this relative motion to occur, at least one of the observers has to move; if both observers remained at rest then there would be no relative motion, in anyone's reference frame. So, if both observers say that they themselves didn't move, that it was their counterpart that moved, then one of them must be wrong; that we cannot determine which one is right and which one is wrong is immaterial, we can reason that one of them must, absolutely, be wrong.


    With two inertial observers at rest relative to each other, the principle of relativity says they cannot determine

    Morbert wrote: »
    And it also resembles a spacetime structure where no such absolute exists.
    Indeed, which is indistinguishable from what we would conclude if all observers were treated as being at absolute rest by their co-ordinate labeling systems.


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  • #61
    Morbert
    Registered Users, Registered Users 2 Posts: 3,457 ✭✭✭Morbert


    roosh wrote: »
    It was more the relativity principles of each that was meant.

    It is probably worth noting that in our deductive process we are speaking solely about relative motion, so the asserted problem with the bit in blue doesn't apply.

    A stated consequence of the PoR is that inertial observers cannot determine, by experiment, if they are "in motion" or "at rest".

    This leaves us with the possibilities that they are "in motion" relative to something or they are "at rest" relative to something. The question we are asking is, what is that something?

    Given that they can determine, by experiment, that they are at rest relative to each other, what is the something, relative to which they cannot determine their motion, or lack thereof?

    Similarly, inertial observers moving relative to each other cannot determine if they are moving or if their counterpart is moving; given that they can determine, by experiment, that they are moving relative to each other, relative to what can they not determine their motion?

    Absolute space. Hence, we are not compelled to assume absolute space even exists. Similarly, we cannot determine by experiment whether or not we are in the Matrix, hence we are not compelled to assume the Matrix exists.
    Absolute motion is a simple "yes" or "no" answer to the question, is there motion? There is no need for absolute space to define it; equally, there is no need for absolute space to define absolute rest, it is, similarly, a "yes" or "no" answer to the question, is something moving. That we cannot determine if one thing or another is moving, does not mean we cannot determine that there is absolute motion; relative motion is proof of absolute motion.

    Again, if by "absolute motion" you mean that there is no reference frame which labels both observers as "at rest", then you are right. But this definition means we still don't have to tacitly assume absolute rest, or absolute space exists, and hence we don't have to assume one reference frame is more correct than another.
    For two relatively moving observers is there motion? Yes, of course there is, so there must be absolute motion; we may not be able to determine which one is absolutely moving, but we can reason that one must absolutely be moving. If neither observer was in motion, then there would be no relative motion, they would be at rest relative to each other.

    If we take the example of two observers at rest relative to each other; then relative motion occurs. In order for this relative motion to occur, at least one of the observers has to move; if both observers remained at rest then there would be no relative motion, in anyone's reference frame. So, if both observers say that they themselves didn't move, that it was their counterpart that moved, then one of them must be wrong; that we cannot determine which one is right and which one is wrong is immaterial, we can reason that one of them must, absolutely, be wrong.

    You are tacitly assuming absolute space here by switching definitions of "absolute motion". We have established that there is no reference frame which labels both observers as at rest. This in no way implies one observer must be wrong, unless you tacitly assume absolute space exists.
    Indeed, which is indistinguishable from what we would conclude if all observers were treated as being at absolute rest by their co-ordinate labeling systems.

    Which is indistinguishable from what we would conclude if all observers assumed absolute rest did not exist. Hence, absolute space and absolute rest are entirely superfluous concepts.


  • #62
    roosh
    Registered Users, Registered Users 2 Posts: 2,553 ✭✭✭roosh


    Morbert wrote: »
    Absolute space. Hence, we are not compelled to assume absolute space even exists. Similarly, we cannot determine by experiment whether or not we are in the Matrix, hence we are not compelled to assume the Matrix exists.
    The point about the matrix is somewhat of a misnomer; because assuming one way or the other makes no difference to the question in hand, while assuming motion or rest does materially affect the conclusions we draw about which theory best describes the universe (or the matrix's projection of the universe). The question of "motion" or "rest" is equally applicable inside the matrix as it is outside it.

    I think the point of the stated consequence, of the different principles of relativity, is being missed, however; the point clearly distinguishes between two possible "states', that of being "in motion" and that of being "at rest"; such that no experiment can distinguish between them. This means that the observer is either "in motion" or "at rest" [relative to something], but can't tell the difference; but it is one or the other.

    You've stated above that the reference frame, relative to which the motion cannot be determined, is the absolute rest frame (or absolute space). This means that either the observer is "in motion" relative to absolute space, or he is "at rest" in absolute space. Either way, the "absolute space" is tacitly assumed. If the observer is "at rest" in absolute space, then Einsteinian relativity treats reference frames as being at "absolute rest"; if the observer is in motion relative to the undetectable, absolute rest frame, then the conclusions are Lorentzian not Einsteinian.


    Morbert wrote: »
    Again, if by "absolute motion" you mean that there is no reference frame which labels both observers as "at rest", then you are right. But this definition means we still don't have to tacitly assume absolute rest, or absolute space exists, and hence we don't have to assume one reference frame is more correct than another.
    I'm not sure how you are drawing the conclusion that that was what was meant by "absolute motion".

    "Absolute motion" is a simple "yes" or "no" answer to the question: is there motion?

    This can be extended to specific objects and observers i.e. is Albert in motion; yes, or no?


    Absolute space is not required for either of the above. The concept of absolute space would be required to measure absolute motion, but measurement, by its very nature, is relative, so absolute motion cannot be measured; but its "existence" can be deduced.

    Again, if we take our two observers - in empty space for simplicity sake; they start off at rest relative to each other (with no assumption of absolute space). In order for there to be relative motion, between them, at least one of them has to move; if neither one of them moves, then they will remain at rest relative to each other; and both reference frames will label both observers as "at rest".


    If relative motion occurs and both observers maintain that they remained at rest, then one of them must be wrong. We can personalise it a bit for the sake of intuition. If you and I are at rest relative to each other and then relative motion occurs, if you and I both maintain that we didn't move, then one of us has to be wrong. We might not be able to determine which one is wrong - as per the principle of relativity - but we can most certainly reason that one of us must be wrong. Because if we are both right, and we both remained at rest, then no relative motion would have occurred.

    Morbert wrote: »
    You are tacitly assuming absolute space here by switching definitions of "absolute motion". We have established that there is no reference frame which labels both observers as at rest. This in no way implies one observer must be wrong, unless you tacitly assume absolute space exists.
    There is no switching of definitions; we can reason all of the above from relative motion alone, without assuming absolute space.

    The point about no reference frame labeling both observers as "at rest" is just an extension of the issue that neither can determine which one is in motion. We can still reason that at least one of them, absolutely, must be in motion - otherwise they would remain at rest, relative to each other.

    Morbert wrote: »
    Which is indistinguishable from what we would conclude if all observers assumed absolute rest did not exist. Hence, absolute space and absolute rest are entirely superfluous concepts.
    I think we can say that all observers assume that absolute rest does not exist, but that the co-ordinate labeling convention tacitly assumes it - which would be fairly representative of the situation as is.

    Are we agreed so, that the treatment of reference frames, under Einsteinian co-ordinate labels, is indistinguishable i.e. is the same as, treating specific reference frames as being at absolute rest?


  • #63
    Morbert
    Registered Users, Registered Users 2 Posts: 3,457 ✭✭✭Morbert


    roosh wrote: »
    The point about the matrix is somewhat of a misnomer; because assuming one way or the other makes no difference to the question in hand, while assuming motion or rest does materially affect the conclusions we draw about which theory best describes the universe (or the matrix's projection of the universe). The question of "motion" or "rest" is equally applicable inside the matrix as it is outside it.

    You are jumping back and forth between points. Your point was that, because asbolute space is referenced in the statement "There is no way to physically distinguish absolute space/rest", it must be assumed. This is false, for the same reason we do not have to assume the Matrix is real even if we say "There is no way to physically determine if we are in the Matrix".
    I think the point of the stated consequence, of the different principles of relativity, is being missed, however; the point clearly distinguishes between two possible "states', that of being "in motion" and that of being "at rest"; such that no experiment can distinguish between them. This means that the observer is either "in motion" or "at rest" [relative to something], but can't tell the difference; but it is one or the other.

    It does not have to be one or the other. You can adopt a third option: space is relative.
    You've stated above that the reference frame, relative to which the motion cannot be determined, is the absolute rest frame (or absolute space). This means that either the observer is "in motion" relative to absolute space, or he is "at rest" in absolute space. Either way, the "absolute space" is tacitly assumed. If the observer is "at rest" in absolute space, then Einsteinian relativity treats reference frames as being at "absolute rest"; if the observer is in motion relative to the undetectable, absolute rest frame, then the conclusions are Lorentzian not Einsteinian.

    It means absolute space is not implied by the physics. We are therefore not compelled to believe it exists. Absolute space is not a consequence of relativity. "In motion", in this case simply means no reference frame labels both observers as at rest. The observers are in motion relative to each other. It in no way implies one reference frame is more correct than another.
    I'm not sure how you are drawing the conclusion that that was what was meant by "absolute motion".

    "Absolute motion" is a simple "yes" or "no" answer to the question: is there motion?

    This can be extended to specific objects and observers i.e. is Albert in motion; yes, or no?

    It cannot be extended to specific objects. Again, it is your misuse of language, and apparent refusal to use rigorous terminology, that is causing the problem.

    Here is what relativity says in the case of two observers moving relative to one another: There is no coordinate system which labels both observers as "at rest". From this, you cannot conclude that therefore there must be an absolute space for one observer to be in motion with respect to.
    Absolute space is not required for either of the above. The concept of absolute space would be required to measure absolute motion, but measurement, by its very nature, is relative, so absolute motion cannot be measured; but its "existence" can be deduced.

    I.e. Absolute space can be deduced. That is incorrect. Absolute space cannot be deduced from the statement "There is no coordinate system which labels both observers as at rest".
    Again, if we take our two observers - in empty space for simplicity sake; they start off at rest relative to each other (with no assumption of absolute space). In order for there to be relative motion, between them, at least one of them has to move; if neither one of them moves, then they will remain at rest relative to each other; and both reference frames will label both observers as "at rest".

    If relative motion occurs and both observers maintain that they remained at rest, then one of them must be wrong. We can personalise it a bit for the sake of intuition. If you and I are at rest relative to each other and then relative motion occurs, if you and I both maintain that we didn't move, then one of us has to be wrong. We might not be able to determine which one is wrong - as per the principle of relativity - but we can most certainly reason that one of us must be wrong. Because if we are both right, and we both remained at rest, then no relative motion would have occurred.

    There is no switching of definitions; we can reason all of the above from relative motion alone, without assuming absolute space.

    The point about no reference frame labeling both observers as "at rest" is just an extension of the issue that neither can determine which one is in motion. We can still reason that at least one of them, absolutely, must be in motion - otherwise they would remain at rest, relative to each other.

    All that physically matters is they move relative to one another. That is what is implied by the statement "There is no coordinate system which labels both observers as at rest". Absolute space cannot therefore be deduced.
    I think we can say that all observers assume that absolute rest does not exist, but that the co-ordinate labeling convention tacitly assumes it - which would be fairly representative of the situation as is.

    We cannot say that the use of coordinate systems is a tacit assumption of absolute rest. Coordinate systems are perfectly consistent with the assumption that no absolute rest exists.
    Are we agreed so, that the treatment of reference frames, under Einsteinian co-ordinate labels, is indistinguishable i.e. is the same as, treating specific reference frames as being at absolute rest?

    We agree that we can metaphysically suppose an absolute space, and it will be consistent with the physics. We also should agree that we can suppose there is no absolute space, and it will be consistent with the physics.


  • #64
    roosh
    Registered Users, Registered Users 2 Posts: 2,553 ✭✭✭roosh


    Morbert wrote: »
    You are jumping back and forth between points. Your point was that, because asbolute space is referenced in the statement "There is no way to physically distinguish absolute space/rest", it must be assumed. This is false, for the same reason we do not have to assume the Matrix is real even if we say "There is no way to physically determine if we are in the Matrix".
    The point wasn't that "absolute rest" must be assumed because it is referenced through the PoR, that particular point was simply that absolute rest is referenced through the PoR.

    The point about the tacit assumption of absolute rest is that we can deduce that it must be a tacit assumption from the Einsteinian treatment of reference frames, the constancy of c, and the fact that light inherits the horizontal velocity of a moving emitter (mirror).


    Morbert wrote: »
    It does not have to be one or the other. You can adopt a third option: space is relative.
    That is the conclusion that we draw when we treat specific reference frames as being at absolute rest.

    Morbert wrote: »
    It means absolute space is not implied by the physics. We are therefore not compelled to believe it exists. Absolute space is not a consequence of relativity. "In motion", in this case simply means no reference frame labels both observers as at rest. The observers are in motion relative to each other. It in no way implies one reference frame is more correct than another.
    Your re-statement of the consequence above - "There is no way to physically distinguish absolute space/rest" -is not entirely complete; more accurately it should be "there is no way to physically distingusih absolute rest from absolute motion", with the implication that bodies are in one or the other state.

    While we are not compelled to believe that an absolute rest state exists, we cannot rule it out, because we cannot determine whether or not we are actually "at absolute rest"; for all we can determine, we could be. That being said, we can actually assume that no reference frame is at absolute rest, however, we can still use the concept to make a number deductions.

    We can start with Albert, who cannot determine if he is at absolute rest, or in motion. We can consider the scenario where he is at absolute rest and see that it resembles, exactly, the treatment of the reference frame under Einsteinian relativity.

    We can then consider the scenario where he is not at absolute rest, but in motion; knowing that the photon in his clock will be imparted with the horizontal velocity of his train carriage (or platform). Under Galilean relativity we would expect Albert to measure a speed of less than c, due to the vertical velocity component being less than c. Einsteinian relativity states that he will measure the speed to be c. In order for this to happen, Albert's instruments must contract by an amount unknown to himself due to his motion relative to the absolute rest frame - this however, is the Lorentzian interpretation.

    Only the scenario where Albert is at absolute rest matches the Einsteinian interpretation.

    Morbert wrote: »
    It cannot be extended to specific objects. Again, it is your misuse of language, and apparent refusal to use rigorous terminology, that is causing the problem.

    Here is what relativity says in the case of two observers moving relative to one another: There is no coordinate system which labels both observers as "at rest". From this, you cannot conclude that therefore there must be an absolute space for one observer to be in motion with respect to.
    Again, the question of absolute motion is a yes or no question; absolute space is not necessary.

    That "there is no coordinate system which labels both observers as "at rest" is just a the consequence of the PoR in a different guise; it simply demonstrates the point that neither observer can determine which one is actually in motion.

    Again, if we consider two observers and only their relative motion, we can deduce absolute motion.

    If the two observers start off at rest relative to each other, then, unless one of them actually moves, they will remain at rest relative to each other. In order for relative motion to occur between them, one of them absolutely has to actually move. Again, if they didn't, they would remain at rest relative to each other.


    This can be extended to specific objects (or indeed observers) simply by asking the question is X moving?
    Morbert wrote: »
    I.e. Absolute space can be deduced. That is incorrect. Absolute space cannot be deduced from the statement "There is no coordinate system which labels both observers as at rest".
    ...
    All that physically matters is they move relative to one another. That is what is implied by the statement "There is no coordinate system which labels both observers as at rest". Absolute space cannot therefore be deduced.
    As mentioned, I don't think absolute space is necessary to answer the question is there motion? We can deduce that there must be motion from relative motion. The above statement simply demonstrates that we cannot actually determine which one is in motion and which (if any) are at rest; hence we cannot, knowingly at least, measure absolute velocity - but we can deduce that there is absolute motion.

    Morbert wrote: »
    We cannot say that the use of coordinate systems is a tacit assumption of absolute rest. Coordinate systems are perfectly consistent with the assumption that no absolute rest exists.
    It's not necessarily the co-ordinate systems alone, as outlined above.

    Morbert wrote: »
    We agree that we can metaphysically suppose an absolute space, and it will be consistent with the physics. We also should agree that we can suppose there is no absolute space, and it will be consistent with the physics.
    But, as above, we can deduce that Einsteinian relativity tacitly assumes absolute rest.


  • #65
    Morbert
    Registered Users, Registered Users 2 Posts: 3,457 ✭✭✭Morbert


    mangaroosh, you are consistently making the same mistakes over and over again. And when I correct mistakes, you revert to earlier examples that had been previously resolved.

    Here is an abbreviation of your logic.

    Suppose two observers are in motion relative to each other.
    Therefore at least one of them has to be in motion with respect to a state of absolute rest.
    Therefore absolute rest exists.

    The argument is wrong because you cannot jump from "Two observers are in motion relative to each other" to "At least one has to be in motion with respect to a state of absolute rest". All you can say is one of them has to be in motion with respect to the other. You cannot tacitly assume a state of absolute rest, define motion as "motion with respect to absolute rest", and then assert that therefore relativity tacitly assumes absolute rest exists. Yes, you can say it doesn't rule it out. That is not in dispute. Just as the laws of physics do not rule out the Matrix. The reference frame formalism of Einstein's relativity is perfectly consistent with the notion that no absolute rest, or absolute space exists.

    Now, if you want to define absolute motion as something other than "motion with respect to absolute rest", then that's fine. But then you cannot use it to infer absolute rest in the presentist, neo-Lorentzian sense (which I am assuming is your goal). For example, if you define absolute motion as non-geodesic spacetime paths, then absolute rest becomes geodesic spacetime paths. Both observers would be considered at absolute rest, even if reference frames describe relative motion between them.


  • #66
    roosh
    Registered Users, Registered Users 2 Posts: 2,553 ✭✭✭roosh


    Morbert wrote: »
    mangaroosh, you are consistently making the same mistakes over and over again. And when I correct mistakes, you revert to earlier examples that had been previously resolved.

    Here is an abbreviation of your logic.

    Suppose two observers are in motion relative to each other.
    Therefore at least one of them has to be in motion with respect to a state of absolute rest.
    Therefore absolute rest exists.

    The argument is wrong because you cannot jump from "Two observers are in motion relative to each other" to "At least one has to be in motion with respect to a state of absolute rest". All you can say is one of them has to be in motion with respect to the other. You cannot tacitly assume a state of absolute rest, define motion as "motion with respect to absolute rest", and then assert that therefore relativity tacitly assumes absolute rest exists. Yes, you can say it doesn't rule it out. That is not in dispute. Just as the laws of physics do not rule out the Matrix. The reference frame formalism of Einstein's relativity is perfectly consistent with the notion that no absolute rest, or absolute space exists.

    Now, if you want to define absolute motion as something other than "motion with respect to absolute rest", then that's fine. But then you cannot use it to infer absolute rest in the presentist, neo-Lorentzian sense (which I am assuming is your goal). For example, if you define absolute motion as non-geodesic spacetime paths, then absolute rest becomes geodesic spacetime paths. Both observers would be considered at absolute rest, even if reference frames describe relative motion between them.
    The abbreviation provided above, demonstrates that there is some confusion about the points that are being made; I have to accept partial responsibility for, perhaps, not distinguishing between the points more clearly, but hopefully we can clarify them.

    Two observers in motion
    Firstly, the point about the two observers in motion, relative to each other, being verification of absolute motion, is separate from the point of absolute rest in Einsteinian relativity. It is a stand-alone point; it isn't being used to infer the existence of absolute space or rest.

    In general it is a riposte to the recurring statement that "it makes no sense to talk about something being actually in motion"; the point demonstrates that it does make sense, even if it can't be determined which one is actually in motion. It is based a definition of absolute motion that doesn't necessarily require the existence of absolute space.

    Absolute rest in ER
    The inference of the absolute rest state in Einsteinian relativity is not based on the above. The deduction, that ER treats specific reference frames as being at absolute rest, is inferred from the treatment of reference frames in ER, the Principle of Relativity - which implies absolute rest, as you mentioned - the measurement of c by an observer (Albert), and the fact about the photon incurring the horizontal momentum of the moving clock/train.


    The conclusions which can be drawn, as outlined above, are either; a) Albert, and his reference frame, are at absolute rest; or b) Albert's instruments are contracted by an amount unknown to himself, due to his motion relative to an undetectable reference frame.


    Principle of Relativity
    The stated consequence of the PoR, as mentioned, effectively says that a state of absolute motion cannot be distinguished from a state of absolute rest; implying that an observer is in one state or the other.

    If an observer is in absolute motion (but can't determine it) and he measures the speed of light in his light clock to be c, then his instruments must be contracted by an amount unknown to himself, due to his absolute motion.

    Alternatively, he is at absolute rest.


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  • #67
    Morbert
    Registered Users, Registered Users 2 Posts: 3,457 ✭✭✭Morbert


    roosh wrote: »
    The abbreviation provided above, demonstrates that there is some confusion about the points that are being made; I have to accept partial responsibility for, perhaps, not distinguishing between the points more clearly, but hopefully we can clarify them.

    Two observers in motion
    Firstly, the point about the two observers in motion, relative to each other, being verification of absolute motion, is separate from the point of absolute rest in Einsteinian relativity. It is a stand-alone point; it isn't being used to infer the existence of absolute space or rest.

    In general it is a riposte to the recurring statement that "it makes no sense to talk about something being actually in motion"; the point demonstrates that it does make sense, even if it can't be determined which one is actually in motion. It is based a definition of absolute motion that doesn't necessarily require the existence of absolute space.

    And I agree that it does make sense, provided in motion does not mean in motion with respect to some absolute space, or state of absolute rest. It is perfectly valid to say the observers are actually in motion with respect to each other.
    Absolute rest in ER
    The inference of the absolute rest state in Einsteinian relativity is not based on the above. The deduction, that ER treats specific reference frames as being at absolute rest, is inferred from the treatment of reference frames in ER, the Principle of Relativity - which implies absolute rest, as you mentioned - the measurement of c by an observer (Albert), and the fact about the photon incurring the horizontal momentum of the moving clock/train.

    The conclusions which can be drawn, as outlined above, are either; a) Albert, and his reference frame, are at absolute rest; or b) Albert's instruments are contracted by an amount unknown to himself, due to his motion relative to an undetectable reference frame.

    Or c) There is no state of absolute rest, no undetectable absolute reference frame, and hence Albert is neither at absolute rest, nor in motion with respect to absolute rest. He measures the speed of light to be c because of the Minkowski geometry relating all events to one another.

    Principle of Relativity
    The stated consequence of the PoR, as mentioned, effectively says that a state of absolute motion cannot be distinguished from a state of absolute rest; implying that an observer is in one state or the other.

    If an observer is in absolute motion (but can't determine it) and he measures the speed of light in his light clock to be c, then his instruments must be contracted by an amount unknown to himself, due to his absolute motion.

    Alternatively, he is at absolute rest.

    It implies no such thing. It implies an absolute rest, and motion with respect to absolute rest, are physically meaningless. Again, you are tendering the false dichotomy: If you are not at absolute rest, then you must be in motion with respect to absolute rest. I have shown that relativity is perfectly consistent with the postulate that absolute rest, and hence motion with respect to absolute rest, does not exist. You say it is implicitly assumed. If this were true, you would be able to show a contradiction between relativity, and the postulate that no absolute rest exists.


  • #68
    roosh
    Registered Users, Registered Users 2 Posts: 2,553 ✭✭✭roosh


    Morbert wrote: »
    And I agree that it does make sense, provided in motion does not mean in motion with respect to some absolute space, or state of absolute rest. It is perfectly valid to say the observers are actually in motion with respect to each other.
    OK, so you would agree that it demonstrates absolute motion; not necessarily motion with respect to absolute space?

    Morbert wrote: »
    Or c) There is no state of absolute rest, no undetectable absolute reference frame, and hence Albert is neither at absolute rest, nor in motion with respect to absolute rest. He measures the speed of light to be c because of the Minkowski geometry relating all events to one another.
    When reference frames are treated as being at absolute rest, then the conclusion of something like Minkowskian geometry is inevitable. I dare say, this is partly the reason why the notion of absoluteness remains in Einsteinian relativity.


    Regardless of the Minkowskian geometry, however, if Albert's clock is in motion, it will be imparted with the horizontal velocity of the train. In order for him to measure the speed of light to be c, his instruments will have to contract by an amount unknown to himself.


    This, I would imagine, is where the notion of absolute spacetime measurements will probably come in.

    Morbert wrote: »
    It implies no such thing. It implies an absolute rest, and motion with respect to absolute rest, are physically meaningless. Again, you are tendering the false dichotomy: If you are not at absolute rest, then you must be in motion with respect to absolute rest. I have shown that relativity is perfectly consistent with the postulate that absolute rest, and hence motion with respect to absolute rest, does not exist. You say it is implicitly assumed. If this were true, you would be able to show a contradiction between relativity, and the postulate that no absolute rest exists.
    The implication of the PoR is not so much that both are physically meaningless, rather that both are physically undetectable; this is an entirely different proposition.

    That we cannot detect absolute rest or motion, doesn't mean that they don't exist, it simply means we cannot tell if we are in either state. They are physically meaningful because we can use both to draw conclusions about the physical world. We can ask the question, are we at absolute rest? The answer is, we don't actually know. We could be, or we might not be. We cannot, therefore, conclude that it doesn't exist.

    Also, there would only be a contradiction between relativity and the postulate that no absolute rest exists, if absolute velocity and relative velocity were contradictory notions; there not, so no contradiction arises.


  • #69
    Morbert
    Registered Users, Registered Users 2 Posts: 3,457 ✭✭✭Morbert


    roosh wrote: »
    OK, so you would agree that it demonstrates absolute motion; not necessarily motion with respect to absolute space?

    Yes, they are absolutely in motion with respect to each other.
    When reference frames are treated as being at absolute rest, then the conclusion of something like Minkowskian geometry is inevitable. I dare say, this is partly the reason why the notion of absoluteness remains in Einsteinian relativity.

    Or when reference frames are treated as arbitrary coordinate labels, making no implicit or explicit statement about absolute rest.
    Regardless of the Minkowskian geometry, however, if Albert's clock is in motion, it will be imparted with the horizontal velocity of the train.

    Yes, if Albert's clock is in motion, with respect to an observer, they will see the photon inherit the horizontal velocity of the train.
    In order for him to measure the speed of light to be c, his instruments will have to contract by an amount unknown to himself.

    This does not follow from the above premises. Albert's clock is absolutely at rest with respect to himself. It is absolutely in motion with respect to the other observer. Since the two observers' perspectives can be transformed into each other via the Lorentz transformation, there is no need to postulate some unknown mysterious set of dynamics unknown to Albert.
    The implication of the PoR is not so much that both are physically meaningless, rather that both are physically undetectable; this is an entirely different proposition.

    That we cannot detect absolute rest or motion, doesn't mean that they don't exist, it simply means we cannot tell if we are in either state. They are physically meaningful because we can use both to draw conclusions about the physical world. We can ask the question, are we at absolute rest? The answer is, we don't actually know. We could be, or we might not be. We cannot, therefore, conclude that it doesn't exist.

    Also, there would only be a contradiction between relativity and the postulate that no absolute rest exists, if absolute velocity and relative velocity were contradictory notions; there not, so no contradiction arises.

    If no contradiction arises, then absolute rest, and hence motion with respect to absolute rest, are not implicitly assumed. So not only are we unable to detect absolute rest/motion with respect to absolute rest, we are not logically compelled to assume it exists, as relativity is perfectly consistent with the assumption that no absolute rest exists.


  • #70
    roosh
    Registered Users, Registered Users 2 Posts: 2,553 ✭✭✭roosh


    Morbert wrote: »
    Yes, they are absolutely in motion with respect to each other.
    And also in absolute motion.

    Morbert wrote: »
    Or when reference frames are treated as arbitrary coordinate labels, making no implicit or explicit statement about absolute rest.
    We seem to be agreed on the fact that the two are at least indistinguishable from each other; but we disagree on the implicit assumptions. The implicit assumption can be deduced however, primarily on the basis of the fact that the photon will inherit the horizontal velocity of the moving train.

    Morbert wrote: »
    Yes, if Albert's clock is in motion, with respect to an observer, they will see the photon inherit the horizontal velocity of the train.
    It is not necessarily the perceived motion that causes the photon to be imbued with the horizontal velocity, it is the actual motion of the train.

    Morbert wrote: »
    This does not follow from the above premises. Albert's clock is absolutely at rest with respect to himself. It is absolutely in motion with respect to the other observer. Since the two observers' perspectives can be transformed into each other via the Lorentz transformation, there is no need to postulate some unknown mysterious set of dynamics unknown to Albert.
    It doesn't matter if Albert's clock is absolutely at rest relative to Albert, because, unless Albert is also at absolute rest [full stop], then the photon will be imbued with a horizontal velocity; that is, if Albert is in motion at all, then the photon in the clock will be imbued with a horizontal velocity. If there is relative motion between Albert and Henry then, at least, one of them has to be in motion, in an absolute sense.

    This means that, at least, one of their photons will be imbued with a horizontal velocity; if they both measure the speed of light to be c, then it means that the instruments belonging to one of them, must be contracted by an amount unknown to themselves.

    This true even if Minkowskian geometry is correct - Minkowskian geometry simply offers the explanation as to why this happens.

    Morbert wrote: »
    If no contradiction arises, then absolute rest, and hence motion with respect to absolute rest, are not implicitly assumed. So not only are we unable to detect absolute rest/motion with respect to absolute rest, we are not logically compelled to assume it exists, as relativity is perfectly consistent with the assumption that no absolute rest exists.
    It is also perfectly consistent with the assumption that reference frames are treated as being at absolute rest.

    No contradiction arises, because relative motion and absolute motion are not contradictory ideas. We can deduce a number of things based on the fact that a photon will be imbued with the horizontal momentum of a clock in motion.Unless the clock is not in motion whatsoever i.e. at absolute rest, then it will be imbued with the horizontal momentum of the clock. If an observer, at rest relative to the clock, measures the speed of the light to be c, then their instruments must contract by an amount unknown to themselves. Minkowskian geometry offers a constructive explanation as to how this can be, but it still implies that it must happen.


  • #71
    Morbert
    Registered Users, Registered Users 2 Posts: 3,457 ✭✭✭Morbert


    roosh wrote: »
    And also in absolute motion.

    We seem to be agreed on the fact that the two are at least indistinguishable from each other; but we disagree on the implicit assumptions. The implicit assumption can be deduced however, primarily on the basis of the fact that the photon will inherit the horizontal velocity of the moving train.

    It is not necessarily the perceived motion that causes the photon to be imbued with the horizontal velocity, it is the actual motion of the train.

    It doesn't matter if Albert's clock is absolutely at rest relative to Albert, because, unless Albert is also at absolute rest [full stop], then the photon will be imbued with a horizontal velocity that is, if Albert is in motion at all, then the photon in the clock will be imbued with a horizontal velocity. If there is relative motion between Albert and Henry then, at least, one of them has to be in motion, in an absolute sense.
    <snip>

    Again, you implicitly assume the thing you are trying to deduce. You are saying, if Albert is not at absolute rest, then he is in motion with respect to an absolute rest. I.e. You are saying absolute rest exists. You are just using different words each time.

    It is also perfectly consistent with the assumption that reference frames are treated as being at absolute rest.

    And that is entirely irrelevant to what you are trying to argue. I have said numerous times before that relativity is consistent with the metaphysical position that absolute rest exists. This is what allows us to make connections between Einsteinian and neo-Lorentzian relativity. But relativity is also consistent with the position that no absolute rest exists. This is what you disagree with. This is what you must address.
    No contradiction arises, because relative motion and absolute motion are not contradictory ideas. We can deduce a number of things based on the fact that a photon will be imbued with the horizontal momentum of a clock in motion.Unless the clock is not in motion whatsoever i.e. at absolute rest, then it will be imbued with the horizontal momentum of the clock. If an observer, at rest relative to the clock, measures the speed of the light to be c, then their instruments must contract by an amount unknown to themselves. Minkowskian geometry offers a constructive explanation as to how this can be, but it still implies that it must happen.

    Here, you repeat your implicit assumption. If it is not assumed that absolute rest exist, then the statement "Unless the clock is not in motion whatsoever i.e. at absolute rest, then it will be imbued with the horizontal momentum of the clock." does not follow. I.e. If absolute rest does not exist, then we are not compelled to say "if the clock is not at absolute rest, then it must have a horizontal velocity with respect to absolute rest".

    Also, if what you say was true, there must be a contradiction between the statement "There is no state of absolute rest." and Einstein's relativity. Otherwise, you cannot say relativity implicitly assumes a state of absolute rest exists.


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  • #72
    roosh
    Registered Users, Registered Users 2 Posts: 2,553 ✭✭✭roosh


    Morbert wrote: »
    Again, you implicitly assume the thing you are trying to deduce. You are saying, if Albert is not at absolute rest, then he is in motion with respect to an absolute rest. I.e. You are saying absolute rest exists. You are just using different words each time.
    Firstly, we can establish absolute motion by considering the example the two observers at rest relative to each other who then move relative to one another. This requires absolute motion, otherwise there would be no relative motion; with absolute motion not being dependent on an absolute reference frame; it is a simple yes or no answer to the question, is something moving or not. We can deduce that yes one of the observers has to be moving; that motion can only be measured relatively is immaterial, because we can still deduce that absolute motion exists.

    Again, not relative to an absolute reference frame, which would be necessary for measuring absolute velocity; absolute velocity, although inextricably linked to the notion of absolute motion, is a distinct concept.

    Where there is relative motion we can reasonably and logically ask the question, are the objects moving. We might not be able to discern which one is moving, but we can deduce that one must be moving, in an actual and absolute sense; again, no reference to an absolute reference frame; although we can hypothesise a theoretical one for the purpose of explanation.

    From this we can deduce that the photon in Albert's clock will be imparted with the horizontal momentum of the actual motion of the train - again, no reference to motion relative to absolute rest, just the deduction that absolute motion must occur for there to be relative motion.


    Morbert wrote: »
    And that is entirely irrelevant to what you are trying to argue. I have said numerous times before that relativity is consistent with the metaphysical position that absolute rest exists. This is what allows us to make connections between Einsteinian and neo-Lorentzian relativity. But relativity is also consistent with the position that no absolute rest exists. This is what you disagree with. This is what you must address.
    The point being made is that it is consistent with the metaphysical position of absolute rest, and that absolute rest is tacitly assumed. We can do this by considering the position of absolute rest, that is compatible with relativity and then seeing what deductions can be made.

    Absolute rest exists, and absolute rest doesn't exist are contradictory statements, so that relativity is compatible with both seems to make it contradictory.

    Morbert wrote: »
    Here, you repeat your implicit assumption. If it is not assumed that absolute rest exist, then the statement "Unless the clock is not in motion whatsoever i.e. at absolute rest, then it will be imbued with the horizontal momentum of the clock." does not follow. I.e. If absolute rest does not exist, then we are not compelled to say "if the clock is not at absolute rest, then it must have a horizontal velocity with respect to absolute rest".
    The clock will be imbued with horizontal momentum regardless of whether or not absolute rest exists, even assuming Minkowskian geometry. If Albert's train is in motion at all, then it will be imparted with a horizontal velocity; only if his train isn't moving will it not.

    We can apply this to all other observers such that, the only way that no photon will be imbued with horizontal momentum, is if no clock, train, or observer is moving. If no observer, train, or clock is moving then there would be no relative motion. That there is relative motion allows us to conclude that some obesrvers instruments must be contracted unknown to themselves.
    Morbert wrote: »
    Also, if what you say was true, there must be a contradiction between the statement "There is no state of absolute rest." and Einstein's relativity. Otherwise, you cannot say relativity implicitly assumes a state of absolute rest exists.
    The contradiction lies in what you say above, that relativity is compatible with two contradictory ideas.

    No contradiction exists between the notion of absolute velocity/motion and relative velocity/motion; hence no contradiction would exist between the idea that no state of absolute rest exists and ER.

    Again, the contradiction lies in the fact that it is compatible with two contradictory ideas.


  • #73
    Morbert
    Registered Users, Registered Users 2 Posts: 3,457 ✭✭✭Morbert


    roosh wrote: »
    Firstly, we can establish absolute motion by considering the example the two observers at rest relative to each other who then move relative to one another. This requires absolute motion, otherwise there would be no relative motion; with absolute motion not being dependent on an absolute reference frame; it is a simple yes or no answer to the question, is something moving or not. We can deduce that yes one of the observers has to be moving; that motion can only be measured relatively is immaterial, because we can still deduce that absolute motion exists.

    Again, not relative to an absolute reference frame, which would be necessary for measuring absolute velocity; absolute velocity, although inextricably linked to the notion of absolute motion, is a distinct concept.

    Where there is relative motion we can reasonably and logically ask the question, are the objects moving. We might not be able to discern which one is moving, but we can deduce that one must be moving, in an actual and absolute sense; again, no reference to an absolute reference frame; although we can hypothesise a theoretical one for the purpose of explanation.

    From this we can deduce that the photon in Albert's clock will be imparted with the horizontal momentum of the actual motion of the train - again, no reference to motion relative to absolute rest, just the deduction that absolute motion must occur for there to be relative motion.

    ---

    The clock will be imbued with horizontal momentum regardless of whether or not absolute rest exists, even assuming Minkowskian geometry. If Albert's train is in motion at all, then it will be imparted with a horizontal velocity; only if his train isn't moving will it not.

    We can apply this to all other observers such that, the only way that no photon will be imbued with horizontal momentum, is if no clock, train, or observer is moving. If no observer, train, or clock is moving then there would be no relative motion. That there is relative motion allows us to conclude that some obesrvers instruments must be contracted unknown to themselves.

    Again, you implicitly assume absolute rest. Here is your line of reasoning:

    Assume Absolute rest exists.
    Consider two observers in motion with respect to each other.
    Therefore at least one observer must be in motion with respect to absolute rest.
    Therefore absolute rest exists.

    We can just as easily consider two observers in motion with respect to each other, while assuming no absolute rest exists. The absolute motion in this case, is absolute motion between the two observers (I.e. If any observer is labelled at rest, the other will be labelled as in motion), and not absolute motion with respect to some state of absolute rest. Therefore, both reference frames, both labelling systems, are equally valid, and length contraction/time dilation emerges from the geometry relating the two arbitrary reference frames.
    The point being made is that it is consistent with the metaphysical position of absolute rest, and that absolute rest is tacitly assumed. We can do this by considering the position of absolute rest, that is compatible with relativity and then seeing what deductions can be made.

    No we can not. I have explained this before. By assuming absolute rest exists, we can show that relativity is consistent with the assumption. But to show that relativity implicitly assumes absolute rest, you must show a contradiction between "No absolute rest" and relativity.
    Absolute rest exists, and absolute rest doesn't exist are contradictory statements, so that relativity is compatible with both seems to make it contradictory.

    The contradiction lies in what you say above, that relativity is compatible with two contradictory ideas.

    Again, the contradiction lies in the fact that it is compatible with two contradictory ideas.

    They are not contradictions. Basic logic shows that two contradictory statements can both be consistent with a third statement. Consider the following three statements:

    1) P → Q
    2) R
    3) ¬R

    2) and 3) are contradictory, but both are consistent with 1), since 1) says nothing about 2) or 3). Similarly, since relativity assumes nothing about absolute rest, it is consistent with absolute rest, and no absolute rest.
    No contradiction exists between the notion of absolute velocity/motion and relative velocity/motion; hence no contradiction would exist between the idea that no state of absolute rest exists and ER.

    Leaving aside problems with the derivation, the conclusion "no contradiction would exist between the idea that no state of absolute rest exists and ER", means ER does not implicitly assume absolute rest.


  • #74
    roosh
    Registered Users, Registered Users 2 Posts: 2,553 ✭✭✭roosh


    Morbert wrote: »
    Again, you implicitly assume absolute rest. Here is your line of reasoning:

    Assume Absolute rest exists.
    Consider two observers in motion with respect to each other.
    Therefore at least one observer must be in motion with respect to absolute rest.
    Therefore absolute rest exists.
    But we don't start off by assuming that absolute rest exists.

    We start by considering only the relative motion between two observers. If we take the example of a door and a door frame, where the door starts off at rest relative to the frame, in the closed position. Subsequently, the door changes to the open position. Here we have only considered relative motion.

    The question is, how can the door go from being closed to open, without either the door, the frame, or both, actually moving i.e. without absolute motion - here we are not assuming absolute motion, we are deducing it.

    Of course, we can define a reference frame where the door is "at rest" and the frame is "in motion", and vice versa, but that just reiterates the idea that we cannot determine the absolute nature of motion i.e. we can't tell if it was the door that actually moved, or if it was the frame; we can, however, deduce that one of them, absolutely must have moved. How else could the door go from being closed to open?
    Morbert wrote: »
    We can just as easily consider two observers in motion with respect to each other, while assuming no absolute rest exists. The absolute motion in this case, is absolute motion between the two observers (I.e. If any observer is labelled at rest, the other will be labelled as in motion), and not absolute motion with respect to some state of absolute rest. Therefore, both reference frames, both labelling systems, are equally valid, and length contraction/time dilation emerges from the geometry relating the two arbitrary reference frames.
    Here you are saying that absolute motion is relative motion; absolute motion in this case, is absolute motion between the two observers; but that is a contradiction in terms.

    Again, it is easier to discern absolute motion by considering the scenario where two observers/objects start off at rest relative to each other and then start moving relative to each other. In order for relative motion to occur, one of them has to start moving in an absolute sense; this will inevitably manifest as relative motion, but still, one of the observers has to actually move in order for there to be relative motion.

    Morbert wrote: »
    No we can not. I have explained this before. By assuming absolute rest exists, we can show that relativity is consistent with the assumption. But to show that relativity implicitly assumes absolute rest, you must show a contradiction between "No absolute rest" and relativity.
    If relativity is consistent with the assumption of absolute rest, then we are perfectly entitled to start with that assumption and see what we can deduce.


    Again, the contradiction lies in the fact that relativity is compatible with two mutually exclusive assumptions.


    Morbert wrote: »
    They are not contradictions. Basic logic shows that two contradictory statements can both be consistent with a third statement. Consider the following three statements:

    1) P → Q
    2) R
    3) ¬R

    2) and 3) are contradictory, but both are consistent with 1), since 1) says nothing about 2) or 3). Similarly, since relativity assumes nothing about absolute rest, it is consistent with absolute rest, and no absolute rest.

    Leaving aside problems with the derivation, the conclusion "no contradiction would exist between the idea that no state of absolute rest exists and ER", means ER does not implicitly assume absolute rest.
    Absolute rest exists is a metaphysical assumption, which is incompatible with the other metaphysical assumption that absolute rest does not exist.

    Absolute rest exists + relativity is contradictory to Absolute rest does not exist + relativity.

    Regardless, however, we can still start off with the assumption of absolute rest and see what we can conclude, if relativity is consistent with that assumption.


  • #75
    Morbert
    Registered Users, Registered Users 2 Posts: 3,457 ✭✭✭Morbert


    roosh wrote: »
    But we don't start off by assuming that absolute rest exists.

    We start by considering only the relative motion between two observers. If we take the example of a door and a door frame, where the door starts off at rest relative to the frame, in the closed position. Subsequently, the door changes to the open position. Here we have only considered relative motion.

    The question is, how can the door go from being closed to open, without either the door, the frame, or both, actually moving i.e. without absolute motion - here we are not assuming absolute motion, we are deducing it.

    Of course, we can define a reference frame where the door is "at rest" and the frame is "in motion", and vice versa, but that just reiterates the idea that we cannot determine the absolute nature of motion i.e. we can't tell if it was the door that actually moved, or if it was the frame; we can, however, deduce that one of them, absolutely must have moved. How else could the door go from being closed to open?

    Here you are saying that absolute motion is relative motion; absolute motion in this case, is absolute motion between the two observers; but that is a contradiction in terms.

    Again, it is easier to discern absolute motion by considering the scenario where two observers/objects start off at rest relative to each other and then start moving relative to each other. In order for relative motion to occur, one of them has to start moving in an absolute sense; this will inevitably manifest as relative motion, but still, one of the observers has to actually move in order for there to be relative motion.

    Your deduction implicitly assumes absolute rest. Your reasoning, which I have pointed out in the previous post, and which you have reiterated above, contains the following:

    1)Consider two observers in motion with respect to each other.
    2)Therefore at least one observer must be in motion with respect to absolute rest.

    2) does not follow from 1) unless you assume absolute rest exists.

    If relativity is consistent with the assumption of absolute rest, then we are perfectly entitled to start with that assumption and see what we can deduce.

    Again, the contradiction lies in the fact that relativity is compatible with two mutually exclusive assumptions.

    Absolute rest exists is a metaphysical assumption, which is incompatible with the other metaphysical assumption that absolute rest does not exist.

    Absolute rest exists + relativity is contradictory to Absolute rest does not exist + relativity.

    Regardless, however, we can still start off with the assumption of absolute rest and see what we can conclude, if relativity is consistent with that assumption.

    I don't think you are following what you are saying. We have the following propositions:

    P: Einstein's Relativity
    Q:Absolute rest

    It is, of course, true that (P ∧ Q) ∧ (P ∧ ¬Q) leads to a contradiction. This, however, has nothing to do with what either of us is saying. I am saying, if Einstein's relativity implies absolute rest, then Einstein's relativity and "no absolute rest", must lead to a contradiction. I.e.

    (P → Q) → ¬(P ∧ ¬Q)

    The contrapositive of this is

    (P ∧ ¬Q) → ¬(P → Q)

    I.e. If Relativity and "No absolute rest" are consistent, then it is not true that relativity implies absolute rest. And this is the case. I can, for example, assume relativity is true, and that there is no absolute rest, and they will be perfectly consistent with each other.

    In short, the fact that relativity is perfectly consistent with the assumption that there is no absolute rest means relativity does not imply absolute rest.


  • #76
    roosh
    Registered Users, Registered Users 2 Posts: 2,553 ✭✭✭roosh


    Morbert wrote: »
    Your deduction implicitly assumes absolute rest. Your reasoning, which I have pointed out in the previous post, and which you have reiterated above, contains the following:

    1)Consider two observers in motion with respect to each other.
    2)Therefore at least one observer must be in motion with respect to absolute rest.

    2) does not follow from 1) unless you assume absolute rest exists.
    I think the problem might lie in the assumptions being made about absolute motion.

    A common representation of absolute motion appears to say that absolute motion is relative to an absolute reference frame; this effectively says that absolute motion is relative, which, of course, would be a contradiction in terms.

    If we think of absolute motion as a simple "yes or no", or "either, or" question, then there is no need to assume an absolute reference frame. Indeed, this would be more in keeping with the idea of the all important, qualifying adjective "absolute".

    We can simply ask the questions "is X moving?" or "is Y moving?"


    This is something which most people take to be common sense; when driving down the road in a car most people would come to the conclusion that it is the car that is actually moving.

    Of course, the earth could be moving too, and the car along with it; but it is possible for the car to subsequently move again. Here, there is no need for an absolute reference frame, it is a simple question of whether or not something is actually moving. Something most people take to be common sense.


    Morbert wrote: »
    I don't think you are following what you are saying. We have the following propositions:

    P: Einstein's Relativity
    Q:Absolute rest

    It is, of course, true that (P ∧ Q) ∧ (P ∧ ¬Q) leads to a contradiction. This, however, has nothing to do with what either of us is saying. I am saying, if Einstein's relativity implies absolute rest, then Einstein's relativity and "no absolute rest", must lead to a contradiction. I.e.

    (P → Q) → ¬(P ∧ ¬Q)

    The contrapositive of this is

    (P ∧ ¬Q) → ¬(P → Q)

    I.e. If Relativity and "No absolute rest" are consistent, then it is not true that relativity implies absolute rest. And this is the case. I can, for example, assume relativity is true, and that there is no absolute rest, and they will be perfectly consistent with each other.

    In short, the fact that relativity is perfectly consistent with the assumption that there is no absolute rest means relativity does not imply absolute rest.

    Relativity is effectively a description of the universe; to say that a description of the universe where absolute rest exists is compatible with a description of the universe where absolute rest does not exist, is contradictory.

    But to say that there should be a contradiction between relativity and "no absolute rest" is an empty statement, particularly when the consequences of "no absolute rest" are functionally equivalent to treating specific reference frames as being at absolute rest.

    To say that relativity is compatible with "no absolute rest" is an equally empty statement if "absolute rest" is tacitly assumed; what needs to be demonstrated is the difference between the two, and how relativity is compatible with both. Simply stating that absolute rest isn't assumed isn't sufficient, when the issue is to demonstrate that it isn't tacitly assumed.


  • #77
    Morbert
    Registered Users, Registered Users 2 Posts: 3,457 ✭✭✭Morbert


    roosh wrote: »
    I think the problem might lie in the assumptions being made about absolute motion.

    A common representation of absolute motion appears to say that absolute motion is relative to an absolute reference frame; this effectively says that absolute motion is relative, which, of course, would be a contradiction in terms.

    If we think of absolute motion as a simple "yes or no", or "either, or" question, then there is no need to assume an absolute reference frame. Indeed, this would be more in keeping with the idea of the all important, qualifying adjective "absolute".

    We can simply ask the questions "is X moving?" or "is Y moving?"

    "Moving", using the concept of notion in relativity, is a coordinate statement. I.e. It implies you are making a statement in the context of a coordinate system. So if you ask "Is X moving?", you are asking "Is X moving, according to an arbitrary coordinate system?". Hence, if you don't also supply the coordinate system, the question is meaningless. So "X is moving and Y is still." implies an arbitrary coordinate system, as does "Y is moving and X is still". They are both equally true statements.
    This is something which most people take to be common sense; when driving down the road in a car most people would come to the conclusion that it is the car that is actually moving.

    Science has repeatedly shown that intuition and common sense is not a reliable litmus test for what is and isn't physical. Just look at Quantum Mechanics for a variety of examples.
    Of course, the earth could be moving too, and the car along with it; but it is possible for the car to subsequently move again. Here, there is no need for an absolute reference frame, it is a simple question of whether or not something is actually moving. Something most people take to be common sense.

    To reiterate my above paragraph. You cannot use the word "moving" without some reference to a coordinate system. "Moving" does not exist independently from coordinate systems.
    Relativity is effectively a description of the universe; to say that a description of the universe where absolute rest exists is compatible with a description of the universe where absolute rest does not exist, is contradictory.

    But to say that there should be a contradiction between relativity and "no absolute rest" is an empty statement, particularly when the consequences of "no absolute rest" are functionally equivalent to treating specific reference frames as being at absolute rest.

    To say that relativity is compatible with "no absolute rest" is an equally empty statement if "absolute rest" is tacitly assumed; what needs to be demonstrated is the difference between the two, and how relativity is compatible with both. Simply stating that absolute rest isn't assumed isn't sufficient, when the issue is to demonstrate that it isn't tacitly assumed.

    This bit in red is the important bit. You are absolutely correct. "No absolute rest" is physically equivalent to the assumption that there is absolute rest. Hence, you cannot say relativity assumes absolute rest, since we can equivalently say relativity assumes no absolute rest. So instead, what we say is statements about absolute rest are not a part of relativity.


  • #78
    roosh
    Registered Users, Registered Users 2 Posts: 2,553 ✭✭✭roosh


    Morbert wrote: »
    "Moving", using the concept of notion in relativity, is a coordinate statement. I.e. It implies you are making a statement in the context of a coordinate system. So if you ask "Is X moving?", you are asking "Is X moving, according to an arbitrary coordinate system?". Hence, if you don't also supply the coordinate system, the question is meaningless. So "X is moving and Y is still." implies an arbitrary coordinate system, as does "Y is moving and X is still". They are both equally true statements.
    Fair enough, but that doesn't mean that an absolute reference frame has to be assumed for the purpose of absolute motion, because to suggest that absolute motion is relative would be a contradiction in terms.

    Morbert wrote: »
    Science has repeatedly shown that intuition and common sense is not a reliable litmus test for what is and isn't physical. Just look at Quantum Mechanics for a variety of examples.
    That's fair enough, but we're talking about what can be deduced from relative motion, and absolute motion is one such thing that can be deduced.

    Morbert wrote: »
    To reiterate my above paragraph. You cannot use the word "moving" without some reference to a coordinate system. "Moving" does not exist independently from coordinate systems.
    You can, we do it everyday of our lives; we talk about the earth orbiting the sun and the earth rotating, as opposed to the sun orbiting the earth; we talk about us moving as we walk down the street, as opposed to us walking on the spot while the world moves past us as though on a giant conveyor belt; we talk about an escalator moving up or down, as opposed to the entire universe shifting in such a way to give the same effect.

    All of these use the word "moving" without reference to a co-ordinate system; that the movement manifests as relative motion is secondary.

    That we cannot determine which is the true case does not mean that both are equally true, it simply means we cannot determine which is the true case; but we can deduce that one of them must be i.e. one of them must actually be moving, in an absolute sense.

    Morbert wrote: »
    This bit in red is the important bit. You are absolutely correct. "No absolute rest" is physically equivalent to the assumption that there is absolute rest. Hence, you cannot say relativity assumes absolute rest, since we can equivalently say relativity assumes no absolute rest. So instead, what we say is statements about absolute rest are not a part of relativity.
    To say that relativity assumes no absolute rest is an empty statement, because the assumption of absolute rest is implicit. That the two are functionally equivalent demonstrates the point, it doesn't invalidate it.


  • #79
    Morbert
    Registered Users, Registered Users 2 Posts: 3,457 ✭✭✭Morbert


    roosh wrote: »
    Fair enough, but that doesn't mean that an absolute reference frame has to be assumed for the purpose of absolute motion, because to suggest that absolute motion is relative would be a contradiction in terms.

    That's fair enough, but we're talking about what can be deduced from relative motion, and absolute motion is one such thing that can be deduced.

    You can, we do it everyday of our lives; we talk about the earth orbiting the sun and the earth rotating, as opposed to the sun orbiting the earth; we talk about us moving as we walk down the street, as opposed to us walking on the spot while the world moves past us as though on a giant conveyor belt; we talk about an escalator moving up or down, as opposed to the entire universe shifting in such a way to give the same effect.

    All of these use the word "moving" without reference to a co-ordinate system; that the movement manifests as relative motion is secondary.

    All of those statements make implicit reference to a coordinate system. Walking down the street is moving "with respect to the street". Orbiting the sun is moving "with respect to the sun". Since all statements of moving make reference to a coordinate system, we cannot therefore infer an "absolute" reference frame where objects are "truly" moving, without the added assumption that absolute rest exists.
    That we cannot determine which is the true case does not mean that both are equally true, it simply means we cannot determine which is the true case; but we can deduce that one of them must be i.e. one of them must actually be moving, in an absolute sense.

    You cannot even deduce that one of them must be a "truer" case, because physics itself, not just experimental apparatus, is invariant in either case. I.e. To speak of a "correct" reference frame is physically meaningless.
    To say that relativity assumes no absolute rest is an empty statement, because the assumption of absolute rest is implicit. That the two are functionally equivalent demonstrates the point, it doesn't invalidate it.

    That the two are physically equivalent completely invalidates your point, as I showed earlier. If you cannot show a logical contradiction between relativity and "no absolute rest", then you cannot say relativity implicitly assumes absolute rest. This is why I have repeatedly asked you for a contradiction between relativity and "no absolute rest".


  • #80
    roosh
    Registered Users, Registered Users 2 Posts: 2,553 ✭✭✭roosh


    Morbert wrote: »
    All of those statements make implicit reference to a coordinate system. Walking down the street is moving "with respect to the street". Orbiting the sun is moving "with respect to the sun". Since all statements of moving make reference to a coordinate system, we cannot therefore infer an "absolute" reference frame where objects are "truly" moving, without the added assumption that absolute rest exists.
    We make plenty of unqualified statements such as "I am moving"; "I didn't move, you moved"; [on a train] "we're moving"; [in traffic] "we're not moving"; and many, many more.

    None of which refer to a reference frame; and none of which assume that absolute rest exists. Indeed, the idea of absolute rest isn't necessary for the concept of absolute motion. To say that absolute motion is motion relative to absolute rest is to say that absolute motion is relative motion, which is a contradiction in terms.

    Absolute motion is the idea of motion that isn't qualified as being relative to anything; it is a "yes or no", "either, or" question.


    While we don't need to assume that any object is in a state of absolute rest, we can use the concept as a purely hypothetical, mathematical construct for the purpose of deduction; we can't measure velocities relative to it, but we can make certain deductions about the physical world by considering it. Something you mention is entirely compatible with Einsteinian relativity.

    Morbert wrote: »
    You cannot even deduce that one of them must be a "truer" case, because physics itself, not just experimental apparatus, is invariant in either case. I.e. To speak of a "correct" reference frame is physically meaningless.
    The issue might lie in stating that we cannot say that one reference frame is more true than any other, and I wouldn't necessarily disagree with that; what we can deduce however, is that, at least one object must absolutely be in motion. This would have certain deductive consequences that would not, necessarily, be revealed by the mathematical reference frames.


    Morbert wrote: »
    That the two are physically equivalent completely invalidates your point, as I showed earlier. If you cannot show a logical contradiction between relativity and "no absolute rest", then you cannot say relativity implicitly assumes absolute rest. This is why I have repeatedly asked you for a contradiction between relativity and "no absolute rest".
    The statement that "relativity doesn't implicitly assume absolute rest" is a bare assertion fallacy; it's an empty statement.

    What you need to demonstrate is the difference between "no absolute rest" and "absolute rest" and how relativity includes one but not the other; because if there is no difference between them, then they are the same thing i.e. what you are asserting isn't absolute rest, is actually absolute rest.

    Bear in mind that the difference between inertial motion [that isn't absolute rest] and absolute rest pertains to the path length of a photon in a light clock.


  • #81
    antiselfdual
    Registered Users, Registered Users 2 Posts: 170 ✭✭antiselfdual


    roosh wrote: »
    We make plenty of unqualified statements such as "I am moving"; "I didn't move, you moved"; [on a train] "we're moving"; [in traffic] "we're not moving"; and many, many more.

    Come on, that's the English language, not physics.

    Can you write down a single physical formula for motion which is equivalent to the statement that something is "absolutely moving"?
    roosh wrote: »
    None of which refer to a reference frame; and none of which assume that absolute rest exists. Indeed, the idea of absolute rest isn't necessary for the concept of absolute motion. To say that absolute motion is motion relative to absolute rest is to say that absolute motion is relative motion, which is a contradiction in terms.

    Motion by definition is something like "change in position with respect to time." Change in position is inherently relative because "position" is a physical property that depends on where you choose to measure from.

    Absolute motion would be motion with respect to an absolutely defined (valid everywhere in the universe) set of position measurements. The motion is relative to those measurements which can be used by anybody anywhere to see if an object is absolutely moving or not absolutely moving.

    For instance, if somebody is "moving" down a street then by that motion we mean that if we measure from the start of the street, or from one metre from the start of the street, that their distance from that point changes.

    If on the other hand we were walking beside this person at the exact same pace in the same direction then they have no motion away from us, so then they are not moving if we choose to measure all motion as motion with respect to our own position.

    There is no physical reason to say "motion with respect to the start of the street" is more fundamental than "motion with respect to my own position." However if there was a notion of absolute motion, ie if there was an absolute set of coordinates that someone walking down the street could use to measure the motion of somebody walking beside them, then they could try to say things like "this person is really moving, absolutely."

    Notice that when I say things like "someone walking down the street" that is not saying "someone is absolutely moving down the street." Someone walking down the street is an English sentence that in proper physical terms means just that another person placed at the start of the street measures the distance between them and the someone as changing.


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  • #82
    roosh
    Registered Users, Registered Users 2 Posts: 2,553 ✭✭✭roosh


    antiselfdual wrote: »
    Come on, that's the English language, not physics.

    Can you write down a single physical formula for motion which is equivalent to the statement that something is "absolutely moving"?
    The english language, like language in general, evolved to allow us to communicate about our experience of the universe; Physics is just an extension of that, and where it uses the english language in its formulation, it isn't completely divorced from it.

    As for writing down an equation, I don't see why it is necessary; we only need to be able to make certain deductions, that don't necessarily involve any measurements or calculations.

    antiselfdual wrote: »
    Motion by definition is something like "change in position with respect to time." Change in position is inherently relative because "position" is a physical property that depends on where you choose to measure from.
    Motion is also a state, the absolute nature of which cannot be determined by experiment.

    Absolute means
    Philosophy
    • a value or principle which is regarded as universally valid or which may be viewed without relation to other things
    So absolute motion would be the state of motion that may be viewed without relation to other things.

    antiselfdual wrote: »
    Absolute motion would be motion with respect to an absolutely defined (valid everywhere in the universe) set of position measurements. The motion is relative to those measurements which can be used by anybody anywhere to see if an object is absolutely moving or not absolutely moving.
    This is saying that absolute motion is relative motion, just motion relative to an absolute reference frame. Absolute motion ins't relative motion, not least because it is possible to experimentally determine relative motion. It would also be a contradiction in terms.
    antiselfdual wrote: »
    For instance, if somebody is "moving" down a street then by that motion we mean that if we measure from the start of the street, or from one metre from the start of the street, that their distance from that point changes.

    If on the other hand we were walking beside this person at the exact same pace in the same direction then they have no motion away from us, so then they are not moving if we choose to measure all motion as motion with respect to our own position.
    If someone is "moving" down the street then we mean that we can measure the change in distance from a given point, but also, we mean that the person is actively "doing the moving", while the street is passive.

    We don't say, as the univers shifted around the person, and the road behaved like a treadmill, so as to cause a change in distance between the person and the point of reference, as they pumped their legs; this is because we attribute the movement to the person walking

    Even if we cannot determine which scenario actually happened, we know that it must have been one or the other, otherwise there would have been no relative motion to measure; the person would have remained at rest relative to the street.

    Yes we can define a frame of reference which labels either as moving, but unless one actually moves, then there would be no relative motion to warrant those labels.

    antiselfdual wrote: »
    There is no physical reason to say "motion with respect to the start of the street" is more fundamental than "motion with respect to my own position." However if there was a notion of absolute motion, ie if there was an absolute set of coordinates that someone walking down the street could use to measure the motion of somebody walking beside them, then they could try to say things like "this person is really moving, absolutely."
    We cannot say that "motion with respect to the start of the street" than "motion with respect to my own position" - let's call that A, and the reverse B - because we cannot determine if that is the case; what we can say, however, is that either A is mor fundamental than B, or B is more fundamental than A i.e. one is more fundamental than the other, we just cannot determine which one.

    Of course, both A and B could be true, but that would just further compound the idea of absolute motion.

    antiselfdual wrote: »
    Notice that when I say things like "someone walking down the street" that is not saying "someone is absolutely moving down the street." Someone walking down the street is an English sentence that in proper physical terms means just that another person placed at the start of the street measures the distance between them and the someone as changing.
    It is an english sentence that attempts to characterise our experience of the physical world; it ascribes the act of motion to the person walking; notice that you don't say that the road is moving [like a treadmill], this is because we view the road as being passive in the scenario where relative motion occurs between us and the road.

    Of course, the road can be moving, as indeed it is, if the earth is in orbit or rotating; but being in motion with it, we can subsequently move again, along the surface of the earth.

    Again, we can define reference frames that label either the road or ourselves as moving, but unless one of us us actually moving, then there would be no relative velocity to cause us to label either as moving. We can't determine which it is, but we can determine it must be one or the other.

    Example
    Just to try and highlight the example again; you start off at rest relative to the road; in order for relative motion to occur either your walking must propel you forward, or you walk as though on a treadmill; those two scenarios account for the relative motion that is measured, but both are two different examples which entail relative motion.

    I don't doubt that you understand the difference.


  • #83
    citrus burst
    Registered Users, Registered Users 2 Posts: 147 ✭✭citrus burst


    I've been following this thread for a while now and have gotten a little lost. Roosh what do you mean by absolute motion? I saw the definition you wrote earlier, but it doesn't really make the idea clear. Its one thing to define something, its another thing to explain something and show that you fully understand it.

    For me the English word absolute, means in a physical sense, something that is observed to agree with all observers no matter how, when, where or what the measurement is taken or the theory is described . There are few instances in science where it is actually used, the only one I can think of is absolute zero.

    Any way from what I can see from what you say by absolute motion, this is an agreed upon reference frame, that the entire universe has decided is moving. No matter where the observer is or what they are doing they will all say it is moving, even if they are moving along with the absolute frame.

    My understanding could be wrong, but to me that seems a little unintuitive.


    As regard to relative motion
    roosh wrote: »
    If someone is "moving" down the street then we mean that we can measure the change in distance from a given point, but also, we mean that the person is actively "doing the moving", while the street is passive.

    We don't say, as the univers shifted around the person, and the road behaved like a treadmill, so as to cause a change in distance between the person and the point of reference, as they pumped their legs; this is because we attribute the movement to the person walking

    This is true, however in a relativistic sense. Although we know that we are doing the moving down the street, both scenarios are equal. Its just a matter of how you set up your initial coordinate system.
    roosh wrote: »
    Even if we cannot determine which scenario actually happened, we know that it must have been one or the other, otherwise there would have been no relative motion to measure; the person would have remained at rest relative to the street.

    This is not entirely true. We could set up a coordinate system where both the street and the person is moving, with the exact same consequences. Although it would be pointless and greatly increase the difficulty of the problem it can still be done.
    roosh wrote: »
    Yes we can define a frame of reference which labels either as moving

    True
    roosh wrote: »
    but unless one actually moves, then there would be no relative motion to warrant those labels.

    Also true, but it would be a terribly very boring universe, in an already boring universe with only a man and a street.:)
    roosh wrote: »

    We cannot say that "motion with respect to the start of the street" than "motion with respect to my own position"

    Again true, they are two different scenarios.
    roosh wrote: »
    - let's call that A, and the reverse B - because we cannot determine if that is the case; what we can say, however, is that either A is mor fundamental than B, or B is more fundamental than A i.e. one is more fundamental than the other, we just cannot determine which one.

    Again true, but not in the sense that you think. Neither is "fundamental," that is a bad choice of words. Both are scenarios that we arbitrarily set up to determine the outcome of the same event. Both are correct, both are equivalent and both are equal. Just a different way of looking at the same thing.

    roosh wrote: »
    Of course, both A and B could be true

    In fact both are true.
    roosh wrote: »
    but that would just further compound the idea of absolute motion.

    Again I need further clarification of what you mean.*
    roosh wrote: »
    It is an english sentence that attempts to characterise our experience of the physical world; it ascribes the act of motion to the person walking; notice that you don't say that the road is moving [like a treadmill], this is because we view the road as being passive in the scenario where relative motion occurs between us and the road.

    English has no place in science :pac:
    roosh wrote: »
    Of course, the road can be moving, as indeed it is, if the earth is in orbit or rotating; but being in motion with it, we can subsequently move again, along the surface of the earth.

    Think of a car and a tree. The tree sees a car coming straight at it at an alarming speed. The car sees a tree coming at it at an alarming speed. We know that the car is doing the "actual" moving ( I think this is what you mean by "absolute motion" ) however both are right. The tree didn't uproot and run at the car.

    Introducing the earth is an unnecessary complication, but we can still use it if we want.
    roosh wrote: »
    Again, we can define reference frames that label either the road or ourselves as moving, but unless one of us us actually moving, then there would be no relative velocity to cause us to label either as moving. We can't determine which it is, but we can determine it must be one or the other.

    This further increases my belief that you mean the "thing" doing the motion when you say "absolute motion." We are lucky (and unlucky) to have a stable reference frame that we call the earth, from which we can make all of our measurements. Most day to day measurements wrt to motion are made relative to this stable frame. As a result humans have a fundamental built in intuition about what moves wrt it. This is not to say that its correct. Essentially everything not moving (trees, buildings, mountains etc) is in the same reference frame as the earth, everything else is in a different frame. Its how we compare these reference frames that matters.

    We use the earth like the street in the earlier argument. For most its a good approximation of a flat infinite plane.

    Hope this all makes sense

    *Just had an idea, by absolute motion, do you mean the thing that is actually doing the motion?


  • #84
    Morbert
    Registered Users, Registered Users 2 Posts: 3,457 ✭✭✭Morbert


    Instead of repeating what citrusburst and antiselfdual have said, I will ask you these question:

    If you believe there is a state of absolute motion, do you believe it is possible to not be in a state of absolute motion? What would you call this state?

    Hopefully these questions should illustrate why you are (perhaps unknowingly) presupposing a state of absolute rest in your understanding of motion.


  • #85
    roosh
    Registered Users, Registered Users 2 Posts: 2,553 ✭✭✭roosh


    Cheers Citrus, it's refreshing to not just get the usual reply that "actually moving" doesn't make sense. I will reply to individual points in your post, but just to say that you are correct in your interpretation, by "absolute motion" I mean "the thing that is actually doing the motion"
    citrus burst wrote: »
    I've been following this thread for a while now and have gotten a little lost. Roosh what do you mean by absolute motion? I saw the definition you wrote earlier, but it doesn't really make the idea clear. Its one thing to define something, its another thing to explain something and show that you fully understand it.

    For me the English word absolute, means in a physical sense, something that is observed to agree with all observers no matter how, when, where or what the measurement is taken or the theory is described . There are few instances in science where it is actually used, the only one I can think of is absolute zero.

    Any way from what I can see from what you say by absolute motion, this is an agreed upon reference frame, that the entire universe has decided is moving. No matter where the observer is or what they are doing they will all say it is moving, even if they are moving along with the absolute frame.

    My understanding could be wrong, but to me that seems a little unintuitive.
    I'm not sure if what you say later in the post supercedes this, but I will address it for the sake of clarity.

    By "absolute motion" I am not suggesting that there is an agreed upon reference frame, that the entire universe has decided is moving.

    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
    That is, the concept of a reference frame doesn't necessarily come into it. It is a statement about the absolute nature of motion, as opposed to the measurement of what that motion is relative to.

    The experimental test of the principle of relativity states that
    Any uniformly moving observer in an inertial frame cannot determine his "absolute" state of motion by a co-moving experimental arrangement.
    Tests of SR

    The term "absolute motion" I take to refer to a "state of motion", without necessarily qualifying it as being relative to something.


    Contextual understanding
    For some reason the idea seems to cause some confusion, but I think some contextual examples should help clarify the meaning.

    I see "absolute motion" as being a "yes or no" question, or an "either, or" question e.g.:
    "Is X moving?"
    "Is Y moving?"
    "Is X or Y moving?"

    None of these make reference to a reference frame, they don't qualify the statement with "relative to Z"; they are questions about the absolute nature of motion i.e. which one is doing the moving.


    Everyday examples
    An everyday example would be driving down the road; we can ask the question "is my car moving?" or "is the road moving?". Yes, the car is moving relative to the road, and the road is moving relative to the car - that is relative motion; but the question of which is actively "doing the moving", without qualifying the statement by adding "relative to X", is a question of "absolute motion".


    Even if we cannot determine which one is actively "doing the moving", we can deduce that, at least one of them has to be.

    citrus burst wrote: »
    As regard to relative motion


    This is true, however in a relativistic sense. Although we know that we are doing the moving down the street, both scenarios are equal. Its just a matter of how you set up your initial coordinate system.
    While we can define different co-ordinate labeling systems which label us as moving relative to the road, and the road as moving relative to us, and both those are perfectly equal; the question of "which one is doing the moving" introduces a disparity, which has logical consequences.

    They represent two different scenarios which result in the same, observed, relative motion, but we can make deductions about the physical consequences, that aren't necessarily revealed by co-ordinate labeling systems,

    citrus burst wrote: »
    This is not entirely true. We could set up a coordinate system where both the street and the person is moving, with the exact same consequences. Although it would be pointless and greatly increase the difficulty of the problem it can still be done.
    Apologies, I should have included that third possibility, but I find that it can, sometimes, help to deal with just the two contrasting possibilities and say that "at least" one of them has to be the case.

    The point is, essentially, wherever there is relative motion, at least one of the relatively moving bodies has to, actually, be doing the moving.

    citrus burst wrote: »
    Also true, but it would be a terribly very boring universe, in an already boring universe with only a man and a street.:)
    Very true; but it would narrow the number of possible answers to the question, "how many roads must a man walk down, before you can call him a man?
    :D

    citrus burst wrote: »
    Again true, they are two different scenarios.
    With different deductive consequences.

    citrus burst wrote: »
    Again true, but not in the sense that you think. Neither is "fundamental," that is a bad choice of words. Both are scenarios that we arbitrarily set up to determine the outcome of the same event. Both are correct, both are equivalent and both are equal. Just a different way of looking at the same thing.
    Again, apologies, I was trying to stick with the terminology that antiselfdual had used, for the purpose of explanation.

    While both scenarios are potentially two different ways of looking at the same thing, I wouldn't necessarily say that they are equal or equivalent; they each have different deductive consequences.

    The mathematical reference frames may be equivalent, or equally valid, but the mathematical reference frames don't allow us to make certain deductions, that considering the two physically different scenarios does.

    citrus burst wrote: »
    In fact both are true.
    I would say that both mathematical reference frames, which label each as moving relative to the other, are true; however, we cannot determine which physical scenario is the true one, or even if both are true; these physical scenarios are independent of the co-ordinate referencing system, despite the fact that the co-ordinate labeling system is entirely dependent on the physical scenario.

    While we cannot determine which of A, B, or C is correct, we can deduce that either A, B, or C has to be correct.

    And each one has different deductive consequences.

    citrus burst wrote: »
    Again I need further clarification of what you mean.*
    You are pretty much spot on with the "addendum"; I am referring to "the thing that is actively, or actually, doing the motion"

    Hopefully the above also helps to clarify it.

    citrus burst wrote: »
    English has no place in science :pac:
    Apparently so!
    :p

    citrus burst wrote: »
    Think of a car and a tree. The tree sees a car coming straight at it at an alarming speed. The car sees a tree coming at it at an alarming speed. We know that the car is doing the "actual" moving ( I think this is what you mean by "absolute motion" ) however both are right. The tree didn't uproot and run at the car.
    I would agree that we can define a reference frame which says the car is moving relative to the tree and a different reference frame which says the tree is moving relative to the car; I would also agree that it is the car that is doing the "actual" moving.

    However, we apparently cannot determine if the car is doing the "actual" moving; for all we know, the earth could be doing the "actual" moving and the cars wheels could just be rotating in the opposite direction to a giant conveyor belt, at the exact speed to offset the speed of the conveyor belt moving in the opposite direction.

    It think, however, that we can deduce that it is, at the very least, one or the other which is true; of course, the cars wheels could be turning at a faster pace than the conveyor belt and both could be true.


    All three scenarios would have different deductive consequences though, which is probably easier to determine if we introduce a light clock for each observer.

    citrus burst wrote: »
    Introducing the earth is an unnecessary complication, but we can still use it if we want.
    I would agree with that, that is why I generally tend to avoid it; we can equally consider just the relative motion between the earth and the sun, but the deductions would be the same.


    citrus burst wrote: »
    This further increases my belief that you mean the "thing" doing the motion when you say "absolute motion." We are lucky (and unlucky) to have a stable reference frame that we call the earth, from which we can make all of our measurements. Most day to day measurements wrt to motion are made relative to this stable frame. As a result humans have a fundamental built in intuition about what moves wrt it. This is not to say that its correct. Essentially everything not moving (trees, buildings, mountains etc) is in the same reference frame as the earth, everything else is in a different frame. Its how we compare these reference frames that matters.

    We use the earth like the street in the earlier argument. For most its a good approximation of a flat infinite plane.
    That is pretty much exactly what I mean, "the 'thing' doing the motion".

    My understanding though, is that everything in the universe is in every reference frame, it just depends on what the motion is measured relative to. That is, the sun is in the reference frame that labels the earth as "at rest", but the sun is labeled as "in motion relative to the Earth", and vice versa.

    The Lorentz transform then allows us to determine the co-ordinates of a different refrence frame, using the co-ordinates of any given reference frame,

    citrus burst wrote: »
    Hope this all makes sense
    Cheers Citrus, it did make perfect sense; I hope that what I said also made sense.

    citrus burst wrote: »
    *Just had an idea, by absolute motion, do you mean the thing that is actually doing the motion?
    Pretty much.


  • #86
    roosh
    Registered Users, Registered Users 2 Posts: 2,553 ✭✭✭roosh


    Morbert wrote: »
    Instead of repeating what citrusburst and antiselfdual have said, I will ask you these question:

    If you believe there is a state of absolute motion, do you believe it is possible to not be in a state of absolute motion? What would you call this state?

    Hopefully these questions should illustrate why you are (perhaps unknowingly) presupposing a state of absolute rest in your understanding of motion.

    If I can just turn the question around: if we can deduce that at least one observer, of two relatively moving observers, has to actually be moving i.e. has to be in a state of absolute motion, is it possible to be in a state of non-absolute motion; what would you call this state of non-absolute motion?

    This should hopefully demonstrate that it is a deduction, not an assumption.


  • #87
    Morbert
    Registered Users, Registered Users 2 Posts: 3,457 ✭✭✭Morbert


    roosh wrote: »
    If I can just turn the question around: if we can deduce that at least one observer, of two relatively moving observers, has to actually be moving i.e. has to be in a state of absolute motion, is it possible to be in a state of non-absolute motion; what would you call this state of non-absolute motion?

    This should hopefully demonstrate that it is a deduction, not an assumption.

    The problem is we can't deduce such a thing. "Motion", in this case, means any coordinate system we use has to label at least one of the observers as in motion. That is all it means. You cannot deduce absolute motion, in the sense of an absolute velocity, from this.

    What is happening is you are deducing a specific concept of motion (The idea that no reference frame labels both observers as at rest), and then unknowingly switching your definition of motion to mean an absolute velocity.


  • #88
    antiselfdual
    Registered Users, Registered Users 2 Posts: 170 ✭✭antiselfdual


    So after thinking about this my own explanation of this argument is the following:

    What you're saying is basically that if X perceives Y to be moving, and itself fixed, and we could also switch to the Y reference frame in which Y is fixed and X is moving, then it must be true that one of X or Y is "actually" moving, which you call "absolute" motion.

    The first point here is that your definition of "absolute motion" is not the same as the standard physics definition of absolute motion (as you yourself have said and which I did not realise at first). So I will therefore term what you are describing as "intrinsic motion." You argue that if both X and Y observe the other to be moving then one of them must have an "intrinsic motion" as otherwise no motion could have occurred.

    The problem is that this notion is completely unphysical, because even if we suppose that object X in some situation has an intrinsic motion we are always able to find a reference frame in which X is not moving (actually we can find an infinite number of reference frames in which X is not moving as well as an infinite number of reference frames in which X is moving). In fact we can describe all of the laws of physics in the reference frame in which X is not moving, and they will be as valid there as in a reference frame in which X is moving. Therefore it makes absolutely no physical difference if we regard X as to have "intrinsic motion" or not.

    As a result I think your argument that "something must actually be moving" is in some sense pure semantics, because there is no way you can draw a physical distinction between X having intrinsic motion or Y having intrinsic motion.


  • #89
    roosh
    Registered Users, Registered Users 2 Posts: 2,553 ✭✭✭roosh


    Morbert wrote: »
    The problem is we can't deduce such a thing. "Motion", in this case, means any coordinate system we use has to label at least one of the observers as in motion. That is all it means. You cannot deduce absolute motion, in the sense of an absolute velocity, from this.

    What is happening is you are deducing a specific concept of motion (The idea that no reference frame labels both observers as at rest), and then unknowingly switching your definition of motion to mean an absolute velocity.

    I think that is where the confusion lies; the purpose isn't to deduce the existence of an absolute velocity, it is to deduce something about absolute motion; that is, to deduce something about the nature of motion as opposed to its measurement.

    When we talk about motion with respect to a reference frame, we are necessarily talking about relative motion, not absolute motion. Absolute motion doesn't necessarily require a reference frame because it pertains to the nature, or state of motion.

    In general, where there is relative motion between two bodies we can determine three physically distinct scenarios which account for the relative motion, all of which make different statements pertaining to the nature of motion of the bodies involved. We can't deduce which scenario is the true one, but we can deduce that one of them must be, and with it that one of the bodies must absolutely be in motion.


  • #90
    roosh
    Registered Users, Registered Users 2 Posts: 2,553 ✭✭✭roosh


    antiselfdual wrote: »
    So after thinking about this my own explanation of this argument is the following:

    What you're saying is basically that if X perceives Y to be moving, and itself fixed, and we could also switch to the Y reference frame in which Y is fixed and X is moving, then it must be true that one of X or Y is "actually" moving, which you call "absolute" motion.

    The first point here is that your definition of "absolute motion" is not the same as the standard physics definition of absolute motion (as you yourself have said and which I did not realise at first). So I will therefore term what you are describing as "intrinsic motion." You argue that if both X and Y observe the other to be moving then one of them must have an "intrinsic motion" as otherwise no motion could have occurred.

    The problem is that this notion is completely unphysical, because even if we suppose that object X in some situation has an intrinsic motion we are always able to find a reference frame in which X is not moving (actually we can find an infinite number of reference frames in which X is not moving as well as an infinite number of reference frames in which X is moving). In fact we can describe all of the laws of physics in the reference frame in which X is not moving, and they will be as valid there as in a reference frame in which X is moving. Therefore it makes absolutely no physical difference if we regard X as to have "intrinsic motion" or not.

    As a result I think your argument that "something must actually be moving" is in some sense pure semantics, because there is no way you can draw a physical distinction between X having intrinsic motion or Y having intrinsic motion.
    The argument only seems like semantics because there appears to be some dispute over what the concept of absolute motion means; I'm trying to use a more rigorous definition that accurately reflects the idea of "absolute" and pertains to the nature of motion. The standard scientific definition, which attempts to define absolute motion as being relative [to an absolute referece frame], is self-contradictory, and only relates to the measurement of motion. The term "intrinsic" is probably helpful in this regard.

    It's interesting that you should say that the intrinsic motion of a body is completely unphysical and then qualify it by saying that we will always be able to find a reference frame in which the body is not moving; when it is, of course, the abstract, mathematical reference frames which have no intrinsic physicality. The intrinsic motion of an object is entirely phyiscal, and is not dependent on mathematical reference frames.

    Indeed, once we establish the idea of intrinsic motion we can then proceed to see what deductive consequences that it has; which, of course, will be entirely phyiscal.


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  • #91
    Morbert
    Registered Users, Registered Users 2 Posts: 3,457 ✭✭✭Morbert


    roosh wrote:
    I think that is where the confusion lies; the purpose isn't to deduce the existence of an absolute velocity, it is to deduce something about absolute motion; that is, to deduce something about the nature of motion as opposed to its measurement.

    When we talk about motion with respect to a reference frame, we are necessarily talking about relative motion, not absolute motion. Absolute motion doesn't necessarily require a reference frame because it pertains to the nature, or state of motion.

    In general, where there is relative motion between two bodies we can determine three physically distinct scenarios which account for the relative motion, all of which make different statements pertaining to the nature of motion of the bodies involved. We can't deduce which scenario is the true one, but we can deduce that one of them must be, and with it that one of the bodies must absolutely be in motion.

    ---

    Indeed, once we establish the idea of intrinsic motion we can then proceed to see what deductive consequences that it has; which, of course, will be entirely phyiscal.

    That is the problem. You have not established the idea of intrinsic motion. We know that the motion of a body is reference-frame dependent, and we know that there are scenarios where no reference frame will label two objects as at rest. This in no way establishes intrinsic motion.


  • #92
    roosh
    Registered Users, Registered Users 2 Posts: 2,553 ✭✭✭roosh


    Morbert wrote: »
    That is the problem. You have not established the idea of intrinsic motion. We know that the motion of a body is reference-frame dependent, and we know that there are scenarios where no reference frame will label two objects as at rest. This in no way establishes intrinsic motion.
    The relative motion of a body is frame dependent; the absolute nature of motion is not.

    And while we know that there are scenarios where no reference frame will label two objects as "at rest", we can distinguish those scenarios physically, in such a manner that makes implications about the absolute nature of the motion, of those objects; we can also deduce that of the possible scenarios, at least one has to be correct - because they are physically different and can't all be simultaneosuly true; from this we are left with the implications about the absolute nature of the motion, of the objects.


  • #93
    Duggys Housemate
    Closed Accounts Posts: 3,298 ✭✭✭Duggys Housemate


    The term absolute is getting abused here. An absolute velocity would be one which all observers could measure against and agree to its velocity. Possibly light has absolute motion.

    Roosh wants to make the term mean the item being propelled by a force to get it to a certain velocity relative to its initial local frame ( generally the local frame is the Earth) and he thinks that is qualitatively different from the relative motion of the frame ( the earth) to the rest of the universe.

    Well as far as I can tell. All of this seems to be off topic to the Lorenz contractions, which, it must be pointed out are confirmed empirically.


  • #94
    roosh
    Registered Users, Registered Users 2 Posts: 2,553 ✭✭✭roosh


    Duggys Housemate wrote: »
    The term absolute is getting abused here. An absolute velocity would be one which all observers could measure against and agree to its velocity. Possibly light has absolute motion.

    Roosh wants to make the term mean the item being propelled by a force to get it to a certain velocity relative to its initial local frame ( generally the local frame is the Earth) and he thinks that is qualitatively different from the relative motion of the frame ( the earth) to the rest of the universe.

    Well as far as I can tell. All of this seems to be off topic to the Lorenz contractions, which, it must be pointed out are confirmed empirically.
    Indeed, the term "absolute" is getting abused here; because some people seem to be insisting on an interpretation of the term absolute that makes it relative; which of course is a contradiction in terms.

    But I think I see the issue; there seems to be confusion about what is being stated; I haven't mentioned anything about an absolute velocity, which, of course, implies a measurable value. I have been speaking, strictly, about absolute motion, which refers to the state of motion of an object.

    To highlight the difference: I can go outside and observe relatively moving objects, without necessarily knowing their relative velocity; obtaining a value for the relative velocity requires me to perform certain subsequent tasks i.e. measurements.

    The nature of motion of an object is not necessarily a measureable quality, and so it doesn't require a reference frame. Again, it is a "yes or no", "either, or" question; or a statement that isn't qualified by saying "relative to X" e.g. "I am moving" as opposed to "I am moving relative to X".

    What I "want to make the term" is consistent and corresponding to its actual meaning, as opposed to defining it in a logically, self-contradictroy manner, as appears to be the case with the historical conceptualisation.

    Lorentz contractions
    It actually does pertain to the topic of Lorentz contractions, because, of course, it pertains to the motion; absolute motion which gives rise to the relative motion between objects, and thus necessitates the use of Lorentz contractions.

    Where I was wrong in my OP was that I wasn't aware of Lorentzian relativity, which also uses the Lorentz transform, but which does include the concept of absolute motion. The issue was the implicit assumption of absolute rest in Einsteinian reference frames, something which isn't the case in Lorentzian relativity.


  • #95
    Morbert
    Registered Users, Registered Users 2 Posts: 3,457 ✭✭✭Morbert


    The relative motion of a body is frame dependent; the absolute nature of motion is not.

    And while we know that there are scenarios where no reference frame will label two objects as "at rest", we can distinguish those scenarios physically, in such a manner that makes implications about the absolute nature of the motion, of those objects; we can also deduce that of the possible scenarios, at least one has to be correct - because they are physically different and can't all be simultaneosuly true; from this we are left with the implications about the absolute nature of the motion, of the objects.

    And by absolute motion, you mean motion intrinsic to the object (which you have not established), as opposed to an absolute statement about the motion of an object, relative to another.

    "Am I moving?" Is a frame-dependant question. The answer will be different for different observers, hence not "absolute".

    "Am I moving, relative to X?" is a frame-independent question. The answer will be the same for all observers. The answer is absolute. This, however, in no way establishes any notion of intrinsic, frame-independent "absolute" motion.


  • #96
    roosh
    Registered Users, Registered Users 2 Posts: 2,553 ✭✭✭roosh


    Morbert wrote: »
    And by absolute motion, you mean motion intrinsic to the object (which you have not established), as opposed to an absolute statement about the motion of an object, relative to another.

    "Am I moving?" Is a frame-dependant question. The answer will be different for different observers, hence not "absolute".

    "Am I moving, relative to X?" is a frame-independent question. The answer will be the same for all observers. The answer is absolute. This, however, in no way establishes any notion of intrinsic, frame-independent "absolute" motion.

    An absolute statement about the motion of an object, relative to another, is entirely distinct from a statement about the absolute, or intrinsic nature of motion, of an object.

    "I am moving, relative to X" is an absolute statement about the motion of an object relative to another, because it specifies the object relative to which "I" am in motion.

    "I am moving" is a statement about the absolute nature of the motion, of an object, precisely because it doesn't make reference to the object, relative to which it is moving.


    "I am moving" isn't frame dependent, because it doesn't specify a frame or a set of co-orindates, relative to which the motion occurs; it is a simple statement about the absolute nature of motion. Regardless of the reference frame, the act of motion is ascribed to a specified object.


    EDIT: We can see that the question "Am I moving?" relates to the absolute nature of motion of an object, by considering the example of the train at rest relative to another train, in the station; when the trains start moving relative to each other, the question "am I (or is our train) moving, or is it the other train that is moving?" clearly relates to a question about the intrinsic motion of the train, because there is no question that the trains are moving relative to one another, or that the observer, asking the question, is at rest relative to their own train. In fact, it is the self-evident relative motion between the trains which prompts the question, which one is actually moving.


    Again, our three scenarios are deductively different, and cannot possibly, all be true; each one makes implicit reference to the intrinsic motion of the objects involved. While we cannot determine which one is true, we can determine that one of them must be true, and with it that objects must have intrinsic motion.


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  • #97
    Duggys Housemate
    Closed Accounts Posts: 3,298 ✭✭✭Duggys Housemate


    I am moving is the same statement as I am moving relative to X, as you always move relative to something. These are word games, which is part of the problem with philosophy. None of it threatens Lorenz contractions which are assumed in theory and verified empirically - GPS satellites have to adjust their clocks.


  • #98
    roosh
    Registered Users, Registered Users 2 Posts: 2,553 ✭✭✭roosh


    Duggys Housemate wrote: »
    I am moving is the same statement as I am moving relative to X, as you always move relative to something. These are word games, which is part of the problem with philosophy. None of it threatens Lorenz contractions which are assumed in theory and verified empirically - GPS satellites have to adjust their clocks.
    I should probably point out again, that this thread was started before I realised that there exists another theory which also uses the Lorentz contractions, but which is based on different, underlying assumptions. I would have been more correct to raise a question about the possible fallacy of the conclusions in Einsteinian relativity.

    As for the word games, you need look no further than post #95 above. I certainly amn't playing them; I'm relating everything I say back to our experience of the physical world, and trying to make logical deductions.


    Above, you say that "I am moving" is the same as saying "I am moving relative to X", because you always move relative to something. Firstly, "I am moving" is entirely distinct from "I am moving relative to X", because depending on what X is, you may not necessarily be moving relative to it. Indeed, it is possible that you and X are both moving but are at rest relative to each other.

    "I am moving" is a statement about the intrinsic nature of "my" motion, precisely because it doesn't relate that motion to anything; it is a practical consequence of absolute motion, in this universe, that something absolutely in motion will also be in motion relative to something else.


    This can be boiled down to a simple question of: are humans capable of motion?


  • #99
    citrus burst
    Registered Users, Registered Users 2 Posts: 147 ✭✭citrus burst


    roosh wrote: »

    Above, you say that "I am moving" is the same as saying "I am moving relative to X", because you always move relative to something. Firstly, "I am moving" is entirely distinct from "I am moving relative to X", because depending on what X is, you may not necessarily be moving relative to it. Indeed, it is possible that you and X are both moving but are at rest relative to each other.

    I'm sorry to have to say this but that is wrong. You do always move relative to something, otherwise it would be totally meaningless. In the world of physics/relativity "I am moving relative to x" and "I am moving" are indistinguishable. The latter is just a short hand way of saying the former.

    It doesn't matter what on x is, if you are not moving relative to x, then the two of you are at rest with each other. You can both be moving (relative to something else) but be at rest with each other. In a universe with only one object (reference frame) there is no motion. In a universe with two objects (reference frames) there is either motion, one object is moving wrt the other (or vice versa) or there is no motion, both objects are at rest with each. You might ask the question but what if the two objects are moving, just not wrt to each other, well its simply meaningless, it can't be detected. Why? Because there is nothing to compare x's motion with other then y's motion so either they are both moving relative to each other or they are at rest to each other. You could add a 3rd object/reference frame to determine if x and y are moving, and are at rest with each other, but then this motion (or rest) would be relative to this new thing in the universe z. You can keep adding reference frames/objects all the way up to infinity, but it will just have the same conclusions, things are moving relative to each other, or they are at rest (not moving) relative to each other.
    roosh wrote: »
    "I am moving" is a statement about the intrinsic nature of "my" motion, precisely because it doesn't relate that motion to anything; it is a practical consequence of absolute motion, in this universe, that something absolutely in motion will also be in motion relative to something else.

    "I am moving" is a statement about your motion, relative to a reference frame, whether or not you state what reference frame it is. Generally we mean the Earth when we say it. You just don't move, you just don't fast, you just don't slow, you just don't big etc.

    Its a practical consequence of thousands of years of evolution on one stable, approximately flat, infinite plane, that only recently humans have discovered to not be the full picture.
    roosh wrote: »
    This can be boiled down to a simple question of: are humans capable of motion?

    I would say yes *goes and gets a cup of tea* :D

    Again, I hope this all makes sense and am open to corrections


  • #100
    roosh
    Registered Users, Registered Users 2 Posts: 2,553 ✭✭✭roosh


    citrus burst wrote: »
    I'm sorry to have to say this but that is wrong. You do always move relative to something, otherwise it would be totally meaningless. In the world of physics/relativity "I am moving relative to x" and "I am moving" are indistinguishable. The latter is just a short hand way of saying the former.
    I'm not suggesting that we won't always measure our motion relative to something else, or that our motion won't manifest relative to something else; but that we will inevitably be moving relative to something, in the universe, doesn't preclude us from having intrinsic motion, that isn't necessarily defined relative to something else.

    "I am moving" and "I am moving relative to X" aren't indistinguishable at all; "I am moving" is a statement about the intrinsic nature of motion of an object, precisely because it doesn't make reference to the object, relative to which it is moving. It is a statement about the absolute nature of motion. It is a statement about the agent of motion i.e. "the thing that is actually doing the moving" which results in the relative motion.

    With two objects at rest relative to each other, one object has to actually "do the moving" in order for relative motion to manifest; if neither object "does the moving" then both objects will remain at rest relative to each other.

    citrus burst wrote: »
    It doesn't matter what on x is, if you are not moving relative to x, then the two of you are at rest with each other. You can both be moving (relative to something else) but be at rest with each other. In a universe with only one object (reference frame) there is no motion. In a universe with two objects (reference frames) there is either motion, one object is moving wrt the other (or vice versa) or there is no motion, both objects are at rest with each. You might ask the question but what if the two objects are moving, just not wrt to each other, well its simply meaningless, it can't be detected. Why? Because there is nothing to compare x's motion with other then y's motion so either they are both moving relative to each other or they are at rest to each other. You could add a 3rd object/reference frame to determine if x and y are moving, and are at rest with each other, but then this motion (or rest) would be relative to this new thing in the universe z. You can keep adding reference frames/objects all the way up to infinity, but it will just have the same conclusions, things are moving relative to each other, or they are at rest (not moving) relative to each other.
    The thing is, we only need to consider the simplest possible scenario of two objects moving relative to each other; it is somewhat easier, I think, when we think of the two objects starting off at rest, relative to each other.

    Where A and B are at rest relative to each other, either A or B will have to "do the moving" in order for relative motion to manifest between them; if neither A nor B "does the moving", then no relative motion will manifest, and they will remain at rest relative to each other. We can add as many reference frames as we like, up to infinity, but wherever we discuss relative motion, the conclusion will be the same.


    Even something you say above reflects the underlying implication of absolute motion: "In a universe with two objects (reference frames) there is either motion, one object is moving wrt the other (or vice versa), or there is no motion, both objects are at rest with [respect to] each other"

    In a universe with two objects, how can one object be moving with repsect to the other and vice versa? This implies that one object is actively moving.

    In a universe with only two objects either both objects are moving with respect to each other (no vice versa) or they are at rest relative to each other.

    To conclude that there is not motion is not justified; what you mean is, there is no relative motion; absolute motion, on the other hand, is an intrinsic characteristic of the bodies, and isn't necessarily relative to anything else, and therefore, isn't necessarily measurable. This, of course, doesn't make it meaningless, as it does have logically deducible consequences.

    Also, where there is no relative motion between two objects those objects could be at absolute rest, or they could absolutely in motion. That we cannot determine either way makes no odds. What we are not free to deduce is that "absolute rest" doesn't exist, simply for the fact that the objects might acutally be at absolute rest.

    Of course, they might not be, but the prefectly plausible possibility that they might be, prevents us from ruling out the existence of absolute rest. And we don't have to asssume absolute rest exists either, we just have to allow for the possibility that it might, or could - as the evidence suggests.

    citrus burst wrote: »
    "I am moving" is a statement about your motion, relative to a reference frame, whether or not you state what reference frame it is. Generally we mean the Earth when we say it. You just don't move, you just don't fast, you just don't slow, you just don't big etc.

    Its a practical consequence of thousands of years of evolution on one stable, approximately flat, infinite plane, that only recently humans have discovered to not be the full picture.
    "I am moving" is a statement about the nature of your motion. "I am going to the shop", or rephrased as "I am moving to the shop" is a statement about you actively moving to the shop, as opposed to the shop actively moving to you.

    The practical consequence of existence on earth is the fact that when we are at rest, realtive to the earth, we share it's intrinsic motion i.e. we are carted along with it on its orbit around the sun - that is, if you believe that the earth is actually orbiting the sun, and not the other way around. This however, doesn't mean that we cannot subsequently move around on the surface of the earth i.e. actually move around on the surface of the earth.

    That the absolute nature of our motion gives rise to relative motion, and that we measure our motion relative to other objects, doesn't mean that we aren't "actually moving"; it just means that our intrinsic motion naturally sets us in motion relative to other intrinsically moving objects.

    The erroneous conclusion that seems to be drawn, from the fact that we cannot determine, by scientific experiment, the absolute nature of our motion, is that the nature of our motion is not absolute; or said another way, just because we cannot measure the absolute nature of our motion, that the nature of our motion is not absolute. This of course isn't a justifiable conclusion, but rather it highlights a limitation on the ability to measure intrinsic properties.

    citrus burst wrote: »
    I would say yes *goes and gets a cup of tea* :D
    Is your capability of motion frame dependent, or it is an intrinsic ability?

    If you were the only object in the universe, would you still be capable of motion?

    When you went to make the cup of tea, was it you that did the moving, or did the entire universe manouevre around you in such a manner as to facilitate the making of the tea?
    citrus burst wrote: »
    Again, I hope this all makes sense and am open to corrections
    It does CB, cheers.

    I hope what I'm saying makes sense too. I genuinely think that an issue here might be to do with conditioned thinking; it might be because we are discussing this purely theoretically, that the theoretical training in relativity is coming to the fore.

    If you go for a walk outside, where you don't see the world through the lense of a mathematical reference frame - regardless of how we can define one - then the question of "am I moving" should hopefully become clearer.


  • #101
    Morbert
    Registered Users, Registered Users 2 Posts: 3,457 ✭✭✭Morbert


    roosh wrote: »
    An absolute statement about the motion of an object, relative to another, is entirely distinct from a statement about the absolute, or intrinsic nature of motion, of an object.

    "I am moving, relative to X" is an absolute statement about the motion of an object relative to another, because it specifies the object relative to which "I" am in motion.

    "I am moving" is a statement about the absolute nature of the motion, of an object, precisely because it doesn't make reference to the object, relative to which it is moving.


    "I am moving" isn't frame dependent, because it doesn't specify a frame or a set of co-orindates, relative to which the motion occurs; it is a simple statement about the absolute nature of motion. Regardless of the reference frame, the act of motion is ascribed to a specified object.


    EDIT: We can see that the question "Am I moving?" relates to the absolute nature of motion of an object, by considering the example of the train at rest relative to another train, in the station; when the trains start moving relative to each other, the question "am I (or is our train) moving, or is it the other train that is moving?" clearly relates to a question about the intrinsic motion of the train, because there is no question that the trains are moving relative to one another, or that the observer, asking the question, is at rest relative to their own train. In fact, it is the self-evident relative motion between the trains which prompts the question, which one is actually moving.


    Again, our three scenarios are deductively different, and cannot possibly, all be true; each one makes implicit reference to the intrinsic motion of the objects involved. While we cannot determine which one is true, we can determine that one of them must be true, and with it that objects must have intrinsic motion.

    I have responded to this in what has become a duplicate thread here.


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