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Question on Lorentz transforms and relativity of simultaneity

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    #122
    roosh
    Registered Users Posts: 2,552 ✭✭✭roosh


    dlouth15 wrote: »
    The problem is you are continually reverting to Albert's frame, i.e. the frame within which Albert is stationary.
    Again this is a description from Albert's frame. The order in which the photons strike is an artifact of that particular frame of reference.
    I'm not reverting back to Albert's frame though, I'm reverting back to the physical world, where Albert's brain operates to prdouce Albert's experiences.

    dlouth15 wrote: »
    There's a conceptual problem I think you're having here. The cause of it I believe is that that some of the events under consideration are Albert's conscious perceptions. This forces the mind into privileging one frame of reference over another. We can't observe Albert's perceptions from another frame of reference. Only he can perceive them and he's stuck in his own frame of reference.
    This is a fact of the physical world, it's how Albert's brain produces Albert's experience.
    dlouth15 wrote: »
    If we replace Albert with a simple physical system with photon detectors and a light that goes on, then this problem goes away. I think you need to examine why you are insisting on a conscious entity rather than a simple physical system.
    The "problem" only goes away because, psychologically, we're able to dismiss it easier, because it is less personalised and less tangible; the logic holds the very same for all machines, conscious or not.

    As I mentioned, we can imagine that Albert has been cryogenically frozen and re-animated in the future, where his visual system has been replaced with the simple circuitry you prescribe; with the detectors and the light that goes on, on his head. That way we have the best of both worlds, and we can see that the logic holds true for that simple circuit as it does for Albert's brain.
    dlouth15 wrote: »
    Because it forces you out of any particular frame. You mention in your post relating spacetime back to the physical observable world, but spacetime is the physical observable world. When you say "we've just been relating it back the physical, observational world.", what you mean is relating it to a particular frame of reference. It looks to me like whenever you talk about Albert's perceptions you are unwittingly reverting a frame of reference in which he is stationary.
    No, what I mean is the physical scenario of Albert standing on the embankment, at rest relative to it, with an observer moving relative to him at sufficient a fraction of the speed of light to make relativistic effects noticeable.

    That Albert's brain processes Albert's experiences "in Albert's reference frame" is just a simple matter of fact.

    EDIT: at the risk that "in Albert's reference frame" might be taken literally, I do of course mean that Albert's brain proceses Albert's experiences such that the physical processes - which lead to Albert's experience - are represeneted by the measurements of S. When it comes to photons which physically strike his retinae, it processes these indiscriminately, because it doesn't choose what photons to process on the basis of what reference frame they are "in", just as it doesn't choose to process his experiences according to the measurements of S. It processes experiences on the basis of physical stimuli which reach the senses, while he is physically standing on the embankment.


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    #123
    dlouth15
    Registered Users Posts: 1,169 ✭✭✭dlouth15


    roosh wrote: »
    As I mentioned, we can imagine that Albert has been cryogenically frozen and re-animated in the future, where his visual system has been replaced with the simple circuitry you prescribe; with the detectors and the light that goes on, on his head. That way we have the best of both worlds, and we can see that the logic holds true for that simple circuit as it does for Albert's brain.
    If you would not mind, then, could you please restate the problem as you see it, purely in terms of the simple circuit: two photon detectors and a device that emits the flash when electric signals from the detectors arrives simultaneously.

    Let's get rid of Albert for the moment. I think we agree on the physical setup here, so there's no need to go into that.


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    #124
    roosh
    Registered Users Posts: 2,552 ✭✭✭roosh


    dlouth15 wrote: »
    If you would not mind, then, could you please restate the problem as you see it, purely in terms of the simple circuit: two photon detectors and a device that emits the flash when electric signals from the detectors arrives simultaneously.

    Let's get rid of Albert for the moment. I think we agree on the physical setup here, so there's no need to go into that.
    It's getting late here and I'm going to try to get to bed soon. If I could see a justification for doing so, then I certainly would, but I think the compromised situation with the replaced visual network should suffice.

    Feel free to just speak about the replaced visual network though, or the non-conscious circuit.


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    #125
    dlouth15
    Registered Users Posts: 1,169 ✭✭✭dlouth15


    roosh wrote: »
    It's getting late here and I'm going to try to get to bed soon. If I could see a justification for doing so, then I certainly would, but I think the compromised situation with the replaced visual network should suffice.

    Feel free to just speak about the replaced visual network though, or the non-conscious circuit.
    Although you've said they are equivalent, I believe that the paradox you believe exists goes away when we're dealing with a simple physical system observable by multiple frames of reference. I won't discuss it beyond that because I run the risk of misunderstanding the problem as you see it. It needs to come from you, imo, but there is no rush. I'm happy to resume the conversation when I've got something to work with.


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    #126
    Morbert
    Registered Users Posts: 3,457 ✭✭✭Morbert


    That would be a case of being deliberately truculent, because making the statement "S' says" is just a short hand way of saying "S' represents the measurements that a relatively moving observer would make, and from these measurements the implication is that"; it doesn't cloud the issue in the manner of saying "in S'".

    Dude... seriously... that is desperate.
    roosh wrote: »
    I'm not ignoring it, I'm simply stating what is physically true. If an observer sees a flash of light from one direction first and a subsequent flash of light from the other direction second, then we can conclude that the photons from one source physically struck one retinae first and the photons from the other source physically struck the other retina second, because that is the only way the observers brain could process such an ordered experience.

    We can, therefore, say that the photons physically struck the observers retinae in the order of one first, then the other.

    If you are talking about a different kind of mathematical simultaneity that doesn't correspond to the physical world, then that just supports the contention being made.

    No, I have mentioned previously that part of the issue is ascribing physical characteristics to mathematical reference frames; statements like "such and such happens in S but not S'" is an example of such; it only serves to cloud the issue.

    There's nothing in that I don't understand. What part of the following do you not understand:
    - we are not interested in how a relatively moving observer would, supposedly, measure Albert's brain activity

    - we're not interested in what he would, supposedly, conclude about Albert's experience, and whether or not he would agree.

    - we are interested in how Albert's brain processes photons which physically strike his retinae, to produce his experience, in the physical world.

    - we know Albert's brain processes photons, which physically strike his retinae, in the order they are received, while he is standing on the embankment.

    - we are interested in how the description of the retinae striking events, as described by S', corresponds to the physical world; that is, do photons physically strike Albert's retinae in the order of one first, then the other, while he is standing on the embankment.

    - with the two pieces of information - how Albert's brain processes photons which physically strike Albert's retinae, and the physicality of the photon strikes which occur in the order of one first then the other - we can deduce how Albert's brain should process Albert's experience, in the physical world, while he is standing on the embankment; no "in" either S or S'.


    Indeed, and from your derivation we find ourselves here.

    EDIT: just to clarify, your derivation is just a mathematical representation of the argument you and others have been making in this thread already; it gives us the co-ordinates for the convergence of the signals on the processing centre in S'. To relate that to the physical example we have been discussing; it is telling us how a relatively moving observer will, supposedly, measure Albert's brain activity and the conclusion he will, supposedly, arrive at about Albert's experience; again, however, we are not intersted in the relatively moving observers opinion on Albert's experience, and whether or not he will agree. We are interested in how Albert's brain will process photons which physically strike his retinae, while he is physically standing on the embankment, to produce Albert's experiences.

    Roosh, you are not doing your homework. You are not even keeping track of what you yourself are saying.

    In a previous post, you say

    "S' says that the photons physically strike in the order of one first, then the other; so Albert's brain should process an ordered experience, because that is how his brain processes all photons which physically strike his retinae, while he is standing on the embankment."

    Then, you say

    "we are not interested in how a relatively moving observer would, supposedly, measure Albert's brain activity

    we're not interested in what he would, supposedly, conclude about Albert's experience, and whether or not he would agree."

    You make a statement about what S' implies, then you state that what S' implies is irrelevant.

    But more importantly, you haven't done your homework when it comes Minkowski spacetime. You keep using the word "physical", but ignore the physical structure of spacetime. Your understanding of reference frames is abysmal, so let's look at the mistake you're making in a frame-independent way.

    Consider a single event. What lies in the past and future of that event depends on the spacetime structure you are considering. Classical, newtonian physics has a causal structure like so

    LVJ8G.png

    The dots are events. The orange event is the event in question, and all other (blue) events (bar one) lie in the past or future of the orange event. There is one event that lies in the present, which is causally unconnected. This is the physical structure of the past and the future according to Newtonian spacetime. If spacetime were like this, you would be correct in saying the ordering of the strikes is physical. You have absolute simultaneity. But spacetime is not like this. Spacetime is minkowskian.

    wtNGb.png

    Here, we see that some events do physically lie in the past or future of the orange event. But we also see than some events don't. These events are all causally unconnected, and unlike Newtonian spacetime, they do not lie one some hypersurface that represents absolute simultaneity. Your case of the retinas being blinded in both eyes falls under this category. You cannot say they are physically ordered such that one lies in the past, future, or present of the other. And since there is not causal connection, the variety of descriptions you get when you introduce reference frames are all consistent.


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    #127
    roosh
    Registered Users Posts: 2,552 ✭✭✭roosh


    Morbert wrote: »
    Dude... seriously... that is desperate.
    What are you on about?

    I have mentioned before that our reasoning can become clouded when we say that events happen a certain way "in" one reference frame, but happen a different way "in" a different reference frame. Events happen in the physical world; period! Reference frames are a mathematical means of representing those events which happen in the physical world; if "events happen a certain way "in" one reference frame", then they, supposedly, happen that way in the physical world; if "they happen a different way "in" a different reference frame" then they, supposedly, happen that way in the physical world. This allows us to speak about how events happen in the physical world, without muddying the issue by speaking about things happen "in" mathematical reference frames.

    Morbert wrote: »
    Roosh, you are not doing your homework. You are not even keeping track of what you yourself are saying.

    In a previous post, you say

    "S' says that the photons physically strike in the order of one first, then the other; so Albert's brain should process an ordered experience, because that is how his brain processes all photons which physically strike his retinae, while he is standing on the embankment."

    Then, you say

    "we are not interested in how a relatively moving observer would, supposedly, measure Albert's brain activity

    we're not interested in what he would, supposedly, conclude about Albert's experience, and whether or not he would agree."

    You make a statement about what S' implies, then you state that what S' implies is irrelevant.
    It's you that is not keeping track; I have emboldened the important qualifiers, highlighting what it is about the relatively moving observers measurements that we're not interested; we're not interested in what he says about Albert's brain activity, because we have established how Albert's brain processes Albert's experiences, in the physical world; we are not interested in the relatively moving observers agreement about what Albert experiences, because it is immaterial whether he agrees or not; Albert's experience is the arbiter here.

    What we are interested in, is the physicality of the retinae striking events, because how photons physically strike Albert's retinae directly impacts the experience Albert will have.

    This has been repeated many times at this stage.
    Morbert wrote: »
    But more importantly, you haven't done your homework when it comes Minkowski spacetime. You keep using the word "physical", but ignore the physical structure of spacetime. Your understanding of reference frames is abysmal, so let's look at the mistake you're making in a frame-independent way.

    Consider a single event. What lies in the past and future of that event depends on the spacetime structure you are considering. Classical, newtonian physics has a causal structure like so

    LVJ8G.png

    The dots are events. The orange event is the event in question, and all other (blue) events (bar one) lie in the past or future of the orange event. There is one event that lies in the present, which is causally unconnected. This is the physical structure of the past and the future according to Newtonian spacetime. If spacetime were like this, you would be correct in saying the ordering of the strikes is physical. You have absolute simultaneity. But spacetime is not like this. Spacetime is minkowskian.

    wtNGb.png

    Here, we see that some events do physically lie in the past or future of the orange event. But we also see than some events don't. These events are all causally unconnected, and unlike Newtonian spacetime, they do not lie one some hypersurface that represents absolute simultaneity. Your case of the retinas being blinded in both eyes falls under this category. You cannot say they are physically ordered such that one lies in the past, future, or present of the other. And since there is not causal connection, the variety of descriptions you get when you introduce reference frames are all consistent.
    You're just ignoring basic facts now!


    Photons physically strike Albert's retinae in the physical world. If photons didn't physically strike his retinae, his brain could not process them. If Albert sees a flash of light from one direction first and the other direction second, it is because the photons from the different events physically strike his retinae from one direction first, then the other; or they physically strike his retinae in the order of one first, then the other.

    You might want to argue that different reference frames say that the photons physically strike his retinae in different orders, but you can't argue that the photons don't physically strike his retinae; and you can't argue that they don't do so in a given order.

    You might want to argue that relativity says the photons don't physically strike his retinae in any order, but if you do, then the conclusion is that the reference frames don't correspond to the physical world; because, as mentioned, photons physically strike Albert's retinae in the physical world to give rise to Albert's experiences; where Albert has an ordered experience, as we all have had, it means that the photons have physically struck his retinae in a given order; if they hadn't there would be no experience to speak about.


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    #128
    roosh
    Registered Users Posts: 2,552 ✭✭✭roosh


    dlouth15 wrote: »
    Although you've said they are equivalent, I believe that the paradox you believe exists goes away when we're dealing with a simple physical system observable by multiple frames of reference. I won't discuss it beyond that because I run the risk of misunderstanding the problem as you see it. It needs to come from you, imo, but there is no rush. I'm happy to resume the conversation when I've got something to work with.
    Does this lead us to the conclusion that relativity is paradoxical for conscious observers, but not for inanimate systems?


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    #129
    dlouth15
    Registered Users Posts: 1,169 ✭✭✭dlouth15


    roosh wrote: »
    Does this lead us to the conclusion that relativity is paradoxical for conscious observers, but not for inanimate systems?
    I don't know. First I want to see if you've identified a paradox for inanimate systems. Hence my request for a restatement in those terms.


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    #130
    Morbert
    Registered Users Posts: 3,457 ✭✭✭Morbert


    Roosh, since you completely ignored my last post, and instead used it as an opportunity to repeat your categorically incorrect statements, I will ignore you, and instead address anyone else masochistic enough to still be reading this.

    The Setup

    Albert is standing between two poles. Each pole is mounted with a laser. The left pole fires and blinds Albert's left eye. The right pole fires and blinds Albert's right eye. Albert measures both poles as firing their lasers at the same time, and thus experiences blindness in both eyes simultaneously.

    Meanwhile, an observer moving relative to Albert measures both poles as firing at different times, and hence Albert's eyes being struck at different times. He agrees, however, that Albert experiences blindness in both eyes simultaneously.

    Who has made the more physically accurate/correct measurements?

    What Relativity Says

    Neither observer is more or less correct than the other. Simultaneity is relative. And since the causal structure of events is agreed upon by both observers, (I.e. Both observers agree that the strikes will cause Albert to experience blindness in both eyes at the same times), there are no contradictions.


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    #131
    citrus burst
    Registered Users Posts: 147 ✭✭citrus burst


    roosh wrote: »
    What are you on about?

    I have mentioned before that our reasoning can become clouded when we say that events happen a certain way "in" one reference frame, but happen a different way "in" a different reference frame. Events happen in the physical world; period! Reference frames are a mathematical means of representing those events which happen in the physical world; if "events happen a certain way "in" one reference frame", then they, supposedly, happen that way in the physical world; if "they happen a different way "in" a different reference frame" then they, supposedly, happen that way in the physical world. This allows us to speak about how events happen in the physical world, without muddying the issue by speaking about things happen "in" mathematical reference frames.
    How can using reference frames cloud our reasoning? Reference frames say nothing of the sort. Things happen the same way in all reference frames. That's what Einstein's first postulate is. The laws of physics are the same in all reference frames.

    The difference is what happens outside these reference frames. What happens between two different reference frames in other words. S doesn't say anything about what happened in S' and vice versa. Reference frames are real. They are places where a measurement takes place. A driver in an ambulance is "physically" in a different reference frame then you as he drives past you. He measures the frequency of his siren to be the same. You on the other hand, "physically" in a different reference frame measure a higher frequency, as the ambulance moves towards you and a lower frequency as it moves away from you.

    The changing frequency happened "outside" of the driver's reference frame S and the constant frequency happened "outside" your reference frame S'. Neither you nor the driver can conclude alone what the other experience without the understanding that there is some "link" between the two observations. ie the relative motion of the ambulance wrt you, caused you to observe a change in frequency. With this in mind, you could figure out that the driver will experience, measure, observe, remember..... that the sound had the same pitch for him, and vice versa the driver can conclude you will have different pitches.

    Similarly, this is true for light, with different variables and as a result different consequences. Both you and the driver will measure that electromagnetic radiation will propagate through space at 2.99.... x10^8 m/s in all directions and at all wavelengths. That is the speed of light is the same for all reference frames. Even if the ambulance moves at 0.9999c relative to you, he will still measure the speed of light moving away from him to be c.

    To go back to the original thought experiment, the driver of the ambulance, Barry, in reference frame S' moving relative to S measures the light hitting Albert's eye at two different times. This happened "outside" his reference frame and he has to come up with some "link" to correspond it to the observations/measurements/memories made by Albert in S moving relative to S' that the light hit his eyes at the same time. Likewise Albert will have to find a "link" that matches with the drives non simultaneous measurement. Perhaps this "link" is the same for the both of them.

    If reference frames cause the argument to become muddled then I suggest you read up on them more, because so far you are the only person who has had any problem with them. This might only be a wikipedia page but it still has some good points about what they are. Notice how there are coordinate (mathematical) reference frames and observational (physical) reference frames. Reference frame
    roosh wrote: »

    It's you that is not keeping track; I have emboldened the important qualifiers, highlighting what it is about the relatively moving observers measurements that we're not interested; we're not interested in what he says about Albert's brain activity, because we have established how Albert's brain processes Albert's experiences, in the physical world; we are not interested in the relatively moving observers agreement about what Albert experiences, because it is immaterial whether he agrees or not; Albert's experience is the arbiter here.
    If we are only interested in what Albert says, then we cannot talk about another reference frame. Similarly Albert cannot talk about any other reference frame. Albert gets blinded simultaneously if he is standing on the platform, in other words not moving relative to the set up, in shorter words; in S. Albert gets blinded non simultaneously on the train, in other words; moving relative to the set up, in shorter words; in S'. That's is, we don't care about other reference frames.

    If we did however, we would conclude that they will all measure a different time between the light hitting Albert's eye. Some will even disagree on what eye got hit first. However if they apply the "link" they will find that he was blinded simultaneously in S, or non simultaneously in S'. In the latter case there will even be a reference frame that will say that Albert was blinded simultaneously.

    However we're not interested in all that^^^^^^
    roosh wrote: »
    What we are interested in, is the physicality of the retinae striking events, because how photons physically strike Albert's retinae directly impacts the experience Albert will have.
    YES!

    But how relatively observers measure this will be different!

    But we don't care about this!
    roosh wrote: »
    Photons physically strike Albert's retinae in the physical world. If photons didn't physically strike his retinae, his brain could not process them. If Albert sees a flash of light from one direction first and the other direction second, it is because the photons from the different events physically strike his retinae from one direction first, then the other; or they physically strike his retinae in the order of one first, then the other.

    YES!!!

    But only for Albert, or anyone else in Albert's reference frame!!! I assume now he is moving relative to the set up, or else the set up has changed, but either way it doesn't matter.

    Observers in different reference frames won't agree with this, but we don't care about them!
    roosh wrote: »
    You might want to argue that different reference frames say that the photons physically strike his retinae in different orders, but you can't argue that the photons don't physically strike his retinae; and you can't argue that they don't do so in a given order.
    No they are observed to hit his eyes in different orders by different reference frames. But using the "link" the different reference frames can deduce whatever happened for Albert, in his different reference frame.
    roosh wrote: »
    You might want to argue that relativity says the photons don't physically strike his retinae in any order, but if you do, then the conclusion is that the reference frames don't correspond to the physical world; because, as mentioned, photons physically strike Albert's retinae in the physical world to give rise to Albert's experiences; where Albert has an ordered experience, as we all have had, it means that the photons have physically struck his retinae in a given order; if they hadn't there would be no experience to speak about.
    No, relativity says that they strike in an order, this order depends on the relative velocity of the reference frame. Reference frames do correspnd to the physical world. Because as mentioned above other reference frames must apply the "link" to give rise to Albert's experiences. But we don't care about them.

    The "link" as it turns out is the Lorentz transformation

    Don't know really what more I can say


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    #132
    ceejay
    Registered Users Posts: 456 ✭✭ceejay


    Roosh,

    Consider this, and see if it helps:

    We use the reference frame S to represent Albert's view of the world, and in this frame of reference Albert is stationary using the co-ordinate system of S.

    We us a different reference frame S' to represent the view of the world from an observer moving relatively to Albert. However from that observer's perspective they are stationary relative to S', while Albert, the platform, the lasers, etc. are all moving at some relative velocity using the co-ordinate system of S'.

    So using the reference frame S Albert is stationary, using S' Albert is moving.

    Does this qualitative difference in the two descriptions (not moving vs. moving) help you feel why the descriptions of the events would be different?

    Yet both descriptions will agree that Albert gets blinded/the light turns on/the building blows up at a single point in spacetime.

    You cannot ignore the processing time in the brain, and you cannot simply assert that because the light arriving at the retinas happens at two different moments as expressed in the co-ordinate system of S' that this means that we can use the co-ordingate system of S to determine how long it takes to process those events to determine if they are simultaneous.

    Using the co-ordinates of S the light hits the eyes simultaneously and they are processed by the brain such that Albert determines it was simultaneous.

    Using the co-ordinates of S' the lasers fire at different times, the light hits the eyes at different times, and the brain processing takes place with each eye's signals being processed at different speeds, with the end result that Albert still determines it was simultaneous.


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    #133
    roosh
    Registered Users Posts: 2,552 ✭✭✭roosh


    dlouth15 wrote: »
    I don't know. First I want to see if you've identified a paradox for inanimate systems. Hence my request for a restatement in those terms.
    I really can't see why it should matter, given we are using the inanimate system already, we're just using as a "prosthetic" in a concsious observer; if we establish that there is no paradox for inanimate systems, we're still left with the paradox for conscious observers; but we can look at it anyway.

    The light
    Taking your diagram, there are two photoreceptors located between two lasers, A and B, which are positioned such that they are equidistant from the laser they are closest to; that is, the left photoreceptor is the same distance from A as the right one is from B. At the midpoint between the lasers, and the photoreceptors, is a light, which will switch on only if it receives the signals from the photoreceptors together, that is "tied for first place"; if the signals arrive in the order of one first, then the other, then the light will not switch on.


    The light system is physically located on the embankment. The light system will process all photons which physically strike the photoreceptors in the order they physically strike the photoreceptors. The light system does its processing on the embankment, in the physical world, and "from its own perspective", not from the perspective of a relatively moving observer. For the light system, as it processes the signals from the photoreceptors, it's own lengths are not contracted and its own time is not dilated, which means that if two photons phyiscally strike the photoreceptors in the order of one first, then the other, while the system is on the embankment, they will not arrive at the light[switch] together, or "tied for first place", and the light will not switch on; if two photons physically strike the receptors together, or "tied for first place", then they will also arrive at the light "tied for first place", and the light will switch on.

    The light system doesn't choose which photons to process and which ones not to process, it will indiscriminately process all photons which physically strike the photoreceptors, in the order they are received.


    Mathematical reference frames
    The mathematical reference frames S and S' represent different descriptions of the physical events; the measurements of S' imply that the photons physically strike the photoreceptors in the order of one first, then the other, while the light system is located on the embankment. S says that the photons arrive tied for first place, not in the order of one first then the other.

    Given how the light system processes all photons which physically strike its photoreceptors, while it is positioned on the embankment, the light should both switch on and not switch on, because S' says that photons physically strike the receptors in the order of one first, then the other, while the light system is on the embankment, and S says that the photons physically strike the receptors "tied for first place", not in the order of one first then the other.



    I'm not sure if that makes any difference, but we can see if there is a paradox for conscious observers but not for inanimate systems.


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    #134
    Morbert
    Registered Users Posts: 3,457 ✭✭✭Morbert


    roosh wrote: »
    Given how the light system processes all photons which physically strike its photoreceptors, while it is positioned on the embankment, the light should both switch on and not switch on, because S' says that photons physically strike the receptors in the order of one first, then the other, while the light system is on the embankment, and S says that the photons physically strike the receptors "tied for first place", not in the order of one first then the other.

    https://www.youtube.com/watch?v=umDr0mPuyQc


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    #135
    Morbert
    Registered Users Posts: 3,457 ✭✭✭Morbert


    *ahem*
    dlouth15 wrote:
    But it is not the order in which the light strikes the retinas but the order in which the signals pass to the processing unit. If the two signals arrive at the same time then it will be processed as simultaneous. I think this is the nub of the issue.

    You are absolutely correct here. Both observers will agree that the signals strike the unit simultaneously, even if they don't agree with whether or not photons strike the receptors simultaneously.

    [edit]- This is possible because the moving observer measures the speed of the signal travelling through the wires as different in each wire, compensating for non-simultaneous strikes.


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    #136
    dlouth15
    Registered Users Posts: 1,169 ✭✭✭dlouth15


    roosh wrote: »
    Given how the light system processes all photons which physically strike its photoreceptors, while it is positioned on the embankment, the light should both switch on and not switch on, because S' says that photons physically strike the receptors in the order of one first, then the other, while the light system is on the embankment, and S says that the photons physically strike the receptors "tied for first place", not in the order of one first then the other.

    I'm not sure if that makes any difference, but we can see if there is a paradox for conscious observers but not for inanimate systems.
    Thanks for the description. We now have a simple system of events that can be analyzed. Later this evening I will try to apply the Lorentz transformation to all aspects of the system to show that "the light should both switch on and not switch on" is not predicted by special relativity thereby resolving the paradox. If you believe that it makes no difference that we're dealing with a simple system as opposed to conscious entities (and I agree with that too) then we've resolved the main paradox.


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    #137
    roosh
    Registered Users Posts: 2,552 ✭✭✭roosh


    Morbert wrote: »
    Roosh, since you completely ignored my last post, and instead used it as an opportunity to repeat your categorically incorrect statements, I will ignore you, and instead address anyone else masochistic enough to still be reading this.
    Again, it's not me that is ignoring what you are saying; you are ignoring some very rudimentary facts about the physical world.

    As you've said yourself, the events are physical; so it follows that the photons physically strike Albert's retinae.

    Now, it is possible that, while Albert is standing on the embankment, his brain will process an experience where he sees two flashes of light happen at the same time, or happen together; it is also possible that his brian will process an experience where he sees one flash first and then a while later he sees the second flash. If you want, we can say "in Albert's reference frame".

    Now the reason his brain processes the experience of the flashes in the first place, is because photons have physically struck his retinae; the reason he has the experience of one light flashing before the other, is because the photons from one flash physically strike his retina, and then, a while later, the photons from the other flash physically strike his retinae. We can phrase this another way, we can say that the photons from one flash physically strike his retinae first and then the photons from the other flash physically strike his retinae; or, we can say it another way, the photons physically strike his retinae in the order of one first, then the other.


    Now, you have a point, to an extent; the ordering isn't physical; that is, there is no physical thing called "an order" that can be picked up or touched by an observer; it isn't physical in the sense that a coffee table is physical, or an atom is physical; but that doesn't mean that the photons don't physically strike in the order of one first then the other; here, it is the photons which strike that are physical, but they happen in a certain order. Again, we can tag on "in Albert's reference frame" to this, just so you don't think we are mistreating reference frames, because that is the same across all reference frames or, at least, that is how things happen in the physical world, and reference frames must reflect that, if they are to correspond to the physical world.


    And if you think that sounds like a semantical argument, you're right, it is, but only because the two statements actually mean different things.

    Just to re-iterate, the photons physically strike the retinae in the order of one first then the other. S says the physically strike in such an order as they are "tied for first place", while S' says the physically strike in the order of one first, then the other; if they don't say this, then they don't correspond to the physical world.
    Morbert wrote: »
    The Setup

    Albert is standing between two poles. Each pole is mounted with a laser. The left pole fires and blinds Albert's left eye. The right pole fires and blinds Albert's right eye. Albert measures both poles as firing their lasers at the same time, and thus experiences blindness in both eyes simultaneously.
    Albert doesn't necessarily measure the photons, in the sense that he doesn't use measuring instruments; we have idealised Albert such that he has a prosthetic visual system which is as infallible as any machine we might choose to use.
    Morbert wrote: »
    Meanwhile, an observer moving relative to Albert measures both poles as firing at different times, and hence Albert's eyes being struck at different times. He agrees, however, that Albert experiences blindness in both eyes simultaneously.

    Who has made the more physically accurate/correct measurements?
    The relatively moving observer says that the photons physically strike Albert's retinae in the order of one first, then the other, while Albert is physically standing on the embankment. If this isn't what he says, then his measurements of non-simultaneous events don't correspond to physical events, in the physical world, because the events in question are photons physically striking Albert's retinae.
    Morbert wrote: »
    What Relativity Says

    Neither observer is more or less correct than the other. Simultaneity is relative. And since the causal structure of events is agreed upon by both observers, (I.e. Both observers agree that the strikes will cause Albert to experience blindness in both eyes at the same times), there are no contradictions.
    What the physical world says
    Albert's brain will process photons which physically strike his retinae, in the order they physically strike his retinae; as far as Albert's brain is concerned, when it is processing Albert's experiencs, on the embankment, at rest relative to it, with a relatively moving observer, it takes the same amount of time for signals from each retinae to arrive at an idealised processing centre; such that, if two photons physically strike his retinae in the order of one first, then the other, then his brain will process an ordered experience. If the the photons arrive in such a manner that they are "tied for first place", Albert's brain will process the flashes, or blinding events as happening simultaneously or, not in the order of one first, then the other.


    What relativity also says
    Relativity says that all reference frames accurately correspond to the physical world, such that the events they describe are real and physical. According to the reference frame S', under relativity, the photons physically strike Albert's retinae in the order of one first, then the other, while he is physically standing on the embankment.

    If this physically happens, then Albert's brain will process an ordered experience.


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    #138
    roosh
    Registered Users Posts: 2,552 ✭✭✭roosh


    dlouth15 wrote: »
    Thanks for the description. We now have a simple system of events that can be analyzed. Later this evening I will try to apply the Lorentz transformation to all aspects of the system to show that "the light should both switch on and not switch on" is not predicted by special relativity thereby resolving the paradox.
    The paradox arises when we apply what relativity says about physical events to the physical world. If you are applying the LT to the light system as it processes the signals from the photoreceptors, then you are simply committing the same error as was being committed with regard to the conscious observer. The light system doesn't process the signals from the perspective of a relatively moving observer, the light system processes photons which phsically strike the receptors in the order they are recived.

    As far as the light system is concerned, when it is processing signals from the photoreceptors, it takes the same time for signals to reach the centre, from both receptors. So, if photons physically strike the receptors in the order of one first, then the other, that is how the light system will process them, and the light won't switch on.

    S' says that photons physically strike the receptors in the order of one first, then the other, so the light should not switch on; reference frame S says that the photons strike in a manner that they are "tied for first place", so the light should switch on.


    Remember, we're not interested in what a relatively moving observer will, supposedly, measure of the light processing system, and the conclusion he will arrive at with regard to the light; we are interested in how the light system processes photons which physically strike its receptors, while it is on the embankment. We are interested in the physicality of the receptor striking events though, because we know how the light system processes signals from its receptors, from its position on the embankment.
    dlouth15 wrote: »
    If you believe that it makes no difference that we're dealing with a simple system as opposed to conscious entities (and I agree with that too) then we've resolved the main paradox.
    If you can't resolve the paradox for conscious observers, but can for inanimate systems, it implies that there might be a difference, and that relativity holds true for inanimate systems but not conscious observers. We would have to consider the case of conscious observers to see if there is a difference.

    I don't think there should be, but I wouldn't simply take my opinion as proof.


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    #139
    roosh
    Registered Users Posts: 2,552 ✭✭✭roosh


    Morbert wrote: »
    https://www.youtube.com/watch?v=
    I did tell him the logic would be the same :D


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    #140
    dlouth15
    Registered Users Posts: 1,169 ✭✭✭dlouth15


    roosh wrote: »
    If you can't resolve the paradox for conscious observers, but can for inanimate systems, it implies that there might be a difference, and that relativity holds true for inanimate systems but not conscious observers. We would have to consider the case of conscious observers to see if there is a difference.

    I don't think there should be, but I wouldn't simply take my opinion as proof.
    Let's take this step by step.


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    #141
    Morbert
    Registered Users Posts: 3,457 ✭✭✭Morbert


    dlouth15 wrote: »
    Later this evening I will try to apply the Lorentz transformation to all aspects of the system to show that "the light should both switch on and not switch on" is not predicted by special relativity thereby resolving the paradox.

    I took the liberty of calculating the relevant transformations. The following assumes Barry is moving at 0.25 c, relative to Albert, and that the signals travel through the wire at a speed less than c (specifically, 0.5 c). The poles are separated by 4 light seconds, the retinas are separated by 1 lightsecond.

    Here is the spacetime diagram according to Albert's reference frame.
    KOvPt.png

    Here is the spacetime diagram according to Barry's reference frame.

    AQtnj.png

    You can see that, in both cases, the signals from the retinas strike the processing unit simultaneously. Hence, no paradox.


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    #142
    Morbert
    Registered Users Posts: 3,457 ✭✭✭Morbert


    Cutting to the salient point.
    roosh wrote: »
    What the physical world says
    Albert's brain will process photons which physically strike his retinae, in the order they physically strike his retinae; as far as Albert's brain is concerned, when it is processing Albert's experiencs, on the embankment, at rest relative to it, with a relatively moving observer, it takes the same amount of time for signals from each retinae to arrive at an idealised processing centre; such that, if two photons physically strike his retinae in the order of one first, then the other, then his brain will process an ordered experience. If the the photons arrive in such a manner that they are "tied for first place", Albert's brain will process the flashes, or blinding events as happening simultaneously or, not in the order of one first, then the other.

    That is not what the physical world says. That would be what the physical world says if the relation between events was Newtonian. The relation, instead, in Minkowskian.

    What relativity also says
    Relativity says that all reference frames accurately correspond to the physical world, such that the events they describe are real and physical. According to the reference frame S', under relativity, the photons physically strike Albert's retinae in the order of one first, then the other, while he is physically standing on the embankment.

    If this physically happens, then Albert's brain will process an ordered experience.

    That is not what relativity says. Relativity says coordinate-dependent qualities, like event ordering, length contraction, time dilation, etc, are unphysical.


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    #143
    dlouth15
    Registered Users Posts: 1,169 ✭✭✭dlouth15


    roosh wrote: »
    The light system is physically located on the embankment. The light system will process all photons which physically strike the photoreceptors in the order they physically strike the photoreceptors. The light system does its processing on the embankment, in the physical world, and "from its own perspective", not from the perspective of a relatively moving observer.
    You've pointed out yourself already that the Lorentz transformation correctly predicts that the electrical signals converge to produce a single event at the central processing unit.

    Where I think there's an issue is illustrated a sentence from the paragraph above: "The light system does its processing on the embankment, in the physical world, and "from its own perspective", not from the perspective of a relatively moving observer." [emphasis mine]

    There is a distinction being made between something that actually physically happens and what merely appears to happen from some perspective.

    From the point of view of relativity this is very much a false distinction and indeed violates the principle of relativity itself. Not merely special relativity but classical relativity too.

    Imagine a ball rolling forward at 3 mph on a train travelling at 60 mph. From the point of view of a passenger on the train, the ball is travelling at 3 mph, but to a person on the embankment the ball is travelling at 63 mph.

    I think you will agree that both these perspectives are equally valid, both equally "physical".

    The same is true for special relativity. He's still moving forward at 3 mph from the point of view of the passenger on the train, but from the point of view of the person on the embankment he's moving at very slightly less than 3 mph. But, again, just as "physical".

    Now when we talk about perspectives, it is natural to wonder what these are perspectives on. And, with respect, this is where I think you are going wrong.

    What I think you are doing is choosing one frame of reference and deciding that that is the true physical reality. All other frames of reference are merely perspectives on this.

    In fact, relativity does not say this. Relativity instead proposes a deeper reality called spacetime. Frames of reference are all equally valid perspectives on this one spacetime.

    Thus person A might measure two events as simultaneous whereas person be measures them as one after the other and both are equally valid, equally "physical", the true reality being that the events are points in a four dimensional spacetime with no intrinsic temporal ordering; the temporal ordering being a matter of perspective.

    Have a look at Morbert's two spacetime diagrams. Notice that the second one is merely a distorted version of the first. Both are depicting the same thing: spacetime. In fact you could just have one picture, with two sets of axes representing the two frames of reference. We can have whatever choice of coordinate system we want but we are still describing the same underlying reality.

    It is a bit like looking at a mountain from various angles. Is one angle more valid than another? No, of course not.

    Now is this spacetime "physical"? Well that is indeed what relativity proposes, and classical mechanics, quantum mechanics and electromagnetism have all been formulated in terms of four dimensional spacetime. (Look up four-vectors, four-momentum, etc.). Physics is expressed without reference to any particular frame.

    No what I'm doing here is merely asserting what relativity itself holds. You may have an aversion to the idea that such a thing could be true and you would be entitled to hold that opinion. But if we are going to say that relativity leads to contradictions then we must start off by assuming it is true and seeing where that leads us.


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    #144
    roosh
    Registered Users Posts: 2,552 ✭✭✭roosh


    citrus burst wrote: »
    How can using reference frames cloud our reasoning? Reference frames say nothing of the sort. Things happen the same way in all reference frames. That's what Einstein's first postulate is. The laws of physics are the same in all reference frames.
    Using reference frames doesn't necessarily cloud our reasoning; what clouds our reasoning is how we tacitly treat reference frames. S and S' are constituted of mathematical co-ordinates, which don't physically exist, and as such "mahtematical things" physical events cannot happen "in" them; physical events can be described "by" them, but events do not hapen "in" them. When we don't make this expressly clear, then our reasoning can become clouded because both statements means very different things.

    citrus burst wrote: »
    The difference is what happens outside these reference frames. What happens between two different reference frames in other words. S doesn't say anything about what happened in S' and vice versa.
    The physical observer Albert, and his retinae, are represented in S' prime using a set of mathematical co-ordinates; his location on the embankment, at rest relative to it, is represented using a set of mathematical co-ordinates; the physical striking of his retinae, by the photons, while he is standing on the embankment, is represented by mathematical co-ordinates.

    S' "says" that the photons strike Albert's retinae in the order of one first then the other; if S' corresponds to the physical world, then S' implies that Albert's retinae get struck in the order of one first, then the other.

    citrus burst wrote: »
    Reference frames are real. They are places where a measurement takes place. A driver in an ambulance is "physically" in a different reference frame then you as he drives past you.
    The ambulance is physical, agreed; the observer standing on the embankment, and the embankment are physical, agreed. But "the ambulance" isn't a representation of the measurements of the relatively moving observer, just as the embankment isn't a representation of the measurements that Albert will, supposedly make; that is the mathematical reference frames S' and S, respectively; S' is not physical, and neither is S.

    citrus burst wrote: »
    He measures the frequency of his siren to be the same. You on the other hand, "physically" in a different reference frame measure a higher frequency, as the ambulance moves towards you and a lower frequency as it moves away from you.

    The changing frequency happened "outside" of the driver's reference frame S and the constant frequency happened "outside" your reference frame S'.
    Why the inverted commas around "physically" and "outside"; this could be misconstrued to mean "not really physically" and "not really outside", but that probably isn't what you meant, but I thought it would be worth hearing a clarifiction.
    citrus burst wrote: »
    Neither you nor the driver can conclude alone what the other experience without the understanding that there is some "link" between the two observations. ie the relative motion of the ambulance wrt you, caused you to observe a change in frequency. With this in mind, you could figure out that the driver will experience, measure, observe, remember..... that the sound had the same pitch for him, and vice versa the driver can conclude you will have different pitches.

    Similarly, this is true for light, with different variables and as a result different consequences. Both you and the driver will measure that electromagnetic radiation will propagate through space at 2.99.... x10^8 m/s in all directions and at all wavelengths. That is the speed of light is the same for all reference frames. Even if the ambulance moves at 0.9999c relative to you, he will still measure the speed of light moving away from him to be c.

    To go back to the original thought experiment, the driver of the ambulance, Barry, in reference frame S' moving relative to S measures the light hitting Albert's eye at two different times. This happened "outside" his reference frame and he has to come up with some "link" to correspond it to the observations/measurements/memories made by Albert in S moving relative to S' that the light hit his eyes at the same time. Likewise Albert will have to find a "link" that matches with the drives non simultaneous measurement. Perhaps this "link" is the same for the both of them.
    As you say, "different variables and different consequences"; it is precisely the idea that the actual speed of light is constant, as opposed to just the measured speed, which leads to the conclusion that simultaneity is relative, or that, according to an oberver moving relative to Albert, the photons physically strike Albert's retinae in the order of one first, then the other.

    People seem to be fond of making the analogy to sound, even though the two examples are materially different to the extent that they are not analgous in every way, and certainly not in the manner we are discussing. If we were talking about the colour of light seen by the observers, the analogy might, perhaps, be valid, but we're talking about the order in which photons physically strike an observers retinae, and the order in which the resulting flashes of light are seen by the observer. Alternatively, if the analogy factored in the order in which the eardrums of the observer are stimulated, it might also be valid.

    citrus burst wrote: »
    If reference frames cause the argument to become muddled then I suggest you read up on them more, because so far you are the only person who has had any problem with them. This might only be a wikipedia page but it still has some good points about what they are. Notice how there are coordinate (mathematical) reference frames and observational (physical) reference frames. Reference frame
    Again, it's not the reference frames themselves, per se, which cause the issue to become muddled, it is the use of certain statements about the reference frames which attribute physical characteristics to what are, in essence, non-physical.

    Indeed, it is helpful to make the distinction between physical frames of reference and mathematical reference frames, which is what I have endeavoured to do in this discussion, by speaking about physical locations in the physical world and the mathematical representation of the same.
    citrus burst wrote: »
    If we are only interested in what Albert says, then we cannot talk about another reference frame. Similarly Albert cannot talk about any other reference frame. Albert gets blinded simultaneously if he is standing on the platform, in other words not moving relative to the set up, in shorter words; in S. Albert gets blinded non simultaneously on the train, in other words; moving relative to the set up, in shorter words; in S'. That's is, we don't care about other reference frames.
    We are interested in the physical world and how Albert's brain processes photons which physically strike his retinae; therefore, we are interested in what the mathematical reference frames "say" about the order in which the photons physically strike Albert's retinae, because we can make deductions about his experience based on that information.

    citrus burst wrote: »
    If we did however, we would conclude that they will all measure a different time between the light hitting Albert's eye. Some will even disagree on what eye got hit first. However if they apply the "link" they will find that he was blinded simultaneously in S, or non simultaneously in S'. In the latter case there will even be a reference frame that will say that Albert was blinded simultaneously.

    Relativity says that, even though they may disagree, they are both right;
    The emboldened bit is the critical piece of information; they will disagree about which eye physically gets struck first, while Albert is standing on the embankment. Some will say that the photons physically strike the retinae in the order of one first, then the other, while he is standing on the embankment; another observer would say they physically strike in the opposite order, while he is physically standing on the embankment; another observer would say that they physically strike such that they are "tied for first place", on the embankment.

    The issue is, we know how Albert's brain processes photons which physically strike his retinae; it processes them in the order in which the photons physically strike his retinae, with time it takes for signals to travel to the "processing centre" being the same for both retinae.

    As you mention above, relativity says that, despite the disagreement between the observers, that all their measurements correspond to the physical world; that is, the following statements are both true:

    - while Albert is standing on the embankment, photons physically strike his retinae in the order of one first, then the other.

    - while Albert is standing on the embankment, the photons don't physically strike his retinae in the order of one first, then the other, they strike such that they are "tied for first place".


    Knowing how Albert's brain processes photons which physically strike his retinae, to produce his experiences, while he is standing on the embankment, this leads to the paradoxical situation where he should have discordant experiences of what are supposed to be the same events.

    Of course, if relativity doesn't say that the photons physically strike his retinae in the order of one first, then the other, while he is standing on the embankment, then the description of events given by S' do not correspond to the physical world, where Albert is standing on the embankment and photons physically strike his retinae.
    citrus burst wrote: »
    However we're not interested in all that^^^^^^
    Just to reiterate what we are interested in; we're intersted in:
    - how Albert's brain operates in the physical world, to produce Albert's experiences
    - how Albert's brain processes photons which physically strike Albert's retinae, while he is standing on the embankment.
    - the physicality of the retinae striking events, as described by both S and S'

    Given this information we can make deductions about Albert's experiences, particularly when we idealise Albert and give him a prosthetic visual network which is as infallible as any inanimate system.
    citrus burst wrote: »
    YES!

    But how relatively observers measure this will be different!

    But we don't care about this!
    We are interested in whether or not the measurements of the relatively moving observer, which lead him to conclude that the photons physically strike Albert's retinae in the order of one first, then the other, while Albert is standing on the embankment are accurate; that is, do the photons physically strike Albert's retinae in the order of one first, then the other, while Albert is standing on the embankment.

    With that information we can make deductions about Albert's experience, because we know how Albert's brain processes Albert's experiences.
    citrus burst wrote: »
    YES!!! [they physically strike his retinae in that order]

    But only for Albert, or anyone else in Albert's reference frame!!! I assume now he is moving relative to the set up, or else the set up has changed, but either way it doesn't matter.

    Observers in different reference frames won't agree with this, but we don't care about them!
    This is precisely the issue I was referring to; perhaps it arises from an unintentioanl conflation of the physical frame of reference with the mathematical reference frame.

    When you say "in Albert's reference frame" do you mean for anyone "standing on the embankment" or, more precisely, "anyone in the physical world who is not physically moving relative to the embankment"?

    Remember that S' is the set of mathematical co-ordinates used to describe events in the physical world; S' =/= the train, becuase the train is physical the co-ordinates aren't; S' is a set of co-ordinates used to describe events as they would supposedly be measured from the train; S' also describes Albert's location on the embankment, at rest relative to it; it describes the events which are the photons physically striking Albert's retinae, and it describes them as physically striking his retinae in the order of one first, then the other.
    citrus burst wrote: »
    No they are observed to hit his eyes in different orders by different reference frames. But using the "link" the different reference frames can deduce whatever happened for Albert, in his different reference frame.
    Appearances can be deceptive; it's possible that an observer making such a judgement, from a train moving very fast [relative to the events he is observing] could be mistaken.

    However, it's a little more rigorous than that isn't it; relativity says that his measurements lead him to the conclusion that the photons physically strike Albert's retinae in the order of one first, then the other, while Albert is standing on the embankment.

    If these measurements are accurate, and the photons do physically strike Albert's retinae in the order of one first, then the other, then we know how his brain will process them.

    citrus burst wrote: »
    No, relativity says that they strike in an order, this order depends on the relative velocity of the reference frame. Reference frames do correspnd to the physical world. Because as mentioned above other reference frames must apply the "link" to give rise to Albert's experiences. But we don't care about them.
    The measurement of the order depends on the relative motion of the observer, in the physical world; but the measurements supposedly correspond to the physical world; the observer on the train will supposedly make measurements which imply that the photons physically strike Albert's retinae in the given order, while he is standing on the embankment.
    citrus burst wrote: »
    The "link" as it turns out is the Lorentz transformation
    When Albert's brain is processing Albert's experiences, from its location on the embankment, at rest relative to it, it doesn't need to apply the LT to itself.
    citrus burst wrote: »
    Don't know really what more I can say
    We can try and boil it down to a few simple questions, because there are certain things you don't seem to be disputing, and it is directly from those, apparently, undisputes points that our deduction follows. Maybe we can isolate the point of disagreement, a little more specifically.

    Do you agree with the the following?

    - Albert is physially located on the embankment, at rest relative to it.

    - photons physically strike Albert's retinae while he is standing on the embankment.

    - Albert's brain processes all photons which physically strike his retinae, while he is standing on the embankment.

    - if two photons physically strike Albert's retinae in the order of one first, then the other, while he is standing on the embankment, his brain will process an ordered experience that corresponds to the order in which the photons physically strike his retinae.

    - S' "says" that the photons physically strike Albert's retinae in the order of one first, then the other, while he is standing on the embankment.


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    #145
    roosh
    Registered Users Posts: 2,552 ✭✭✭roosh


    ceejay wrote: »
    Roosh,

    Consider this, and see if it helps:

    We use the reference frame S to represent Albert's view of the world, and in this frame of reference Albert is stationary using the co-ordinate system of S.

    Albert is stationary relative to what? In the physical world Albert cannot be stationary relative a set of mathematical co-ordinates which do not physcially exist. Albert is at rest relative to the platform and in motion relative to the observer on the train; this is reflected by both S and S'

    We us a different reference frame S' to represent the view of the world from an observer moving relatively to Albert. However from that observer's perspective they are stationary relative to S', while Albert, the platform, the lasers, etc. are all moving at some relative velocity using the co-ordinate system of S'.

    So using the reference frame S Albert is stationary, using S' Albert is moving.
    Albert is "stationary" or "moving" relative to what? In the physical world Albert cannot be in motion relative to a set of mathematical co-ordinates which do not physically exist, nor can be be at rest relative to them. In the physical world, Albert is at rest relative to the embankment and he, the embankment, and the lasers are in motion relative to the train; both S and S' reflect this.

    S and S' are supposed to represent events which happen in the physical world, as measured by different observers; as such, we can make deductions about what they imply.

    But we're not limited to simply accepting "what the reference frames tell us" as "the gospel truth"; we can apply what we know about the physical world to the deductions about what the mathematical reference frames imply, and make further deductions.


    All of what you said above leads us to the conclusion that the mathematical reference frame, S', implies that the photons physically strike Albert's retinae in the order of one first, then the other, while he is physically standing on the embankment.
    ceejay wrote: »
    Does this qualitative difference in the two descriptions (not moving vs. moving) help you feel why the descriptions of the events would be different?
    I understand why the descriptions are different; the issue arises when we make deductions from what the descriptions say about the physical world, namely the order in which the photons physically strike Albert's retinae, while he is standing on the embankment, and apply it to what we know about how Albert's brain processes photon which physically strike is retinae, while he is standing on the embankment, at rest relative to it; in the process of producing Albert's experiences in the physical world.

    ceejay wrote: »
    Yet both descriptions will agree that Albert gets blinded/the light turns on/the building blows up at a single point in spacetime.
    Again, we're not interested in how a relatively moving observer will, supposedly, measure Albert's brain activity, or the conclusion he will, supposedly, reach about Albert's experience.

    Again, we're interested in how Albert's brain processes Albert's experiences, from its location on the embankment, at rest relative to it; we're not interested in the perspective an observer on a relatively moving train, supposedly, has of Albert's brain.

    We are, however, interested in the physicality of the photon striking events, because we can apply this information to how Albert's brain processes photons, to produce Albert's experience.
    ceejay wrote: »
    You cannot ignore the processing time in the brain, and you cannot simply assert that because the light arriving at the retinas happens at two different moments as expressed in the co-ordinate system of S' that this means that we can use the co-ordingate system of S to determine how long it takes to process those events to determine if they are simultaneous.
    The point being made is that, if the events, as expressed in the co-ordinate system of S', correspond to the physical world, then it means that photons physically strike Albert's retinae in the order of one first, then the other, while he is physically standing on the embankment.

    We know how Albert's brain processes Albert's experiences, from it's location on the embankment, at rest relative to it; it processes them in the order they are received, with two photons which physically strike his retinae "tied for first place" arriving at the processing centre "tied for first place"; where two photons physically strike his retinae in the order of one first, then the other, they will arrive at the processing centre in that order also; because that is how Albert's brain processes Albert's experiences, from its location on the embankment.


    S0, I'm not ignoring the processing time in the brain at all, in fact, a large part of the argument is based on the processing time in Albert's brain while it processes Albert's experinces, from its location on the embankment, at rest relative to it.

    ceejay wrote: »
    Using the co-ordinates of S the light hits the eyes simultaneously and they are processed by the brain such that Albert determines it was simultaneous.
    Yes, because, in the physical world Albert's brain processes photons which physically strike his retinae in the order they are received; where photons that physically strike his retinae "tied for first place", or "not in the order of one first, then the other", will reach the idealised processing centre "tied for first place", not in the order of one first, then the other.

    ceejay wrote: »
    Using the co-ordinates of S' the lasers fire at different times, the light hits the eyes at different times, and the brain processing takes place with each eye's signals being processed at different speeds, with the end result that Albert still determines it was simultaneous.
    If the photons physically strike Albert's retinae in the order of one first, then the other, while he is physically standing on the embankment, then his brain will process them as it processes all photons which physically strike his retinae, from its own perspective according to how it would measure itself, not how a relatively moving observer would, supposedly, measure it.

    This might lead us to think that we cannot consider how a relatively moving observer would measure the retinae striking events, but the relatively moving observer's measurements imply that the photons physically strike Albert's retinae in the order of one first, then the other; if these measurements correspond to real physical events, then we can apply how Albert's brain process photons which physically strike his retinae to arrive at our conclusion.


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    #146
    roosh
    Registered Users Posts: 2,552 ✭✭✭roosh


    Morbert wrote: »
    I took the liberty of calculating the relevant transformations. The following assumes Barry is moving at 0.25 c, relative to Albert, and that the signals travel through the wire at a speed less than c (specifically, 0.5 c). The poles are separated by 4 light seconds, the retinas are separated by 1 lightsecond.

    Here is the spacetime diagram according to Albert's reference frame.
    <snip>

    Here is the spacetime diagram according to Barry's reference frame.

    <snip>

    You can see that, in both cases, the signals from the retinas strike the processing unit simultaneously. Hence, no paradox.
    This is just the same point that has been repeatedly addressed, only with pictures.


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    #147
    roosh
    Registered Users Posts: 2,552 ✭✭✭roosh


    Morbert wrote: »
    Cutting to the salient point.

    That is not what the physical world says. That would be what the physical world says if the relation between events was Newtonian. The relation, instead, in Minkowskian.
    Even under a Minkowskian relation between events, when Albert's brain is processing Albert's experiences, from its location on the embankment, and from its own perspective - which is how Albert's brain processes Albert's experiences - the time it takes for signals to reach the processing centre is the same from both retinae; from the perspective of Albert's brain, which is the perspective Albert's brain processes Albert's experiences.

    Under a newtonian relation, a relatively moving observer would agree with Albert on the simultaneity of events; he would agree that the photons don't physically strike Albert's retinae in the order of one first, then the other, while Albert is standing on the embankment

    Under a Minkowskian relation, the relatively moving observer disagrees with Albert about the order in which the photons physically strike Albert's retinae, while he is standing on the embankment. The relatively moving observer would also measure Albert's brain activity differently to how Alberts brain would measure its own activity; but again, Albert's brain doesn't process Albert's experiences by viewing itself from a relatively moving train, so the LTs are not applied to determine how Albert's brain processes Albert's experiences, from its location on the embankment.
    ceejay wrote: »
    That is not what relativity says. Relativity says coordinate-dependent qualities, like event ordering, length contraction, time dilation, etc, are unphysical.
    The mathematical reference frames employed in Einsteinian relativity are supposed to be representations of events which happen in the physical world; as such, it is implied that they are supposed to correspond to the physical world, or at least, their descriptions are.

    In the physical world, an observer's brain processes photons which physically strike the observers retinae; observers in the physical world have ordered experiences, where they see such things as flashes of light happening in sequence; the reason they see this is because their brains have processed ordered experiences; the reason their brains process ordered experiences of such things as flashes of light, is because the photons from the different flashes physically strike their retinae, such that the brain can process them; that doesn't explain why the brain processes an ordered experience, however, it simply explains how observers experience flashes of light; the reason that observers experience sequential flashes of light is because the photons from the different flashes physically strike their retinae in sequence, or in a given order.


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    #148
    Morbert
    Registered Users Posts: 3,457 ✭✭✭Morbert


    roosh wrote: »
    This is just the same point that has been repeatedly addressed, only with pictures.

    It explicitly and precisely shows how no paradox exists. All reference frames agree with what physically happened.


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    #149
    Morbert
    Registered Users Posts: 3,457 ✭✭✭Morbert


    roosh wrote: »
    Even under a Minkowskian relation between events, when Albert's brain is processing Albert's experiences, from its location on the embankment, and from its own perspective - which is how Albert's brain processes Albert's experiences - the time it takes for signals to reach the processing centre is the same from both retinae; from the perspective of Albert's brain, which is the perspective Albert's brain processes Albert's experiences.

    Under a newtonian relation, a relatively moving observer would agree with Albert on the simultaneity of events; he would agree that the photons don't physically strike Albert's retinae in the order of one first, then the other, while Albert is standing on the embankment

    Under a Minkowskian relation, the relatively moving observer disagrees with Albert about the order in which the photons physically strike Albert's retinae, while he is standing on the embankment. The relatively moving observer would also measure Albert's brain activity differently to how Alberts brain would measure its own activity; but again, Albert's brain doesn't process Albert's experiences by viewing itself from a relatively moving train, so the LTs are not applied to determine how Albert's brain processes Albert's experiences, from its location on the embankment.

    I can't make sense of this. Nobody is saying Albert's brain processes Albert's experiences by viewing itself from a relatively moving train. That you would think anyone is saying this seriously suggests you do not understand the responses you are getting. For one thing, it doesn't even make sense to say the brain processes experiences. Instead, the brain generates experience, based on stimulus.
    The mathematical reference frames employed in Einsteinian relativity are supposed to be representations of events which happen in the physical world; as such, it is implied that they are supposed to correspond to the physical world, or at least, their descriptions are.

    In the physical world, an observer's brain processes photons which physically strike the observers retinae; observers in the physical world have ordered experiences, where they see such things as flashes of light happening in sequence; the reason they see this is because their brains have processed ordered experiences; the reason their brains process ordered experiences of such things as flashes of light, is because the photons from the different flashes physically strike their retinae, such that the brain can process them; that doesn't explain why the brain processes an ordered experience, however, it simply explains how observers experience flashes of light; the reason that observers experience sequential flashes of light is because the photons from the different flashes physically strike their retinae in sequence, or in a given order.

    You can repeat this falsehood as often as you want. I will continue to correct you.

    1) The simultaneity of events is a frame-dependent observation, and not a physical or absolute characteristics of events.

    2) There are no contradictions or paradoxes, as explicitly shown in my diagrams, as all observers agree on what events are co-incident, even if they don't agree on ordering of events separated by a spacelike interval.

    Now.... Do you know what I mean by 1) and 2)


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    #150
    roosh
    Registered Users Posts: 2,552 ✭✭✭roosh


    dlouth15 wrote: »
    You've pointed out yourself already that the Lorentz transformation correctly predicts that the electrical signals converge to produce a single event at the central processing unit.
    But they also predict that the photons will physically strike the photoreceptors in the order of one first, then the other, while the light system is physically located on the embankment.

    If we take this, supposed, physical - not absolute - fact and apply it to what we know about how light system processes photons which physically strike its receptors, while it is located on the embankment, then our paradox arises.

    If the description of events in the reference frame correspond to the physical world, then we are perfectly entitled to take that information and apply it.
    ceejay wrote: »
    Where I think there's an issue is illustrated a sentence from the paragraph above: "The light system does its processing on the embankment, in the physical world, and "from its own perspective", not from the perspective of a relatively moving observer." [emphasis mine]

    There is a distinction being made between something that actually physically happens and what merely appears to happen from some perspective.

    From the point of view of relativity this is very much a false distinction and indeed violates the principle of relativity itself. Not merely special relativity but classical relativity too.
    Einsteinian relativity implies that, for Albert, in his location on the embankment, at rest relative to it, for him, lengths are not contracted and time is not dilated; so this would naturally apply to his brain, or the the inanimate system at rest on the embankment. So, in the physical world, when the light system is processing the signals from the photoreceptors, from its own perspective - which is how it physically processes the signals, in the physical world - it takes the same time for each signal to reach the processing centre.

    The light system doesn't choose which photons to process and which ones not to, and it doesn't process photons on the basis of how a mathematical reference frame says it should; it will process all photons, which physically strike its receptors, in the same manner; in the order they physically strike.


    Now, you might think we are choosing one reference frame and saying that it represents the true physical reality, but we're not; that the reference frame S best describes how Albert's brain processes Albert's experiences, from his position on the embankment, at rest relative to it, is probably more to do with how the reference frame is constructed; similarly, S' more accurately describes how the relatively moving observer's brain processes his experiences; so we're not simply choosing one reference frame and saying it represents the true physical reality.

    Albert's brain processes Albert's experiences, in the physical world, from its location at rest relative to the embankment, in a manner that is best described by the measurements of S, not because we choose S as the one true reference frame, but because of how S is constructed. If mankind had never come up with the concept of a reference frame, Albert's brain would still process Albert's experiences in this manner.

    In the physical world, Albert's brain processes photons in the order they physically strike his retinae; S' says they phyiscally strike in the order of oen first, then the other.
    ceejay wrote: »
    Imagine a ball rolling forward at 3 mph on a train travelling at 60 mph. From the point of view of a passenger on the train, the ball is travelling at 3 mph, but to a person on the embankment the ball is travelling at 63 mph.

    I think you will agree that both these perspectives are equally valid, both equally "physical".


    The same is true for special relativity. He's still moving forward at 3 mph from the point of view of the passenger on the train, but from the point of view of the person on the embankment he's moving at very slightly less than 3 mph. But, again, just as "physical".
    From the point of view of the passenger on the train, the ball is traveling at 3mph relative to the train; from the perspective of the observer on the embankment, the ball is traveling at 3mph relative to the train. For both, the ball is traveling at 63mph relative to the observer on the embankment.

    Light is different, however, because we don't do a simple addition of velocities, and it is this which leads us to our issue in the first place.

    ceejay wrote: »
    Now when we talk about perspectives, it is natural to wonder what these are perspectives on. And, with respect, this is where I think you are going wrong.

    What I think you are doing is choosing one frame of reference and deciding that that is the true physical reality. All other frames of reference are merely perspectives on this.
    This has been addressed above.
    ceejay wrote: »
    In fact, relativity does not say this. Relativity instead proposes a deeper reality called spacetime. Frames of reference are all equally valid perspectives on this one spacetime.
    And we have been considerig the issue as such; the idea of perspectives on spacetime is just background information about how Relativity of Simultaneity is supposedly possible.
    ceejay wrote: »
    Thus person A might measure two events as simultaneous whereas person be measures them as one after the other and both are equally valid, equally "physical", the true reality being that the events are points in a four dimensional spacetime with no intrinsic temporal ordering; the temporal ordering being a matter of perspective.
    I have to wonder why there are inverted commas around the word physical.

    But taking it to refer to the physical world, where an observer such as Albert is standing on an embankment, it means that the description of events which says that the photons physically strike Albert's retinae in the order of one first, then the other, while he is standing on the embankment, is as valid as the reference frame which says they don't physically strike his retinae in sequence; that implies that photons physically strike his retinae in sequence, and we know how his brian will process them if they do.
    ceejay wrote: »
    Have a look at Morbert's two spacetime diagrams. Notice that the second one is merely a distorted version of the first. Both are depicting the same thing: spacetime. In fact you could just have one picture, with two sets of axes representing the two frames of reference. We can have whatever choice of coordinate system we want but we are still describing the same underlying reality.
    The spacetime diagrams are just visual representations of the points that have been repeatedly made and repeatedly addressed in this thread; they don't add anything new to the discussion except as a visual aid to the point that has been addressed.
    ceejay wrote: »
    It is a bit like looking at a mountain from various angles. Is one angle more valid than another? No, of course not.
    It's not quite the same thing though is it; it's like two observers looking at the same mountain from different perspective with one observer, Henry, saying that the photons, which reflect from the mountain, strike Albert's retinae in the order of one first, then the other; while the Albert saying that the photons physically strike Albert's retinae not in the order of one first, then the other, but "tied for first place".

    ceejay wrote: »
    Now is this spacetime "physical"? Well that is indeed what relativity proposes, and classical mechanics, quantum mechanics and electromagnetism have all been formulated in terms of four dimensional spacetime. (Look up four-vectors, four-momentum, etc.). Physics is expressed without reference to any particular frame.
    This doesn't change the points that have been made.
    ceejay wrote: »
    No what I'm doing here is merely asserting what relativity itself holds. You may have an aversion to the idea that such a thing could be true and you would be entitled to hold that opinion. But if we are going to say that relativity leads to contradictions then we must start off by assuming it is true and seeing where that leads us.
    I'm not sure starting off assuming its validity is the way to go; we can say that, if it is valid, then we can make these deductions - that photons physically strike in sequence, as per S' - which we can couple with other things we know to be valid - how Albert's brain processes Albert's experiences - and see what further deductions we can make - discordant experiences.


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    #151
    roosh
    Registered Users Posts: 2,552 ✭✭✭roosh


    Morbert wrote: »
    It explicitly and precisely shows how no paradox exists. All reference frames agree with what physically happened.
    They disagree on the order in which the photons physically strike Albert's retinae, while he is physically standing on the embankment.

    This, together with how Albert's brain processes Albert's experiences; or more pointedly, how his brain processes photons which physically strike his retinae, to produce his experiences, from its location on the embankment, at rest relative to it, the paradox arises.


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