On Sat, Mar 1, 2014 at 7:09 PM, Edgar L. Owen <[email protected]> wrote:
> Jesse, > > To address your points in order: > > 1. Yes, you said that proper ages are invariant. But note the important > point that the proper age of A to himself is a direct observation (he looks > at his age clock), but to anyone else is a computation and NOT an > observation. > If he "looks at his age clock", that's a direct measurement that is not specifically tied to ANY frame, including his own comoving frame. And there's nothing stopping an observer who is moving relative to him from stealing a glance at his age clock too as she passes him nearby (or looks at him through her telescope), so she can make a direct measurement of his age just as easily. A reference frame only needs to be used when you want to PREDICT some fact you don't already know through direct measurement, given some other known facts. For example, if you know that someone has a coordinate velocity v at coordinate time t0 in some frame, and you know their proper age is T0 at coordinate time t0, then as long as they move inertially, you can PREDICT that at some later coordinate time t1, their proper age T1 will be equal to T0 + (t1 - t0)*sqrt[1 - (v/c)^2]. Of course if you happen to be using the person's inertial rest frame where v=0, this formula reduces to the simple one T1 = T0 + (t1 - t0), but this still qualifies as a CALCULATION to predict his proper age at a later coordinate time t1, not a direct measurement. > In fact from their native comoving frames they will observe A at some > other age than their calculation. So the calculations trump the views. > Huh? You're not making any sense--you just got through agreeing "proper ages are invariant", how can you still maintain they'll "observe A at some other age than their calculation" if you agree all frames will predict exactly the same age for him at any event on his worldline, and this will also be the age that he will be observed to have on his personal clock at that event? Do you just mean that the time coordinate they assign to that event may be different than his proper age? That would be true, but no one familiar with relativity would conflate a time coordinate with an "age", and anyway it's quite possible to have an inertial coordinate system where he's at rest but his age still doesn't match the coordinate time, because his birth is assigned some time coordinate different from t=0. > > Thus it is valid in relativity to CALCULATE things we CANNOT OBSERVE from > our frame. > Actual physical measurements can be seen by any observer, like the example of looking at the age clock of someone you're in motion relative to, so there's nothing that one person can "observe" that someone else "cannot observe" just because they're in a different rest frame, if by "observe" you mean "measure using a physical instrument". Of course, actual physical measurements may be interpreted differently depending on what frame we use--for example, if I see an object pass the x=10 meters mark on some ruler when the clock there reads t=5 seconds, and later pass the x=20 meters mark on the same ruler when the clock there reads t=6 seconds, then if I am using a frame that defines the ruler and clocks to be at rest and the clocks to be synchronized, I'll say these measurements imply the object had a velocity of 10 meters per second, but if I'm using a frame where the ruler itself is moving and the clocks are out of sync, I can say that the velocity of the object itself was larger or smaller. > That's what I do to establish 1:1 correlations of actual ages. I use > calculations that trump Views, that trump observations. We don't always > have to use frame views to establish relativistic truth. Do you agree with > that? You must if you accept proper age invariance. > Of course, you can determine relativistic truth by direct measurement, like looking at someone's clock. But this only applies to quantities that are frame-invariant, like proper time or proper acceleration. Other quantities are DEFINED with respect to reference frames, there's absolutely no way to determine them in a way that doesn't involve a frame. The x-coordinate of an event would be an example of a quantity that's defined in terms of a reference frame, you can't determine some object's x-coordinate except in reference to a particular coordinate system that has a particular spatial origin and its x-axis oriented in a particular direction. Likewise, the t-coordinate of an event can only be defined relative to a particular frame, and since simultaneity is DEFINED in relativity to mean nothing more than "events that have the same t-coordinate", simultaneity can only be defined relative to a particular frame (talking specifically about physical definitions of simultaneity in relativity--this doesn't preclude the possibility of some "metaphysical" truth about simultaneity that's impossible to demonstrate experimentally, and of course it's conceivable that relativity will turn out to be incorrect as a physical theory). > > Also note that the ticks of the symmetric twins' own comoving clocks serve > as event markers. So if the proper ages of the twins are invariant to all > observers, then all observers can simply observe their clock tick markers > reading exactly the same for the same proper ages of both twins. > Sure, they can observe that for each twin, the event of their clock reading X coincides with their actually being X years old biologically, if that's what you mean by "their clock tick markers reading exactly the same for the same proper ages". > That PROVES the 1:1 correlation that the real actual ages of the symmetric > twins always occur at the same clock tick markers and thus they are the > same proper ages at the same times. > Total non sequitur, you are just confusing two different meanings of the word "same" here. It's true that for any individual twin, their biological age being X always occurs at a reading on their OWN clock that has the "same" value of X. But this in no way leads to the conclusion that the age/clock reading of one must be the "same" as the age/clock reading of the other when they apart--that's an entirely different statement involving the simultaneity of distant events, not just about ages coinciding with local clock readings for each individual twin. After all, even if the twins accelerated NON-symmetrically so you WOULDN'T claim that they must have the same ages as one another, it would still be true that for each individual twin, their biological age being X would occur when their age clock shows the "same" reading X, so everyone would still see "their clock tick markers reading exactly the same for the same proper ages". > > Thus all observers agree that the proper ages of both twins occur at the > same clock tick marker readings of the twins own proper clocks. > > This is one more proof the actual ages of the symmetric twins are equal > during the trip, and EVERY OBSERVER AGREES ON THIS. Thus it is a real > physical fact. > Nope, your argument is just based on equivocating what you mean by "same proper ages", whether you are comparing biological ages to age clock readings for each individual twin, or making a judgment about simultaneity in ages for two different twins. > > > 2. What all these quotes mean in saying that all frames are equally valid > is that all observer VIEWS are real actual VIEWS of reality. That they are > what the observer actually observes. I certainly agree with that. However > as I've pointed out they don't all preserve the actual physical reality of > SPECIFIC facts. > The quotes don't just say they are "real actual VIEWS of reality", they use language like "equally valid" (a phrase used in two of the quotes, along with "equally good frames for observing nature" and "equally suitable for the description of nature" in the remaining two). If one person has a view of a situation that is objectively incorrect, and another has a view of the same situation that's objectively correct, then they are both "real actual views" of different people, but they are certainly not equally VALID (nor would they be equally "good" or "suitable" as descriptions of nature), any educated English-speaking person should understand that to say two perspectives are "equally valid" in a scientific context implies there is no objective basis for favoring one over the other. I am sure we could easily find the email of any of the three living authors of the quoted statements (they're all professionals who would have contact info available online), and ask them if they think there are ANY cases (like the case of symmetrically-accelerating twins) where they think one frame's conclusions about simultaneity (or any other frame-dependent quantity) represent "actual physical reality" while other frames' do not. Do you really believe any of them would agree with you on this, or do you understand on some level that what you are proposing is your own "interpretation" of relativity which differs from the understanding of all mainstream physicists? If the former, I would be happy to make a friendly wager on this, with you only having to pay me a tenth of what I will pay you depending on who the person we email ends up agreeing with. > I just pointed out how they don't with respect to the invariance of proper > times which are not observable views but calculations. Proper age > invariance is a physical fact at odds with the notion that all frames are > equally valid as anything else than VIEWS. > > 3. No. By "the different ages of twins in relative motion are not agreed > and thus are views rather than actual physical facts" I mean just that, and > just what I've always said. The 1:1 correlation is NOT the VIEW of one twin > of the other's clock. It is a logical calculation and not a view that > establishes that 1:1. > You are speaking very confusingly--if you think there's a 1:1 correlation that everyone should agree on if they do the correct "logical calculation", then you should say "the different ages of twins in relative motion are not agreed"! Are you just saying that they will not agree if they fail to consider your "logic" and look solely at how simultaneity is defined in their own rest frame? > > 4. ******You now say you "DON'T CLAIM YOU PROVE P-TIME SIMULTANEITY IS NOT > TRANSITIVE!". OK, great. Wonderful! That's progress, and a complete change > from what you said previously. > Hell no it isn't, Edgar. From the beginning when I first presented the proof, I always maintained that the assumptions that lead to a contradiction are a COMBINATION of the assumption "for inertial observers at rest relative to one another, events which are simultaneous in their mutual rest frame are also simultaneous in p-time" AND two other assumptions which I figured would be natural to just about any reasonable presentist theory, namely the assumption that events that coincide at the same space and time coordinate in some inertial frame must be simultaneous in p-time, and the assumption that p-time simultaneity is transitive. In the very first post where I presented this proof of a contradiction at https://groups.google.com/d/msg/everything-list/jFX-wTm_E_Q/pxg0VAAHJRQJ(from Feb 9, almost a month ago) I said: "Summing it all up, if we use BOTH the rule that a pair of clocks at rest relative to one another and sychronized in their rest frame must also be synchronized in p-time, AND the rule that events which coincide at the same point in spacetime must happen at the same p-time, we get the following conclusions" then I presented an itemized list of conclusions about p-time which lead to a contradiction, and said: "I am sure you would not accept such a conclusion, but it is an unavoidable consequence of the two rules for p-time simultaneity I listed above, so if you want to avoid the conclusion you have to either ditch one of the rules or say that p-time simultaneity is not transitive" So you can see here that in this post I did list all three rules that together lead to the contradiction, and I only mentioned transitivity as an afterthought because it seemed pretty nuts to me that anyone who advocates an absolute present would deny that absolute simultaneity is transitive. In a post two days later on Feb. 11 at https://groups.google.com/d/msg/everything-list/jFX-wTm_E_Q/dWd90MiKvzgJ I also specifically said that of all the assumptions you might choose to drop once you realized the contradiction, it seemed most likely you would drop the one I had labeled as "C) if two objects are at rest relative to each other, readings on their clocks that are simultaneous in their inertial rest frame are simultaneous in p-time"--I went on to say "If I have found a contradiction of course this doesn't disprove the very idea of p-time, but it would probably imply that you have to drop assumption C)". So if you ever thought I was trying to prove that p-time simultaneity cannot be transitive, this is obviously a case of you misreading something I wrote. Feel free to look through old posts on the "block time" thread at https://groups.google.com/forum/#!forum/everything-list or look at the alternate archive at http://www.mail-archive.com/[email protected]/ which has a better search function, so you can look for specific posts that have "Jesse" and "transitive" in them, or "Jesse" and "transitivity"--I will eat my hat if you find any where I said anything resembling your idea that I was specifically trying to disprove transitivity. > You then are apparently trying to prove something else. But please, > respectfully, you are trying to disprove MY theory, so please let ME state > MY theory and then try to disprove that rather than trying to disprove > something that isn't my actual theory. > > I just gave a concise statement of my theory earlier today. Can you > disprove it or can't you? > > Your concise statement didn't clearly mention the specific rule I was trying to show led to a contradiction, namely the rule that if two inertial clocks at rest relative to one another are synchronized in their common inertial rest frame, then they must be synchronized in p-time. I don't think there's any ambiguity that you believe in this rule though, since you had said (in a statement I quoted in the original Feb 9 post), 'Yes is the answer to your question "if two clocks are at rest relative to one another and "synchronized" according to the definition of simultaneity in their mutual rest frame, do you automatically assume this implies they are synchronized in p-time?" ' So, if you still believe in that rule, and you also agree that events with the same space and time coordinates in a given inertial frame must be simultaneous in p-time, and that p-time simultaneity is transitive, then please look at the Alice/Bob/Arlene/Bart scenario I presented in the Feb. 9 post at https://groups.google.com/d/msg/everything-list/jFX-wTm_E_Q/pxg0VAAHJRQJand tell me if you can find any basis for disagreeing with the numbered statements 1-4 there. Jesse -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/groups/opt_out.
