On Thu, Feb 13, 2014 at 2:21 PM, Edgar L. Owen <edgaro...@att.net> wrote:
> Jesse, > > You still don't get it. > > There is no frame dependent notion of clock time simultaneity in > relativity, but when one compares the 2 frames that relativity uses to > describe a single scenario from both observer frames, one does get a 1:1 > correspondence of which clock times of A's comoving clock corresponds to > which clock times of B's comoving clock. I've explained that method in > detail with nearly a dozen examples. > You've never explained it with a single NUMERICAL example in which you actually show the specific relativistic equations you think can be used to "show" this, only abstract verbal descriptions which just make assertions about how the 1:1 correspondence works (like the assertion that if both observers move inertially after synchronizing their clocks at a common point in space, their clock readings will continue to be identical in the 1:1 correspondence). In none of your posts have you actually given a mathematical derivation to justify these assertions using textbook equations of relativity. You also didn't answer my question about whether you agree the existence of such an objective 1:1 correspondence is an original conclusion you have made that all mainstream physicists have missed, or if you claim it's actually recognized by physicists. Can you please address this? > > You are still stuck in some particular individual frame, but relativity > specifies both of the 2 frames for every scenario, one for each of the 2 > observers. > I have considered both frames. In my example, I specifically talked about which events would be simultaneous in Alice's rest frame (where Alice being 25 is simultaneous with Bob being 20), AND which would be simultaneous in Bob's rest frame (where Bob being 25 is simultaneous with Alice being 20, and likewise Bob being 20 is simultaneous with Alice being 16). > > You keep fixating on your tape measure example which I've answered 2 or 3 > times. It has nothing to do with p-time... > As I've told you several times already, the point of the measuring tape example is to discount the notion that there is an ARGUMENT for p-time which doesn't just assume the existence of p-time from the start, but rather uses observations about how relativity itself works to show that there is a NEED for p-time. My point is that for any "observation about how relativity itself works" in the context of the twin paradox example--i.e. observations which do NOT assume p-time from the start--there is an analogous "observation about how Cartesian geometry works" in the context of the measuring tape example. If you want to say "yes, I agree there's no argument that shows why p-time is needed (or even an argument that shows why an objective 1:1 correspondence is needed) that is based solely on reasoning about the quantitative facts that would appear in a standard textbook analysis of the twin paradox", then I will drop this line of discussion about measuring tapes. On the other hand, if you do think there's such an argument, then it's quite relevant to ask whether you think any of these "quantitative facts that would appear in a standard textbook analysis of the twin paradox" that don't have directly analogies in how Cartesian geometry could be used to analyze the measuring tape. So, please just tell me which of these statements A) or B) better matches your view: A) There's is NOT an argument that shows why p-time is needed (or even an argument that shows why an objective 1:1 correspondence is needed) that is based solely on reasoning about the quantitative facts that would appear in a standard textbook analysis of the twin paradox, without assuming objective simultaneity as a starting premise A) There IS an argument that shows why p-time is needed (or even an argument that shows why an objective 1:1 correspondence is needed) that is based solely on reasoning about the quantitative facts that would appear in a standard textbook analysis of the twin paradox, without assuming objective simultaneity as a starting premise > > > No, you have not established ANY contradiction in either my p-time theory, > OR between p-time and relativity. > But I have--you just seem to be confused about the meaning of one of the assumptions I made in that example. In any case, you have never directly responded to that example to point out which specific conclusion 1-4 about p-time simultaneity you would disagree with (or if you actually disagreed with any of my statements about what SR would predict for clock readings and positions of each observer at various time and space coordinates). > > Your final argument is ambiguous. But if "in any relativistic coordinate > system two events A and B would have identical (clock) time coordinates AND > identical spatial coordinates" AND assuming originally synchronized clocks, > then certainly A and B occur in the same p-time. They are at the same place > at the same p-time. > > If you don't assume originally synchronized clocks then A could just > happen to pass through that point in space earlier than than B with the > same clock reading that A had when he got there later in actual p-time. If > you originally synchronize clocks I don't see how that could happen. > Huh? If we have some coordinate system where relativity predicts the event of Alice's clock reading 30 happens at exactly the same space and time coordinates as the event of Bob's clock reading 40, do you agree or disagree that this means relativity automatically predicts these two events would satisfy the various operational meanings of "same point in spacetime" I gave at https://groups.google.com/d/msg/everything-list/jFX-wTm_E_Q/AZOhnG04__AJ , regardless of whether Alice and Bob had synchronized their clocks in the past or not? Please give me a clear agree/disagree answer to this question (if you disagree, then you are really deeply confused about what it means to assign events coordinates in SR). > > The real test, of course, is whether A and B are at the same point in > space at the actual same time as tested by their ability to shake hands and > compare watches. Doesn't matter what their clocks read or their actual ages > are if they can do that... > If they simply pass briefly through the same point in spacetime without actually coming to rest relative to each other, it may be difficult for them to shake hands if they pass by each other at some relativistic velocity. That's why I gave other types of operational consequences in that post at https://groups.google.com/d/msg/everything-list/jFX-wTm_E_Q/AZOhnG04__AJ , like the "timing the reflected light" test, or the test where one of them sets off a bomb that creates a localized explosion and we check if they are both killed or only the one who set off the bomb is. If Alice sets off a localized explosion when she turns 30, and Bob is killed at age 40 by this explosion, doesn't this mean the event of Alice turning 30 and Bob turning 40 were at the "same point in spacetime" for you, even if they didn't ever synchronize their clocks in the past? Jesse On Thursday, February 13, 2014 1:22:56 PM UTC-5, jessem wrote: > > > > On Thu, Feb 13, 2014 at 12:34 PM, Edgar L. Owen <edga...@att.net> wrote: > >> Liz, >> >> 'Any point' for observers in different frames is well defined by >> relativity theory itself. The very fact that relativity theory can provide >> 2 equations, one for each separate frame, for any SINGLE relativistic >> scenario requires that to be true. >> > > By "point" do you mean "point in time"? If so, are you saying that even > for observers at different points in space, "relativity theory itself" > provides a unique definition of which points on their worldlines are at the > same "point" in time? This is obviously not true, since there is no > preferred definition of simultaneity in relativity theory itself. You may > think you can deduce the *need* for some "true" definition of simultaneity > in order to make sense of relativity's claims, but objective simultaneity > is clearly not a part of the theory itself in the sense that it won't > appear in any textbooks on the theory. > > > > >> That is what I've continually pointed out to Jesse that's gone over his >> head, that relativity itself uses a common computational background for all >> frames. >> > > It hasn't gone over my head, I have responded over and over again by > pointing out that any mathematical statement about relativity has an > analogue in a purely geometric scenario involving things like tape measures > on a 2D plane. Just as we can describe the twin paradox with different > inertial frames that disagree about which pairs of events have the same > t-coordinates, we can describe things on the plane using different > Cartesian coordinate systems which disagree about which pairs of markings > on the measuring tapes have the same y-coordinate. Does your ill-defined > terminology of "common computational background" refers to the notion of a > unique objective frame-independent analogue of "same t coordinate" (the > analogue being 'same p-time')? If so, my point as always is that you > *don't* similarly conclude that the different Cartesian coordinate systems > in the measuring tape scenario require a "common computational background" > in the sense of an objective coordinate-independent analogue of "same > y-coordinate". And if a perfectly analogous argument involving coordinate > systems in space leads to a conclusion that even you would agree is > erroneous, that implies there is something wrong with the logic of your > argument involving frames in spacetime. > > Even though I've asked you over and over again whether you think there's > any quantitative fact about SR and different frames' descriptions of the > twin paradox scenario which DOESN'T have a direct analogue in the tape > scenario, you've never given a yes-or-no answer to this question, let alone > pointed to a specific quantitative fact you think has no analogue. From > your continued ducking of this question, I guess you probably recognize on > some level that this analogy is problematic for your position. > > > > >> If it didn't it couldn't properly describe relativistic scenarios from >> the separate frame dependent views of all involved observers. >> > > Do you think algebraic geometry (i.e. geometry where we describe shapes in > the context of a 2D coordinate system) "can't properly describe geometric > scenarios from the separate views of all involved coordinate systems"? > > >> >> This hidden and unstated assumption of relativity itself is the basis of >> p-time. >> > > If it's "hidden and unstated" than it isn't part of "relativity theory > itself" in its standard textbook form. It's rather a conclusion that you > draw about the implications of the theory. > > >> >> The dozen or so examples I've given to Jesse show how to compare >> different relativistic frames in a manner completely consistent with >> relativity >> > > > But I've given my own example that shows that your assumptions about > p-time lead to a direct contradiction. You objected to the idea that > "events which occur at the same point in spacetime must have the same > p-time", which was one of the assumptions I used to derive a contradiction, > but clearly you had misunderstood what I meant by "same point in spacetime" > since in https://groups.google.com/d/msg/everything-list/jFX-wTm_ > E_Q/GZznkprLuo8J you said "I pointed out maybe a week ago with examples > why your notion of "a same point in SPACEtime" is not the same as a same > point in p-TIME. They are the same is true only when A and B are at the > same point in SPACE". But as I explained in my response at > https://groups.google.com/d/msg/everything-list/jFX-wTm_E_Q/6NoHUw_x0tsJ, > same point in spacetime DOES always include the notion of "same point in > SPACE", this is always how I have used "same point in spacetime" and it's > obvious this must be true from the operational definition I gave (how could > the time for a light signal to reflect off the other observer and return > approach zero if the distance wasn't approaching zero too?). > > So, now that I have clarified that to say events A and B happened "at the > same point in spacetime" means that in any relativistic coordinate system > they would have identical time coordinates AND identical spatial > coordinates, would you now agree that if A and B happened at the same point > in spacetime, they must have been at the same point in p-time? If you do > agree with that, then this is sufficient to derive a contradiction when > combined with your other assumptions (that p-time simultaneity is > transitive, that clocks at rest relative to each other in the absence of > gravity that are synchronized in their rest frame must be synchronized in > p-time too), as I showed with the Alice/Bob/Arlene/Bart example in > https://groups.google.com/d/msg/everything-list/jFX-wTm_E_Q/pxg0VAAHJRQJ. So > if you would agree that events A and B having the same position > coordinates AND the same space coordinates implies they are simultaneous in > p-time, please then look over that example and tell me if you disagree with > any of the numbered conclusions 1-4 about simultaneity in p-time. > > 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 everything-list+unsubscr...@googlegroups.com. 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