Jason, No, your graph is incorrect. As I said it's the horizontal grid lines of the graph paper itself that represent present time. Where those intersect the two world lines represents the shared present moment P-time... The lines are NOT slanted like you have them...
Edgar On Thursday, January 2, 2014 1:45:21 PM UTC-5, Jason wrote: > > > > > On Thu, Jan 2, 2014 at 1:01 PM, Edgar L. Owen <[email protected]<javascript:> > > wrote: > >> Jason, >> >> Taking your points in order. >> >> No contradiction. Sam and Pam do experience 10 and 6 years of clock time >> respectively, but it's all experienced in a common present moment which >> doesn't have a separate measurable t value of its own. Only clock time has >> measurable t values, but they all occur in the present moment. This is a >> direct consequence of what we started out with, that clock time t values >> vary differently, but always in the same present momemt. No contradiction. >> that's just the way things work. >> >> No, present moment time is NOT equivalent to the lengths of the paths >> traced by each twin through spacetime. Imagine the paths are drawn on graph >> paper, Sam's points directly above one another and Pam's in a curve off to >> the side from Sam's start point to Sam's end point. Present moment time is >> simply the horizontal lines on the graph paper that connect the two world >> lines. There is always a horizontal graph paper line that connects both >> world lines so there is always a shared present moment but the clock time t >> values are different for those intersections. >> > > > [image: Inline image 1] > > That is not quite true. If Pam's path curves off to the side, then > horizontal lines stop reaching Pam after Sam's sixth year. > > If, however, you connect points (which I have done with black lines) that > correspond to equal coordinate times (that is, where the total length of > the blue and pink lines traced out is the same) then you get the versions > of Sam and Pam that can interact with one another. > > If you consider things from Pam's reference frame, then the horizontal > lines you proposed would be different than if you considered the situation > from Sam's reference frame. > > >> >> Again, the only way to compare differing clock time values is with >> respect to the common present moment represented by the horizontal graph >> paper lines which both twins exist in when they compare. That is the only >> way a comparison is even possible. >> >> > Are you saying it is impossible to say how old Sam is when Pam gets to > Proxima Centauri? If so, then I agree. However if it is impossible to > give a definite agree for Sam when Pam gets there, it seems that rules out > the notion of a common present. > > > > >> I'm not sure I'm clear by what you mean by "coordinate time" and how it >> differs from my 'clock time'. Aren't they the same? >> > > No, clock time is proper time, the "y-axis" in the above graph. > Coordinate time, however, is the clock time of each individual's rest > frame. In other words, what they consider their proper time to be. It is > equal in the above graph where the lengths of the blue and pink lines are > equal. That is, when Sam is 1 year old, both he and Pam have gone one light > year through space-time, and likewise, when Pam is 1 year old, she > considers both her and Sam to have traveled one light year through space > time. In both of these instances, the coordinate time is equal. > > >> Assuming so then in your last paragraphs you are once again doing an >> entirely correct analysis of clock time variations which I accept >> completely but which does not describe Present moment P-time. >> >> You have to stop trying to measure and analyze Present moment time by >> clock time arguments. It doesn't work because they are two completely >> separate kinds of time. Present moment time is measured not by clock time t >> values but by the fact two observers exist in the same present moment and >> thus are able to shake hands and compare (differing clock time t values). >> > > I have no problem with explaining how both of them can shake hands, but > your theory of P-time seems to have a problem with answering how old Sam is > when Pam gets to Proxima centauri. This must have an objective definite > answer if there is a common objective present, but it has no definite > answer unless an inertial reference frame is given (or assumed). > > If you assume some inertial reference frame, then that is fine. You can > say there is one unique present, but what is the motivation to give this > inertial frame some privilege over the others? How do we decide what > absolute rest is? > > Jason > > >> >> I think you may suspect I'm on to something here, and I think you may be >> getting close to getting it. It's really quite a simple obvious concept. >> You just have to put aside the old paradigm of a single kind of time and >> think it through. >> >> Edgar >> >> >> >> >> >> On Thursday, January 2, 2014 12:32:19 PM UTC-5, Jason wrote: >> >>> >>> >>> >>> On Thu, Jan 2, 2014 at 11:54 AM, Edgar L. Owen <[email protected]> wrote: >>> >>>> Jason, >>>> >>>> Sorry, but you didn't address the argument I presented. I don't see how >>>> I can make it any clearer. Please, I respectfully ask you to reread it and >>>> think it through. >>>> >>>> >>>> And there are only 2 frames under consideration in our example. >>>> >>> >>> Okay, let's use a concrete example from here on, because I think it will >>> help: >>> >>> Two twins, Sam and Pam are born on the same day in the year 2000. Sam >>> remains on Earth, and Pam goes to Proxima Centauri (4 light years away) at >>> 80% the speed of light and then comes back at the same speed. When the >>> twins are reunited in 2010, Sam is 10 years old and Pam is 6 years old. >>> >>> I think you are asking me to consider the two frames of each twin. I >>> agree that every moment between when Pam and Sam are separated, until they >>> are reunited, each twin exists and is doing something, and this is >>> necessary the case in all possible frames from all possible external >>> observers too, since they eventually meet up again. >>> >>> However, to me there is already one apparent contradiction in the idea >>> of a common present when considering this example. Sam experiences 10 years >>> of time, 10 years of biological ageing and 10 years of memories, yet Pam >>> only experiences 6. If there is a common present, how can Sam "experience >>> more of them" than Pam? It seems Pam only experiences 60% of the present >>> moments that Sam does. How do you account for this with P-time? >>> >>> >>>> Forget about all others. Second you are again trying to analyze present >>>> moment time with SR. It won't work for reasons I've repeatedly explained. >>>> >>>> 4 dimensionalism (SR and GR work great - for clock time, not for >>>> Present moment time which you've already agreed is a whole different kind >>>> of time)... >>>> >>> >>> "Present moment time" in the twin example is equivalent to the lengths >>> of the paths traced by each twin through space time. Pam's journey toward >>> proxima centauri is the hypotenuse of a 3-4-5 triangle. She moves 4 light >>> years through space, and 3 through proper time (she is 3 when she gets to >>> the destination), but the path through space time is the hypotenuse, which >>> is 5 light years long. Meanwhile, 5 years have transpired on Earth and Sam >>> is 5 years old. >>> >>> During Pam's return voyage, each twin traces out another 5 light years >>> through space time. So when the twins are reunited, in 2010, Sam's >>> coordinate time is sqrt(0^2 + 10^2) (going 0 ly through space and 10 >>> through proper time), and Pam's coordinate time is sqrt(8^2 + 6^2), having >>> gone a total of 8 ly through space and 6 through proper time. Since things >>> only interact when their x,y,z, and (coordinate time) t are the same, the >>> 10 year old Sam who shakes hands with Pam is shaking hands with the >>> 6-year-old Pam, since they both have a coordinate time of 10 light years. >>> >>> >>>> In the common present moment someone is either actually dead or not >>>> dead. It is true that it's not alway possible to measure when this >>>> happened >>>> in any particular clock time frame. But that is just trying to assign a t >>>> value to the time of death. Nevertheless someone is always either dead or >>>> not dead in the actual shared present moment.... >>>> >>> >>> You can say the common universal present is all things that have the >>> same coordinate time t, but only in the context of a particular inertial >>> frame. The moment you allow different intertial frames, there can be no >>> agreement on what the current coordinate time is for different things that >>> are in different locations. >>> >>> Consider Pam's perspective during her trip from Earth to Proxima >>> Centauri. She might consider herself to be at rest, and Earth, Sam and >>> Proxima Centauri to be flying through the universe at 80% c. Since these >>> things are moving so fast, she measures the distance between Earth and >>> Proxima centauri to be length contracted to 60% of what Sam believes it to >>> be. She thinks it is 2.4 ly, not 4 ly. Therefore, at Proxima Centauri's >>> present speed it will take 3 years to get to her (2.4 / 0.8). By the time >>> Proxima Centauri arrives, she believes her coordinate time is only 3 light >>> years (as is Sam's from her perspective), she thinks Sam is only (3 * 60%) >>> = 1.8 years old, while Sam thinks he is 5 by the time she gets to Proxima >>> centauri. How does your notion of a common present address this? >>> >>> How can Sam believe he is 5, while Pam believes he is 1.8 (when Pam >>> arrives at her destination). Note both twins agree that Pam is 3 at the >>> time she arrives at Proxima Centauri, and both twins agree that when they >>> meet at Earth in 2010 that Sam is 10 and that Pam is 6. >>> >>> This shows you can't extrapolate from common agreements when two people >>> are together to common agreements when two people are apart, just because >>> there is agreement when they meet up again. >>> >>> Jason >>> >>> >>> >>>> >>>> >>>> On Thursday, January 2, 2014 9:56:44 AM UTC-5, Jason wrote: >>>> >>>>> >>>>> >>>>> >>>>> On Thu, Jan 2, 2014 at 8:50 AM, Edgar L. Owen <[email protected]> wrote: >>>>> >>>>>> Hi Jason, >>>>>> >>>>>> No, sadly you haven't quite gotten it yet but you are getting closer >>>>>> it seems. >>>>>> >>>>>> First the twins do NOT have the same (x,y,z,t) coordinate times (that >>>>>> would be true of an SR constant velocity example, but not the twins' GR >>>>>> acceleration based example). Their watches show they don't, and when >>>>>> they >>>>>> compare watches both twins agree with the readings on both watches. Not >>>>>> only do the twins have different ages but their clocks accurate show >>>>>> that >>>>>> age difference. Both twins agree that the traveling twin aged less >>>>>> because >>>>>> comparing their clocks both mechanical and biological confirms that. >>>>>> >>>>>> Thus they have different (x,y,z,t) coordinates yet they DO interact. >>>>>> Why? Only because they share the exact same present moment which is the >>>>>> only place interactions can occur whether clock times are the same or >>>>>> not. >>>>>> And that present moment P-time is a completely independent kind of time >>>>>> from clock time. There is simply no way around this. >>>>>> >>>>>> >>>>> You are describing coordinate time. >>>>> >>>>> >>>>>> Yes, you are correct the twins shaking hands and comparing watches >>>>>> confirms a shared present moment by direct experiment if the (x,y,z) >>>>>> coordinates are the same but not they they different. However the >>>>>> argument >>>>>> to deduce a common present moment when (x,y,z) coordinates are different >>>>>> is >>>>>> simple and clear. I've already posted it a couple of times but will >>>>>> summarize it again. >>>>>> >>>>>> The twins start and end at the same (x,y,z) coordinates. At both >>>>>> times we agree they share the same present moment. Their passages from >>>>>> point A to point B must both be represented by continuous lines, one >>>>>> curved, one straight. During every point during that passage both twins >>>>>> continuously experience their own present moment time without >>>>>> interruption >>>>>> and those present times are the same when they start and when they meet >>>>>> up >>>>>> again. Thus we must logically conclude that at every present time moment >>>>>> for either observer there absolutely must have been a corresponding >>>>>> present >>>>>> time moment for the other. >>>>>> >>>>> >>>>> You have demonstrated it for two observers at the same x,y,z, but it >>>>> does not logically follow for different x,y,z's. >>>>> >>>>> >>>>>> This is not directly observable >>>>>> >>>>> >>>>> So we should maintain some doubt.. >>>>> >>>>> >>>>>> but is the only logical conclusion >>>>>> >>>>> >>>>> SR shows there is another possible conclusion. >>>>> >>>>> >>>>>> based on their starting and ending at a shared present moment and >>>>>> both their spacetime travels being continuous with no breaks in between. >>>>>> >>>>> >>>>> This can also be explained by a an (approximately) continuous, >>>>> four-dimensional reality, in which all events are embedded. >>>>> >>>>> >>>>>> >>>>>> The easy way to understand this is that every present moment for >>>>>> either twin, the other twin must actually exist and be doing something >>>>>> too. >>>>>> >>>>> >>>>> In some relativistic frames, with separated twins might be considered >>>>> dead, and the other still alive, while in another frame, the former twin >>>>> is >>>>> still and the other is dead. The only sense in which the other is >>>>> guaranteed to exist and be doing something is that both twin's "world >>>>> tubes" exist and are eternally embedded in the four dimensional reality. >>>>> >>>>> >>>>>> There is absolutely no way around that! Thus they must share a common >>>>>> present moment in which they are existing and doing something even when >>>>>> they are separated spatially. Clearly this cannot be experimentally >>>>>> confirmed (measured) but it is the only tenable logical conclusion >>>>>> unless >>>>>> you think things pop in and out of existence which they don't. >>>>>> >>>>>> >>>>> Now again for the nth time. don't try to analyze this by relativistic >>>>>> clock time theory. That correctly describes how clock times change >>>>>> during >>>>>> the trip but has no relevance to present time whatsoever! Two completely >>>>>> different kinds of time. >>>>>> >>>>> >>>>> I fail to see how this is any different from coordinate time vs. >>>>> proper time in SR. >>>>> >>>>> >>>>>> >>>>>> Thus the only possible conclusion is that there is a common universal >>>>>> shared present moment time which is completely different from clock time. >>>>>> >>>>>> >>>>>> >>>>> >>>>> Why doesn't four dimensionalism work? >>>>> >>>>> Jason >>>>> >>>>> >>>>>> >>>>>> >>>>>> >>>>>> On Wednesday, January 1, 2014 3:15:27 PM UTC-5, Jason wrote: >>>>>> >>>>>>> Edgar, >>>>>>> >>>>>>> I believe I may understand your point about a universal present, but >>>>>>> it is something relativity handles, as far as I can see, without having >>>>>>> to >>>>>>> postulate anything new. Anything having the same (x, y, z, t) >>>>>>> coordinates >>>>>>> can interact, where t is coordinate time. It seems like you believe >>>>>>> that >>>>>>> because the twins are different ages (in different proper times), that >>>>>>> they >>>>>>> cannot interact. But they can, because each has traced exactly 10 light >>>>>>> years through space-time (their coordinate times are the same). >>>>>>> >>>>>>> So you might say everything with the same coordinate time, at the >>>>>>> same place (x, y, z) the same, shares a present moment. But you cannot >>>>>>> use >>>>>>> this fact to extrapolate to spatially separated things sharing a >>>>>>> present. >>>>>>> For this, the definition of a present (what things exist having the >>>>>>> same >>>>>>> coordinate times) differs in different reference frames. >>>>>>> >>>>>>> Jason >>>>>>> >>>>>>> >>>>>>> On Wed, Jan 1, 2014 at 3:01 PM, Jason Resch <[email protected]>wrote: >>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> On Wed, Jan 1, 2014 at 8:41 AM, Russell Standish < >>>>>>>> [email protected]> wrote: >>>>>>>> >>>>>>>>> On Mon, Dec 30, 2013 at 01:20:35AM -0800, Edgar L. Owen wrote: >>>>>>>>> > Jason, >>>>>>>>> > >>>>>>>>> > That's a totally off the wall answer. When the two shake hands >>>>>>>>> it's not >>>>>>>>> > just photons that are interacting, it's the electrons, protons >>>>>>>>> and neutrons >>>>>>>>> > of the matter of their hands which don't travel at the speed of >>>>>>>>> light. >>>>>>>>> > >>>>>>>>> > Goodness gracious! >>>>>>>>> > >>>>>>>>> > Edgar >>>>>>>>> > >>>>>>>>> >>>>>>>>> Jason is correct - electron-electron and electron-proton >>>>>>>>> interactions >>>>>>>>> are mediated by photons. Only nucleon-nucleon interactions are >>>>>>>>> mediated by different stuff (gluons in that case), but for all >>>>>>>>> practical purposes, the strong force is irrelevant to the >>>>>>>>> phenomenon >>>>>>>>> of handshaking. >>>>>>>>> >>>>>>>> >>>>>>>> And if it were, say in some particle accelerator, the gluons also >>>>>>>> travel at the speed of light and their present is spread across all >>>>>>>> proper >>>>>>>> times. >>>>>>>> >>>>>>>> >>>>>>>>> >>>>>>>>> Which gets us to the more important point. You idealise a >>>>>>>>> handshake as >>>>>>>>> instantaneous as a demonstration of your "present moment", but in >>>>>>>>> fact >>>>>>>>> those interactions Jason was alluding to are smeared out over a >>>>>>>>> temporal duration of the order of a few picoseconds (a duration >>>>>>>>> well >>>>>>>>> measurable by current day technology - my laptop's CPU clock >>>>>>>>> cycles on >>>>>>>>> a sub-picosecond timescale, for example). >>>>>>>>> >>>>>>>> >>>>>>>> You must have a VERY fast laptop! :-) >>>>>>>> >>>>>>>> Jason >>>>>>>> >>>>>>>> >>>>>>>>> This doesn't matter much for human affairs, but becomes quite >>>>>>>>> significant when extrapolating over cosmological scales. >>>>>>>>> >>>>>>>>> Cheers >>>>>>>>> -- >>>>>>>>> >>>>>>>>> ------------------------------------------------------------ >>>>>>>>> ---------------- >>>>>>>>> Prof Russell Standish Phone 0425 253119 (mobile) >>>>>>>>> Principal, High Performance Coders >>>>>>>>> Visiting Professor of Mathematics [email protected] >>>>>>>>> >>>>>>>>> University of New South Wales http://www.hpcoders.com.au >>>>>>>>> ------------------------------------------------------------ >>>>>>>>> ---------------- >>>>>>>>> >>>>>>>>> -- >>>>>>>>> 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. >>>>>>>>> >>>>>>>> >>>>>>>> >>>>>>> -- >>>>>> 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. >>>>>> >>>>> >>>>> -- >>>> 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. >>>> >>> >>> -- >> 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] <javascript:>. >> To post to this group, send email to [email protected]<javascript:> >> . >> Visit this group at http://groups.google.com/group/everything-list. >> For more options, visit https://groups.google.com/groups/opt_out. >> > > -- You received this message because you are subscribed to the Google Groups "Everything List" group. 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