Edgar, You have not yet answered what I consider to be the most important question concerning this example:
How old is Sam when Pam arrives at Proxima Centauri? Sam says 5, Pam says 1.8, some alien might say 4. Is there a definite answer to this question according to P-time? Is one of the right and the others wrong? Jason On Thu, Jan 2, 2014 at 1:57 PM, Edgar L. Owen <edgaro...@att.net> wrote: > 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 <edga...@att.net> 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 <edga...@att.net> 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 <edga...@att.net>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 <jason...@gmail.com>wrote: >>>>>>>> >>>>>>>>> >>>>>>>>> >>>>>>>>> >>>>>>>>> On Wed, Jan 1, 2014 at 8:41 AM, Russell Standish < >>>>>>>>> li...@hpcoders.com.au> 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 hpc...@hpcoders.com.au >>>>>>>>>> >>>>>>>>>> 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 everything-li...@googlegroups.com. >>>>>>>>>> To post to this group, send email to everyth...@googlegroups.com. >>>>>>>>>> >>>>>>>>>> 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 everything-li...@googlegroups.com. >>>>>>> To post to this group, send email to everyth...@googlegroups.com. >>>>>>> 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 everything-li...@googlegroups.com. >>>>> To post to this group, send email to everyth...@googlegroups.com. >>>>> 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 everything-li...@googlegroups.com. >>> To post to this group, send email to everyth...@googlegroups.com. >>> 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 everything-list+unsubscr...@googlegroups.com. > To post to this group, send email to everything-list@googlegroups.com. > 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 everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at http://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/groups/opt_out.
