Jesse, Again, if I understand you, this is just a way to define 'same points in spacetime'. Again there is no calculation that tells us the twins will meet at a new same point in spacetime from the original same point in spacetime. Or are you claiming that every point in this lattice is somehow a 'same point in spacetime'? If so then it seems like everything in the lattice, and thus everything without exception would be at some unique same point at spacetime. Not the SAME SAME point in spacetime but SOME same point in spacetime.
If so that just sounds like saying there is an actual, clock time independent, same point in spacetime for every point in the lattice. To me that sounds exactly what the present moment is (local same present moment, not global. That still has to be independently proven). Correct me if I'm wrong and tell me what that calculation is in terms of this lattice to predict the the twins start from the same point in spacetime and end up at another same point in spacetime with different clock times. Edgar On Wednesday, February 5, 2014 4:00:43 PM UTC-5, jessem wrote: > > > > On Wed, Feb 5, 2014 at 3:10 PM, Edgar L. Owen <edga...@att.net<javascript:> > > wrote: > >> Jesse, >> >> No, what the equations of relativity say, and the only thing they >> compute, is that WHEN the twins meet up again at the same point in space, >> that they will have different clock times. >> >> But what is that 'WHEN'? It is not A's clock time and it is not B's clock >> time. >> > > > It is the coordinate time, and as I've mentioned to you several times, it > is ideally defined in terms of local readings on a lattice of coordinate > clocks and rulers filling up the area of space that the coordinate system > is intended to cover, as illustrated at > http://www.upscale.utoronto.ca/GeneralInterest/Harrison/SpecRel/SpecRel.html#Exploring > > The idea is to imagine a lattice of physical rulers, with some parallel to > the direction we call the x-axis and marked with x-coordinates, some > parallel to the direction we call the y-axis and marked with y-coordinates, > and some parallel to the direction we call the z-axis and marked with > z-coordinates. At each point where 3 such rulers oriented in different > directions meet, there is a clock attached. All the clocks at all points in > this lattice have been mutually "synchronized" using what's known as the > Einstein synchronization convention, which involves the assumption that > light should be measured to have the same coordinate speed in all > directions in the rest frame of the lattice, so for example if you set off > a flash of midpoint along a line between two clocks, they should be set in > such a way that they both read the same time at the moment the light hits > them. > > So for example, say some frame says "A turned 30 and B turned 40 at the > same coordinates of x=10 light-years, y=15 light-years, z=5 light-years and > t=50 years". Now imagine looking at the clock that's attached to the > unique intersection point between three rulers where the marking "10 > light-years" appears on the x-ruler, the marking "15 light-years" appears > on the y-ruler, and the marking "5 light-years" on the y ruler. Let's > label this "clock C". Then the meaning of the statement above about A and B > is that these THREE events all happened at the same point in spacetime > (which again can be defined in the operational way I discussed): > > 1. "A's life clock shows a time of 30 years" > 2. "B's life clock shows a time of 40 years" > 3. "clock C shows a time of 50 years". > > In practice of course physicists don't actually build networks of clocks > of this sort, but the point is that once you have deduced how to write the > equations of the laws of physics expressed in terms of coordinates defined > by such a lattice, it's often easy in practice to figure out what local > coordinate-clock readings *would* coincide with various events if such a > lattice were in place, without actually needing to construct one in > reality. For example, you can use optical methods to deduce the distance to > events in your frame without actually needing a ruler stretching from your > location to the location of the distant event, and if you know an event > occurred X light-years away, you can just subtract X years off the time the > light from the event reached your position in order to determine the time > coordinate of the event, which should be no different from what a > synchronized clock would have read if it was right next to the event when > it happened. > > But in principle, using such local readings on a set of clocks and rulers > is probably the best way to define the meaning of position and time > coordinates in a particular frame, the definition that will lead to the > least conceptual confusion about the meaning of these coordinates. In > particular, you can see that coordinate time is just a third type of clock > time. These coordinate clocks are particularly *useful* because they allow > you to express the laws of physics using a neat set of equations that > doesn't depend on the velocity of the coordinate clocks relative to > anything else (for example, if a light flash is emitted from a coordinate > clock when that clock reads t1, and received by another coordinate clock > when that clock reads t2, and the distance along the ruler between them is > d, then it's guaranteed that (t2 - t1)/d = c, meaning light always has a > velocity of c in these coordinates). But other than that they are no > different than any other type of clock. > > Jesse > > > >> Thus it is a completely necessary but UNSTATED assumption of a completely >> different common point in time different from and outside of the 2 clock >> times, in which the 2 clock times differ and that can be agreed on by both >> twins. >> >> Thus relativity itself implicitly and cryptically assumes a common >> present moment in which the results of spaceCLOCKtime calculations are >> compared and make sense. >> >> I'll ask you again: What is the choice of frame in relativity that >> computes the fact that the twins meet in the agreed SAME POINT of spacetime >> with different clock times? I don't think there is any.... >> >> Of course you can always avoid this question by noting that they are at >> the same point of spacetime when they are. That's an oxymoron. But what's >> the calculation that predicts that from beginning to end? There simply >> isn't any.... >> >> Edgar >> >> On Wednesday, February 5, 2014 2:54:39 PM UTC-5, jessem wrote: >>> >>> >>> >>> On Wed, Feb 5, 2014 at 2:35 PM, Edgar L. Owen <edga...@att.net> wrote: >>> >>>> Jesse, >>>> >>>> Let me ask you this simple question. You agree that there is "a same >>>> point in spacetime" that both twin meet at and in which their clock times >>>> are different. >>>> >>>> How does your theory, or relativity, account for or predict this same >>>> point with different clock times starting from when the one twin leaves on >>>> his journey? >>>> >>>> Is there any choice of frames which computes this result in relativity >>>> theory? If so what? >>>> >>> >>> >>> Yes, all of them predict it. In the context of any allowable choice of >>> coordinate system, if two events occur at exactly the same position and >>> time coordinates, then that leads to the conclusion that they must have >>> occured at the "same point in spacetime" in a coordinate-independent sense >>> (understood either in terms of spacetime geometry or in terms of the >>> operation definition I mentioned). So if any given frame assigns the same >>> space and time coordinates to a pair of clock-readings for each twin, like >>> "twin A turns 30" and "twin B turns 40", that implies these events happened >>> at the same point in spacetime, and it always works out that other frames >>> assign this pair of events identical coordinates too. >>> >>> Jesse >>> >>> >>> >>>> >>>> If not then we must assume a separate kind of time in which it is true. >>>> That is p-time. >>>> >>>> I think this question gets to the crux of the disagreement.... >>>> >>>> Edgar >>>> >>>> On Wednesday, February 5, 2014 1:40:41 PM UTC-5, jessem wrote: >>>>> >>>>> >>>>> >>>>> On Wed, Feb 5, 2014 at 10:53 AM, Edgar L. Owen <edga...@att.net>wrote: >>>>> >>>>>> Jesse, >>>>>> >>>>>> A couple of points in response: >>>>>> >>>>>> 1. Even WITHOUT my present moment, the well established fact of a 4-d >>>>>> universe does NOT imply block time nor require it. Clock time still >>>>>> flows >>>>>> just fine in SR and GR. >>>>>> >>>>> >>>>> I would agree that the 4D mathematics of relativity theory doesn't >>>>> require the ontology of block time, though I don't see any alternative to >>>>> block time besides some sort of "metaphysically preferred" definition of >>>>> simultaneity (which wouldn't contradict relativity as long as long as >>>>> this >>>>> definition wasn't "preferred" by the measurable laws of physics). I don't >>>>> know what you mean by "clock time still flows" in SR and GR--it only >>>>> "flows" in the sense that its value is different at different points >>>>> along >>>>> a worldline, the same sense in which we could say that "distance from the >>>>> end of the wire" flows along a piece of wire (i.e. the value of "distance >>>>> from the end of the wire" is different at different points along the >>>>> wire). >>>>> >>>>> >>>>> >>>>> >>>>>> No clock time simultaneity of distant (relativistic is a better >>>>>> descriptor) events does NOT imply time is not flowing at those events. >>>>>> This >>>>>> is quite clear. It's a fundamental assumption of relativity that time >>>>>> flows. >>>>>> >>>>> >>>>> What mathematical element of relativity corresponds to your notion of >>>>> "flow"? >>>>> >>>>> >>>>>> >>>>>> In fact relativity itself conclusively falsifies block time as it >>>>>> requires everything to be at one and only one point in clock time due to >>>>>> the fact that everything always travels at the speed of light through >>>>>> spacetime. I find it baffling that so many can't grasp this simple fact. >>>>>> >>>>> >>>>> Huh? "Everything moves at the speed of light through spacetime" is not >>>>> how most physicists would describe relativity, and those few who do are >>>>> just speaking in a colorful way about the magnitude of the 4-velocity >>>>> always being equal to c. And the 4-velocity is just defined as a vector >>>>> whose components give you the rate of change of the spacetime coordinates >>>>> t,x,y,z relative to proper time. >>>>> >>>>> Nothing about this notion is contrary to the notion of block time--as >>>>> an analogy, if we have a piece of wire embedded in a block of ice and >>>>> forming some type of curved shape, and we use an x,y,z coordinate system >>>>> to >>>>> describe different points within the block and on the wire, then at every >>>>> point along the wire we can define a vector whose components give the >>>>> rate >>>>> of change of x, y, z coordinates relative to "proper length" at each >>>>> point >>>>> (where "proper length" refers to the distance between that point and the >>>>> end of the wire--or some point along the wire marked "0"--as measured >>>>> along >>>>> the the wire itself). And in fact it's not hard to show (I can give you >>>>> the >>>>> derivation if you like) that using these purely spatial definitions, the >>>>> magnitude of *this* vector must always be 1 at every point on the wire, >>>>> regardless of the shape of the wire. Would you describe this situation by >>>>> saying "every wire-point moves at the same speed through the block of >>>>> ice", >>>>> even though we are talking about wires that from our point of view are >>>>> completely static, frozen in a particular shape within the block? >>>>> >>>>> >>>>> >>>>> >>>>>> >>>>>> >>>>>> 2. You complain about me not answering a few of your questions. As >>>>>> I've explained before I have limited time to post here because running >>>>>> my >>>>>> business keeps me very busy. >>>>>> >>>>>> And please note that a lot of my posts have received NO answers at >>>>>> all either, e.g. >>>>>> >>>>>> a. Several major posts, some as new topics, on my theory of how >>>>>> spacetime emerges from quantum events. Apparently this has just sailed >>>>>> over >>>>>> everyone's heads with not a single meaningful comment, not even any >>>>>> negative ones which is pretty surprising among this crowd! Apparently no >>>>>> one is interested in understanding the nature of time at the quantum >>>>>> level? >>>>>> >>>>>> b. My post on a solution to Newton's Bucket. Also no relevant >>>>>> responses. >>>>>> >>>>>> c. Several thought experiments lending very strong support to my >>>>>> present moment theory, posted just a couple days ago. Again zero >>>>>> response. >>>>>> And weren't those directed to YOU? >>>>>> >>>>>> d. Several thought experiments designed to dig into the fine points >>>>>> of various aspects of time dilation. Again only a vague comment or two >>>>>> on >>>>>> 'asymmetry' but zero actual analysis of the points I raised. >>>>>> >>>>>> e. Several other new topics on basic issues of science and >>>>>> epistemology. Again no relevant responses. >>>>>> >>>>> >>>>> Those posts were not part of an ongoing discussion with *me*, though. >>>>> I'm not asking you to respond to every argument I make, just to respond >>>>> to >>>>> posts that are part of ongoing discussions with you, in which I raise >>>>> serious difficulties with arguments you have presented to me. And I don't >>>>> mind if you take your time in getting back to me, but it is rather >>>>> suspicious when you continually ignore my requests to address specific >>>>> issues I've raised with you, even when you do apparently have time to >>>>> respond to other posts of mine. >>>>> >>>>> >>>>> >>>>>> >>>>>> As for your comment that "you have no idea what moving in clock time >>>>>> could mean" pull your head out of your physics books and watch your >>>>>> watch >>>>>> for a little while and see if the hands are moving. If not, you are in >>>>>> block time. >>>>>> >>>>> >>>>> >>>>> So does your argument for "movement in clock time" depend on our >>>>> conscious perceptions, rather than any sort of well-defined quantitative >>>>> measurements? It's not obvious to me that my perception of movement is >>>>> anything more than a mental comparison between what I'm seeing now and my >>>>> very short-term memory of what I was seeing half a second or less >>>>> earlier...and of course the idea of comparing memories or other records >>>>> with current observations still makes perfect sense in a block time view. >>>>> >>>>> I am interested in the issue of the difference between conscious >>>>> perceptions ("qualia" as philosophers refer to them) and objective >>>>> physical >>>>> facts, and I have considered the possibility that if there is a "theory >>>>> of >>>>> consciousness" of the type that the philosopher David Chalmers discusses, >>>>> then perhaps the "flow of time" would play a more fundamental role there >>>>> than it does in physics. But I don't see that this implies any *unique* >>>>> subjective present--if I can imagine a multiverse where different >>>>> versions >>>>> of me are having different experiences, I can equally well imagine that >>>>> there are different mes-at-different-ages having distinct experiences, >>>>> each >>>>> of them experiencing their own "flow" of time...it'd be a bit like a >>>>> series >>>>> of TV screens which are each playing the same movie, but where each >>>>> screen >>>>> is one frame ahead of the screen to its left, so screens at sufficiently >>>>> far-apart positions can be showing completely different parts of the >>>>> movie. >>>>> >>>>> 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-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 <javascript:>. >> To post to this group, send email to everyth...@googlegroups.com<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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