On Wed, Feb 5, 2014 at 11:22 AM, Edgar L. Owen <[email protected]> wrote:
> Jesse, > > I didn't answer these 3 because you are once again describing well known > aspect of CLOCK time simultaneity with which I probably agree. > Uh, no they weren't, each of them concerned questions about YOUR definitions and arguments about simultaneity in p-time. --question 1 dealt with the question of how YOU would define p-time simultaneity in a cosmological model where there's no way to slice the 4D spacetime into a series of 3D surfaces such that the density of matter is perfectly uniform on each slice (and that uniform can be characterized by the parameter Omega), unlike in the simple FLRW model where matter is assumed to be distributed in this perfectly uniform way. --question 2 dealt with YOUR argument for an absolute truth about which points on separated twin's worldlines happened at the "same point on time" independent of any choice of coordinate system based on mere clock simultaneity (i.e. same actual p-time)--the argument with the labeled steps that you presented at https://groups.google.com/d/msg/everything-list/HeLo1QmdHFQ/XHyse24U_xIJ . I pointed out that I could come up with a seemingly exactly analogous argument that deals only with spatial positions (time is not involved in the argument at all, not clock-time and not p-time), with an analogue for each of the steps you wrote down, the purports to show there is an absolute truth about which point on different roads occur at the "same point in y" independent of any choice of coordinate system based on an arbitrary choice of x and y axes. If you'd like me to repeat this "analogous argument" in the same step-by-step manner as your argument for p-time simultaneity, I'd be happy to do so. --question 3 was about YOUR claim that for every observer in the universe, "Every one of them is always currently in their own local actual time, their present moment." I was asking whether you meant that there is a single point on each observer's worldine that is "their own local actual time", or whether you were just saying that at each point on the observer's worldline, the version of the observer at that age has a different definition of "their own local actual time", without saying anything one way or another about whether all these different ages and their definitions are equally real. If you mean the first one, I was also asking whether this was an essential assumption in the argument with the labeled steps that I linked to above in the question 2 summary--if it is then your argument for absolute p-time simultaneity is completely circular, since you are assuming p-time from the start. > These have nothing to do with the concept of a present moment independent > of clock time within which clock times run at different rates. > > You need to understand the distinction. > I understand the distinction perfectly, if you think I am confusing them you simply haven't understood (or read carefully enough) my posts to you. While I recognize the notion of an absolute time distinct from clock time as a logical possibility, I don't see any compelling NEED to assume such a thing, and my second two questions above are questioning your own arguments for the NEED for a "present moment independent of clock time". Question #1 is about whether you would have any EMPIRICAL way to define absolute p-time simultaneity (given that you can't just define it in terms of 3D slices where the density of matter is perfectly uniform within each slice, as you might in an ideal FLRW universe), or whether you just take it on faith that there's a truth about absolute simultaneity even if there's no empirical way to decide what it is. > > Refer to my 2 thought experiments of a day ago. 1. The billion twins > example. 2. The all observers in the universe example. > I did refer to the post where you presented these thought experiments, question #2 that I wanted you to respond to was from my own detailed response at https://groups.google.com/d/msg/everything-list/HeLo1QmdHFQ/Mw8jXkmytGoJwhich you never bothered to respond to. Again, I showed that one could come up with a perfectly analogous argument in 2D space involving roads that diverge and later converge (three roads, a billion roads, all the roads in the entire infinite 2D space, it doesn't matter), which purports to show that there must be an absolute truth about which points on separated roads are at the "same point in y". Since this conclusion seems obviously silly, it indicates that the argument is flawed (a reductio ad absurdum). Again, if you didn't follow that analogous argument I can restate it or answer questions about it, but so far you have just blatantly ignored the argument altogether. > > However these won't do you any good until you understand and accept the > basic well established FACT that the clock times of the twins differ in the > exact same present moment they both share. > The clock times differ when they are at the same point in spacetime (defined operationally in terms of them being able to send light to the other one and get the reflected light back in a negligible amount of their own clock time, with the light coming back showing the clock time of the other one). If you don't mean anything more by "the clock times of the twins differ in the exact same present moment they both share" than what I mean by "the clock times differ when they are at the same point in spacetime", then I agree with your FACT. If you do mean something more I'm not sure I agree, you would have to give me some operational definition of how they determine they are in the "same present moment" that goes beyond my operational definition of "same point in spacetime" above--unless you don't mean "same present moment" to be defined operationally at all, and are just assuming p-time from the start. 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.
