On Fri, Dec 27, 2013 at 6:57 PM, Edgar L. Owen <edgaro...@att.net> wrote:
> All, > > I haven't made any progress getting the idea of a common universal present > moment across so here's another approach with a thought experiment.... > I and others have provided numerous thought experiments that disprove the necessity of presentism, and moreover, others have shown the idea of an objective universal present to be incompatible with special relativity. While we have responded to all of your points, you seem to ignore many of the points myself and others have raised in response to your posts. It is quite possible you are right and the rest of us are wrong. However, if it is the case that your theory is right and ours is wrong, I would expect to see more instances of you offering cases that stump us and the theories we are assuming. > > To start consider two observers standing next to each other. Do they share > the same common present moment? Yes, of course. Any disagreement? > How are you defining "present moment"? It is not an easy question to answer, and Einstein spent a considerable amount of time defining what he meant by present in his paper on special relativity. If you use the same definition of "present" as Einstein used, then the answer is "yes if they are in the same inertial frame, and no if they are in different inertial frames". I think Russel may be right that you are using the word "present" in the way that conventionally means "event". > > Now consider those two observers, one in New York, one in San Francisco. > Do they share the same common present moment? > >From whose point of view, and which observers at which times? Let's say Alice is in NY and Bob is in San Francisco. There is an Alice at time 1, and time 2, there is also Bob at time 1 and time 2. From some observer's point of view, Alice 1 and Bob 1 are in his present. From another observer's view, Alice 1 and Bob 2 are in the same present. From a third, Alice 2 and Bob 1 are in that observer's present. Whether or not Bob 1 or Bob 2 are in Alice 1's present or not depends on Alice's and Bob's relative motions. Your questions do not have simple "yes/no" answers, they are not sufficiently well-defined. > In other words is the one in San Fran doing something (doesn't matter > what) at the exact same time the one in New is doing something? > This is assuming the idea of an objective global time makes sense, but it doesn't in the four-dimensional view of reality implied by relativity. > Yes, of course they do share the same present moment. Any disagreement? > I disagree. All we can objectively say about Alice and Bob concerning time is that they share an existence in a four-dimensional space-time. > Now consider an observer on earth and an observer in some far away galaxy. > But with the condition that they share the exact same relativistic frame in > the sense that there is zero relative motion and the gravities of their > planets are exactly the same so that clock time is passing at the exact > same rate on both their clocks. > > Now are these two observers sharing the exact same present moment as well? > Given the specification that they share the same relative motion, then from each of their perspectives, they share the same present moment. However, a third observer, Carol, might believe Alice and Bob to inhabit different present moments. > Note that we just extended the exact same relativistic circumstances of > the previous two examples so there can be no relativistic considerations. > Do these two observers also share the exact same present moment as well? > Yes, of course they do. Not only do they share the exact same present > moment but they also share the exact same clock time t value. Any > disagreement? > When the three dimensional hyperplane of Alice's present is the same as Bob's, then you can say they are in the same present moment relative to each other. This does not, however, mean they share some objective present. > > OK, if you agree then you have to take a partial step towards accepting my > thesis of a common universal present moment. > If you believe we move through the dimension of time at the speed of light, then time is a dimension that is no different from any of the spatial dimensions. If all the dimensions are equal, then the idea of a universal "when" that all observers share is as preposterous as the idea of a universal "where" that all observers share. Certainly all observers do not have to exist in the same place, so why (if the four dimensions are the same) should all observers have to exist in the same time? > You now must agree that there is at least a common universal present > moment across the universe for all observers in the same relativistic > frame. > > Agreed? > > But not all observers are in the same inertial frame. Do you agree that there is a different present for each set of observers in a common frame? How do you square this with the idea of a single global and objective present to which all observers belong? Jason -- 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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