Stephen Paul King writes: > I would agree that Time is just a coordinate (system), or as Leibniz > claimed "an order of succession", if we are considering only events in > space-time that we can specify, e.g. take as a posteriori. What I am trying > to argue is that we can not do this in the a priori case for reasons that > have to do with Heisenberg's Unceratanty Principle. Since it is impossible > to construct a space-time hypersurface where each point has associated with > it all of the physical variables that we need to compute the entire global > manifold, from initial Big Bang singulary to the, possibly, infinite future, > it is a mistake to think of time simply as a coordinate. OTOH, it is > consistent if we are dealing with some particular situation and using > Special (or General) Relativity theory to consider the behavious of clocks > and rulers. ;-)

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I agree that in our particular universe the role of time is complex. Since we don't have a unified theory yet, we really can't say anything definitive about what time will turn out to be. It's entirely possible that time may yet turn out to be a simple coordinate. Wolfram is pushing ideas where the universe is modeled as a cellular automaton (CA) which has discrete units of space and time. Of course his theories don't quite work yet, but then, nobody else's do, either. > I am trying to include the implications of QM in my thinking and hence > my point about time and my polemics against the idea of "block" space-time. > I do not care how eminent the person is that advocates the idea of Block > space-time, they are simply and provably wrong. In this universe, perhaps so, although as I argued above absent a true and accurate theory of physics I don't agree that we can so assertively say that block models are disproven. But I do agree that a simple, relativity-based block model (if such exists) is incomplete as a model for our universe since it does not include QM. BTW there is also a block-universe type construction possible in QM. Let phi(t) represent the state function of the entire universe at time t. Then Schrodinger's equation H(phi) = i hbar d/dt(phi) shows how the wave function will evolve. It is determinstic and in a many worlds interpretation this is all there is to the underlying physics. So this is a block-universe interpretation of QM. However, it is non relativistic. From what I understand, a full marriage of QM and special relativity requires quantum field theory, which is beyond my knowledge so I don't know whether it can be thought of as a block universe. And then of course that still leaves gravitation and the other phenomena of general relativity, where we have no theory at all that works. Whether it will be amenable to a block universe view is still unknown as far as I understand. I don't see why you are so bound on rejecting block universes. You just don't like them? > If you look around in the journals and books you will find discussion of > the implications of multiple-time dimensions. For example: Sure, in fact I first learned of the idea from one of Tegmark's papers, he who is unknowingly one of the founding fathers of this list. http://space.mit.edu/home/tegmark/dimensions.html describes his ideas for why universes with 2 or more time dimensions are unlikely to have observers. The point is, you can't go quoting Leibniz about this stuff. We've left him far behind. Hal Finney