Jesse, Good physics based post. Yes, Brian Greene mentions "everything travels through spacetime at the speed of light" in both his books but only in passing as a curiosity without recognizing its profound significance.

Thanks for your link to your physicsforums post. The meaning of 'speed through time' is actually pretty clear as it's based on the universally accepted fundamental equation for 4-d spacetime in which the t variable has to be multiplied by c to make sense. That has to be accepted if we accept that spacetime is a single 4-dimensional structure which everyone agrees is fundamental to relativity theory. The equation for velocity through spacetime works the same way and has to be accepted for the same reason. Once you accept time as distance along a 4th dimension you have to accept velocity through time and all the math of relativity works fine and is consistent. I don't think there should be any reservations about this. The problem with all your other comments (which I agree with as I scanned them) is they refer to clock time, not the P-time of the present moment. Of course clock time t values vary in a number of ways, but the key insight is they always vary in the exact same present moment which is proved by the time traveling twins reuniting with different clock time t's but always in the exact same present moment. This proves there is a single common universal present moment in which all clock time variations occur. And as you infer proper time is the direct experience of P-time which is the same for all observers even as their clock times are running at different relativistic rates. Edgar On Tuesday, December 24, 2013 8:26:00 PM UTC-5, Edgar L. Owen wrote: > > Liz states that "Special relativity shows that there is no such thing as > a "common present moment". but this is incorrect. > > Actually special relativity shows exactly the opposite. In my book I > explain how this works. It is well known, though little understood, that > everything without exception continually travels through spacetime at the > speed of light according to its own comoving clock. I call this the STc > Principle. This is a well known consequence of special relativity but > actually as I point out in my book this is an even more fundamental > Principle than Special Relativity and Special Relativity is properly a > consequence of it and can be derived from it. > > What the STc Principle says is that the total velocity through both space > and through time of everything without exception is = to the speed of > light. This is the reason that time slows on a clock moving with some > relative spatial velocity, as Special Relativity tells us. > > It also demonstrates that the speed of light is properly understood as the > speed of TIME. That's what c really is. Light just happens to move entirely > in space according to its own comoving clock, therefore its entire > spacetime velocity is in space only. > > Anyway it is precisely this STc Principle that puts both the arrow of time > and a privileged present moment on a firm physical basis. Why? Because it > requires that everything must be in one particular place in spacetime (the > present moment) and moving at the speed of light (the arrow of time). > > So exactly contrary to your statement, it is precisely special relativity, > properly understood, that puts both the arrow of time and a common present > moment on a firm physical basis. > > This insight simultaneously solves two of the big problems of the > philosophy of science, the source of the arrow of time, and the reason for > a common present moment, though no one seems to have recognized this prior > to my exposition in 1997 in my paper 'Spacetime and Consciousness'. > > Edgar > > > -- 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.