ptmikulski -> RE: Richard and other thinkers (Mar. 3 2014 14:34:22)
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The spring board for considering the possibility of time travel traces back to the interconnectedness of space and time in the theory of special relativity. For any observer of an event, that observer can give that event a stamp (x,y,z,t) but each observer marking the event would give a stamp based off of his frame of reference consisting of his spatial grid and his stopwatch. The mathematics of showing the connection between any two stamps of the same event (the rules for transforming from one frame to anothers) is pretty mind blowing for a few reasons that come to mind: 1) It requires that we abandon the notion of an absolute frame of reference (a kind of "God's point of view"). While we might be accustomed to working in different frames practically, most of us prior to Einstein had no problem with the idea of marking up the universe with one absolute grid and stopwatch with rules for connecting to that absolute frame keeping space and time separate. 2) The rules for transforming from one frame to another mix space and time together mathematically. The equations look so symmetric that we can make the misstep here of thinking that in some sense time is "just another dimension". That is very misleading, the connections between dimensions (the metric is the lingo) is very rich with unsymmetric structure in it). My view on this is that the way to wrestle with this new perspective is to shift ones center, meaning special relativity forces us to shift what one holds as a kind of understood assumption about things. In the past, the notion of absolute space and time was there, but now it is more about that metric: points of view are seamlessly, mathematically connected in a consistent way. Our universe is infinite set of events, all that has happend and that will be. While our universe is seamlessly connected: any entity be it an observer or a particle of light traces a particular and restricted path through space-time, paths that never wind back on themselves. This is not an edict, it is just what happens according to the rules when an entity can not travel any faster than light in vacuum. This puts restrictions on events that can have a direct effect on one another and pretty much shuts down the possibility of time travel. To put it all another way: While the space-time stamps that any individual may put on whatever events may vary from person to person, the essential connectedness between events is unaltered, you can stretch, compress, bend, rotate, translate, speed up, slow down according to the transformation rules of special and general relativity but you can not cut and restitch (or at least according to the rules that got our imaginations running wild to begin with). There is nothing to stop us from wondering if the rules are in fact the rules, that is the job of anyone with an imagination including physicists and this wondering has thankfully no end. But so far there is not anything that I am aware of that in anyway suggests I may need to consider the possibility of time travel in order to make sense of my world. It is still fun to think about though, but when I do, I think I quickly get tied in a knot because it actually is not possible. But then again maybe my mind doesn't see the new required shift of center.
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