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Tachyons travel backward in time? 
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#19
Jan2708, 01:30 PM

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I've just never heard an explanation as to why a "normal particle backwards in time" model is any less "real" and more of simply a "trick" than a "antiparticle forwards in time" model. Seems to me like people use the latter view just to comfort themselves into believing in the absolute nature of linear time.
I also find it incredibly interesting that a 4dimensional Euclidean view of Relativity has particles moving faster than the speed of light as moving backwards in time as well. These particles would be indistinguishable from antiparticles. But, again, we don't use that model, and instead use the Minkowski model, simply to keep our minds at ease that time always moves forward. [Edit] Just wanted to add, in that model,whether the particle is a "real" particle or "anti" particle is framedependent. In other words, _all_ of the quantum numbers, not just mass, become frame dependent. Doesn't this make for a simpler unified theory? 


#20
Jan2708, 01:59 PM

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#21
Jan2708, 02:03 PM

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#22
Jan2708, 05:28 PM

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And, as far as the Minkowski model, if you draw the worldlines of various particles moving at relativistic speeds, none are ever moving in the t direction for any observer. In a 4dimensional Euclidean relativity, with time on equal footing with space, if you continue to accelerate "past" 'c' relative to an observer you wind up moving backwards in time relative to that observer. By extension, that observer would believe you to be made of "antimatter". 


#23
Jan2708, 05:37 PM

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#24
Jan2708, 05:45 PM

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Take a twodimensional Minkowski diagram for any particle, one axis being "x", one being "T", where T=ict. dT/dx is always >= 1 and, obviously, is always greater than 0. That's what I mean by "forward" in time. 


#25
Jan2708, 06:21 PM

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#26
Jan2708, 06:42 PM

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#27
Jan2708, 06:45 PM

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#28
Jan2708, 08:16 PM

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I'm sorry that I misunderstood your point. The way I misunderstood it was pretty interesting though. I haven't thought about it enough to attach to it any physical significance yet, but I think that there may be something geometrically or topologically different between the two ends of a timelike line and that there is not such a difference between the two ends of a spacelike line. I could easily be wrong on that point, and even if I am right I haven't thought it through to a physical conclusion, but I find it interesting. 


#29
Jan2708, 08:33 PM

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#30
Jan2808, 05:29 AM

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The fact that diagrams and equations show that something could travel back in time doesn't mean it's a fact, it just shows the maths can go both ways  we developed the maths to explain observed results. Time doesn't exist, it's simply what we measure as the passing of one moment to the next.
Light doesn't govern the passage of time, we base the measurment of time on the speed of light but something travelling ftl doesn't mean it travels back in time. What we observe in experiments involving such particles is not neccessarily what is actually happening  our observations are limited by the speed of light afterall. 


#31
Jan2808, 08:38 AM

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#32
Jan2808, 10:05 AM

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#33
Jan2808, 10:41 AM

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#34
Jan2808, 10:49 AM

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#35
Feb208, 01:00 PM

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Ok I finally figured out how to say what I mean mathematically.
Nothing goes backwards in time because for every "t" coordinate, there can be one and only one observed value of "x,y,z". 


#36
Feb208, 01:23 PM

P: 7

So in an imaginary negative energy "anti"world a signal would go backwardtime to the sender of the photon that came here. That would make a "real time" loop.?



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