
#1
Nov1605, 03:24 PM

P: 309

If one admit that the particle has the "real objective(observer independent ?)" trajectory x(t), then if it is "observed" from point O, then, the observed trajectory is x'(t')...One could simplify by taking t'=t, because it is not here an observer transformation. Then, there should exist a relationship of the form x'(t)=x(tx1(t1)/c)....The problem is that I don't understand anymore the physical intuition that able to say if x1=x or x1=x' and which value t1(=t(?)) should have.
Thanks for any simple explanation. 



#2
Nov1605, 04:19 PM

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#3
Nov1705, 04:59 AM

P: 309

I just mean that when the first trajectory is specified x(t), then it's just a mathematical description that does not include the speed of light needed for the observer placed at the origin to "measure/see" the particle describing it's trajectory.
But it is not even clear in my mind how I should formalize this... 



#4
Nov1705, 11:32 AM

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Speed of light limit>delay 



#5
Nov1805, 12:05 AM

P: 309

No, it's not here the observer dependent "reality". it's not the einsteinian observer dependent philosophy..it makes the assumption that there exists a reality independent of any observer..hence it is not "as seen"...the "as seen" has to be computed out of this one...but this is just a mind game again...




#6
Nov1805, 12:34 AM

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#7
Nov1805, 01:45 AM

P: 309

In special relativity it is not clear to me if there is such an observer independent reality, except all only on c=celerity of light based quantities of course..for Galileo it was t=time is observer independent makeable quantity...Infact if you have an observer independent reality, then you can deduce the observer transformation laws (which is basically a school homework),since SR is in fact just basing it's idea on Lorentz transform....So I take the same exercise : let's take an observer independent physical reality, but instead of c or ds^2..let's take a whole function X_reality(t) and let's find how two observers of this "weird observer independent reality" see it....is this is more understandeable for you ?




#8
Nov1805, 01:56 AM

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#9
Nov1805, 03:35 AM

P: 309

Well, yes by observer transformation rules, I mean how do coordinates of events (in relativity), but it could be other physical quantities, when you change your observer. For example mass tranformation laws....I have two remarks :
1) precise domain : how do you deduce mass tranformation between different observer via Lorentz tranformation. 2) generally (meta dialog about this method) : don't forget that when you make transformation laws between frame of reference, you pass under silence (because we don't know how to do it i suppose), that the lawmaker itself is in a frame of reference).. Then, I just want to compute the following : the "lawmaker" trajectory is x_reality(t)...how does the two observer see that trajectory, so that i can deduce the transformation rules between their frame of reference... Your question about Newton is well done, because I asked once in this forum if somebody could reexplain me Newtons time concept in view of Einstein's review...for me it is as if nowadays, Newton't Time concept is a global concept valid for every observer, and hence in conflict with the local based time of einstein... 



#10
Nov1805, 03:56 AM

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#11
Nov1805, 06:22 AM

P: 309

Right...the other stuff with the x(t) instead of ds as invariant is even for me not clear...but it is some kind of generalization of "observer independent" reality...if you want on a more human cognition based approach, if i say "black on white"...we could have several interpration of these words...(it's some kind of physical semiotic if you want..but in fact i don't even know what semiotic exactly means...)




#12
Nov1805, 05:02 PM

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#13
Nov1805, 10:42 PM

P: 309

I think we really don't get along, because I told you from the beginning on, x_reality(t) was taken, as a starting hypothesis, as being an invariant quantity. Do you have medication for schizophrenia ??? I know they can cause connection problem in the brain....or maybe you just want to fool around ??? I think you use psychiatrist like approach to tickle the "unstable" candidate to push it in the hole....?? Just by "normal curiousity"....Or maybe it's just you don't want to enter the game proposed...free to you to remain on your battleside, it's often like that in coopworking, nobody want to be the project depositer (because it's dumb), neither the worker (because there is calculation to do)




#14
Nov1805, 11:18 PM

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#15
Nov1805, 11:38 PM

P: 309

Well I think you just are too much metathinking...we don't care about what x_reality(t) in the phyiscal reality is, we just make a math games...if i remember well from the first message, i wrote something like : observer independent trajectory...which is of course understandble physically by nobody, because we all are observers, so if you are an observer you cannot observe, nor understand what that is because you need to be not an observer..(which is different than : equals for all observer...or am I mixing myself in literal problems ?)....does this is clearer that in this framework, even I cannot exlain you what x_reality(t) is, in this math exercise ?? Yes I understood, I should have written : observer free...which is almost the same difference between timeless and everlasting/eternal I see 2 ways of doing the case : either you have no observer, which is quite weird, or you say : it's valid for every observer, but then I wonder if it is the same as finding a "law" depending on every observer (if you know all the cases, then the global theory is applicable to everyone of them)....
I think in physics there is a parallel between the two aspects of that science : phenomemology : you take all the experimental cases (passive theory making)...and then you put them together in the hope to find a law..and then you apply the laws (active theory applying)...which with social laws leads to some (funny) problems. 



#16
Nov1905, 12:52 AM

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P: 8,470

In any case, is there anything about the problem you're trying to describe that's specific to relativity, or does it apply to all of physicist's attempts to describe the world using math? If the latter, maybe it would make more sense to move this discussion to the general philosophy, metaphysics & epistemology or philosophy of science, math & logic forum? 



#17
Nov1905, 01:28 AM

P: 309

Yes, you're right, the only thing that was specific to relativity, is the maximal speed limit, inducing a change in the trajectory observed from a different standpoint than the one where it is described. Which puts forward the problem : what is it meant by giving a trajectory x(t) in a given frame ? Does it comprises the speed of light delay ? I think it would be a better idea to put in epistemology of science, it's a too basic notion to put it her....I don't how to move a complete thread...



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