Questions on world-line
in [Relativity]
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From: Mike on 23 Aug 2006 16:36 kenseto wrote: > "Mike" <eleatis(a)yahoo.gr> wrote in message > news:1156342431.430984.214950(a)h48g2000cwc.googlegroups.com... > > > > kenseto wrote: > > > "Mike" <eleatis(a)yahoo.gr> wrote in message > > > news:1156277943.578929.7420(a)b28g2000cwb.googlegroups.com... > > > > > > > > kenseto wrote: > > > > > In SR the world line is the path of an object in space with the > passage > > > of > > > > > time. Each object has its own world-line. > > > > > > > > Not exactly but ok for starters. > > > > > > > > > > > > > Questions: > > > > > 1. Does this mean that the world-line of an object is the result of > the > > > > > individual motion of the object? > > > > > > > > You do not need the term "individual". nd you must add ...motion of > the > > > > object in spacetime (not quite but ok for starters) > > > > > > > > It seems you are setting up a straw man argument using the word > > > > "individual". > > > > > > > > > 2. SR says that there is no such thing as individual motion. There > is > > > only > > > > > relative motion then how does an individual object have world-line? > > > > > > > > Here we go again. The straw man is here. SR does not "say" anything > > > > about "individual" motion. The subject of individual motion is > > > > traditionally a subject of metaphysics and fundational physics > > > > questions not dealt by experimental physics. Despite that, your > > > > question is meaningless anyway. The other name for Relativity is > > > > "Theory of Absolutes", suggested by Planck but rejected by Einstein > > > > because he thought, although it was the correct name, it was too late > > > > to change it. > > > > > > > > You probably confuse absolute motion with individual motion. Absolute > > > > motio is motion WRT an absolute media, such as an absolute spacetime. > > > > Individual motion exists in both absolute and relational spacetimes. > In > > > > the former it can be measured WRT the absolute media. In the latter it > > > > can only be measured WRT another body in motion. That you need another > > > > body to measure the motion of a body does not negate individual > motion. > > > > Actually, "it takes two to tango". > > > > > > You did not answer my question: What is the motion of an object that > causes > > > it to have a world-line??? > > > > Why do you think anyone can answer your straw man question? Try you > > local priest for a reference to prayers about Creation of the Universe > > by God. > > > > "Causes" is not the subject of experimental physics. You have been told > > that zillion times bozzo. > > Hey idiot.....a line trace out by an object in space-time requires some kind > of motion. So what > is that motion? I tell you. Go to a beach and use your little fingure )for a change) to scribe a line on the sand. Make circles and triangles. Call other kids to play with you and make all sorts of line shapes. Ask one of the kids what was the cause of those shapes. She will point to your fingure for the cause. If you keep on asking her she will get upset and trhow mud on your face....hahahahahahahahaha Hello crank Mike
From: YBM on 23 Aug 2006 19:31 kenseto a ?crit : > "YBM" <ybmess(a)nooos.fr> wrote in message > news:44ec8a99$0$19782$636a55ce(a)news.free.fr... > >>kenseto a ?crit : >> >>>The point is: worldline or trajectory in spacetime requires some kind of >>>motion to happen. In SR there is only relative motion.....does that mean >>>that worldline of an object is the result of relative motion?? >> >>I should be dreaming... You are just about to get it ! > > > RFOTFLOL this idiot falls into the trap.....an object doesn't need any > reference to have a worldline. Well, I'm right not to have bet on that... not that I did believe it actualy. Back to basics : the worldline of Ken Seto is defined in a specific frame F as the set of the t-uples (x,y,z,t) tagging in F the events "at time t, Ken Seto is at coordinates (x,y,z)". Is their anything else than your relative motion (or rest) wrt F which completely define this set called "worldline" ? [ ] No [ ] Yes. Please fill here : ______________________________
From: Barry on 23 Aug 2006 19:54 kenseto wrote: > What I am asking is: what motion of an object that gives rise to it > worldline? Is it the object's absolute motion (individual motion)? If not > why not? In SR, the motion of an object that gives rise to it's worldline is it's motion through time at "c". If the Earth is considered to "stationary" in space, then it's world line is straight but the moon's worldline (and yours) is a kind of helix. If the Sun is considered to "stationary" in space, then it's world line is straight but the Earth's worldline is a kind of helix. If the Galaxy is considered to "stationary" in space, then it's world line is straight but the Sun's worldline is a kind of helix. Since they can't figure out who is stationary, then they can't figure out the absolute worldline (i.e. the absolute motion through space). What they can figure out is that if the Earth moves more, spatially, than the sun then the Earth also travels more, temporally, than the sun. That's called gravitation. Barry
From: Ahmed Ouahi, Architect on 24 Aug 2006 06:57 The iterating of these lines brings gold The framing of this circle on the ground Brings whirlwinds tempests thunder and lightning -- Marlowe Faustus -- Ahmed Ouahi, Architect Best Regards! "Barry" <sasalobo(a)squaw.ca> wrote in message news:CZ5Hg.10913$EF2.1877(a)newsfe23.lga... > kenseto wrote: > > What I am asking is: what motion of an object that gives rise to it > > worldline? Is it the object's absolute motion (individual motion)? If not > > why not? > > In SR, the motion of an object that gives rise to it's worldline is it's > motion through time at "c". > > If the Earth is considered to "stationary" in space, then it's world > line is straight but the moon's worldline (and yours) is a kind of helix. > > If the Sun is considered to "stationary" in space, then it's world line > is straight but the Earth's worldline is a kind of helix. > > > If the Galaxy is considered to "stationary" in space, then it's world > line is straight but the Sun's worldline is a kind of helix. > > Since they can't figure out who is stationary, then they can't figure > out the absolute worldline (i.e. the absolute motion through space). > > What they can figure out is that if the Earth moves more, spatially, > than the sun then the Earth also travels more, temporally, than the sun. > > That's called gravitation. > > Barry
From: Mike on 24 Aug 2006 08:21
Paul B. Andersen wrote: > Igor wrote: > > surrealistic-dream(a)hotmail.com wrote: > >> Not true. SR treats accelerations as absolute, but velocites and > >> positions as relative. > > > > Wrong. There is a Lorentz transformation for acceleration also. > > No, it's correct. > But the acceleration that is absolute is the proper acceleration, > that is the acceleration measured in the instant inertial > rest frame of the object. It is the acceleration that is > measured by an accelerometer. This acceleration is absolute, > that is independent of frames of reference. > The co-ordinate acceleration is however frame dependent. The term "absolute" implies a much broader range of possibilities than simply "independent of FoR". It is better to call proper acceleration an invariant. However, this whole thing is a math trick. There is no physical significance to an "instant inertial rest frame co-moving with an object". In lieu of the math trick, acceleration must be referenced wrt an absolute space of some kind or wrt the mass distribution in the universe as Mach insisted, which makes any attempt to develop a relativity theory hopeless. What this instant inertial frame means essentially, is that any accelerated motion can be broken down to a series of inertial motions, something that is totally absurd. This error has been pointed out by many as back as 300 years ago, before Einstein and SR. It turns out that while the thinking is wrong the result turns out correct accidentaly. There is no way to define an instant inertial frame because an instant in the motion of an object cannot be defined. Motion is continuous to arbitrary accuracy. Mike > > Example: > If you travel in space with a rocket with constant thrust, > you will have a constant proper acceleration. > (Assume the mass of of the ship is constant.) > Your accelerometer shows a constant acceleration of - say 1g. > This acceleration is absolute, independent of frames of reference. > > But your co-ordinate acceleration measured in some inertial frame > is NOT constant. As your speed in this frame of reference > (after a year or so) approaches c, your co-ordinate acceleration > approaches zero. > > >> With the exception of the worldline of a particle moving at light > >> speed, the worldline of a particle is a specific 'curve' (or piecewise > >> collection of curves and/or line segments) in a specific spacetime > >> diagram. This curve is generally timelike and not an invariant of a > >> Lorentz transformation. > > > > Wrong again. The worldline is invariant regardless of whether it is > > spacelike, timelike, or lightlike. > > An interval between two events is timelike if it is > possible for a massive object to be present at both events. > The word line of an object is its path through space-time. > Any interval between events on this world line must thus per > definition be time-like. > There is no such thing as a "space-like world line". > > Paul |