The moving system is not an inertial frame in 1905 Relativity
in [Relativity]
|
From: harald on 30 Jun 2010 18:45 On Jun 30, 10:03 pm, va...(a)icmf.inf.cu wrote: > In a recent thread we established that > Centre of mass inertial frames are the unique ones in 1905 > Relativityhttp://groups.google.com.cu/group/sci.physics.relativity/browse_frm/t... > We cant have two (or more) of them at the same time, because the > bodies belonging to all of them determine a unique centre of mass > inertial frame. As a result, in 1905 Relativity the moving system (MS) > can be only a body (or subset) belonging to the body set of the unique > inertial frame (the stationary system). The MS can be moving with any > velocity compatible with the same laws valid in every inertial frame, > not being then in general an inertial one. As you (should) know by now, that's not true: "Let us take a system of co-ordinates in which the equations of Newtonian mechanics hold good. In order to render our presentation more precise and to distinguish this system of co-ordinates verbally from others which will be introduced hereafter, we call it the ``stationary system.'' [...] Theory of the Transformation of Co- ordinates and Times from a Stationary System to another System in Uniform Motion of Translation Relatively to the Former [..] the axes of the moving system are [...] parallel to the axes of the stationary system." > See the example at the end > of paragraph 4 of the 30Jun1905 Einsteins paper (rotating Earth). And which you cannot understand. For the sake of others I copy-paste my recent clarifications to you which you apparently also cannot understand (and I won't try anymore): At the beginning of paragraph 2 in the 30Jun1905 paper, Einstein writes: 1. The laws by which the states of physical systems undergo change are not affected, whether these changes of state be referred to the one or the other of two systems of co-ordinates in uniform translatory motion. Those changes of state stem from classical (Newtonian) theory, and he referred to Newtonian coordinate systems. That he had such a physical consideration of systems along with the mathematical one is essential for understanding his paper, and the part about moving clocks in particular. Probably it's best to first discuss the predictions from the older, classical theory for this case; and then you will probably immediately understand the prediction with the new one. First, take Newton's theory. You surely know that that theory predicts that uniform motion does not at all affect the rate of a clock as determined in a "stationary" system; and as also Einstein emphasized, the word "stationary" commonly doesn't mean anything special, it's just a Newtonian system that we pick. Now take a clock that is moving uniformly in another direction, starting with a physical consideration. Surely you understand that it has qualitatively the *same* state of motion; the direction of motion cannot make a difference for the prediction. Thus logically, the same can be said for a clock that is moving along a polygonal trajectory, since an infinitely quick change of direction does not affect the indication of a good clock. Mathematically this physical understanding can be verified by performing Galilean transformations at the turning points: the time t is of course the same when we shift our coordinates, while the time t' that we locally read cannot be affected by our change of ruler position (please think this over). *If* we next assume that also acceleration has no effect on clock rate, then we can extrapolate (by simple integration) this result to a circular trajectory. As a matter of fact, this is what always *was* assumed by everyone, based on Newtonian mechanics. Now take the new theory. This one has the following "physical meaning": "The time marked by [a uniformly moving] clock (viewed in the stationary system) is slow by 1 - sqrt{1-v^2/c^2} seconds per second." Following the same *physical* logic as in the old theory, the direction of motion cannot affect the physics; thus "It is at once apparent that this result still holds good if the clock moves from A to B in any polygonal line". This can be verified mathematically (which takes a little longer than the immediate physical insight based on state of motion) by performing Lorentz transformations at the turning points. Then we verify that when switching to another location, the time t remains of course the same. Also the corresponding t' at that point (a physical event) cannot be affected by our change of ruler position, as that would contradict with what is observed with the first ruler position. Next, "*If* we assume that the result proved for a polygonal line is also valid for a continuously curved line", Einstein comes to his prediction about a clock moving in a circular trajectory. [NOTE: just as as the earlier, Newtonian prediction, that prediction has nothing to do with confusing non-inertial frames with inertial frames!] Following that, he makes a prediction in which he lets go of his overly simple example of Newtonian systems that are determined by means of "stationary" clocks and rods on a fixed body; instead he now refers to the ECI coordinate system which is in nearly uniform motion but in which almost no reference matter is perfectly in rest. As PD also pointed out, this was already well understood in Newtonian mechanics and Einstein based himself on the use of Newtonian reference systems. Best regards, Harald
From: artful on 30 Jun 2010 19:12 On Jul 1, 6:03 am, va...(a)icmf.inf.cu wrote: > In a recent thread we established that > Centre of mass inertial frames are the unique ones in 1905 > Relativityhttp://groups.google.com.cu/group/sci.physics.relativity/browse_frm/t... That is just plain wrong. You may THINK you've established it, but you have no idea. Any inertial frame is fine. Nothing to do with any mass, [snip rest of nonsense]
From: whoever on 30 Jun 2010 20:22 >wrote in message >news:cf9a3f56-d5ca-4a3e-8df9-29d3d626153c(a)5g2000yqz.googlegroups.com... > >On 30 jun, 15:13, stevendaryl3...(a)yahoo.com (Daryl McCullough) wrote: >> va...(a)icmf.inf.cu says... >> >> >> >> >In a recent thread we established that >> > Centre of mass inertial frames are the unique ones in 1905 >> >Relativity >> >> There is nothing in the development of relativity that in any >> way depends on a frame being defined by a center of mass. That's >> completely barking up the wrong tree. >> >> -- >> Daryl McCullough >> Ithaca, NY > >I will answer you with the same initial post of the referred thread: Repeating nonsense does not make it true > [Let be any body set with a material point modelling each one. OK .. so you start off with an ungrammatical sentence which makes no sense. Try again [snip more nonsense] --- news://freenews.netfront.net/ - complaints: news(a)netfront.net ---
From: valls on 1 Jul 2010 06:42 On 30 jun, 19:22, "whoever" <whoe...(a)whereever.com> wrote: > >wrote in message > >news:cf9a3f56-d5ca-4a3e-8df9-29d3d626153c(a)5g2000yqz.googlegroups.com... > > >On 30 jun, 15:13, stevendaryl3...(a)yahoo.com (Daryl McCullough) wrote: > >> va...(a)icmf.inf.cu says... > > >> >In a recent thread we established that > >> > Centre of mass inertial frames are the unique ones in 1905 > >> >Relativity > > >> There is nothing in the development of relativity that in any > >> way depends on a frame being defined by a center of mass. That's > >> completely barking up the wrong tree. > > >> -- > >> Daryl McCullough > >> Ithaca, NY > > >I will answer you with the same initial post of the referred thread: > > Repeating nonsense does not make it true > > > [Let be any body set with a material point modelling each one. > > OK .. so you start off with an ungrammatical sentence which makes no sense. > > Try again > A body modelled by a material point is a very basic Newtonian concept. Without it, the Newtonian mechanics laws have no sense at all. The position of a body in some space at the corresponding instant of some time, is the position of the material point modelling the body. Any force acting in a body is a force acting in a straight line crossing the material point modelling the body. The distance between two bodies (to appy the gravitation law) is the distance between the material points modelling the two bodies. You need more? Try again. RVHG (Rafael Valls Hidalgo-Gato)
From: valls on 1 Jul 2010 07:38
On 30 jun, 18:12, artful <artful...(a)hotmail.com> wrote: > On Jul 1, 6:03 am, va...(a)icmf.inf.cu wrote: > > > In a recent thread we established that > > Centre of mass inertial frames are the unique ones in 1905 > > Relativityhttp://groups.google.com.cu/group/sci.physics.relativity/browse_frm/t... > > That is just plain wrong. You may THINK you've established it, but > you have no idea. > > Any inertial frame is fine. Nothing to do with any mass, > You forget that the topic in this thread is 1905 Relativity, where an inertial frame, denoted by 1905 Einstein stationary system, is related with mass without any doubt at all. To help you the understanding of it, I will put here some text from the 30Jun1905 Einsteins paper (between [ ]): Almost at the end of the Introduction: [The theory to be developed is based like all electrodynamics- on the kinematics of the rigid body, since the assertions of any such theory have to do with the relationships between rigid bodies (system of co-ordinates), clocks, and electromagnetic processes.]. See here how 1905 Einstein identify systems of co-ordinates with rigid bodies. Can you conceive a rigid body without mass? At the beginning of paragraph 2, where he defines stationary system: [Let us take a system of co-ordinates in which the equation of Newtonian mechanics hold good.]. A direct identification between inertial system with massive system of co-ordinates. At the beginning of paragraph 3: [Let us in stationary space take two system of co-ordinates, i.e. two systems, each of three rigid material lines, perpendicular to one another, and issuing from a point.]. A single material point is already a massive entity, and we have here RIGID MATERIAL LINES associated with the inertial frames. I will suppose this is already sufficient for you to understand that to talk about a non-massive inertial frame in 1905 Relativity is a complete absurd. RVHG (Rafael Valls Hidalgo-Gato) |