According to 1905 Relativity, a single material point must be always at rest
in [Relativity]
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From: Dono. on 21 May 2010 09:53 On May 21, 3:18 am, va...(a)icmf.inf.cu wrote: > On 20 mayo, 19:30, "Dono." <sa...(a)comcast.net> wrote: > > > On May 20, 4:39 pm, va...(a)icmf.inf.cu wrote: > > > > and I was born long after that epoch). > > > Judging by your advanced level of senility, this isn't true. > > Hello Dono, you don't finish yet to calculate the Sun's trajectory in > the ECI? I am still waiting for it. > > RVHG (Rafael Valls Hidalgo-Gato) Keep waiting, imbecile. A few more years and you'll kick the bucket so you'll stop polluting the internet.
From: PD on 21 May 2010 11:22 On May 21, 6:27 am, va...(a)icmf.inf.cu wrote: > On 20 mayo, 13:09, PD <thedraperfam...(a)gmail.com> wrote: > > > On May 20, 8:19 am, va...(a)icmf.inf.cu wrote: > > > > In his first Relativity paper (30June1905), after declaring the ether > > > superfluous, Einstein considers a material point at rest. He uses a > > > system of Cartesian coordinates in which the equations of Newtonian > > > mechanics and Euclidean geometry hold good. If the massive body is > > > alone (and then without a Newtonian gravitational force acting on it), > > > it must remains forever at rest in its own centre of mass inertial > > > frame. > > > Yes. So? > > > Every object lives in an infinite multitude of frames. The ones that > > have constant velocity with the frame you just described, plus this > > frame itself, constitutes the set of inertial frames. > > If we apply that to the single material point case, the result is an > infinite number of inertial frames where the single material point can > be moving with any velocity v. Any velocity of magnitude less than c, yes. So? > Once the ether is put out by 1905 > Einstein (and with it the Newtonian absolute space and time), can you > explain to me with respect to what a single material point can have > then a velocity different from zero? A reference frame does not require a material "anchor" object, for which that anchor object is at rest in that frame. If that were the case, then for two reference frames to even exist, you'd need two objects. For three, you'd need three objects. This however, is not the case. A reference frame has a perfectly well- defined meaning with or without a material anchor in it. Thus, a single material object lives in not one, but an infinitude of reference frames. In one of those inertial reference frames, the object happens to be at rest. > The question of interest is what is the relationship between various > > physical properties, as measured in different inertial frames? > > Yes, but before addressing that we must put clear which are the > inertial frames involved. > > RVHG (Rafael Valls Hidalgo-Gato)
From: PD on 21 May 2010 11:23 On May 21, 6:01 am, va...(a)icmf.inf.cu wrote: > On 20 mayo, 21:42, "Inertial" <relativ...(a)rest.com> wrote:> <va...(a)icmf.inf.cu> wrote in message > > >news:c13b9123-0513-4072-8dc5-54557b8cfaf5(a)y12g2000vbr.googlegroups.com.... > > > > In his first Relativity paper (30June1905), after declaring the ether > > > superfluous, Einstein considers a material point at rest. He uses a > > > system of Cartesian coordinates in which the equations of Newtonian > > > mechanics and Euclidean geometry hold good. If the massive body is > > > alone (and then without a Newtonian gravitational force acting on it), > > > it must remains forever at rest in its own centre of mass inertial > > > frame. > > > RVHG (Rafael Valls Hidalgo-Gato) > > > Yeup .. do you think that is a problem? > > Not for me, but maybe for other persons. > In the Newtonian view (with absolute space and time), a single > material point can have any constant velocity v in an infinite > quantity of different inertial frames. > In the 1905 Einsteinian view (without absolute space and time), the > same single material point can have only the constant velocity v=0 in > a unique inertial frame. > Are we in agreement about that? No. > > RVHG (Rafael Valls Hidalgo-Gato)
From: Darwin123 on 21 May 2010 16:00 On May 20, 6:17 pm, va...(a)icmf.inf.cu wrote: > On 20 mayo, 11:57, Darwin123 <drosen0...(a)yahoo.com> wrote:> On May 20, 12:28 pm, va...(a)icmf.inf.cu wrote:> On 20 mayo, 08:50, harald <h...(a)swissonline.ch> wrote:> On May 20, 3:19 pm, va...(a)icmf.inf.cu wrote: > > At the > > > end of paragraph 4 in the referred 1905 Einsteins paper, you can find > > > already the ECI (the rotating Earth with a centre of mass at rest) > > > with the moving system (clock at the equator) forming part of it. > > > Ahh, now I see what you are driving at. Einstein is referring to the > > ECI as an inertial frame, when it is obviously not an inertial frame. > > The centre of mass inertial reference frame (CM) corresponding to a > determined body set is a Newtonian concept developed long before 1905 > Einstein. If the body set is composed by all parts of the real Earth > (including today all GPS satellites and clocks), the corresponding CM, > that I denote as ECI (between ), is the stationary system used > by 1905 Einstein with its centre of mass (as all the rotating axis, > including the poles) at rest. True. The title refers to Einstein's 1905 article, which I don't have access too. If we restrict the discussion to Einstein's original 1905 paper, and nothing afterward, then the title and OP make no sense. In Newtonian physics, in ANY physics, a point is always at rest with respect to its own frame. In other words, a point is always at rest with respect to itself. The center of mass point of the earth is always at rest with respect to itself. The center of mass point of the solar system is always at respect to itself. The center of mass of the galaxy is always at rest with respect to itself. The center of mass of any particle of dust is always at rest with respect to itself. The word "material" doesn't clarify anything. If you define the position of an infinitesimal particle as a "material point", it is always at rest with respect to itself. The title could have read, "According to 1905 relativity, a single material point must always be in motion". A "material point" (particle) must always be in motion compared to another particle that is moving at a relative nonzero velocity with respect to it. A point must always be in motion if the origin of ones coordinate system has a nonzero velocity with respect to it. In fact, any point must be in motion against any other point that is moving with a nonzero velocity with respect to it. It is nonsense even to bring up the 1905 paper. A point is always at rest with respect to itself. That is an assumption in geometry that didn't need Einstein. The OP implied that there was something confusing the poster. Because the statement seemed too trivial, I was looking for whatever issue was confusing the OP. My mind considered other issues that had once confused me that could be described by similar words. I remembered being confused by the fact that in several papers I read, one by Einstein and one by Kafele, the center of mass of the earth was considered as the origin of an inertial frame. That was a source of my confusion at some point, when looking at the effect of motion of clocks on the surface of the earth. I apologize. I do not know what issue is confusing you. The relativity that I know, which includes later articles by Einstein, specifies the definition of inertial frame. At least one of Einstein's early papers refers to a frame where both the laws of mechanics, optics, and electrodynamics are valid. He then analyzes clocks on the surface of the earth, under the assumption that the center of mass of the earth is the origin of that frame. Einstein was wrong in that assumption, but I later understood that this is just an approximation. I think most physicists, including the ones who were most influenced at the time, thought this obvious. I am not one of those physicists who understood the approximation right away. I do not know what your title means, nor what the text in the posted message meant. It does not seem to have anything to do with relativity. A coordinate system is a coordinate system. However creative he was with the uses of coordinate systems, he did not make any statement that everything in the universe has to stand still. That is what your statement seems to imply. I note that there were many replies to your post. It appears that many people did not think your statement trivial or obscure. Maybe they also thought it was a point of actual confusion on your part. Maybe they also thought that things actually move in the universe, even under Einstein's assumptions. I no longer have any idea of what you are talking about. I am spending so much time answering to encourage you to express your concept better. >That CM is without any doubt a system > of co-ordinates in which the Newtonian equations hold good (using > 1905 Einstein literal words). Not always. Newtonian equations as described in Principia don't always work at a center of mass (CM). The Newtonian equations wouldn't even work in every CM even if every word of Principia were precisely true. Relativity isn't the issue. Let me explain. Consider massive particles in the absolute space defined by Newton. A similar argument would apply in the inertial frames of Einstein. However, let us for the minute consider Newton's Laws to be exactly true in some absolute space. Consider a set of massive particles. The set of masses (set S) have a well defined center of mass (CM) point. These particles may exert forces on each other, called internal forces. However, there are particles outside of set S. Unless S was the universal set of massive points, there are massive particles that aren't part of set S. Lets call the complement set of massive particles S'. A particle in S' can in principle apply a force to a particle in S. The set of forces of particles in S' have on particles in set S are called external forces. If there are no external forces, then the center of mass can not accelerate in the absolute space. The laws of Newton apply in any nonrotating coordinate system that is centered on the center of mass point of S. Call this point CM_S. For example, a massive point in S will travel in a straight line unless acted on by some other massive point. Newton's Third Law ensures that the center of mass won't budge, even if the particles in S are exerting forces on each other. Suppose there is an external point acting on any particle in S. The point CM_S will accelerate. The center of mass is determined by the position of all the particles in S. Therefore, if any particle of S' acts on any particle in S', CM_S has the potential to accelerate. Suppose we decide to use CM_S as the origin of our coordinate frame. The CM includes the coordinates of all the particles in S, whether they accelerate or not. Newton's third law doesn't apply in this coordinate system, because the center of mass itself is accelerating in absolute space. Now, the equations of Newton may not work on particles in S. If the origin of the coordinate system is accelerating in absolute space, then any of particles in S not acted on by an outside force may accelerate. This violates Newton's first law. This applies in any frame moving at a constant velocity to CM_S. If there is an external force acting on the particles. If you claim that Newton's Laws have to apply to a coordinate system, you have made a very restrictive claim. This was all determined a long time before Einstein. > The Earths surface is rotating in that > CM with a determined angular velocity. I remember you that in the > today GPS ECI, the I is for Inertial, but take into account that > in 1905 the GPS doesnt exist yet. Whoever decided on the GPS jargon wasn't a perfectionist. The ECI is not an inertial frame, and never will be. It approximates an inertial frame for may applications. I think that is what the I means. It approximates an inertial frame. > He is considering in first place the linear velocity v of the Earths > equator, knowing that it is zero at the poles. An acceleration doesnt > appear at all in any 1905 Relativity formula. I remember reading the 1905 paper long ago. I don't remember the details. However, I remember he used a formula for centripetal acceleration at least once in the article. He calculated the change in velocity (including the change in direction) in a small interval of time, "dt". He didn't use the word "acceleration", but he described acceleration in his equations. The magnitude of the velocity was constant, not the direction of the velocity. Today we would use the word speed to designate what he called v. He probably used the word velocity because the sign of v was important (i.e., - clockwise or +counterclockwise). So the one dimensional "direction" was important. However, the three dimensional direction of velocity is changing all the time. If the direction of the velocity wasn't changing, there could be no permanent time dilation effect. Maybe that is what you meant by "a point not moving". The point on the surface of the earth was always accelerating toward the pole. However, it stays on the surface of the earth. > > Even having the linear velocity v of its equator a near to c > value, 1905 Relativity formulas and procedures remain valid. The velocity of the surface is not "linear", in the sense of moving in a straight line. It is traveling a curved path. I don't remember Einstein referring to this velocity as linear. If he called the velocity "linear," I will admit he made a big mistake. Most physicists in 1905 knew the earth was round. Using a formula for centripetal acceleration makes no sense if the earth is round. Any formula that uses the radius of the earth implies that the earth is round. I don't think that Einstein was a flat earther. However, that may be bias on my part. We Einsteinians are always in denial |:-) > The Earth > is rotating in the stationary space corresponding to the considered > centre of mass (CM) inertial frame. > What 1905 Einstein does is to consider the moving system (the clock > at the equator) with an instantaneous uniform velocity v, Aahhh. Uniform doesn't always mean linear. I think he does use the word "uniform" in a later article to mean "linear". However, not in the 1905 article. "Uniform" here means that the magnitude of the velocity doesn't change. >that is > not uniform at all, because the clock is really centripetal > accelerated. We can have here a uniform speed (scalar), but not a > uniform velocity (vector). To convince about it, read the relevant > text almost at the end of paragraph 4: > If we assume that the result proved for a polygonal line is also > valid for a continuously curved line, we arrive at this result: If one > of two synchronous clocks at A is moved in a closed curve with > constant velocity until it returns to A, the journey lasting t > seconds, then by the clock which has remained at rest the travelled > clock on its arrival at A will be (1/2)tv^2/c^2 second slow. > Then, 1905 Relativity can be applied with ANY moving system, not > only a one moving with a uniform velocity. This is supported by the > huge experimental evidence of today GPS (including clocks centripetal > accelerated). Einstein should have said a uniform speed, not a uniform velocity. However, the helicity of the motion is important in the analysis. If the earth were to suddenly reverse direction, without changing the speed, it would have a big effect. Then, he was referring to the speed as a velocity because it had a rotational direction: clockwise or counterclockwise. Denial. It is not just a river |:-)
From: Androcles on 21 May 2010 16:26
"Darwin123" <drosen0000(a)yahoo.com> wrote in message news:a9be0b5a-b781-472d-9986-69ff0d1d502a(a)q23g2000vba.googlegroups.com... On May 20, 6:17 pm, va...(a)icmf.inf.cu wrote: > On 20 mayo, 11:57, Darwin123 <drosen0...(a)yahoo.com> wrote:> On May 20, > 12:28 pm, va...(a)icmf.inf.cu wrote:> On 20 mayo, 08:50, harald > <h...(a)swissonline.ch> wrote:> On May 20, 3:19 pm, va...(a)icmf.inf.cu wrote: > > At the > > > end of paragraph 4 in the referred 1905 Einstein�s paper, you can find > > > already the �ECI� (the rotating Earth with a centre of mass at rest) > > > with the �moving system� (clock at the equator) forming part of it. > > > Ahh, now I see what you are driving at. Einstein is referring to the > > ECI as an inertial frame, when it is obviously not an inertial frame. > > The centre of mass inertial reference frame (CM) corresponding to a > determined body set is a Newtonian concept developed long before 1905 > Einstein. If the body set is composed by all parts of the real Earth > (including today all GPS satellites and clocks), the corresponding CM, > that I denote as �ECI� (between � �), is the �stationary system� used > by 1905 Einstein with its centre of mass (as all the rotating axis, > including the poles) at rest. True. The title refers to Einstein's 1905 article, which I don't have access too. If we restrict the discussion to Einstein's original 1905 paper, and nothing afterward, then the title and OP make no sense. In Newtonian physics, in ANY physics, a point is always at rest with respect to its own frame. In other words, a point is always at rest with respect to itself. The center of mass point of the earth is always at rest with respect to itself. The center of mass point of the solar system is always at respect to itself. The center of mass of the galaxy is always at rest with respect to itself. The center of mass of any particle of dust is always at rest with respect to itself. The word "material" doesn't clarify anything. If you define the position of an infinitesimal particle as a "material point", it is always at rest with respect to itself. The title could have read, "According to 1905 relativity, a single material point must always be in motion". A "material point" (particle) must always be in motion compared to another particle that is moving at a relative nonzero velocity with respect to it. A point must always be in motion if the origin of ones coordinate system has a nonzero velocity with respect to it. In fact, any point must be in motion against any other point that is moving with a nonzero velocity with respect to it. It is nonsense even to bring up the 1905 paper. A point is always at rest with respect to itself. That is an assumption in geometry that didn't need Einstein. The OP implied that there was something confusing the poster. Because the statement seemed too trivial, I was looking for whatever issue was confusing the OP. My mind considered other issues that had once confused me that could be described by similar words. I remembered being confused by the fact that in several papers I read, one by Einstein and one by Kafele, the center of mass of the earth was considered as the origin of an inertial frame. That was a source of my confusion at some point, when looking at the effect of motion of clocks on the surface of the earth. I apologize. I do not know what issue is confusing you. The relativity that I know, which includes later articles by Einstein, specifies the definition of inertial frame. At least one of Einstein's early papers refers to a frame where both the laws of mechanics, optics, and electrodynamics are valid. He then analyzes clocks on the surface of the earth, under the assumption that the center of mass of the earth is the origin of that frame. Einstein was wrong in that assumption, but I later understood that this is just an approximation. I think most physicists, including the ones who were most influenced at the time, thought this obvious. I am not one of those physicists who understood the approximation right away. I do not know what your title means, nor what the text in the posted message meant. It does not seem to have anything to do with relativity. A coordinate system is a coordinate system. However creative he was with the uses of coordinate systems, he did not make any statement that everything in the universe has to stand still. That is what your statement seems to imply. I note that there were many replies to your post. It appears that many people did not think your statement trivial or obscure. Maybe they also thought it was a point of actual confusion on your part. Maybe they also thought that things actually move in the universe, even under Einstein's assumptions. I no longer have any idea of what you are talking about. I am spending so much time answering to encourage you to express your concept better. =========================================== He doesn't know either, he's Cuban. You two should get along well together. |