According to 1905 Relativity, a single material point must be always at rest
in [Relativity]
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From: Androcles on 25 May 2010 15:25 "blackhead" <larryharson(a)softhome.net> wrote in message news:f0475c63-2a6c-45a9-a85c-0fdfa561de0c(a)f14g2000vbn.googlegroups.com... On 24 May, 07:44, "Androcles" <Headmas...(a)Hogwarts.physics_z> wrote: > "blackhead" <larryhar...(a)softhome.net> wrote in message > > news:70a4084b-2807-4b96-8581-028720ba39c1(a)m21g2000vbr.googlegroups.com... > On 23 May, 01:45, "Androcles" <Headmas...(a)Hogwarts.physics_z> wrote: > > > > > > > "blackhead" <larryhar...(a)softhome.net> wrote in message > > >news:23dacda0-1876-4750-a477-8ea0a987b6b4(a)j27g2000vbp.googlegroups.com... > > On 22 May, 02:19, "Androcles" <Headmas...(a)Hogwarts.physics_z> wrote: > > > > "blackhead" <larryhar...(a)softhome.net> wrote in message > > > >news:f6138a42-e150-411c-9bed-3f510209de99(a)e21g2000vbl.googlegroups.com... > > > | On 21 May, 12:01, 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? > > > | > > > | You've forgotten that inertial frames can be rotated wrt with one > > > | another with v = 0 for the material point. > > > | > > > You've forgotten (or more likely never knew) that Einstein didn't have > > > anything to do with Newton's inertial frames and are irrelevant to SR. > > > Einstein defines a frame of reference where the laws of > > electrodynamics and mechanics holds good. > > =============================================== > > The laws of electrodynamics and mechanics hold good in all > > frames of reference, you just don't know what they are. > >http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/fw/gifs/coriolis.mov > > The Coriolis force is fictitous and not physical. > =================================== > Who mentioned any force? > Certainly not I. > > Androcles' first law of rotating frames of reference: In a rotating frame > of > reference every body perseveres in its state of circular motion, or of > uniform motion in a perfect circle, unless it is compelled to change that > state by forces impressed thereon. Newton's definition of a force changed the velocity of a body. What is Androcles's definition of a force? ============================================== My definition is the same as Newton's, I add that a force changes angular velocity in a rotating frame of reference. I also define a blackhead as a small plug of sebum blocking the duct of a sebaceous gland especially on the face (aka a zit or pimple). http://www.merriam-webster.com/dictionary/blackhead Einstein doesn't have a definition of a physical law. What is Zit Pimple's definition of "the same laws of electrodynamics and optics will be valid for all frames of reference for which the equations of mechanics hold good"? > The laws of electrodynamics in rotating frames of reference apply to > electric motors and generators, look up Fleming's left hand rule. > > In the frame of reference of the overhead camera the ball follows a > straight > line. > In the frame of reference of the carousel camera the ball follows a > circle. > No forces involved, fictitious or otherwise. > There is only one ball, but two frames of reference. > > The laws of electrodynamics and mechanics hold good in all frames of > reference, *you* just don't know what those laws are and the pathetic > ranting dork Einstein hasn't told you, he didn't know either. > > You obviously don't know any physics, all you know is SR. > SR is fictitious and not physical.- Hide quoted text - SR postulates that physics has another symmetry - Lorentz covariance. =============================================== Zit Pimple is lying. SR postulates "We will raise this conjecture (the purport of which will hereafter be called the ``Principle of Relativity'') to the status of a postulate, and also introduce another postulate, which is only apparently irreconcilable with the former, namely, that light is always propagated in empty space with a definite velocity c which is independent of the state of motion of the emitting body. These two postulates suffice for the attainment of a simple and consistent theory of the electrodynamics of moving bodies based on Maxwell's theory for stationary bodies", then adds a third postulate, 'the ``time'' required by light to travel from A to B equals the ``time'' it requires to travel from B to A'. Of course neither Zit Pimple nor Einstein can count to three or even know what a postulate is. SR is fictitious and not physical.
From: Sue... on 25 May 2010 15:57 On May 25, 11:19 am, va...(a)icmf.inf.cu wrote: > On 24 mayo, 07:27, PD <thedraperfam...(a)gmail.com> wrote: > > > On May 24, 6:13 am, va...(a)icmf.inf.cu wrote: > > > > On 21 mayo, 10:22, PD <thedraperfam...(a)gmail.com> wrote: > > > > > 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. > > > > What do you say is totally valid in today Special Relativity, but not > > > in 1905 Relativity. See the following references to the 30Jun1905 > > > text. > > > Almost at the end of the Introduction: > > > R1. [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.] > > > At the beginning of paragraph 3: > > > R2. [Let us in stationary space take two systems of co-ordinates, > > > i.e. two systems, each of three rigid material lines, perpendicular to > > > one another, and issuing from a point.] > > > In R1 a system of co-ordinates is identified with a rigid body, and in > > > R2 (more detailed) with a system of tree rigid material lines. Even a > > > single material point must have some mass, imagine tree material > > > lines. Do you continue thinking that in 1905 Relativity a reference > > > frame does not require something material to establish the rest? > > > Yes. Just because Einstein uses a material framework to *explain* his > > position does not mean that it is essential to the conceptual > > framework. The idea of reference frames without material anchors > > preceded Einstein by at least a century. > > And what? How many centuries preceded Ptolemaic view the Newtonian > one? > Taking out the ether with its Newtonian absolute space and absolute > time is the essence of the Einsteinian relativistic view. In it remain > only the material bodies themselves to determine inertial frames. > You are free to support the old Newtonian view if you want, but that > doesnt give you the right to say that in 1905 Relativity a reference > frame does not require something material. You cant change what 1905 > Einstein writes, even thinking you that it is something wrong. > > > > > > > > > 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. > > > > Exactly. See in the previous reference R2 a different material object > > > for each one of the two different reference systems introduced.> This however, is not the case. A reference frame has a perfectly well- > > > > defined meaning with or without a material anchor in it. > > > > A valid assertion in today Special Relativity, but a totally invalid > > > one in 1905 Relativity. In this thread we are addressing only 1905 > > > Relativity (see the title). > > > This, in my opinion, is a boondoggle. > > I don't see the point of it at all. > > Relativity is relativity. It is not a *creation*, it is a discovery. > > When the first sailors navigated to the New World, they drew maps that > > represented their view of their discovery. Of course, those maps did > > not at all accurately represent the shape of the Americas. It does > > absolutely no good to take one of those maps and say, "But this is the > > America of 1500." It is not. The shape of the continent has not > > substantively changed since 1500. The America of 1500 is the same as > > the America of 2010. It's just that how people have described it is a > > little different from 1500 to 2010. > > If I am interpreting well, you are suggesting that 1905 Relativity > contains errors (first sailors making bad America maps) that were > already corrected in today Special Relativity. And surely you think > that the need to have material bodies to determine an inertial frame > is one of these errors. > 1916 Einstein introduces the word Special to distinguish the > previous Relativity (denoted SR) from his General Relativity (GR) that > he is just introducing. But we have here a very strange situation. The > essence of the new GR is precisely the introduction of material > (massive) bodies that warp the space-time (without material bodies!) > introduced by 1907 Minkowski (1907M). Then, 1907M is the one putting > out the material bodies from 1905 Relativity, conceiving a space-time > totally independent from them (similar in that to the Newtonian > absolute space and time, but now with a very strong relationship > between space and time). Einstein accepts the changes 1907M introduces > in Relativity and works for years (without success) in the developing > of a relativistic gravitation. He ends declaring Relativity (the > modified one by 1907M) not able to address gravitation, developing his > successful 1916GR gravitation theory. He works then the rest of his > life trying (without success) to put into accord GR with the rest of > Physics, a problem that remains open until our days. > Suppose now that somebody finds the way to explain GR effects (like > the ones necessary to adjust GPS clocks in the Earths gravitational > field), but using only 1905 Relativity (Newtonian mechanics, Euclidean > geometry). Would you consider that a boondoggle? (English is not my > mother language, and I dont know the meaning of that word). > > > > > > > > > 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 Earth modelled as a single material point in its centre of mass is > > > at rest in the GPS ECI System, moving in a monthly almost circular > > > trajectory around the centre of mass of the Earth-Moon System (CMEM), > > > and that CMEM is moving in a yearly trajectory around the centre of > > > mass of the Solar System (CMSS). The CMSS has a velocity of about > > > 250Km/s in the Galaxy System, etc. Are these systems the ones you have > > > in mind when talking about infinite ones? ================ > > > No, because they aren't inertial, are they? > > Of course that they are inertial ones, or maybe consider you that an > inertial frame is only a mathematical entity? The Solar System is the > more exact real inertial system used by men. And we can make a similar > remark referring to the GPS ECI. By the way, they are both centre of > mass inertial systems, supported by huge experimental evidence. The earth moves on an elliptical path around the moon. A surf fisherman can perform gravito-inertial experiments to detect that motion. (sit still while boots dry) << Einstein's relativity principle states that: All inertial frames are totally equivalent for the performance of all physical experiments. In other words, it is impossible to perform a physical experiment which differentiates in any fundamental sense between different inertial frames. By definition, Newton's laws of motion take the same form in all inertial frames. Einstein generalized this result in his special theory of relativity by asserting that all laws of physics take the same form in all inertial frames. >> http://farside.ph.utexas.edu/teaching/em/lectures/node108.html Sue... > > > > > > > > Do you consider that the > > > different states of motion of the Earth in those different systems are > > > totally equivalent ones? Or maybe some one is more valid that some > > > other? > > > > > > 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) > > > > RVHG (Rafael Valls Hidalgo-Gato) > > I noted you dont answer my questions about the validity of different > inertial systems. Have you some problem with it? > > RVHG (Rafael Valls Hidalgo-Gato)
From: valls on 25 May 2010 17:42 On 21 mayo, 15:00, Darwin123 <drosen0...(a)yahoo.com> wrote: > 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. Have no sense for you to address the origin of Einsteins Relativity? My denotation 1905 Relativity (1905R) has the primary intention to separate from Relativity the 1907 Minkowski contribution. Then, in 1905R we have Cartesian coordinates, Euclidean geometry and Newtonian mechanics. What is then new in 1905R? The extension of Galileos Principle of Relativity to all Physics (particularly to electrodynamics) and the rejection of the ether (and with it the absolute space and the absolute time Newtonian concepts). We had found that from 1905R in its very limited historical context, effects today only explained with General Relativity (GR) could be derived in a different and very much simple way. Taking into account that Einstein expends the rest of his life trying (without success) to put into accord GR with the rest of Physics (a problem that remains open until our days), I consider very important that 1905R opened alternative. What do you think about? > 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. In Newtonian physics, with or without bodies, ANY space point is always at rest in the unique and privileged absolute space and time inertial frame, doesnt exist any privileged space point. If you have any closed and insolate body set, its centre of mass can be moving with ANY uniform velocity v in the privileged frame. The centre of mass (CM) is then NOT a space point, but can be considered a material point modelling the body set as a whole entity and having all its mass. In 1905R physics we have a very different situation. We have no more a privileged frame (with no relation at all with bodies) with all its points at rest. You need to consider always some determined closed and insolate body set, deriving from it (RELATIVE to it) a UNIQUE inertial frame, denoted the centre of mass one, having a UNIQUE space and a UNIQUE time. The CM is now a privileged space point that remains ALWAYS at rest (and with it all the others space points). The space and the time are unique, but not absolute, they are both RELATIVE to the starting (primary) body set considered. Put your attention in the differences between Newtonian and 1905R physics, but over all, the differences between 1905R and today Special Relativity (SR). > 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. A material point is a concept that belongs to the Newtonian view since its beginning, and it is very distant from your infinitesimal particle. The whole Solar System can be modelled by a single material point in its centre of mass to describe its trajectory in the Galaxy. To say that a material point is at rest with respect to itself conveys no information at all. The important thing is to say that a material point is at rest with respect to the specific body set it is modelling as a whole unique entity. > 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. Maybe in Special Relativity, but NOT in 1905 Relativity where a rest clock at a pole cant be moving with respect to a moving clock at the equator considered at rest. See the end of paragraph 4 of the 30June1905 Einsteins text. You can obtain it at http://www.fourmilab.ch Take also there the 27Sep1905 text, only 3 short pages showing the mass-energy universal relationship. By the way, reading with care this last text you will know that in 1905R the rest mass of ANY body measures its ABSOLUTE potential energy (without any arbitrary additive constant), and including ALL kind of potential energies that can be present, known or for known. Very different from today Special Relativity, where the rest mass of any body is a constant and intrinsic attribute. > 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. The Earths centre of mass is not only related with an inertial frame, but with the UNIQUE one in which the men living in its surface can do real experiments. The Hafele&Keating experiment was a simple one compared with the today GPS continuous permanent behaviour. In the GPS all relative velocities are totally useless. The ECI is the UNIQUE inertial system that the real (fluid) rotating Earth and its satellites determine. You will see in the future how all essentials GPS clock corrections can be computed using only 1905R physics. All GPS is a huge experimental evidence supporting 1905 Relativity. 1905 Einstein was the first synchronizing MOVING clocks with the time of rest ones, exactly what it is done today with all GPS clocks (in satellites or at ground), with gravitation present, the one excluded from Special Relativity by 1916 Einstein. > 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. 1905 Einstein knows very well that all the Earths rotating axis (with both poles and the centre of mass included) is at rest in the stationary system he is using (the today denoted ECI). He knows that in that frame the clock at the equator is moving and the one at a pole is at rest. The 1905 Einstein assumption that you mention is totally supported by the huge experimental evidence of today GPS. > 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. Detail to me what approximation are you talking about, and why you say that 1905 Einstein is wrong in his assumption. In 30June1905 Einstein know nothing about the influence of gravitation on clocks, but this doesnt imply that he was wrong. Without taking the effect of gravitation, a clock at the equator runs slower than one at a pole by the quantity predicted by 1905 Einstein (for ANY clock speed v in the today ECI frame, the 1905 text includes the exact relativistic formula, not only the approximated one for v<<c). Today GPS engineers know this very well. By the way, I can advance you that the gravitation effect on atomic clocks is owed (following 1905R) to a change in the rest mass of the electrons involved in the change of state inside the atoms. The higher the gravitational potential, the higher the rest mass measuring the corresponding higher gravitational potential energy. And the emitted frequency of the atomic clock is proportional to the electron rest mass (I advanced you already a little above that the rest mass of any body measures its total and absolute potential energy, following 1905R). > 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 am completely sure that you will advance very rapid in the understanding of my topic. By the way, if Physics laws are the same in all inertial frames (Principle of 1905 Relativity), that refers clearly to all Universe. > 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. > I hope you have already a better knowledge of what we have between hands. You write a lot, forcing me to work also a lot, but I am very happy with your contribution. > >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. Take into account that the good holding of Newtonian equations is 1905 Einstein definition of the type of reference systems he is addressing. The CM inertial system corresponding to a determined body set is a well-established concept in Newtonian mechanics, jointly with the Theorem stating the CM state of motion independence from all body set internal interactions. > 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 you suppose determined S and S, consider then the two body sets S +S united in a single one. You have then only internal forces. In reality this is always implicit in any CM calculation. If you take into account only a determined body set when computing its CM, this already implies that you consider that dont exist any other body in the model you are making. On what extend your model represents the chosen real part of the Universe, is another story. But we really need that no external force exists at all? Analysing it more carefully, we find that it is sufficient that the external force provokes the same (approximate) acceleration in all bodies of the set. Internally, the system is considered with its CM at rest, externally, the system (modelled by a material point in its CM) can be accelerated in any way. Doesnt seem this similar to the elevator falling free in a uniform gravitational field of the General Relativity? We can generalize then Galileos Principle of Relativity changing the requirement of a uniform constant velocity by ANY kind of velocity. You dont note that the Earth orbiting the Sun (with its monthly dance with the Moon) is the same Earth at rest in the ECI? We have then an interesting duality, a unique body (system) has two faces (to name it in some way), the external and the internal ones. I can advance you that exist 4 different energies associated to any body, the external and internal potential and kinetic ones. You can add the external potential and kinetic ones, or the internal potential and kinetic ones (adding the ones corresponding to each component body), obtaining in both cases the same result with a unique total energy measured by the body total mass. It is clear that we are taking for granted the Conservation Principle of Energy in all CM inertial frames. > 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. I dont care at all with any thing related with the absolute space that already is put out by 1905 Einstein. What occurs in S and S are already separated by the equal acceleration assumption, and Newtons laws hold good in both systems. S is always a part of S+S, and the acceleration of S that you are mentioning is with respect to the system S+S. By the way, that acceleration belong to its external face as a component of S+S. In its internal face the CM of S remain at rest and the whole S doesnt exist at all. If you are confused, consider S the GPS ECI and S+S the Solar System and you will see that all become very clear. And remember that all huge GPS experimental evidence is supporting us. > 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. > ANY real inertial frame is an approximate one, only pure mathematical concepts can be absolutely exact. Anyway, SS and GPS ECI are very exact real inertial systems supported by a huge experimental evidence. The Earth surface is NOT approximated as an inertial system in the ECI (and also NOT in 1905R). And the ECI is the inertial system where the Earths surface is moving. I am (almost) sure that you are confused about it. The ECI is nothing more that the today denotation of what 1905 Einstein uses already. I have experience programming computers, an activity where one is constantly involved in errors and correcting them. If I am the confused one in this point (or in any other), please, dont end until convincing me about it. (I have frequent problems here managing large posts. I will end this here, considering that already has a lot of very important content) RVHG (Rafael Valls Hidalgo-Gato)
From: Darwin123 on 25 May 2010 20:16 On May 25, 5:42 pm, va...(a)icmf.inf.cu wrote: > On 21 mayo, 15:00, Darwin123 <drosen0...(a)yahoo.com> wrote:> 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: > ANY real inertial frame is an approximate one, only pure mathematical > concepts can be absolutely exact. An inertial frame is a limiting case that can never be achieved precisely. However, like all limiting cases, it is well defined in terms of tests. If one has a well defined reference frame, where the motion of its origin is well defined, then there is a test as too how close to being an inertial frame. Einstein started out with "a frame for which the laws of mechanics applies." There is the inertial frame test. Later on he revised that to "a frame where the laws of mechanics applies to first order." I reading this with a late twentieth century hindsight interpreted the laws of mechanics as being the laws of motion in Principia. All the laws of Principia involve forces. Thus, the test of whether a frame is an inertial frame has to involve forces, or the accelerations attributed to forces. The "first order" is first order in velocity divided by speed of light in vacuum. I think it is pretty clear that the center of mass of the earth can not be precisely the origin of an inertial frame. This is because there are forces acting on the earth as a whole system. There are external forces acting on the entire earth that cause acceleration of the center of mass. However, there are even greater forces involved on the surface of the earth. Any clock on the surface of the earth near the equator is going to undergo far greater external forces than a clock at the center of the earth. So, in any experiment involving the surface of the earth, the center of mass can be considered the origin of an inertial frame. > Anyway, SS and GPS ECI are very > exact real inertial systems supported by a huge experimental evidence. That is a qualitative statement. One could be more quantitative from the very start of the calculation. Both the center of mass of the earth and the surface of the earth at the equation are in motion. This motion is well known from astronomical measurements. The curvature of these orbits are to first order in v/c caused by centripetal forces. To first order, gravity can be considered a force. Yes, I know there is a GR complication that makes gravity different from other forces. However, this difference won't really be very important in SR. The gravity of the sun causes the earth to move in an ellipse, the gravity of the moon causes the earth to wobble in a known way, and the gravity of the galaxy causes the earth to move in a curve that probably also resembles ellipse with some wave motion thrown in. All these forces can be calculated, and make the center of mass different from an inertial frame point. A clock at the center of the earth will be subject to all these forces, and hence can't precisely be considered an inertial clock. Consider a clock on an airplane just above the surface of the earth. It is subject to the same forces that affect the clock in the center of the earth. Gravity from the sun, gravity from the moon, and gravity from the galaxy. However, it is also subject to two additional force: the force of the seat that holds the clock, and the force of gravity. The total of the last two forces is the centripetal force on the clock caused by surface motion. This centripetal acceleration is huge compared to the centripetal accelerations of the first three forces (sun, moon, galaxy). So we can ignore these smaller accelerations on the problem. With respect to the noise in such experiments, the acceleration caused by sun, moon and galaxy is negligible. We only have to consider the forces of the seat and earths gravity on the surface. We can approximate the earths center as the origin of an inertial frame. However, we know a priori this is an approximation and we can even give an upper bound to the errors caused by this approximation. > The Earth surface is NOT approximated as an inertial system in the ECI > (and also NOT in 1905R). I agree. Why do you claim I said otherwise? The earths surface is not an inertial system in 2010, and was not considered an inertial system by Einstein in 1905. The center of mass of the earth was treated like an inertial frame, with respect to suggested clock experiments on the surface of the earth. The sun, the moon, and the galaxy are not important for such experiments. The center of mass of the earth is not an inertial frame. Really sensitive experiments, not possible yet, would measure the effect of the sun, the moon, and the galaxy. > Earths surface is moving. I am (almost) sure that you are confused > about it. The ECI is nothing more that the today denotation of what > 1905 Einstein uses already. > I have experience programming computers, an activity where one is > constantly involved in errors and correcting them. If I am the > confused one in this point (or in any other), please, dont end until > convincing me about it. Just a minor nit. I made the mistake of thinking the OP was confused on this issue. I am sorry my reply confused you. However, I just want you to note. Hypothetically, an experiment may come along where the annual motion of the earth impacts the final results. In the experiments so far performed to validate relativity, the annual motion of the earth is negligible. The noise level is just small enough to measure the effect of the daily motion, caused by the spin of the earth. The noise level of the instruments has been far too big to allow one to measure the effect of the annual motion. If I were writing a computer program, I would be very careful about documenting the specific conditions under which the code will be valid. Basically, I would be concerned at what point my code would become obsolete. If instruments and techniques come along to measure the affect of the annual motion on top of the effect of the earths spin, then the approximation that the CM is the origin of an inertial frame would be obsolete. I suggest that you note it, but not to worry about it. Right now, it is a minor point. The technology makes it trivial. I was answering another question, which was somewhat ill posed to begin with. > > (I have frequent problems here managing large posts. I will end this > here, considering that already has a lot of very important content) > > RVHG (Rafael Valls Hidalgo-Gato)
From: valls on 26 May 2010 16:49
On 25 mayo, 10:46, PD <thedraperfam...(a)gmail.com> wrote: > On May 25, 10:19 am, va...(a)icmf.inf.cu wrote: > > > > > > > On 24 mayo, 07:27, PD <thedraperfam...(a)gmail.com> wrote: > > > > On May 24, 6:13 am, va...(a)icmf.inf.cu wrote: > > > > > On 21 mayo, 10:22, PD <thedraperfam...(a)gmail.com> wrote: > > > > > > 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. > > > > > What do you say is totally valid in today Special Relativity, but not > > > > in 1905 Relativity. See the following references to the 30Jun1905 > > > > text. > > > > Almost at the end of the Introduction: > > > > R1. [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.] > > > > At the beginning of paragraph 3: > > > > R2. [Let us in stationary space take two systems of co-ordinates, > > > > i.e. two systems, each of three rigid material lines, perpendicular to > > > > one another, and issuing from a point.] > > > > In R1 a system of co-ordinates is identified with a rigid body, and in > > > > R2 (more detailed) with a system of tree rigid material lines. Even a > > > > single material point must have some mass, imagine tree material > > > > lines. Do you continue thinking that in 1905 Relativity a reference > > > > frame does not require something material to establish the rest? > > > > Yes. Just because Einstein uses a material framework to *explain* his > > > position does not mean that it is essential to the conceptual > > > framework. The idea of reference frames without material anchors > > > preceded Einstein by at least a century. > > > And what? How many centuries preceded Ptolemaic view the Newtonian > > one? > > Taking out the ether with its Newtonian absolute space and absolute > > time is the essence of the Einsteinian relativistic view. > > Yes. > > > In it remain > > only the material bodies themselves to determine inertial frames. > > No. Again, you feel it is essential to anchor a frame to *something* > material for some reason. Thus, if the aether is removed, then to you > it MUST be material bodies. And if loosed from material bodies, then > to you this DEMANDS the aether back again. This is simply wrong. > Reference frames do not need material anchors, period. And they did > not, for a long time preceding Einstein. Newtonian mechanics easily > considered motion in frames in which there was no material object, > including any supposed ether, at rest. > The fact is that all Newtonian mechanics is based in its absolute space and time, the unique privileged inertial frame considered real and true. You are right saying that in it is very easy to consider motion in frames without a material object, because an empty frame moving with ANY uniform velocity v with respect to the privileged one is also an inertial frame (even if considered apparent and false). Then, we have in Newtonian mechanics ALL possible inertial frames, and ALL of them without the need of a single material body. The situation is totally different in 1905 Relativity. Once the privileged frame with absolute space and time is declared superfluous, ALL the others empty frames moving with respect to it with any uniform velocity v result also superfluous. Velocity with respect to nothing simply cant exist in 1905 Relativity. From where do you take a reference frame without material bodies? It is moving or at rest? If moving, with respect to what? And if at rest, with respect to what? And if you say that it is at rest with respect to itself, you are simply repeating Newtons primary absolute frame already put out by 1905 Einstein. In any case, in this thread we are considering only 1905 Relativity, where a system of coordinates is identified with tree rigid material lines, as the 1905 Einstein text put out of any doubt. And you have no right at all to put in 1905 Relativity what you want without the support of a 1905 text. > > > > > > You are free to support the old Newtonian view if you want, but that > > doesnt give you the right to say that in 1905 Relativity a reference > > frame does not require something material. You cant change what 1905 > > Einstein writes, even thinking you that it is something wrong. > > > > > > 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. > > > > > Exactly. See in the previous reference R2 a different material object > > > > for each one of the two different reference systems introduced.> This however, is not the case. A reference frame has a perfectly well- > > > > > defined meaning with or without a material anchor in it. > > > > > A valid assertion in today Special Relativity, but a totally invalid > > > > one in 1905 Relativity. In this thread we are addressing only 1905 > > > > Relativity (see the title). > > > > This, in my opinion, is a boondoggle. > > > I don't see the point of it at all. > > > Relativity is relativity. It is not a *creation*, it is a discovery. > > > When the first sailors navigated to the New World, they drew maps that > > > represented their view of their discovery. Of course, those maps did > > > not at all accurately represent the shape of the Americas. It does > > > absolutely no good to take one of those maps and say, "But this is the > > > America of 1500." It is not. The shape of the continent has not > > > substantively changed since 1500. The America of 1500 is the same as > > > the America of 2010. It's just that how people have described it is a > > > little different from 1500 to 2010. > > > If I am interpreting well, you are suggesting that 1905 Relativity > > contains errors (first sailors making bad America maps) that were > > already corrected in today Special Relativity. And surely you think > > that the need to have material bodies to determine an inertial frame > > is one of these errors. > > Not errors per se. Just not completely worked out, and so there is an > incomplete presentation of the model. > > A map of the eastern seaboard of the Americas is not inaccurate, but > it is not a good map of the Americas, either, because it is not > completely articulated. > That you consider 1905 Relativity incomplete dont give you the right to complete it in the way you want. You (or anyone) can modify it in any way, but not with the right to continue naming it 1905R. We cant change history, and I have powerful reasons to consider 1905R as it is. You will know about them in my next comment in this same post. > > > > > > 1916 Einstein introduces the word Special to distinguish the > > previous Relativity (denoted SR) from his General Relativity (GR) that > > he is just introducing. But we have here a very strange situation. The > > essence of the new GR is precisely the introduction of material > > (massive) bodies that warp the space-time (without material bodies!) > > introduced by 1907 Minkowski (1907M). Then, 1907M is the one putting > > out the material bodies from 1905 Relativity, conceiving a space-time > > totally independent from them (similar in that to the Newtonian > > absolute space and time, but now with a very strong relationship > > between space and time). Einstein accepts the changes 1907M introduces > > in Relativity and works for years (without success) in the developing > > of a relativistic gravitation. He ends declaring Relativity (the > > modified one by 1907M) not able to address gravitation, developing his > > successful 1916GR gravitation theory. He works then the rest of his > > life trying (without success) to put into accord GR with the rest of > > Physics, a problem that remains open until our days. > > Suppose now that somebody finds the way to explain GR effects (like > > the ones necessary to adjust GPS clocks in the Earths gravitational > > field), but using only 1905 Relativity (Newtonian mechanics, Euclidean > > geometry). Would you consider that a boondoggle? (English is not my > > mother language, and I dont know the meaning of that word). > > By my guest. Would love to see it. > Let be two material points M and m (one with a great mass M, and the other with a small mass m<<M). We can consider then M practically the Centre of Mass (CM) of the 2-point system (for example, M and m can model Earth and an electron). In the corresponding CM inertial system, let be r the distance between M and m. From the 27Sep1905 paper we know that The mass of a body is a measure of its energy-content. In 1905, a body Total Energy E=K+U, where K is the Kinetic Energy and U the Potential Energy. If the body is at rest, K=0, being then U measured by the rest mass. In the case we are addressing, for the body m we have then U(r)=m_0(r) c^2, where m_0(r) is the body m rest mass and c the constant vacuum light speed. We know that the gravitational potential energy increases when r increases. Its limit maximal value when r tends to infinite is then m_0m c^2, where m_0m is the corresponding limit maximal value of the rest mass m_0. We have then U(r)= m_0(r) c^2=m_0m c^2 (GM/r)m_0(r) Here G is the Newtonian gravitational constant, and (GM/r) is the gravitational potential owed to M with a supposed arbitrary value 0 at r infinite. As you can see, U(r) takes the very definite maximal value m_0m c^2 at r infinite. With some simple algebraic handling we obtain m_0(r)=m_0m/(1+GM/rc^2) We have then derived from 1905R how the rest mass of a small body changes as a function of its position r in the central gravitational field of a great mass M body. Note the absent of any constant arbitrary potential energy and the presence of an ABSOLUTE zero potential energy point at r=0. If M and m are the Earth and an electron, m_0m is the ordinary rest mass of a free electron (its maximal value at r infinite). The frequency emitted by an atomic clock is proportional to the rest mass of the electron involved in the change of state. In GR the rest mass is supposed a constant an intrinsic electron attribute, justifying the change in frequency with the warp of the space-time provoked by M. As you see, the things in 1905R are very much simple. I left to you the verification that the change of frequency predicted by 1905R coincides with the GR one in all the range of practical r values in real experiments like the Pound&Rebka one. By the way, the 1905R formula applies for ALL values of r from 0 to infinite, while the GR one has a limited range of application owed to the presence in it of a singularity that is absent in the 1905R one. > > > > > > > > > > > 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 Earth modelled as a single material point in its centre of mass is > > > > at rest in the GPS ECI System, moving in a monthly almost circular > > > > trajectory around the centre of mass of the Earth-Moon System (CMEM), > > > > and that CMEM is moving in a yearly trajectory around the centre of > > > > mass of the Solar System (CMSS). The CMSS has a velocity of about > > > > 250Km/s in the Galaxy System, etc. Are these systems the ones you have > > > > in mind when talking about infinite ones? > > > > No, because they aren't inertial, are they? > > > Of course that they are inertial ones, or maybe consider you that an > > inertial frame is only a mathematical entity? > > No, they are not. Circularly or elliptically moving systems are not in > inertial motion. > See at the end an analysis about what kind of systems are managed by 1905R. > > > > > > The Solar System is the > > more exact real inertial system used by men. And we can make a similar > > remark referring to the GPS ECI. By the way, they are both centre of > > mass inertial systems, supported by huge experimental evidence. > > > > > Do you consider that the > > > > different states of motion of the Earth in those different systems are > > > > totally equivalent ones? Or maybe some one is more valid that some > > > > other? > > > > > > > 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) > > > > > RVHG (Rafael Valls Hidalgo-Gato) > > > I noted you dont answer my questions about the validity of different > > inertial systems. Have you some problem with it? > > The frames you mentioned are not inertial. Circularly moving bodies > are not in inertial motion. > Let us revise what kind of reference frames are managing 1905 Einstein. At the beginning of paragraph 1 (30Jun1905 paper) we can read: [Let us take a system of co-ordinates in which the equations of Newtonian mechanics hold good.] That type of system is denoted by 1905 Einstein stationary system. By the way, in all his 1905 text he not use the word inertial, but taking into account that the equations of Newtonian mechanics hold good (and then also all its laws, including the first), I consider safe to interpret that stationary system is what today is named inertial frame. But in all 1905 text we dont find any mention at all about a possible movement of the stationary system, and much less specifying that it must be with uniform velocity following a straight line. At the end of paragraph 4 in the 30Jun1905 paper, we find as the stationary system what today is denoted GPS ECI, the real Earth rotating in the inertial frame determined by itself with its centre of mass at rest (as all the rotating axis, including the poles). We find there also as the moving system a clock at the equator moving in a CIRCULAR path. Taking into account that in a 1905R (without absolute space and time) all inertial frames must be derived from the bodies themselves, the stationary system must be then some CM inertial frame, being the moving system any of its component bodies that can be moving in any way compatible with Newtons laws. All this is supported with the huge GPS ECI experimental evidence. Note that the Solar System (SS) can be considered at rest as a whole entity (the more exact inertial frame known by men) for internal affairs, but moving not in the inertial way as a component of the Galaxy. The Earth, an SS component, is in a similar situation. Considered at rest for internal affairs (the GPS very successful function!), but moving not in the inertial way as a part of SS. All seem to indicate that without absolute space and time, what characterize the inertial attribute of a system as a whole is only the rest (v=0) of its CM, not the any uniform velocity v movement (that seem to belong only to the Newtonian infinite empty inertial frames already put out in 1905 Relativity). As the title of this thread states, according to 1905 Relativity, a single material point (modelling an inertial frame) must be always at rest. Because already it is not present the absolute space and time permitting it to move with any uniform v velocity. > > > > > > RVHG (Rafael Valls Hidalgo-Gato) RVHG (Rafael Valls Hidalgo-Gato) |