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zheng89120
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because it seems the Lorentz transformations constitute special relativity itself
But there are two classes of experimental facts hitherto obtained which can be represented in the Maxwell-Lorentz theory only by the introduction of an auxiliary hypothesis which in itself--i.e. without making use of the theory of relativity--appears extraneous.
It is known that cathode rays and the so called beta rays emitted by radioactive substances consist of negatively electrified particles (electrons) of very small inertia and large velocity. By examining the deflection of these rays under the influence of electric and magnetic fields, we can study the law of motion of these particles very exactly.
In the theoretical treatment of these electrons, we are faced with the difficulty that electrodynamic theory of itself is unable to give an account of their nature. For since electrical masses of one sign repel each other, the negative electrical masses constituting the electron would necessarily be scattered under the influence of their mutual repulsions, unless there are forces of another kind operating between them, the nature of which has hitherto remained obscure to us. If we now assume that the relative distances between the electrical masses constituting the electron remain unchanged during the motion of the electron (rigid connection in the sense of classical mechanics), we arrive at a law of motion of the electron which does not agree with expereience. Guided by purely formal points of view, H.A. Lorentz was the first to introduce the hypothesis that the form of the electron experiences a contraction in the direction of motion in consequence of that motion, the contracted length being proportion to the expression[tex]\frac{1}{\gamma}[/tex]This hypothesis, which is not justifiable by any electrodynamical facts, supplies us then with that particular law of motion which has been confirmed with great precision in recent years.
The theory of relativity leads to the same law of motion, without requiring any special hypothesis whatsoever as to the structure and the behaviour of the electron.
...
[The following concerns the Michelson and Morley experiment]
Lorentz and Fitzgerald rescued the theory from this difficulty by assuming that the motion of the body relative to the aether produces a contraction of the body in the direction of motion, the amount of contraction being just sufficient to compensate for the difference in time mentioned above.
zheng89120 said:because it seems the Lorentz transformations constitute special relativity itself
Dschumanji said:According to the book that Einstein wrote to explain the special and general theories of relativity to the layman:
If I understand this correctly, it seems that Lorentz used his transformation to model the contraction of electrons as they moved at high speeds. He also used it to save the aether theory. Einstein's theory of special relativity applies to more than just electrons and rejects the idea of the aether. Lorentz was on the right track, he just didn't make that extra step that Einstein did.
harrylin said:That only related to Lorentz's theory of electrons; the new theory (both Lorentz's and Einstein's accounts) applied to all matter and EM waves.
Note: I wonder why there is an issue about "who derived" SR, and not about "who derived" QM...
zheng89120 said:because it seems the Lorentz transformations constitute special relativity itself
I've heard that this wasn't the case...Zentrails said:Einstein was not a particularly good mathematician. Someone else had to point out to him that Rieman geometry would be apropos for his General Relativity theory.
Dschumanji said:According to the book that Einstein wrote to explain the special and general theories of relativity to the layman:
If I understand this correctly, it seems that Lorentz used his transformation to model the contraction of electrons as they moved at high speeds. He also used it to save the aether theory. Einstein's theory of special relativity applies to more than just electrons and rejects the idea of the aether. Lorentz was on the right track, he just didn't make that extra step that Einstein did.
Isn't length contraction alone enough to explain MMX, without time dilation or relativity of simultaneity? I thought Lorentz derived it as the transformation that would preserve Maxwell's laws of electromagnetism in different frames.GrayGhost said:Not exactly. Lorentz derived his transformations to force-fit the MMX null result.
JesseM said:Isn't length contraction alone enough to explain MMX, without time dilation or relativity of simultaneity?
JesseM said:I thought Lorentz derived it as the transformation that would preserve Maxwell's laws of electromagnetism in different frames.
JesseM said:Isn't length contraction alone enough to explain MMX, without time dilation or relativity of simultaneity? I thought Lorentz derived it as the transformation that would preserve Maxwell's laws of electromagnetism in different frames.
Well, you could either just use the Galilei transformation for the Earth frame with the understanding that coordinate length was different than ruler length along the axis of motion relative to the aether, or you could come up with a new coordinate transformation such that coordinate length still matched ruler length in the Earth frame, if we say the aether frame is unprimed and the Earth frame is primed (and the aether is moving parallel to the x' axis of the Earth frame) it would just look like this:GrayGhost said:Well, the assumption back then was isotropic light in only the aether frame. From the POV of an aether frame observer, I suppose one could show length contraction w/o time dilation. I don't see how one could do it from the Earth frame POV though, w/o invoking time dilation ... it seems to me that the explanation would have been incomplete.
zheng89120 said:because it seems the Lorentz transformations constitute special relativity itself
Dschumanji said:I've heard that this wasn't the case...
nitsuj said:I think Einstien by leaps and bounds "theoretically derive[d] special relativity" before Lorentz (or anyone else for that matter). His intuition is remarkable even in the context of civilizations greatest scientists.
I forget where but I heard someone say "If I could ask Eistien one question it would be 'how did you know your thinking was on the right track?'"
So true, people everywhere think about this stuff and go off in some pretty fantastic directions, but Eistien was right. And pursued his intuition like he had read the theory from God's physics handbook.
Einstiens low profile may have helped keep him under the radar of other great minds of the time, so no direct competition. (I think with GR he did have some racing to beat him to the finish line, but from a mathimatical perspective)
A good story with a simular "who came up with it first?" Watson & Crick's pursuit of DNA (specificaly it's shape, solid proof), a very competitive race for sure.
Zentrails said:I was speaking relatively. LOL
He was a far better mathematician than me or anyone I know, of course.
Just not as good as the top physics scientists he was competing with at the time.
nitsuj said:I think Einstien by leaps and bounds "theoretically derive[d] special relativity" before Lorentz (or anyone else for that matter). His intuition is remarkable even in the context of civilizations greatest scientists.
I forget where but I heard someone say "If I could ask Eistien one question it would be 'how did you know your thinking was on the right track?'"
So true, people everywhere think about this stuff and go off in some pretty fantastic directions, but Eistien was right. And pursued his intuition like he had read the theory from God's physics handbook.
Einstiens low profile may have helped keep him under the radar of other great minds of the time, so no direct competition. (I think with GR he did have some racing to beat him to the finish line, but from a mathimatical perspective)
A good story with a simular "who came up with it first?" Watson & Crick's pursuit of DNA (specificaly it's shape, solid proof), a very competitive race for sure.
ZealScience said:But Watson & Crick pursuit of DNA also is sort of contraversial considering the contribution from Franklin (a female biologist, Ican't remember the full name)
JesseM said:Well, you could either just use the Galilei transformation for the Earth frame with the understanding that coordinate length was different than ruler length along the axis of motion relative to the aether, or you could come up with a new coordinate transformation such that coordinate length still matched ruler length in the Earth frame, if we say the aether frame is unprimed and the Earth frame is primed (and the aether is moving parallel to the x' axis of the Earth frame) it would just look like this:
x' = gamma*(x - vt)
y' = y
z' = z
t' = t
...then you could use this transformation to figure out how fast light moves in different directions in the Earth frame, given that it moves at c in all directions in the aether frame. Should then get the same prediction for the MMX in the Earth frame as you got in the aether frame, with no time dilation needed.
GrayGhost said:Maybe so, but one would have an incomplete and incorrect model of nature.
Lorentz and Einstein obtained the same LTs. One assumes an invariant c in only the master aether frame, and the other assumes invariant c in any and all inertial frames. Now, I'm not very familiar with the Lorentz derivation, but here's the thing ... Einstein generates his linear coefficients alpha(v) and phi(v). He deterimines by logical deduction that phi(v)=1, and thus that aplha(v) = 1/beta(v) ... beta(v) being known as gamma(v) today. IOWs, Einstein did no force-fitting of group symmetries to obtain his transforms.
If I may ask you ... did Lorentz force-fit his coefficients to obtain the group symmetry that he (and Poincare) knew was required to ensure the principle of relativity, or did they naturally evolve as in the case of OEMB?
GrayGhost
http://en.wikisource.org/wiki/Electromagnetic_phenomenaThe value of the constant must be unity, because we know already that, for w=0, l=1.
We are therefore led to suppose that the influence of a translation on the dimensions (of the separate electrons and of a ponderable body as a whole) is confined to those that have the direction of the motion, these becoming k times smaller than they are in the state of rest.
Zentrails said:If I remember Watson's "Double Helix" book correctly, Watson & Crick were far ahead of their ONLY competitor (Linus Pauling) because Linus was convinced a triple helix was the correct structure. Watson's Cambridge group collaberated with Franklin's Kings college group, before which there were only 3 groups in the DNA "race."
Time sure have changed since then.
harrylin said:What do you mean with "force-fit"? Lorentz found by logical deduction that only a coefficient l=1 leads to the correct equations...
harrylin said:It's perhaps useful to point out that in 1904 he thus derived the Lorentz contraction from the PoR.
How can one know what guarantees the PoR without first deriving it? Before 1904 Lorentz kept the unknown factor l in his discussions, leaving the question open if what we now call Lorentz contraction is indeed the right solution.GrayGhost said:Thanx Harrylin. By force-fit, I meant "not by logical deduction, but rather by insertion". IOWs, if you assume you know the required final form of the equations to guarantee the PoR, you "make it happen" during derivation. From what you say, Lorentz obtained his linear coefficients by deduction, as Einstein did. I'll have to read thru his paper more closely.
Wrt the PoR ... Consider a dual pan balance whereby the line joining the pan midpoints are aligned with the balance's propagational path. Assume the pans are separated by a very long beam, and the wonder beam cannot bend. Further assume that "someone who believes himself at rest in Lorentz's master aether frame" records the balance's motion at luminal v thru the aether. Now, LET and SR produce the very same solns, so in either case, observers at rest with the balance should always witness the same result(s) ... ie, it's presumedly not possible to distinguish between SR & LET by experiement. Now, let's say 2 weights of identical mass drop from the sky, always of identical velocity and strike the balance pads AT ONCE "per an observer at rest with the balance". What would each theory predict wrt the balance beam tilting upon impact?
SR says ... the balance beam would not tilt.
LET (I think) would say ... the balance beam tilts, because the 2 weights do NOT strike the pads AT ONCE per an aether frame observer "if they strike the pads AT ONCE per the observer moving with the balance thru the aether". The aether POV is always right.
Wrt LET theory ... How is it that the PoR is upheld by LET theory? It seems to me that ... even though the LT results are the same in either case, they do not mean the same thing. The PoR "only appears to be upheld" (per LET) from a kinematic standpoint, but not with regards to force, and thus not with regards to energy. What is wrong with my reasoning here?
If all the coefficients were logically obtained by deduction, then I would agree. However, it just seems to me that the PoR is upheld kinematically, but not beyond that. How do you explain the scenario I pose above?
GrayGhost
harrylin said:For a correct understanding of SR it is essential to realize that according to SR you may assume any inertial frame to be "truly in rest" so that the laws of nature should be valid wrt it, without any frame jumping.
Thus rephrased in interpretation-free SR:
"the 2 weights do NOT strike the pads AT ONCE per a rest frame observer if they strike the pads AT ONCE per the observer who is moving with the balance".
Note:a wonder beam that cannot bend cannot exist in SR
Harald
A wonder beam creates a paradox in SR - just as a wonder signal at infinite speed. If you do want to discuss your paradox, please start a separate thread on that.GrayGhost said:harrylinn,
When one says "wonder beam", most folks generally accept that the beam does something that cannot happen in relality, or at least in practice to date. No different from discussing a wonder-traveler who attains c, which everyone knows cannot happen. But just for the sake of point, let's assume a wonder beam.
Sorry but evidently you did not understand my reply to you: According to the PoR the same laws of physics must be valid in any inertial frame, "ether" frame or not. Consequently, any problem that you imagine for "LET" is identical for standard SR, in which "ether frame" merely serves as a lable for a certain "rest frame". The laws of physics - even for moving balances (but not for wonder beams which break those laws) - must be valid wrt such a frame, as otherwise absolute inertial motion could be detected. The balance beam cannot tip according to the PoR, and both POV's must agree that the beam does not tip; that was the purpose of both Lorentz-1904 and Einstein-1905.Well, I understand how SR handles my stated scenario. You skipped over that at first, and it remains clear that you are misreading it based on your prior response. [..]
GrayGhost
harrylin said:...
GrayGhost said:LET an SR are not the same theory. Some folks here claim that the theories are identical, except that any aether frame is superfluous per SR, and that it's impossible to detect the truly existent aether frame per LET.
GrayGhost said:What I was asking about was (1) did Lorentz force-fit his LT derivation to accommodate the PoR (you say no), and (2) does the PoR truly apply to the all-of-physics under LET, or does it apply only kinematically?
Indeed it was not you but me who suggested that your example is a paradox (=apparent contradiction): I actually understood that according to you, "the observer at rest in the aether frame would predict" that "the balance beam would tip", while according to "observers at rest with the balance" "the balance beam would not tilt". Sorry that I misunderstood you.GrayGhost said:Harrylinn,
I never suggested any paradox exists.
[..] I also never suggested that observers of differing frames would disagree as to whether the beam tips.
Lorentz [managed to] bring [his hypothesis] into accord with the postulate of the complete impossibility of determining absolute motion [..] in his article entitled Electromagnetic phenomena in a system moving with any velocity smaller than that of Light (Proceedings de l’Académie d’Amsterdam, May 27, 1904).
As I already mentioned, according to Einstein a new theory emerged with the writings of Lorentz in 1904 and his own in 1905; I agree with that. However there is a subtle difference between the two interpretations of the theory: whereas Lorentz found it useful to distinguish between what appears to happen and what "really" happens from an unknown perspective that cannot be detected, Einstein found it better to only discuss the phenomena (=appearances, not what "truly" happens!).GrayGhost said:[...] LET an SR are not the same theory.
Some folks here claim that the theories are identical, except that any aether frame is superfluous per SR, and that it's impossible to detect the truly existent aether frame per LET. Light speed is defined differently per each theory. One theory says that what you measure matches what is real, while the other says length-contractions prevent your contracted ruler from measuring the true-contractions. It seems to me that there is more a difference between the 2 theories than these alone. Lorentz disagrees that 2 inertial clocks synchrionised-with-each-other moving thru the aether are "truely simultaneous" per themselves. Is this correct, or not?
GrayGhost