Eckard
I presume the exchange you referred to ran in 3 different threads in early November.
1 Infinity
There is no such thing as infinity in the physical existence we are examining. Because we are trapped in a closed system, ie a form of existence which is finite. Assertions outwith that form can only be belief, ie 'anything goes' and is of equal validity, or non-validity, whichever-as they are the same. The point being once extrinsic to the form of existence we can know, there is no validity reference. George Ellis's argument, which is a common one, that: "Anything to do with "infinite" is an unprovable hypothesis", confuses the logical possibilities as to what existence might be, with the form of existence we can know. [Remember our exchange on God with Ben, and you agreed with me. This is the same logical point]. Logically, existence might have a feature we refer to as infinity. But scientifically we cannot transcend one particular form of existence, so, as with any other such ideas, we cannot know, it is just a belief and therefore not part of science. The form of physical existence we are able to examine, objectively, is, by definition, finite. Though in terms of mathematical/narrative representation thereof, tends towards infinity, is correct, ie indicating that there is a definite quantity but it is too large to quantify. This might at first appear to be 'nit-picking', but this is a classic example of the failure to understand the nature of what is being investigated first, before constructing representations of it.
2 Dimension alteration (Length contraction)
Whether this actually occurs is something that needs to be proven, but that is a separate issue.
Whilst it was thought to be the explanation of the null result of M&M, whether it was, or a false interpretation, or the experiment was invalid, etc, is all irrelevant. The critical point is that they believed it to be so, which initiated a certain train of thought, but ultimately was not a driver in the resulting theory of relativity. That is, for example, it caused them to be concerned about relatively moving objects and hence their use as a reference. Because such objects were so moving as the force (really a differential) causing that, also caused dimension alteration. So they introduced a non-existent variable in their thinking, which then needed to be rationalised. This morphed into time variation (ie time alteration-again there is a tendency as with length to only refer to one effect-dilation). The quantification of these effects is the same, and is wrong anyway, since all it (gamma) really amounts is a comparison of the transversal with the vertical. The concept that there was dimension alteration also gave 'background comfort' to the notion of timing devices varying as their momentum varied, ie their tick rate might be so affected as they contracted/dilated. The supposed variance in time is derived via another route, the closest we get to this notion is a reference to a "normal" clock. You should also note that Einstein concluded: "that the expected difference is much too small to be noticeable in the measurement of earth's surface" (section 22 Foundation 1916)
3 The real point here being that relativity is the function of two interrelated fundamental errors:
-the assumption that there is duration in physical existence, which manifests as the incorrect application of x = vt . That is, time is reified.
the conflation of physical existence and light existence (ie what we receive, but do not confuse this with the subsequent processing thereof, which is irrelevant). That is, the elimination of time delays which actually occur whilst light travels, the reification of c as the constant/limiter-a determinant of physical existence-which it is not, AND its use in the incorrect application of x = vt.
In simple language: the existent time delay whilst light travels is conflated with a non existent time variation in physical existence. Which is, as Peter Jackson will confirm, what I have been saying for the past 18 months. It has nothing to do with presuming c to be constant, which is a valid simplification, and it has nothing to be with all these torturous arguments about the processing of physical input received.
4 I would need to know what you are referring to as SR. It was not 1905. Another factual point I keep making, like the one about light is just a moving entity therefore its speed depends on the reference used to calibrate it. Einstein was perfectly clear as to what constituted SR, it was a theoretical circumstance without gravitational forces, so it involved only uniform rectilinear and non-rotary motion, fixed shape bodies, and light that travelled at a constant speed in straight lines. Remember, in 1905 we had dimension alteration, ie not fixed shaped bodies. This contradiction in 1905 was because matter was not 'in vacuo', whereas light was. He was aware of a problem, hence the two postulates were "only apparently irreconcilable", and this was 'reconciled in section 7 1916.
5 It sounds as if the Feynman lectures you refer to are not available on-line(?)
Paul