- #36
oldman
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I seem to have inadvertently diverted this thread away from its main thrust, which was
The discussion so far has been concerned largely with Lieu's paper (which includes much special pleading) and with the puzzling Pioneer anomaly. But it is clear that apart from disturbing Lieu, many of the knowledgeable folk who post in this forum and accept the consensus LCDM model do so only as a working hypothesis, sometimes reluctantly and for various reasons. For instance, I notice that Marcus joins that august publication, The Economist, in labelling LCDM a kludge:
I suggest that when rectifying kludges it is often useful to go back to the very beginning and re-examine the fundamentals. In this vein GR is a target for Marcus, and for Garth, who prefers the alternative of his Self-Creation cosmology.
I'm an outsider who finds the description of gravity given by GR convincing, at least as a working model. But perhaps there are alternatives to modifying GR. Take the founding
observation of modern cosmology, the redshift, which Lieu mis-spells in his Table 2 and attributes simply to "the expansion of space", whatever this is. (Note that some deny that space expands, some find "space" a convenient didactic fiction, while others -- like myself -- are mystified by the very concept of space. See several threads in these forums.)
What if the founding observation of the redshift has been misinterpreted in the context of a correct theory, namely GR?
Remember that astronomers have long been accustomed to measuring spectral shifts to determine, say, the radial velocities of stars and rotation speeds of galaxies. This is the context in which the redshift was discovered and interpreted. It was therefore natural, in the R-W metric, to account for the redshift with a scale factor that serves as a common multiplier for the metric coefficients of the space dimensions. This preserved the link to the then-prevalent Doppler-shift wisdom about spectral shifts. So much for how the founding notion of isotropic expansion became embedded in cosmological thinking some eighty years ago.
But the cosmological redshift is sharply distinguished from all other astronomical spectral shifts by its symmetry, which is seldom explicitly considered. Perhaps this special feature tells us that the R-W metric is universal. Or perhaps it tells us that something like the symmetric laws of perspective are involved. Or there may be alternative ways of incorporating this symmetry in GR, without throwing the entire LCDM model out with the bathwater, as it were.
How do contributers to this thread view the symmetry of the redshift? Too simple to discuss?
Garth said:... intended as a discussion of observations that may raise questions about the consensus ...
The discussion so far has been concerned largely with Lieu's paper (which includes much special pleading) and with the puzzling Pioneer anomaly. But it is clear that apart from disturbing Lieu, many of the knowledgeable folk who post in this forum and accept the consensus LCDM model do so only as a working hypothesis, sometimes reluctantly and for various reasons. For instance, I notice that Marcus joins that august publication, The Economist, in labelling LCDM a kludge:
Marcus said:I think LCDM looks like a KLUDGE, tinkered manyways to fit...
I suggest that when rectifying kludges it is often useful to go back to the very beginning and re-examine the fundamentals. In this vein GR is a target for Marcus, and for Garth, who prefers the alternative of his Self-Creation cosmology.
I'm an outsider who finds the description of gravity given by GR convincing, at least as a working model. But perhaps there are alternatives to modifying GR. Take the founding
observation of modern cosmology, the redshift, which Lieu mis-spells in his Table 2 and attributes simply to "the expansion of space", whatever this is. (Note that some deny that space expands, some find "space" a convenient didactic fiction, while others -- like myself -- are mystified by the very concept of space. See several threads in these forums.)
What if the founding observation of the redshift has been misinterpreted in the context of a correct theory, namely GR?
Remember that astronomers have long been accustomed to measuring spectral shifts to determine, say, the radial velocities of stars and rotation speeds of galaxies. This is the context in which the redshift was discovered and interpreted. It was therefore natural, in the R-W metric, to account for the redshift with a scale factor that serves as a common multiplier for the metric coefficients of the space dimensions. This preserved the link to the then-prevalent Doppler-shift wisdom about spectral shifts. So much for how the founding notion of isotropic expansion became embedded in cosmological thinking some eighty years ago.
But the cosmological redshift is sharply distinguished from all other astronomical spectral shifts by its symmetry, which is seldom explicitly considered. Perhaps this special feature tells us that the R-W metric is universal. Or perhaps it tells us that something like the symmetric laws of perspective are involved. Or there may be alternative ways of incorporating this symmetry in GR, without throwing the entire LCDM model out with the bathwater, as it were.
How do contributers to this thread view the symmetry of the redshift? Too simple to discuss?
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