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trinitree88
2011-Aug-04, 02:26 PM
History always seems to have a few more wrinkles in it than I thought. This is one of them. SEE: http://arxiv.org/ftp/arxiv/papers/1108/1108.0709.pdf

Tensor
2011-Aug-04, 05:09 PM
History always seems to have a few more wrinkles in it than I thought. This is one of them. SEE: http://arxiv.org/ftp/arxiv/papers/1108/1108.0709.pdf

The problem with that paper is it demonstrates a bit of bias by leaving out a major piece of information. The offending line is: "1929, Hubble repeats Lemaître’s work with essentially the same data and obtains similar results." It's that "essentially" that is hiding most of the information. Hubble also used his observations of Cepheid variables to determine that the nebulae (which is what the galaxies were thought to be at the time) were actually galaxies in their own right.

But he also could determine the distance independently of the redshift, knowing that the absolute magnitude of the Cepheids could be determined by the length of the period of the Cepheids. Knowing the absolute magnitude, the distance to the cepheid could be determined using the apparent magnitude and the inverse-square law.

Without the Cepheid observations, there was no way of knowing, at that time, if the apparent brightness was due to distance or possible dust. The cepheids allowed Hubble to actually verify the redshift-distance relationship, something Lemaître couldn't do with his data.

ngc3314
2011-Aug-04, 09:54 PM
But the range of Hubble's Cepheid detections was, even at the time, clearly not large enough to be relevant to a redshift-distance relation, except to estimate a sort of zero point (the most remote was perhaps M33). He was using such tricks as the mean magnitude of multiple galaxies in a group to estimate relative distances.