Redshift Periodicites of Quasars and Galaxies

When we talk about the overall structure of the Universe, we assume what's called the cosmological principle. The cosmological principle states that the Universe, on average, looks the same no matter where you are. The trick, of course, is that you have to average over a couple hundred million light years.

This week I read two papers, however, which tried to challenge this assumption. They didn't succeed, but I'll tell you about them, anyway. The two papers are Redshift Periodicity in Quasar Number Counts from Sloan Digital Sky Survey and Spatial Periodicity of Galaxy Number Counts from Fourier Analysis of the Large Scale Surveys of Galaxies in the Universe. Both papers are by J.G. Hartnett, a young earth creationist. His method was to take data sets from the SDSS (Sloan Digital Sky Survey) and 2dF GRS (2 degree Field Galaxy Redshift Survey) and look for periodicities, or harmonic components, in their radial distribution.

Now, the radial distribution is measured by their redshifts, which, by Hubble's law, are proportional to their distance. Hartnett looked and found such harmonic components in both the quasar and galaxy populations. He claims that the quasar harmonics show that quasar redshifts do not follow Hubble's law, but rather are an intrinsic property of quasars, themselves. At the same time, he claims that the galaxy harmonics show that galaxies sit on concentric spheres centred on the Milky Way. Now, if either of these claims were true then things would be difficult for the cosmological principle.

Lucky for the cosmological principle, the claims don't hold any water. Here's why: the quasar harmonics are spurious and the galaxy harmonics are explained (and predicted) by cosmological large-scale structure. First for the quasars, the harmonics are due to a selection effect. The SDSS cannot detect quasars at certain redshifts because they look just like stars, so we see artificial valleys in the radial distribution. Of course, because these are due to a selection effect, they can't have any implication on cosmology.

The galaxy harmonics that he found do appear to be real, but they certainly aren't due to concentric spherical shells of galaxies. He demonstrated this himself when he looked in two different directions and didn't see the same harmonics. How can they be spherical shells if they aren't spherically symmetric? They can't: that's how. Rather, the length scales of these harmonics matches rather well to the the length-scale of large-scale filaments seen in the Millennium Run, the largest cosmological computer simulation yet completed.

Hartnett concludes that the cosmological principle is in question. But a careful review of his papers shows that the only thing questionable is his research.

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References:
Hartnett, J. G., arXiv:0711.4885v2
Hartnett, J. G., arXiv:0712.3833v2