Thomas et al. use publicly-released catalogs from the Sloan Digital Sky Survey to select more than 700,000 galaxies whose observed colors indicate a significant redshift and are therefore presumed to be at large cosmological distances. They use the redshift of the galaxies, combined with their observed positions on the sky, to create a rough three-dimensional map of the galaxies in space and to assess the homogeneity on scales of a couple of billion light years. One complication is that Thomas et al. measure the density of galaxies, not the density of all matter, but we expect that fluctuations of these two densities about their means to be proportional; the constant of proportionality can be calibrated by observations on smaller scales. Indeed, on small scales the galaxy data are in good agreement with the standard model. On the largest scales, the fluctuations in galaxy density are expected to be of order a percent of the mean density, but Thomas et al. find fluctuations double this prediction. This result then suggests that the universe is less homogeneous than expected. [http://physics.aps.org/articles/v4/47]
The supreme task of the physicist is to arrive at those universal elementary laws from which the cosmos can be built up by pure deduction. There is no logical path to these laws; only intuition, resting on sympathetic understanding of experience, can reach them
Thursday, June 16, 2011
The UNiverse seems less smooth than theory
If so, there will need some new understanding. Since Einstein's application of his grand theory, GRT, to comprehending the cosmos, a lot of observations have been achieved during the past years, especially about the cosmological structure on large scales. This allows one to make relatively accurate estimate about the mass and energy distribution, by calibration with GRT. Great fitting has been found if dark matter and dark energy are presumed up till now, when people find that, the universe is much more clumpier than expected on larger scale.
labels:
astrophysics,
cosmology,
dark energy,
dark matter,
fluctuations,
space,
time
Subscribe to:
Post Comments (Atom)
No comments:
Post a Comment