The large-scale smoothness of the Universe

[摘要] The Universe is inhomogeneous-and essentially fractal-on the scale of galaxies and clusters of galaxies, but most cosmologists believe that on larger scales it becomes isotropic and homogeneous: this is the 'cosmological principle'. This principle was first adopted when observational cosmology was in its infancy, and was then little more than a conjecture. The data now available offer a quantitative picture of the gradual transition from small-scale fractal behaviour to large-scale homogeneity.

[关键词] MICROWAVE BACKGROUND ANISOTROPIES;2-DIMENSIONAL POWER SPECTRUM;ANGULAR-CORRELATION FUNCTION;2-POINT CORRELATION-FUNCTION;CAMPANAS REDSHIFT SURVEY;APM GALAXY SURVEY;RADIO-SOURCES;IRAS GALAXIES;LOCAL GROUP;SKY SURVEY