Labels:book | bulletin board | reckoner OCR: Our grasp of the conditions that prevailed in the early universe does not translate into full understanding of how galaxies formed Neverthe less we do have quite a few pieces of the puzzle Gravity causes the growth 01 density fluctuations in the distribution Of matter because it more strongly slows the expansion of denser regions, making them grow still denser This process IS observed in the growth of nearby clusters of galaxies and the galaxies themselves were probably assembled by the same process on a smaller scale The growth of structure in the early universe was prevented by radiation pressure but that changed when the universe had expanded to about 0.1 percent of its present size At that point, the temperature was about 3 000 kelvins cool enough to allow the ions and electrons to com ...
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