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The Question

(Submitted November 07, 2007)

According to WMAP results, galaxies were seeded in the very early universe. Is there no problem in explaining how these seeds could survive the universal maelstrom before matter became atomic?

The Answer

The most likely seeds of galaxies are density fluctuations, which are a fundamental property of the quantum mechanics that we believe, at least to a good approximation, describe the Universe. The early Universe was hot enough to ionize atoms, but not hot enough to get rid of these fluctuations.

The bigger problem is actually how to make these fluctuations grow large enough and fast enough to explain the large scale structure that we see today. Most theories use the idea of mergers to grow things quickly - the idea is that relatively small regions of matter self-gravitate into clumps, and then these clumps aggregate into bigger clumps, and so on.

Jay and Jeff
for Ask an Astrophysicist

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