Although astronomers understand certain aspects of the universe clearly, others are more muddled. The Big Bang has a mountain of evidence behind it, while the picture of how protogalaxies evolved into normal galaxies in the first few billion years of the cosmos is just coming together. But what happened, exactly, at the end of the cosmic Dark Ages, following the Big Bang, that brought together the seeds of matter to form the first stars and galaxies? That question is still wrapped in a hazy cloud of mostly speculation.
