Origin of Galaxies

To follow the modern view of the origin of heavenly bodies, we must go back to the ancient time where we left the story of the world periods in Chap. 24: at about 400,000 years after the Big Bang, when the universe was filled uniformly by a hydrogen-helium gas at the temperature of 3,000°C. Today, when about 14 billion years have passed, we find that galaxies have formed and we are inside one of them, the Milky Way. Its estimated 200 billion stars and innumerable gas clouds of different sizes orbit around its center. When we look further, we see an enormous expanse of galaxies, more or less like our own stellar system. The hundreds of billions of galaxies in the sky are widely separated in space but belong to just a small number of classes being mainly elliptical and spiral, both of these made mainly of dark matter and a smaller amount of stars and gas. This suggests that the galaxies have their deep roots in just one basic process, occurring everywhere in the universe. How was the smooth and featureless state transformed into the complex system of superclusters, voids, and chains we see today?