Ask Ethan: What were the “dark ages” of the Universe?

Today, in all directions, no matter where we look, there are luminous sources of energy to behold. Stars, galaxies, nebulae, and even energy-emitting black holes populate the Universe wherever matter has clumped and clustered together sufficiently. Even though there are great cosmic voids that span up to around a billion light-years in diameter, they’re merely holes in the cosmic “Swiss cheese” of structure. From all directions, the light still gets in, and illuminates even the darkest corners of the Universe. But that’s what things are like now, 13.8 billion years after the Big Bang. As we look deeper and deeper into the Universe, we see that the story gradually begins to change. Past a certain threshold, galaxies appear redder and fainter than expected: as though something were in the way, blocking that light. That effect gets more severe with distance, where only the brightest of galaxies can be perceived at all. At last, we run out of light to see, suggesting that there were “dark ages” beyond a certain point. What were those dark ages like? That’s what Predrag Branković wants to know, asking: <a href="https://medium.com/starts-with-a-bang/ask-ethan-what-were-the-dark-ages-of-the-universe-e6ddc9d34670">Read More</a>