Large-scale structure formation

The Universe began with a hot big bang nearly 14 billion years ago. In the early Universe, it was too hot for even atoms to form. But after about 400,000 years, the expanding Universe was cool enough for hydrogen atoms to form. At this time the Universe was dark – there were no stars or galaxies. The Dark Ages ended with the Cosmic Dawn, after about 100 million years, which is roughly how long it took for the first generation of stars to form from huge clouds of hydrogen and helium and to fill the Universe with starlight. After about 500 million years, the first galaxies began to form. Ever since that time, new galaxies have been forming and existing galaxies have been evolving (sometimes merging together). We estimate that today there are about 400 billion galaxies in the observable part of the Universe that surrounds our Milky Way galaxy. This evolving distribution of galaxies forms a vast network – the Cosmic Web of large-scale structure. Understanding the formation and evolution of large-scale structure from origins at the birth of the Universe, requires a number of ingredients, including theory (based on Einstein’s theory of gravity) and computation (super-computer simulations of billions of galaxies). Using this analysis, we are able to identify signatures in the patterns and evolution of large-scale structure. These signatures contain information about the Universe, about the Dark Matter that speeds up the formation of galaxies and keeps galaxies from disintegrating together, and about the Dark Energy that fills the Universe and that has been accelerating the expansion of the Universe for the last 5 billion years or so.