Image: Spiral galaxy Messier 83 Credit: NASA/ESA Most of the matter that we can see in the universe is concentrated into galaxies and galaxy clusters. We live in a galaxy called the Milky Way. Yet our galaxy is merely one of billions, perhaps hundreds of billions of other galaxies. Wherever we look in the universe we find galaxies. So how and when did they form? Using telescopes, such as Hubble, astronomers have deduced that the first galaxies began forming around 12 billion years ago, more than a billion years after the Big Bang. This answers when galaxies formed, but how did they form? Astronomers know very little about how the first galaxies formed. However, they do know some of the basics about how it happened. Sometime after the Big Bang, most of the visible matter in the universe consisted of hydrogen and helium gas clouds. All this matter was uniformly spread across the universe. However, due to small fluctuations in the gravitational fields of these clouds, there were some areas that were slightly denser than others. Over the course of millions of years, the hydrogen gas clumps together and collapses, leading to the formation of the first stars. Vast numbers of stars would have formed. Stars that formed relatively close together would be bound together by their gravity. As more stars came together to form larger clusters, their gravity would have become stronger, allowing them to pull in even more stars. The first galaxies were being born. There's a problem with this. How was there fluctuations in the early universe that caused some areas to be more dense than others? The best explanation is inflation. Almost immediately after the Big Bang, the universe went through a phase of rapid expansion in which space expanded faster than light speed. Quantum fluctuations or jitters, which happen in the quantum realm, would have happened in the macroscopic world due to the extreme amounts of energy during inflation. These quantum jitters caused some regions to be slightly denser than others. (Second comment below 👇👇👇) - January 03, 2016 at 01:15AM Source: https://scontent.cdninstagram.com/hphotos-xtp1/t51.2885-15/e35/12393863_813008625475740_99501127_n.jpg #nasa #space #iss #isro #mars #marsorbiter #outerspace #lightyears #milkyway #universe #galaxy #stars #sun #moon #saturn #jupiter #stumble #stumblespace

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