The Solar System

How do galaxies form?
Answered by Discovery Channel
  • Discovery Channel

    Discovery Channel

  1. Can you believe that the universe started out almost 14 billion years ago as a tiny pinpoint of matter that contained the whole world in its entirety? According to the big bang theory, this pinpoint exploded, sending radiation and subatomic particles out into the universe. Scientists speculate that galaxies (more than 100 billion of them) were formed in one of two ways. Bottom-up theorists hypothesize that the particles were compressed into huge clusters that then merged to form galaxies. Top-down theorists believe that these same clusters were the size of numerous galaxies and then broke down to form individual ones. In either case, these clusters resulted in protogalaxies made up of hydrogen gas and dark matter. The hydrogen remained at the center of the galaxy while the dark matter surrounded it in a kind of halo.

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